scoping study on co2 mineralization technologies report · co 2 mineralization technologies report...

Confidential between CGS and South African Centre for Carbon Capture and Storage - 1 -

Scoping Study on CO2 Mineralization Technologies

Report No CGS- 2011-007

Prepared by Dr Frédéric J. DOUCET

Council for Geoscience

Private Bag X112, 280 Pretoria Street, Pretoria 0001

Phone: 012 841 1300 E-mail: [email protected]

Prepared for South African Centre for Carbon Capture and Storage

CEF House, 152 Ann Crescent, Strathavon, Sandton

Phone: 010 201 4937

Publication date 11 February 2011

Carbonated peridotite, Oman (Photographer: Dr Matter)

CONFIDENTIAL

CONTRACT REPORT


EXECUTIVE SUMMARY

The South African Centre for Carbon Capture and Storage appointed the author (Council for Geoscience) for

carrying out a Scoping Study on Carbon Mineralization Technologies. In preparation for this Scoping Study

Report, the author has critically assessed the published international literature, has listed patented processes,

has participated at the Third International Conference on Accelerated Carbonation for Environmental and

Materials Engineering (ACEME-10) held in Turku, Finland from 29th November to 1st December 2010 where he

was exposed to the latest development in the field and networked with international experts, and has visited

R&D facilities in Finland (Thermal and Flow Engineering Group, Åbo Akademi University), Norway (Institute for

Energy Technology) and Germany (ALCATRAP CO2 mineralization pilot plant). Financial sponsorship for the

conference participation and the European trip was provided by the South African Centre for Carbon Capture

and Storage.

To date, the most widely advocated method of carbon capture and storage (CCS) in South Africa involves the

injection of CO2 into underground geological formations. Key to the development of this geo-sequestration

technology is the existence of suitable high-integrity geological sites for the safe, long-term storage of CO2. A

theoretical estimate of the storage capacity for South Africa has recently been published in the Atlas on

Geological Storage of Carbon Dioxide in South Africa. Although a total storage capacity potential of about 150

Gt may be offered by South African geological reservoirs, the reservoirs are predominantly located off-shore and

at considerable distances from fixed CO2 point sources. Therefore, the risk remains that potentially-suitable

reservoirs may turn out to be insufficient, uneconomic or impractical. It is therefore imperative that South Africa

diversifies its CO2 management options and gives due consideration to every possible option of CO2 storage

which appears technologically possible. The consideration of such options would therefore act as an important

risk mitigation strategy for South Africa’s CCS activities.

Carbon capture and mineral carbonation (CCMC), also called CO2 mineralization, has been identified by the

Intergovernmental Panel on Climate Change (IPCC) as a possible promising additional technology in the CCS

portfolio. CCMC is a process whereby CO2 is chemically reacted with calcium- and/or magnesium- containing

minerals to form stable carbonate materials which do not incur any long-term liability or monitoring commitments.

The IPCC also highlighted that the “highly verifiable and unquestionably permanent” nature of this storage

mechanism is likely to lead to CCMC enjoying greater public acceptance than traditional geological CCS

approaches. Therefore, CCMC does not present the environmental, safety and legacy concerns of

geosequestration.

The perception gained at the ACEME-10 conference was that scientific effort is academic-oriented and at the

research stage, as already stated in the IPCC report of 2005, albeit at a much more advanced stage of R&D. A

number of processes under development stood out of the crowd, such as the ARC and the ǺA process routes,

the CO2 Energy Reactor©, and the chemical and biological catalytic enhancement as new CCS technology.

However, this is in contrast with the pilot and demonstration stages at which the processes of at least 8 start-up

companies from the USA, the UK and Australia – which have been launched during the last five years – stand.

Interestingly, the CCMC process developed by US-based Calera Corporation has recently been adopted by

China Huaneng Group, the largest electricity generator in China and the largest in the world, to be fitted onto its

power plant in the Xilinguole region of Inner Mongolia. Presumably this move in China exemplifies the

confidence which is developing in the future of CCMC.


CCMC is only now just coming onto the CCS radar screen. In recent years, R&D activities on CCMC have

increased rapidly. In the United Kingdom, the Energy Technologies Institute LLP (the ETI) is commissioning a

£1-million study paper to assess opportunities that CCMC may present for the country. It is therefore

conceivable, and perhaps even anticipated, that South Africa will host a number of CCMC plants in the

foreseeable future.

For CCMC to make a significant contribution to South Africa’s CO2 emission reduction, economically-viable and

environmentally-friendly processes need to be developed. Worldwide the focus is on mining, physically activating (e.g. via crushing, milling, elevated temperature and pressure), chemically activating (e.g. acid leaching, use of

chemical ligands), and carbonating the minerals called olivine ((Fe,Mg)2SiO4) and serpentine (Mg3Si2O5(OH)4),

which are naturally and abundantly present in geological formations, for the sole purpose of CCMC. The

challenge is to develop practical industrial processes with acceptable reaction kinetics, acceptable carbon

capture and conversion ratio (tons of CO2 per ton of feedstock), acceptable energy and mass balancing,

beneficial materials logistics, and lucrative markets for formed products. There does not appear to be any

economically-viable CCMC process in the public domain or in the academic world, but the 8 aforementioned and

fairly secretive commercial ventures seem to have integrated CCMC processes which may – or may not – be

scaled up to commercial level in the next few years.

South Africa is in a unique position where considerable amounts of suitable magnesium- and calcium- rich rocks

and minerals have already been mined, crushed and at times milled as part of the mining activities associated with the extraction of valuable industrial commodities (e.g. platinum, diamond). These materials form large piles

of waste rocks and mine tailings at numerous mine sites around the country. These tailings may represent a

considerable untapped resource for CCMC at a fraction of the costs likely to be incurred overseas. This

resource, combined with the concentrated, storage-ready CO2 stream emitted by Sasol, may suggest that South

Africa could become a leading player in this field.

Potentially-suitable raw materials that are available for CCMC in South Africa include:

- PGM (Platinum Group Metals) mine tailings: During the period June 2009 to June 2010, the major

“players” in the PGM industry (i.e. Anglo, Implats, Northam and Lonmin) produced 77.5 million tons of

Meresky, UG2 and Platreef tailings, which could theoretically sequester up to 13.9 million tons of CO2 per

annum. This represents 43% of the concentrated CO2 stream emitted annually by Sasol’s coal-to-liquid plant

in Secunda, and a volume of annual sequestrable CO2 which is about 4 times larger than the current world’s

largest geological storage site. - Diamond mine tailings: A South African diamond mine (Premier, at Cullinan, East of Pretoria) has

generated over a billion ton of mine tailings over the years. These tailings are likely to contain rocks such as

gabbro and norite which are suitable for CCMC. The kimberlite mines and occurrences in South Africa are

also likely to feature magnesium-rich mine tailings. No quantification of the volume of CO2 that could be

sequestered in these tailings is currently available.

- Chromium (Cr2O3) and Phosphorus pentoxide (P2O5) mine tailings: Large deposits of Cr2O3 (Bushveld

Norite) and P2O5 (Phalaborwa) surrounded by mafic and ultramafic rocks are mined and have generated

over a billion ton of mine tailings each at these two sites alone over the years. These tailings are likely to

contain significant amounts of Mg-rich rocks which are suitable for CCMC. No quantification of the volume of

CO2 that could be sequestered in these tailings is currently available.


- Asbestos mine tailings: There is published evidence that asbestos minerals can be converted into benign,

asbestos-free products by CCMC. CCMC may therefore be a potentially effective method for the remediation

of asbestos in mine tailing. The volume of CO2 that could be sequestered is probably limited in comparison

to the total emissions in South Africa, but it may bring the added benefits of remediating asbestos-

contaminated land and of generating marketable aggregates from the tailings.

- In situ CCMC in South African basaltic and andesitic rocks: Practical and cost-effective technology for in

situ carbon mineralization in Icelandic (i.e. The CarbFix project), Californian and Indian basalts is currently

under development. It is currently uncertain whether South African basaltic and andesitic rocks exhibit

suitable properties (e.g. composition, porosity, permeability, weathered state) for in situ CCMC. Their

properties are likely to be less favourable than those currently studied overseas, but they might nevertheless be suitable for in situ carbon mineralization under similar conditions than those currently investigated.

Alternatively, there may be CO2 injection strategies that are better suited for in situ carbon mineralization in

South African basalts than those used for overseas basalts. - Industrial alkaline wastes: The most promising wastes for CCMC are steel furnace slags, phosphogypsum

and coal-combustion fly ash. Millions of tons of these wastes are piled up in dams and are practically

unused. The volumes of CO2 that can be sequestered in such wastes are low in comparison to annual South

African emissions, but are likely to be substantial at the individual plant level.

Potentially available markets for products generated by CCMC in South Africa include:

- Minerals and mining industry: recovery of high-value residual metals and other commodities (e.g. Fe, Co, Ni,

rare-earths, precious metals, diamond); on-site clean electricity

- High-purity silica; bicarbonate chemicals

- Precipitated Calcium Carbonate (PCC; global market: 13Mt pa) and Ground Calcium Carbonate (GCC; global market: ca. 65Mt pa)

- Remediation value from carbonation of landfill wastes, mine tailings and hazardous wastes

- Cementitious phase carbonates to substitute Portland and pozzolanic cements

- Construction sector: low-embodied carbon building materials / construction aggregates

- CO2 credits from displaced quarrying and cement processes

It is the author’s opinion that CCMC should not simply be perceived as a CO2 sequestration option. CCMC offers the opportunity of producing construction materials from waste materials (i.e. CO2 and e.g. mine tailings, wastes

products from industrial thermal processes) and of recovering valuable materials from wastes. CCMC is

therefore also a waste-to-product valorisation industry. The sustainable use of solid residues and CO2, two of the

largest and most important wastes generated in South Africa, is an urgent issue both for the industries involved

and society as a whole, considering the financial and environmental repercussions of their production. In Prof

Petrie’s words, “mineral carbonation should be pursued as an anchor technology within an integrated minerals-

energy complex, stimulating its own industrial ecology, wherein synergistic opportunities for material and energy

exchange are exploited to the mutual benefit of all partners in such a collaborative network. The added value

created by such a complex has the potential to significantly off-set the direct costs and energy penalties of

mineral carbonation.”

To this effect, it is recommended that the primary projective goal of South Africa be to build a validated

knowledge base necessary to construct pilot plants followed by demonstration plants capable of effectively


sequestering CO2 in mine tailings in a timeframe of around 6 years for the pilot plant. Additional

recommendations are listed below. Specific suggestions for further study include:

1) Detailed evaluation and mapping of suitable mineral deposits for CCMC and correlating with past, current

and future mining activities, combined with the elemental and mineralogical characterization of the

corresponding mine tailings and estimates of their total CO2 storage capacity for each mining sector (e.g.

PGM, diamond, Cr2O3, P2O5, asbestos). 2) Preliminary testing of reactivity of mine tailings using most promising CCMC processes (e.g. ARC process,

ǺA process route, CO2 Energy Reactor©, Chemical and biological catalytic enhancement; and any near-

commercial process we can access (e.g. Calera)) for comparison purposes. This could include rate and

extent of carbonation, energy and mass balances, and analysis of formed products. Opportunities for recovery of high-value residual metals (e.g. Fe, Co, Ni, rare-earths, precious metals, diamond) should also

be assessed. The findings would provide a good foundation to select the most promising process which

requires optimization for each mine tailings.

3) Life Cycle Analysis applied to findings from 2) for each tested process.

4) Detailed evaluation/characterization and mapping of South African basaltic and andesitic rocks to assess

their suitability for in situ carbon mineralization.

5) Assessment of each small-scale commercial process (e.g. Calera, Cambridge Carbon Capture) regarding

their possible integration to South African plants from different sectors (e.g. power generation, cement

manufacture, steel manufacture, mining, petrochemical etc).

6) Fast-tracking of Fe recovery from and CCMC of steel furnace slags to reach pilot scale experiment within

three years.

7) Assessment of industrial alkaline wastes (coal-combustion fly ash, phosphogypsum, industrial brines) for

CCMC; this should include the elemental and mineralogical characterization of the wastes and estimates of

their total CO2 storage capacity for each industrial sector, and preliminary testing of their reactivity using

most promising CCMC processes.

8) Assessment of the potential for CCMC to be applied to the pre-treatment of extracted displaced natural

brines from deep saline reservoirs to the surface prior to desalination for the production of freshwater.

9) Desktop study of the South African markets for building materials and aggregates. This R&D endeavour would preferably require the creation of a working team for each main raw material [e.g. (1)

PGM mine tailings, (2) Diamond mine tailings, (3) Asbestos mine tailings, (4) Cr2O3 and P2O5 mine tailings, (5)

industrial alkaline wastes (steel slags, phosphogypsum, fly ash, brines). The working teams would need to liaise

on a regular basis to share knowledge and experiences, and should include chemists, chemical and process

engineers, geologists, and representatives from the relevant industrial sectors.

Because of many fundamental advantages of CCMC (e.g. long-term stability, large capacity, favourable

thermodynamics), the unique position of South Africa with its fine mine tailings and the opportunities of

producing low-cost building aggregates, using carbon mineralization to sequester CO2 appears attractive.

Government support and industrial participation will be required for progress to be accelerated and early small-

scale sequestration testings to be built. In the medium-term, South Africa could also drive efforts on the African

continent where mining activities abound.


CONTENTS

Page EXECUTIVE SUMMARY 2

CONTENTS 6

LIST OF TABLES 8

LIST OF FIGURES 8

1. INTRODUCTION 10

1.1. South Africa’s carbon mitigation strategy 10

1.2. Nature and scope of study 12 2. CARBON CAPTURE AND STORAGE FOR CO2 MANAGEMENT 13

2.1. Definition of Carbon Capture and Storage (CCS) 13

2.2. Definition of Carbon Capture and Mineral Carbonation (CCMC) 13 3. CARBON CAPTURE AND MINERAL CARCONATION 15

3.1. Raw materials for CCMC processes 15

3.2. Process routes for CCMC 20 3.2.1. Ex-situ CCMC 21

3.2.1.1. Direct carbonation 21

3.2.1.1.1. Gas-solid carbonation 21

3.2.1.1.2. Aqueous carbonation 21

3.2.1.2. Indirect carbonation 22

3.2.1.2.1. Gas-solid carbonation 22

3.2.1.2.2. Aqueous carbonation 23 3.2.2. In situ CCMC 23

3.2.2.1. In situ accelerated CCMC 23

3.2.2.1.1. Basaltic bedrock (‘CarbFix’) 23

3.2.2.1.2. Peridotite 24

3.2.2.1.3. Improved sealing of deep saline formations 24

3.2.2.2. CO2 Energy Reactor© 28

3.2.3. Other CCMC route 29

3.2.3.1. Biomineralisation 29

3.3. Critical issues in R&D 31 4. SCALE OF CURRENT AND PLANNED OPERATIONS 35

4.1. Technological status and economic aspects 35 4.1.1. Ex situ 35

4.1.1.1. The Calera Process 35

4.1.1.2. The ǺA process route for serpentinite 38

4.1.1.3. The Albany Research Center (ARC) process 40

4.1.1.4. Chemical and biological catalytic enhancement as novel carbon capture

and storage technology 41

4.1.1.5. The ALCATRAP (Alkaline carbon TRAPing) process 45 4.1.2. In situ 46

4.1.2.1. The CarbFix project 46

4.1.2.2. CO2 Energy Reactor© 47

4.2. Promising applications and markets 47


5. CARBON CAPTURE AND MINERAL CARBONATION IN SOUTH AFRICA 54

5.1. Availability of raw materials in South Africa 54

5.1.1. Platinum Group Elements (PGE) mine tailings 55

5.1.2. Findings from the Carmex research project about South African mine tailings 60

5.1.3. Diamond mine tailings 62

5.1.4. Other mine tailings 63

5.1.4.1. Chromium and phosphorus pentoxide mine tailings 63

5.1.4.2. Asbestos mine tailings 63

5.1.5. In situ CCMC in South African basalts 64

5.1.6. Industrial alkaline wastes 65

5.1.6.1. Steel furnace slags 65

5.1.6.2. Phosphogypsum 69

5.1.6.3. Coal-combustion fly ash 70

5.1.6.4. Industrial brines 70

5.1.7. Natural brines 70

5.2. South African studies 72

5.3. Possible applications and markets in South Africa 72 6. CONCLUSIONS 73

SUGGESTIONS FOR FURTHER STUDY 73

REFERENCES 74

APPENDICES 85

Appendix A – List of patents on CCMC 85

Appendix B – Proceedings of ACEME-10 88 ACKNOWLEDGEMENTS 88


LIST OF TABLES

Page

Table 1 Examples of substantial mineral carbonation projects funded by the US Department of Energy. 11

Table 2 List of natural minerals studied for CCMC since 2008. 16

Table 3 Compositions of various minerals and their CO2-specific sequestration characteristics. 18

Table 4 Examples of mining activities around the world. 18

Table 5 List of industrial alkaline wastes studied for CCMC since 2008. 18

Table 6 List of publications subdivided into research using captured CO2 vs CO2-laden industrial

flue gas for the investigation of CCMC of natural minerals and industrial residues for the years 2008-2010. 22 Table 7 Conceptualized mineral slurry and CO2 injection strategies. 25

Table 8 Process conditions for the treatment of sewage sludge in a deep-shaft reactor. 28

Table 9 List of chemical additives used or mentioned in the published literature over the

period 2008-2010. 32 Table 10 Chemical composition (in weight %) of the Northam and BRPM tailings. 58

Table 11 Bulk mineralogy of the Northam and BRPM tailings samples. 58

Table 12 Characteristics of the selected ore deposits related to ultramafic rocks. 62

Table 13 Chemical composition of selected BOF and EAF steel slags generated in and outside South Africa. 67

Table 14 ‘Theoretical’ CO2-specific sequestration capacity of selected steel slags generated in and outside

South Africa. 68

Table 15 Mineralogical composition of selected steel slags generated in South Africa. 71

LIST OF FIGURES

Figure 1 Number of publications on mineral carbonation published on a per-annum basis since 1990. 11

Figure 2 Number of patents on mineral carbonation filed on a per-annum basis since 1990. 12

Figure 3 List of countries represented at ACEME-10 conference. 12

Figure 4 The distribution of the carbonate rocks in South Africa. 14

Figure 5 Thermodynamic stability diagram of carbon. 15

Figure 6 Schematic representation of the processing steps involved in the mineral carbonation of CO2 for 15

long-term storage. Figure 7 Simplified periodic table depicting elements which can form carbonates. 16

Figure 8 CCMC process routes. 21

Figure 9 Locations of terrestrials basalts that could serve as in situ mineral carbonation sites. 24

Figure 10 Conceptualized mineral slurry and CO2 injection strategies for a hypothetical geological cross-section. 26

Figure 11 Schematic representation of the CO2 Energy Reactor©. 30

Figure 12 Schematic representation of a geoengineered tailings management for CO2 sequestration. 31

Figure 13 Critical issues to be considered in the design of optimal carbonation processes. 34

Figure 14 Flow diagram of the Calera process. 37

Figure 15 Schematic representation of the Calera ABLE process. 37

Figure 16 Process overview of the ÅA process route. 39

Figure 17 Fluidized-bed reactor setup at ÅA. 39

Figure 18 Photograph depicting the fluidized-bed reactor setup at ÅA. 40

Figure 19 Effect of chemical additives on olivine dissolution kinetics. 42

Figure 20 Effect of types of chelating agents. 42

Figure 21 Mg extraction yield (%) for dissolution of olivine and serpentine in oxalate solution. 43


Figure 22 Speciation of precipitated Mg. 43

Figure 23 Proposed reaction model with Mg- and Si-targeting chelating agents. 44

Figure 24 Schematics of the proposed engineered mineral weathering process. 44

Figure 25 Use of carbonic anhydrase in the proposed engineered mineral weathering process. 45

Figure 26 Suspension tank in which ash is dispersed in aqueous media. 46

Figure 27 Calera SCM compressive strength performance. 48

Figure 28 Possible applications for carbonated products and other by-products generated by CCMC. 48

Figure 29 Production of carbon-negative materials using the Calera process. 49

Figure 30 Carbon negative building materials generated by the Calera process and their market shares. 50

Figure 31 Product development time and possible markets for the products generated by the Calera process. 50

Figure 32 Embodied carbon: Novacem vs current cement production. 53

Figure 33 Ca- and Mg-mineral occurrences in South Africa. 55

Figure 34 The distribution of the Bushveld Complex mafic rocks. 56

Figure 35 Map of Platinum Group Metals (PGM) operations in the Bushveld Igneous Complex in South Africa. 57

Figure 36 Size by size modal abundance for sequestrable minerals in the a) Northam and b) BRPM mine

tailings samples. 59 Figure 37 Estimated theoretical annual CO2-specific sequestration capacity of PGM tailings from the four major

players in South Africa. 60 Figure 38 Map matching fixed CO2 sources with ore deposits related to ultramafic rocks. 61

Figure 39 Kimberlite mines and occurrences in South Africa. 63

Figure 40 Asbestos mines and occurrences in South Africa. 64

Figure 41 The distribution of basaltic and andesitic rocks in South Africa. 65

Figure 42 Schematic representation of the process of steel manufacture. 66

Figure 43 Block diagram of conceptualized process: Fe recovery combined to CO2 sequestration by indirect

mineral carbonation. 69


1. INTRODUCTION

1.1. South Africa’s carbon management strategy

The most widely advocated method of carbon capture and storage (CCS) in South Africa involves the injection of

carbon dioxide (CO2) into deep underground geological formations. Key to the development of this geo-

sequestration technology is the existence of suitable high-integrity geological sites for the safe, long-term

storage of CO2. A theoretical estimate of the storage capacity for South Africa has recently been published in the

Atlas on Geological Storage of Carbon Dioxide in South Africa (Cloete, 2010). Although an estimated total

storage capacity potential of about 150 Gt may be offered by South African geological formations, 98% of the

reservoirs are located off-shore, at appreciable distances (500-1500 kms) from the largest fixed CO2 sources.

These findings mean that elevated transport and sequestration costs can be anticipated. It is also generally

accepted that the actual storage potential of a reservoir is several times lower than the estimated theoretical capacity. Regardless of these challenges, South Africa’s CO2 emissions level (ca. 440 Mt p.a.) is such that the

country must continue investigating its geological storage options. However, it is also imperative that South

Africa diversifies its CO2 management options and gives due consideration to every possible option of CO2

storage which appears technologically possible. The consideration of such options would act as an important

risk mitigation strategy for South Africa’s CCS activities.

Accelerated CO2 mineralization is another possible sequestration option which was identified by the

Intergovernmental Panel on Climate Change (IPCC, 2005) and which was briefly discussed in the context of

South Africa (Engelbrecht et al., 2004). The state of the technology was at the early stages of R&D at the time

and the grandeur of the task at hand regarding the large-scale processing of mineral deposits for the purpose of

CO2 sequestration was considered by many as insurmountable. Nevertheless, a handful of academic and

consulting engineering teams persevered with their CO2 mineralization R&D activities using modest funds.

Accelerated CO2 mineralization is the main sequestration option for countries such as Finland, Estonia and

Portugal which have no suitable geological reservoirs. It is also receiving renewed attention in the US where the

Department of Energy (DOE) has recently invested over US $56,000,000 in cumulated shares (Carbon Capture

Journal 23 July 2010; Table 1) in projects aimed at fast-tracking R&D and at testing this technology at pilot and

demonstration scales. Today approximately 25 countries are actively involved in CO2 mineralization for carbon

mitigation and utilization. The numbers of peer-reviewed publications (Figure 1) and filed patents (Figure 2;

Appendix A) have been steady over the last decade, although there is little data available on energy

consumption. ACEME (Carbonation for Environmental and Materials Engineering), the international conference

solely directed to CO2 mineralization, is growing in success. The 3rd edition of the conference took place in

Finland from 29 November to 1 December 2010, after having been held in England in 2006 and in Italy in 2008.

It was attended by over 70 participants from 24 different countries including Australia, Belgium, Canada, China,

Denmark, Estonia, Finland, France, Germany, Italy, Norway, Poland, Portugal, Singapore, Slovakia, South

Africa, South Korea, Spain, Sweden, Switzerland, The Netherlands, UK, Ukraine and USA (Figure 3) who

contributed to the 348 pages of the Conference Proceedings (See Appendix B). The author participated at the 2010 conference and presented a paper entitled “Application of mineral carbonation engineering to geological

CO2 sequestration: A conceptual approach to improved reservoir integrity” and a poster entitled “Mineral

carbonation of a fly ash / brine system”. The next three conferences will take place in Belgium (2012), Australia

(2014) and the USA (2016) respectively.


Table 1 Examples of substantial mineral carbonation projects funded by the US Department of Energy

(Carbon Capture Journal of 23 July 2010).

Calera Corporation (Los Gatos, California) : DOE share: $19,895,553

Calera Corporation is developing a process that directly mineralizes CO2 in flue gas to carbonates that can be converted into

useful construction materials. An existing CO2 absorption facility for the project is operational at Moss Landing, California, for

capture and mineralization. The project team will complete the detailed design, construction, and operation of a building

material production system that at smaller scales has produced carbonate-containing aggregates suitable as construction fill

or partial resource for use at cement production facilities. The building material production system will ultimately be integrated

with the absorption facility to demonstrate viable process operation at a significant scale.

Skyonic Corporation (Austin, Texas) DOE share: $25,000,000

Skyonic Corporation will continue the development of their SkyMine® mineralization technology – a potential replacement for

existing scrubber technology. The SkyMine process transforms CO2 into solid carbonate and/or bicarbonate materials while

also removing sulphur oxides, nitrogen dioxide, mercury and other heavy metals from flue gas streams of industrial

processes. Solid carbonates are ideal for long-term, safe aboveground storage without pipelines, subterranean injection, or

concern about CO2 re-release to the atmosphere. The project team plans to process CO2-laden flue gas from a Capital

Aggregates, Ltd. Cement manufacturing plant in San Antonio, Texas.

Alcoa, Inc. (Alcoa Center, Pennsylvania) DOE share: $11,999,359

Alcoa’s pilot-scale process will demonstrate the high efficiency conversion of flue gas CO2 into soluble bicarbonate and

carbonate using an in-duct scrubber system featuring an enzyme catalyst. The bicarbonate/carbonate scrubber blow down

can be sequestered as solid mineral carbonates after reacting with alkaline clay, a by-product of aluminium refining. The

carbonate product can be utilized as construction fill material, soil amendments, and green fertilizer. Alcoa will demonstrate

and optimize the process at their Point Comfort, Texas aluminium refining plant.

Figure 1 Number of publications on mineral carbonation published on a per-annum basis since 1990

(Source: Torróntegui, 2010; the list is incomplete for the year 2010 and only features publications until March

2010).


Figure 2 Number of patents on mineral carbonation filed on a per-annum basis since 1990 (Source:

Torróntegui, 2010; the list is incomplete for the year 2010 and only features publications until March 2010).

Figure 3 List of countries represented at the ACEME-10 conference (Figure kindly provided by Prof Ron

Zevenhoven, Chair of ACEME-10 conference organizing committee).

1.2. Nature and scope of study

In preparation for this Scoping Study Report, the author has critically assessed the published international

literature, has listed patented processes, has participated at the Third International Conference on Accelerated

Carbonation for Environmental and Materials Engineering (ACEME-10) held in Turku, Finland from 29th

November to 1st December 2010 where he was exposed to the latest development in the field and networked

with international experts, and has visited R&D facilities in Finland (Thermal and Flow Engineering Group, Åbo

Akademi University), Norway (Institute for Energy Technology) and Germany (ALCATRAP CO2 mineralization

pilot plant). Financial sponsorship for the conference participation and the European trip was provided by the

South African Centre for Carbon Capture and Storage.

0

2

4

6

8

10

12

FI IT UK EE SE NO DE NL BE FR ES PT CH SK PL UA US CA ZA AU

other

poster

speaker


The Scoping Study Report defines the concept of accelerated CO2 mineralization, provides a critical account of

the most promising processes which may be of interest to South Africa, and summarizes the outcome from the

visits to the three European R&D centres. The Report also discusses the current situation in South Africa

regarding the technology and provides recommendations to the Centre for Carbon Capture and Storage on

possible ways forwards.

2. CARBON CAPTURE AND STORAGE FOR CO2 MANAGEMENT

2.1. Definition of carbon capture and storage (CCS)

Carbon capture and storage (CCS) is an integrated technological process which involves the separation of CO2

from industrial and energy-related sources, the transport of CO2 to a suitable location and its long-term and safe

storage and isolation from the atmosphere. Potential technical storage methods include geological storage, ocean storage, and industrial mineral fixation of CO2 into inorganic carbonates (i.e. accelerated CO2

mineralization). However, CCS has become synonymous to CO2 capture and geological sequestration as a

result of the well-established practice of oil and gas recovery from oil- and gas-depleting reservoir by CO2

injection. Nevertheless, accelerated CO2 mineralization has recently received renewed attention, as illustrated in

the introduction to this document. In this report, accelerated CO2 mineralization will be called carbon capture and

mineral carbonation (CCMC).

2.2. Definition of carbon capture and mineral carbonation (CCMC)

The concept of binding anthropogenic CO2 chemically via mineral carbonation to form stable carbonate minerals

was first proposed by Seifritz (1990). It was discussed further by Dunsmore (1992) and subsequently followed by the first detailed exploration of this approach (Lackner et al., 1995). Significant progress has been made over the

last 15 years and different aspects of CCMC have been reviewed (Lackner, 2002; Huijgen and Comans, 2003;

Huijgen and Comans, 2005a, 2005b; Sipilä et al., 2008; Doucet, 2011).

CCMC was inspired by one of the most ancient global biogeochemical cycles in the natural environment: the

cycle of calcium carbonate (CaCO3) (Berner et al., 1983; Murray and Wilson, 1997; Ridgwell and Zeebe, 2005).

This cycle illustrates the effectiveness with which CO2 has been naturally removed from the atmosphere and

safely stored as carbonate rocks for billions of years. In the main, the lithosphere acts as an overwhelmingly

dominant natural CO2 sink (Liu and Zhao, 1999), with 99.94% of the carbon trapped in the rocks of the Earth’s

crust. Worldwide these carbonate rocks cover an area of about 22 million km2 (Yuan, 1997), with over 90% of

rock-forming carbonates consisting of calcite (CaCO3) and dolomite (CaMg(CO3)2) (Reeder, 1983). For instance,

Figure 4 illustrates the distribution of the carbonate rocks in South Africa, which consists essentially of dolomite

as well as very small occurrences of limestone. Another example is the ongoing natural mineral carbonation of

peridotite which occurs in Oman (Kelemen and Matter, 2008; see photograph on the cover page).

Mineral carbonation is therefore a naturally occurring geological weathering process that involves the reaction of

CO2 with common mineral silicates to form geologically stable solid inorganic carbonates. An engineered

process of carbon capture and mineral carbonation (CCMC) mimics natural silicate rock weathering by reacting


calcium (Ca) – and/or magnesium (Mg) – bearing materials with CO2 to form thermodynamically stable1 (Figure

5) and environmentally benign carbonate minerals. The industrial processing steps involved in CCMC are

depicted in Figure 6, while the carbonation process can be illustrated by the following general reaction scheme:

2322 ),(),( ySiOCOCaMgxxCOOSiCaMg yxyx +→++

+ heat [1]

Figure 4 The distribution of the carbonate rocks in South Africa.

The process is exothermic and thermodynamically favoured2, with typical enthalpies of reaction ranging from 50 to 100 kJ/mole (Lackner et al., 1998), depending on the resource materials used (89, 64 and 90 kJ/mole CO2 at

298 K for olivine, serpentine and wollastonite respectively; IPCC, 2005). To set the scale, the heat of combustion

of coal is 394 kJ/mole. At ambient temperature, the carbonate is the thermodynamically favoured state, i.e. the

Gibbs free energy change of the reaction is negative. This means that the reaction with CO2 should proceed

spontaneously as it indeed does in nature on geological timescales. Whilst carbonation reactions are

thermodynamically favoured, the extraction of alkaline ions (Ca, Mg) from suitable resources is kinetically

unfavourable under atmospheric temperature and pressure conditions. Therefore, the challenge lies in the slow

1 The stability of calcium and magnesium carbonates was validated under conditions representative of an acidic aqueous

environment (e.g. acid rain), which confirmed that local environmental effects at a mineral carbonate storage site are very

unlikely (Teir et al., 2006). 2 In the presence of suitable bases, carbonates have the lowest free energy of formation and are therefore the lowest energy

state for carbon, i.e. lower than carbon which is fully oxidized as CO2. The formation of carbonates from CO2 is therefore

exothermic.


kinetics of the process. Such reactions must therefore be accelerated with minimal energy penalty. Resolving

this difficulty is key if an engineered carbonation process is to be implemented at industrial scale with acceptable

economics. This is universally relevant, regardless of the nature or the origin of the resource. The latter can

either be natural silicate minerals or industrial alkaline wastes.

Carbon

CO2

Carbonate

∆rHC-CO2

∆rHCO2-CO3

Carbon

CO2

Carbonate

∆rHC-CO2

∆rHCO2-CO3

Figure 5 Thermodynamic stability diagram of carbon.

Figure 6 Schematic representation of the processing steps involved in the mineral carbonation of CO2 for

long-term storage (IPCC, 2005).

3. CARBON CAPTURE AND MINERAL CARBONATION

3.1. Raw materials for CCMC processes

Both alkali and alkaline earth metals and numerous other elements are suitable candidates for carbonation

(Figure 7). However, most of these elements are too rare or too valuable, or form carbonated species which are

too soluble to form a stable product for the long-term sequestration of CO2. As a result, the only suitable


elements for the formation of geologically stable carbonates are the alkaline-earth metals calcium (Ca) and

magnesium (Mg), which are also by far the most ubiquitous in the natural environment.

Figure 7 Simplified periodic table depicting elements which can form carbonates (Santos et al., 2010).

Oxides and hydroxides of Ca and Mg represent the perfect materials for CCMC but they rarely occur in nature.

These two elements are rather most commonly found in silicate minerals (e.g. olivine, serpentine), which can

also be carbonated since carbonic acid (H2CO3; pKa = 6.3) is a stronger acid than silicic acid (Si(OH)4; pKa =

9.50). As such, mafic and ultramafic silicate rocks are generally considered to be the most suitable resources

owing to their occurrence as large deposits at numerous locations in the world. As many as 13 natural silicate

minerals have been investigated for the purpose of CCMC since 2008 (Table 2; Torrontegui, 2010), although the

majority of publications are dominated by olivine and serpentine. The CO2-specific sequestration characteristics

of the most important minerals are illustrated in Table 3 and are expressed as the mass ratio of rock to CO2 for

CO2 fixation (RCO2). These figures indicate the sizeable amount of minerals which would be required to

sequester CO2 on industrial scale (≥ 1.8 ton of rock per ton of sequestered CO2), although the scale of operation

is not unusual and would be similar to a typical metal ore or mineral mining and processing activity (Table 4).

A potential alternative resource for CCMC exists in the form of industrial alkaline wastes (Table 5), which can

provide the calcium, and to a lesser extent the magnesium needed to convert CO2 into carbonates. A number of

arguments are in favour of their use, such as their availability at low cost, their high reactivity when compared to

that of natural minerals, their proximity to fixed CO2 sources, and the possibility of improving their environmental quality through the encapsulation of potentially-toxic elements (Meima et al., 2002). Their higher chemical

reactivity implies that less extreme reaction conditions (e.g. lower temperature and pressure, large particle size)

can be suitable to achieve acceptable rate of CO2 conversion (Huijgen et al., 2004). However, industrial wastes

are available in smaller amount than natural minerals, which makes their CCMC suitable for niche markets, e.g.

on an individual plant level only.

Table 2 List of natural minerals studied for CCMC since 2008 (adapted from Torrontegui, 2010).

Mineral Chemical formula References

Basalt Depends on basaltic formation - Alfredsson et al. (2008)

- Assayag et al. (2009)

- Matter and Kelemen (2009)

- Matter et al. (2009)

- Schaef et al. (2009)

- Gislason et al. (2010)

- Goldberg et al. (2010)

Brucite Mg(OH)2 - Zhao et al. (2010)

Chrysotile (asbestos) Mg3Si2O5(OH)4 - Dufaud et al. (2010)


- Larachi et al. (2010)

Dunite 90% olivine - Andreani et al. (2009)

- Koukouzas et al. (2009)

Forsterite Mg2SiO4 - Kwak et al. (2010)

Harzburgite CaMgSi2O6 + (Fe,Al) - Koukouzas et al. (2009)

Olivine (Mg,Fe)2SiO4 - Balaz et al. (2008)

- Haug et al. (2008)

- Machenbach et al. (2008)

- Turianicova et al. (2008)

- Jarvis et al. (2009)

- Munz et al. (2009)

- Prigiobbe et al. (2009a)

- Prigiobbe et al. (2009b)

- Prigiobbe et al. (2009c)

- Bonfils et al. (2010)

- Dufaud et al. (2010)

- Fabian et al. (2010)

- Haug et al. (2010)

- Teir et al. (2010)

- Turianicova and Balaz (2010)

Orthopyroxene CaMgSi2O6 + (Fe,Al) - Dufaud et al. (2010)

Peridotite Depends on rock formation - Kelemen and Matter (2008)

- Matter and Kelemen (2009)

- Rudge et al. (2010)

Pyroxenite Mixture of pyroxene rocks - Koukouzas et al. (2009)

Serpentine Mg3Si2O5(OH)4 - Zevenhoven et al. (2008)

- Boerrigter (2009)

- Krevor and Lackner (2009)

- Li et al. (2009)

- Bonfils et al. (2010)


- Wang and Maroto-Valer (2010)

- Werner and Mazzotti (2010)

Serpentinite Depends on rock formation - Boschi et al. (2008)

- Boschi et al. (2009)

- Fagerlund et al. (2009)


- Balucan et al. (2010)

- Nduagu and Zevenhoven (2010)

- Romão et al. (2010)

- Said et al. (2010)

- Zevenhoven et al. (2010)

Wollastonite CaSiO3 - Daval et al. (2009a)

- Daval et al. (2009b)

- Kawatra et al. (2009)

- Baldyga et al. (2010)

- Ghoorah et al. (2010)



Table 3 Compositions of various minerals and their CO2-specific sequestration characteristics (Lackner

et al., 1995; Wu et al., 2001).

Rock MgO (wt %) CaO (wt %) RCO2 (ton rock / ton CO2)

Dunite (olivine)

Serpentine

Wollastonite

Talc

Basalt

49.5

40

-

44

6.2

0.3

0

35

0

9.4

1.8

2.3

3.6

2.1

7.1

Table 4 Examples of mining activities around the world (compiled by Sipilä et al., 2008 from Infomine,

2007).

Name/Location Mining activity Ore mining rate (Mt/y)

Escondida, Chile

Morenci, USA

Antamina, Peru

Venetia, South Africa

Malmberget, Kiruna, Sweden

Copper

Copper

Copper, Zinc

Diamond

Iron

374

256

123

70

37

Table 5 List of industrial alkaline wastes studied for CCMC since 2008 (adapted from Torrontegui, 2010).

Industrial alkaline wastes Industrial sector References

Argon Oxygen Decarbonisation (AOD) slag Steel manufacture - Baciocchi et al. (2010a)

- Baciocchi et al. (2010b)

- Santos et al. (2010)

Air pollution control fly ash (APC) - - Sun et al. (2008)

- Baciocchi et al. (2009a)

- Prigiobbe et al. (2009d)

- Baciocchi et al. (2010c)

Biomass ash Energy production - Gunning et al. (2008)

- Gunning et al. (2010)

Blast furnace slag Steel manufacture - Eloneva et al. (2008a)

Bottom ash Energy production - Baciocchi et al. (2008)



Industrial brines Energy production - Muriithi et al. (2009)

- Muriithi et al. (2010)


Cement wastes (e.g. kiln dust) Cement - Gunning et al. (2008)

- Huntzinger et al. (2009)

- Kawatra et al. (2009)

- Grandia et al. (2010)


Chrysotile mining tailings Asbestos mining - Beaudoin et al. (2008)

- Dipple et al. (2008)

- Power et al. (2010)

Coal-combustion fly ash Energy production - Reddy et al. (2008)

- Montes-Hernandez et al. (2009)


- Bauer et al. (2010)

- Mlambo et al. (2010)




- Reddy et al. (2010)

Ladle slag Steel manufacture - Doucet F.J. (2008)

- Diener et al. (2010)

Lignite-combustion fly ash Energy production - Back et al. (2008)

- Uliasz-Bochenczyk et al. (2009)

Mine tailings (e.g. platinum, asbestos) Mining - Doucet F.J. (2008)

- Dalwai and Smith (2009)

- Wilson et al. (2009)

- Hitch et al. (2010)

- Vogeli et al. (2010)

MSWI ash Municipality - Gunning et al. (2008)

- Clarens et al. (2010)


Nirex reference vault backfill Radioactive waste

management

- Sun and Simons (2008)

Oil shale ashes Oil extraction - Uibu et al. (2008)

- Kuusik et al. (2010)

- Uibu et al. (2010a)

- Uibu et al. (2010b)

- Velts et al. (2010)

Paper mill waste Paper manufacture - Perez-Lopez et al. (2008)

Paper wastewater incineration ash Paper manufacture - Gunning et al. (2008)


Pressed lime-waste composites - Purnell et al. (2008)

Steelmaking slag Steel manufacture - Doucet (2008)

- Doucet (2009a)

- Doucet (2009b)

- Doucet (2010a)

- Eloneva et al. (2008b)

- Kodama et al. (2008)

- Nienczewski et al. (2008a)

- Nienczewski et al. (2008b)

- Van der Laan et al. (2008)


- Doucet (2009)

- Baciocchi et al. (2010a)


- Bao et al. (2010)

- Diener et al. (2010)

- Eloneva et al. (2010)

- Quaghebeur et al. (2010)

- Sanchez and Martinez (2010)


Although the knowledge gained on the carbonation of natural minerals can, in principle, be applied to CO2

sequestration by the carbonation of alkaline wastes, significant differences exist between the two materials,

which have important implications for CO2 sequestration and long-term environmental stability (Huijgen and

Comans, 2005b). For instance, the predominant alkaline element in industrial wastes is Ca whereas natural

minerals (except wollastonite) are predominantly rich in Mg. The fact that Ca is carbonated more rapidly than Mg

(Huijgens and Comans, 2003) explains, in part, that the rate of carbonation of wastes is greater than that of

minerals. This is further substantiated by the relatively open structure and greater reactive surface area of most

wastes, and the geochemical stability, hence elevated reactivity, of wastes that were formed at high

temperatures and were subsequently quenched rapidly (e.g. slags, ashes).

Mine tailings form a class of materials which are generated from mining activities and are therefore classified as

wastes. However, most of them contain minerals which have not been modified by mining excavation, crushing,

milling and commodity extraction processes (e.g. olivine, serpentine). They can therefore represent an ideal

resource of Ca and Mg and often represent a mixture of natural minerals. They could therefore be equally listed

in Table 2 or Table 5. All mine tailings are not rich in Ca and/or Mg. Their compositions depend on the minerals

present in the vicinity of the mined commodities. In South Africa, Platinum Group Metals (PGM) mine tailings

from the Bushveld complex may represent an ideal resource for CCMC since they contain a substantial amount

of Mg and have been finely milled during the PGM recovery process (see section 5.1.1).

3.2. Process routes for CCMC

Numerous process routes for CCMC have been suggested and researched, and vary in their degrees of

complexity. Figure 8 provides an updated version of the CCMC process routes which draws from earlier versions of the classification (e.g. Huijgen and Comans, 2003, 2005a; Sipilä et al., 2008; Torrontegui, 2010). Process

routes have been classified under three headings, namely ‘ex-situ CCMC’, ‘in-situ CCMC’ and ‘other CCMC

routes’. The ‘ex-situ CCMC’ refers to the original approach to CCMC, which involves the aboveground

carbonation of natural minerals and industrial alkaline wastes via industrial processes. In contrast, the ‘in-situ

CCMC’ has developed more recently and differ from conventional geological storage in that CO2 is injected

underground under optimized conditions which are meant to accelerate the natural process of mineral

carbonation. Carbonation routes which do not fall into one of these two categories are amalgamated under the

‘other CCMC routes’ heading. In recent years, the direct use of flue gas in place of captured CO2 in CCMC

processed has gained interest to avoid the cost penalty of pre-capturing CO2 prior to carbonation; this is

reflected in Table 6.


Figure 8 CCMC process routes (modified from Huijgen and Comans, 2003, 2005a; Sipilä et al., 2008;

Torrontegui, 2010)

3.2.1. Ex-situ CCMC

The ‘ex-situ CCMC’ route refers to the original approach to CCMC, which involves the aboveground carbonation

of natural minerals and industrial alkaline wastes via industrial chemical processes (Figure 6). For natural

minerals, this scenario includes the mining, crushing and milling of the mineral-bearing ores prior to carbonation.

3.2.1.1. Direct carbonation

3.2.1.1.1. Gas-solid carbonation

The direct reaction of gaseous CO2 with solid mineral or alkaline waste is the most straightforward CCMC route.

However, it suffers from very slow reaction rates and has practically been abandoned. Only two research groups

(Reddy et al., 2008; Baciocchi et al., 2009; Prigiobbe et al., 2009d) are still somewhat involved in this process

using reactive wastes, but this route is unlikely to develop further than the research stage and will not reduce

CO2 emissions substantially.

3.2.1.1.2. Aqueous carbonation

Direct aqueous carbonation involves three coexistent mechanisms in a single reactor: (i) aqueous dissolution of

CO2, (ii) aqueous dissolution of Ca- and Mg-bearing mineral phases, and (iii) precipitation of carbonates. It is

generally accepted that silicate dissolution is the rate-limiting step, and as a result effort has focused on

improving the kinetics of silicate dissolution using a wide range of additives and by varying operating conditions

such as temperature, pressure, CO2 concentration, solid to liquid ratio, and particle size. A number of

researchers have recently investigated this route for the conversion of minerals (e.g. portlandite (Lopez-Periago

Ex - situ CCMC

Gas - solid CCMC

Aqueous CCMC Single -step

Single -step straightforward

Additive -enhanced

Direct CCMC

Indirect CCMC Gas - solid CCMC

Aqueous CCMC

Multi- step

In - situ CCMC

Other CCMC routes

CO 2 Energy Reactor ©

In situ accelerated CCMC

Basaltic bedrock (‘ CarbFix )

Peridotite

Passive CCMC

Biomineralisation

Improved sealing of deep saline formations

Ex - situ CCMC

Gas - solid CCMC

Aqueous CCMC Single -step

Single -step straightforward

Additive -enhanced

Direct CCMC

Indirect CCMC Gas - solid CCMC

Aqueous CCMC

Multi- step

In - situ CCMC

Other CCMC routes

CO 2 Energy Reactor ©

In situ accelerated CCMC

Basaltic bedrock (‘ CarbFix )

Peridotite

Passive CCMC

Biomineralisation

Improved sealing of deep saline formations


et al., 2009; Regnault et al., 2009); synthetic larnite powders (Santos et al., 2009); forsterite (Kwak et al., 2010);

brucite (Zhao et al., 2010)) and alkaline wastes (e.g. APC, stainless steel slag, bottom ash (Baciocchi et al.,

2008, 2009a, 2009b); alkaline paper mill waste and coal-combustion fly ash (Perez-Lopez et al., 2008; Montes-

Hernandez et al., 2009); waste cement kiln dust (Huntzinger et al., 2009); lignite fly ash (Back et al., 2008;

Uliasz-Bochenczyk et al., 2009)) with and without the use of additives.

Table 6 List of publications subdivided into research using captured CO2 vs CO2-laden industrial flue gas

for the investigation of CCMC of natural minerals and industrial residues for the years 2008-2010 (Torrontegui

(2010).

Pure or captured CO2 CO2-laden industrial flue gas

Natural mineral Industrial waste Natural mineral Industrial waste

Refe

ren

ces

- Machenbach et al.

(2008)

- Zevenhoven et al.

(2008)

- Boerrigter (2009)

- Andreani et al. (2009)

- Daval et al. (2009)


- Fagerlund et al.

(2009)

- Jarvis et al. (2009)

- Koukouzas et al.

(2009)

- Krevor & Lackner

(2009)

- Munz et al. (2009)

- Schaef et al. (2009)



- Kwak et al. (2010)

- Larachi et al. (2010)

- Zhao et al. (2010)

- Baciocchi et al. (2008)

- Back et al. (2008)

- Eloneva et al. (2008a)



- Perez-Lopez et al.

(2008)

- Purnell et al. (2008)

- Baciocchi et al.

(2009a)

- Baciocchi et al.

(2009b)

- Montez-Hernandez et

al. (2009)

- Uliasz-Bochenczyk et

al. (2009)


- Brent (2008)

- Li et al. (2008)

- Li et al. (2009)

- Kodama et al. (2008)

- Reddy et al. (2008)

- Sun et al. (2008)

- Uibu et al. (2008)

- Van der Laan et al.

(2008)

- Baciocchi et al.

(2009a)

- Prigiobbe et al.

(2009c)

- Uibu et al. (2010)

3.2.1.2. Indirect carbonation

Indirect carbonation is a route whereby the overall CCMC process is divided into two or more steps. For

instance, the extraction of Ca and/or Mg from the feedstock, the dissolution of CO2 (in the case of aqueous

carbonation) and the precipitation of carbonate materials take place as separate steps and/or in different

reactors.

3.2.1.2.1. Gas-solid carbonation

It was previously mentioned that direct gas-solid carbonation suffers from poor reaction kinetics. This limitation

can be overcome by adopting an indirect staged gas-solid dissolution/carbonation process. This route has been

intensively researched by Prof Zevenhoven’s group in Finland since 2000 for the carbonation of serpentine rocks


(see section 4.1.1.2), which the author visited last December. It has also been the subject of one study using a

mixture of 10% CO2 and 90% N2 (Lin et al., 2008).

3.2.1.2.2. Aqueous carbonation

The characteristic of indirect aqueous carbonation is the adoption of two aqueous separate steps for the

extraction and the carbonation of Ca and/or Mg respectively. The advantage of this route is that the two steps

can be optimized separately, incorporating additional steps if needed. This approach makes use of additives to

optimize the operating conditions. A challenge which is generally experienced in this route is the recovery of the

additives. However, it improves the feasibility of producing valuable pure materials for further applications.

3.2.2. In-situ CCMC

3.2.2.1. In situ accelerated CCMC

Mineral storage in geological formations may be accelerated by injecting CO2 into silicate rocks rich in divalent metal cations (Ca, Mg) such as basalts (Gislason et al., 2010) and peridotites (Kelemen and Matter, 2008) rather

than in sandstones or other porous formations. The advantages of this route over ex situ CCMC are that mining,

transporting and pre-treatment of the minerals as well as the use and recovery of additives are not required

(Oelkers et al., 2008). However, it also presents a number of limitations, including the availability of water for

CO2 injection, and the need for impermeable cap rocks over basalt or ultramafic formations (a rare feature). In

situ accelerated CCMC can be considered as a variant of the direct carbonation route described in section

3.2.1.1.2.

3.2.2.1.1. Basaltic bedrock (‘CarbFix’)

Very large volumes of basalts are present on the Earth’s surface (Figure 9) and the Columbia River basalts in the USA alone have a total estimated capacity to sequester over 100 Gt of CO2 (McGrail et al., 2006). Some

scientists believe in situ CCMC in basalts to be amongst the most promising options for CO2 storage (O’Connor

et al., 2003; Oelkers et al., 2008). Key to the successful sequestration of CO2 in basalts via in situ accelerated

CCMC is the rapid dissolution of silicate minerals and glasses releasing the divalent cations and their

preferential precipitation as carbonates over the formation of other secondary minerals such as oxides, clays and zeolites (Gislason et al., 2010). Optimization of these processes can be achieved by the careful selection of the

silicate rock (crystallinity and rock composition; Wolff-Boenisch et al., 2006), by improving the mineral-fluid

interfacial surface area using highly porous rock formations and/or via hydro fracturing during CO2 injection, and by the choice of temperature and injection fluid composition. The best known project on the in situ accelerated

CCMC in basaltic rocks is the CarbFix project as detailed in Section 4.1.2.1.


Figure 9 Locations of terrestrial basalts that could serve as in situ mineral carbonation sites (Oelkers et

al., 2008).

3.2.2.1.2. Peridotite

Peridotite, although less abundant than basalt, is an ultramafic rock which also takes up CO2 naturally, and is

found in large volume in the Sultanate of Oman and in smaller amount along the east and west coast of North

Africa (Matter and Kelemen, 2009). A method to enhance this natural CO2 uptake mechanism was proposed

(patent-pending; Kelemen and matter, 2008). It involves (1) drilling of the peridotite beneath impermeable cap

rock, (2) hydrofracturing of the peridotite, (3) injection of hot fluid (H2O, CO2, flue gas, etc) to increase the environment temperature to ca. 185°C, and injection of CO2 or CO2-saturated H2O at 100-300 bars PCO2. An

alternative is to use surface water saturated in atmospheric PCO2 – this is a slower carbonation mechanism but

potentially less expensive. The authors speculated that under these conditions the temperature could be

maintained by the exothermic carbonation reactions which are fast enough for heat production to exceed

diffusive heat loss to cold surroundings and advective heat loss to cold CO2-rich fluid pumped at ca. 1cm/s. They

also estimated that the carbonation rate could be up to 4 x 109 tons of CO2 per annum. A preliminary modelling

exercise suggested that the proposed method might be able to enhance the front velocity of carbonation from the natural weathering rate of tenths of mm/year to an industrial rate of hundreds of m/year (Rudge et al., 2010).

The energy penalty compared to ‘straight’ injection into subsurface pore space is 9 to 23%.

3.2.2.1.3. Improved sealing of deep saline formations

The possible application of CCMC engineering principles to the improvement of the sealing capacity of deep saline formations for geological CO2 sequestration has recently been suggested (Mlambo et al., 2010). The idea

is that the controlled injection of reactive mineral slurries at strategic sites of the formation may help prevent the

migration of CO2 plumes beyond their confining layers via induced in situ localized, accelerated mineral

carbonation. Researchers at the Albany Research Centre (USA) have previously suggested this possibility of co-injecting ultramafic mineral slurries (e.g. olivine, serpentine) with CO2, and reflected on several conceivable

scenarios (O’Connor and Rush, 2005). In the context of South Africa, coal-combustion fly ash is abundant and

readily-available at no cost, and is generally much more reactive than primary mineral deposits. In addition, it

can be classified into very small sizes (sub-45µm), presents favourable rheological properties for easy transport

and injection, and could therefore provide calcium (Ca) and magnesium (Mg) cations to accelerate the

precipitation of CO2 as mineral carbonates.


Four distinct scenarios for the co-injection of CO2 and mineral slurries were proposed by O’Connor and Rush

(2005) and are summarized in Table 7 and Figure 10, along with the personal views of Mlambo et al. (2010). The

most conceivable application of induced localized, accelerated mineral carbonation to geological sequestration

of CO2 appears to be offered by the possibility of engineering a “carbonate curtain”. The curtain must be placed between the primary injection site of CO2 and potential weakness points (i.e. fault zones, fractures, facies

changes) in the target formation where CO2 could migrate towards and across with subsequent rapid leakage

outside the borders of the formation. The “carbonate curtain” would form from the volume expansion occurring

upon carbonate formation, which would fill the pore spaces between the formation grains, and would thereby act

as a barrier preventing the injected CO2 to migrate further towards the aforementioned weakness points. Such a

migration process of CO2 and the injected fly ash slurry must be imagined as a progressing mineralization front, like probably occurs during the origin of e.g. hydrothermal ore deposits. The migration however must be bedding

confined, without blocking the porosity, and the mineralization must be confined to the site of precipitation. Apart

from the injection strategy regarding locations of wells previously discussed, an important issue evolving around

the feasibility of such a scenario includes the concentration of mineral reactant to be injected, the kinetics of

formation of the carbonate curtain, and the range of pressures such a curtain would be able to sustain.

Table 7 Conceptualized mineral slurry and CO2 injection strategies (Mlambo et al., 2010). Theoretical scenarios 1) Co-injection of the mineral slurry with CO2 in the main injection well It was suggested that the simultaneous co-injection of CO2 and the mineral slurry through a single primary well may help envelope the CO2 plume with an “engineered carbonate curtain” or barrier and thereof prevent the uncontrolled diffusion of CO2 outside the confined layers of the saline formation (O’Connor and Rush, 2005). However, as already discussed, it is anticipated that this scenario would cause premature clogging of the pore spaces with newly-formed mineral carbonates at proximity of the injection well and would subsequently, and possibly rapidly, prevent further CO2 injection. 2) a. Fracture-filling to inhibit excessive porosity/permeability b. Emplacement of a slurry wall or grout curtain between the CO2 flood and known fault zones or facies changes These two scenarios involve the injection of CO2 at the primary well and that of the mineral slurry at secondary wells in order to place a mineral slurry wall at strategic places around the CO2 plume, in existing fractures or between CO2 and fault zones or facies changes, which will promote accelerated carbonation at key areas and thereby prevent the migration of CO2 outside the confined layers of the reservoir. Whilst this will prevent premature carbonate precipitation at the primary injection well, it will require additional costs for the construction of secondary injection wells. Key to this scenario for horizontal isolation of the CO2 plume will be the selection of the appropriate locations and depths of the wells with regard to zones of faults or fractures within the target formation, the appropriate well spacing, and the appropriate concentration of mineral reactant to inject into these secondary wells. This procedure will however also require an extremely detailed knowledge of the lateral and vertical distribution of mineralogy, porosity, of the storage horizons and the sites of possible zones of weakness of the geological seals. 3) Fracture-filling in the overlaying caprock It was also proposed that minor faults in overlaying caprocks could also be filled with mineral slurries in order to ensure vertical isolation of the CO2 plume through minimization or prevention of the risk of leakage through caprock (O’Connor and Rush, 2005). While this approach is theoretically conceivable, it is unlikely that injection under these conditions would be well-received owing to the obvious risk of leakage which may be caused by excess pressure resulting from injection into the caprock. A key aspect of all CCS options is the sealing efficiency of caprocks above potential CO2 storage reservoirs. A real, continuous and ubiquitous vertical CO2 migration process in the form of diffusive loss of CO2 through pore spaces of the caprock (e.g. Busch et al., 2008) or by upward capillary percolation due to the re-activation of micro-fractures in the caprock (e.g. Angeli et al., 2009) is generally accepted, but rapid leaching by seal-breaching would represent a real, unacceptable threat in the case of fracture-filled overlaying caprocks. It would also be impossible to monitor such leakage over long periods, which is necessary as leakage sites would tend to grow through dissolution of minerals affected by acidic waters and CO2. How efficient the so-formed carbonate curtain will be in preventing CO2 migration is unsure at this stage and the

monitoring of this efficiency several hundred meters below the sea level and deep in oceanic sediments and

underlying sedimentary rocks imposes many difficulties that would need to be resolved. As discussed earlier, the

CO2 fluid-mineral slurry reactions are likely to increase the solid volume through carbonate formation. In the ideal

case scenario, the reactions will be self-limiting since they will fill porosity, reduce permeability and create

carbonated envelopes, which will act as boundary layers between formation weakness points and the CO2 fluid.


These types of reactions are commonly observed for the hydration and carbonation of basalts (Schramm et al.,

2005). However, there is also report that precipitation reactions of super-saturated minerals in pore spaces is not

always self-limiting and can cause rock fractures, which has the effect of maintaining permeability and exposing

new mineral surfaces for further precipitation. For instance, such reaction-driven cracking appears to occur during the natural carbonation of peridotite to form fully carbonated liswanites in Oman (e.g. Nasir et al., 2007)

and elsewhere (e.g. Ucurum, 2000), during replacement processes of e.g. leucite by analcime (Jamtveit et al.,

2009). Simple models of reaction-induced fracturing are being developed to better understand the chemical weathering processes taking place (Rudge et al., 2010).

The feasibility of the proposed concept will therefore depend on the mechanism and kinetic of formation and the

structural properties of the carbonated curtain and on the range of geochemical changes induced by the co-

injection strategy in the target geological formations.

Basement rock

Sandstone

Shale

Upper formationsSurface

Injection well

Mineral slurry

+

CO2

Hypothetical geological cross-section

Fracture

Scenario 1

Basement rock

Sandstone

Shale


Injection well

Mineral slurry

+

CO2


Fracture

Basement rock

Sandstone

Shale


Injection well

Mineral slurry

+

CO2


Fracture

Scenario 1


Basement rock

Sandstone

Shale


Injection well

CO2


FractureInjection well

Mineral slurry

b)a)

Injection well

Mineral slurryScenarios 2a and 2b

Basement rock

Sandstone

Shale


Injection well

CO2


Fracture

Basement rock

Sandstone

Shale


Injection well

CO2


FractureInjection well

Mineral slurry

b)

Injection well

Mineral slurry

b)a)

Injection well

Mineral slurry

a)

Injection well

Mineral slurryScenarios 2a and 2b

Basement rock

Sandstone

Shale


Injection well

Mineral slurry


Fracture

Scenario 3c

Basement rock

Sandstone

Shale


Injection well

Mineral slurry


Fracture

Scenario 3c

Figure 10 Conceptualized mineral slurry and CO2 injection strategies for a hypothetical geological cross-

section (Mlambo et al., 2010).

In conclusion, the volume expansion, which may occur following induced, in situ localized accelerated mineral

carbonation of injected mineral slurries with sc-CO2 fluid may prove to be an effective tool to enhance the natural

seals for the saline formations. While this theoretical concept is conceivable, numerous challenges would need

to be overcome before the proposed scenario can become technologically feasible for the safe, long-term geo-

sequestration of CO2 in such environments.


3.2.2.2. CO2 Energy Reactor©

The CO2 Energy Reactor© (patent-pending, NL2004851) is being developed by Innovation Concepts B.V.

(Gorinchem, The Netherlands; http://www.innovationconcepts.eu). The concept is based on the deep-shaft

technology which was first introduced as part of the VerTech process by Mannesmann in 1995 (Mannesmann,

1995). The VerTech technology makes use of a deep-shaft reactor to treat sludge and polluted wastewater in a

thermal wet oxidizing process (Mazumder and Dikshit, 2002). This process was used under the conditions

illustrated in Table 8 in Apeldoorn (The Netherlands) from 1992 to 2004 to treat between 20,000 and 28,000 tons

of dry sludge per annum. Providentia Environment Solutions B.V. is currently working on an updated version of

the system with the assistance of Innovation Concepts B.V.

Table 8 Process conditions for the treatment of sewage sludge in a deep-shaft reactor. Depth 1200 m

Highest temperature 280ºC

Flow 100 m3/hr

Medium Liquid, viscous sewage sludge (5% total solids)

Oxidization - Initially with air

- Subsequently replaced with pure O2

The CO2 Energy Reactor© is schematically represented in Figure 11. The reactor consists of an underground U-

shaped well with a length of 1,000 to 2,000 metres. The mineral slurry is pumped downward in the reactor. CO2

is injected at varying depths to induce accelerated carbonation of the slurry. The carbonated slurry returns to the

surface where it can be further treated depending on the specifications of the application it is intended to. The

advantages that an underground reactor offers are that the hydrostatic pressure in the system can be used in

lieu of high-pressure pumps, and the geothermal heat of the formation coupled to the heat generated by the

carbonation process can accelerate the reaction without the need to provide external heat input.

Specific features of the system include:

− CO2 resource: Given that the pressure and temperature conditions in the upper part of the reactor are

subcritical, CO2 is fed in its gaseous form. However the CO2 plume will be a dense, supercritical liquid in the lower part of the reactor where the pressure and temperature will be greater than ca. 73 bars and 31°C. It

can therefore be expected that the reactivity of CO2 with the mineral slurry will be variable across the

reactor. Direct flue gas would usually be too diluted for this process and a 70% CO2 stream is believed to be

a minimum requirement since CO2 will be the source of energy via the exothermic carbonation reaction. In

the case scenario where concentration of CO2 from flue gas is required, for instance using amines, it is

claimed that the energy recovery from the carbonation process in the shaft reactor would be sufficient to

regenerate the amines used in the capture process.

− Mineral slurry: The mineral slurry is made up of mined primary minerals such as olivine or serpentine. South

Africa has the advantage of having large volumes of mine tailings containing Mg- and Ca-rich minerals which

may be suitable resources for this process.

− Shaft reactor: For a demonstration plant, the diameter of the well is 80 cm. Corrosion tables indicate that

expensive alloys are not required for the material of construction of the reactor. The casing can therefore be

made of slightly improved carbon steel.


− Process conditions: For a demonstration plant, it is expected that the flow of the slurry will be about 100

m3/hr (same range as for the known VerTech process). The process is continuous and is characterized by a

residence time ranging from 45 to 60min, depending on the input materials and the maximum temperature

generated by the reaction.

− Deep shaft reactor: The reactor is built in the shape of a U-tube well which can go down to 1,000+ metres

depth. At the deepest part of the reactor the temperature and pressure are elevated without requiring the

input of external energy. These process conditions accelerate the kinetics of the reaction at minimal costs.

− Heat exchanger: The design of the reactor is such that the in-flowing liquid is pre-heated by the out-flowing

liquid which has gained higher temperatures owing to the exothermic nature of the carbonation reaction.

− Enhanced attrition: The flow of the mineral slurry combined to the injection of CO2 at varying depths entrains

some level of turbulence in the reactor, promoting bouncing of the particles against each other. This has the

desired effect of preventing the formation of a passive layer of carbonates at the surface of the particles.

− Extent of conversion: Extent of conversion is expected to reach at least 70%.

3.2.3. Other CCMC routes

3.2.3.1. Biomineralisation

Power et al. (2009, 2010) suggested the possibility of creating a geoengineered tailings facility (Figure 12) where

cyanobacteria and sulphate reducing bacteria could be used to accelerate the oxidation of acid-generating

substances (AGS) and produce leachate waters which could then be directed into a closed basin where

carbonate precipitation can be promoted either by evaporation or by cyanobacteria. The effectiveness of such a

facility is however unclear at this stage.


surface

CO2

surface

*

Legend:* Mineral slurry

CO2

Mineral slurry20°C, 10 bar

Steam (energy recovery)50°C, 20 bar

casing

Increasingtemperature and pressure

Diameter of well: 80 cm

surface

CO2

surface

*

Legend:* Mineral slurry

CO2

Mineral slurry20°C, 10 bar

Steam (energy recovery)50°C, 20 bar

casing

Increasingtemperature and pressure

Diameter of well: 80 cm

Figure 11 Schematic representation of the CO2 Energy Reactor© (drawn by Frédéric Doucet, Council for

Geoscience. Reviewed and approved by Pol Knops, Innovation Concepts B.V.).


Figure 12 Schematic representation of a geoengineered tailings management for CO2 sequestration

Power et al. (2010).

3.3. Critical issues in R&D

The design of optimal carbonation processes for CO2 disposal requires a number of critical issues to be

considered at four different stages of research and development (Figure 13).

Stage 1: Selection, preliminary characterization and activation of resources for CCMC

The most important considerations when selecting potentially suitable resources are their total calcium and

magnesium content, the mineralogical phases these elements are contained in, and the reactivity of the

minerals. A general rule is that the smaller the particle size, the larger the surface area per unit mass, and the more reactive the particles are. This has been confirmed by several studies (Huijgen et al., 2005; Alexander et

al., 2007). However, excessive comminution must be avoided since it is not cost-effective for industrial

processes. The reactivity of the minerals can be enhanced by other physical activation processes as well as by

chemical activation processes. Examples of physical activation methods include surface agitation of particles during dissolution (e.g. ultrasound, acoustic, in situ grinding, microwave) (Park and Fan, 2004), and heat

treatment with or without steam. Attempts to chemically activate resources are numerous and as many as 33

additives have been investigated in the period 2008-2010 (Table 9). An issue associated with the use of

additives is the need for recycling at acceptable costs.

Stage 2: Selection of CCMC route

The selection is essentially dictated by the economics (energy and mass balances) of the process for each raw

material and by the possible applications for the formed products. Although numerous processes have been

proposed and investigated, only a few (Section 4) show encouraging data and may eventually be scaled up to

commercial scale.

Stage 3: Post-treatment steps

The post-treatment steps required following carbonation will also dictate whether a process can be adopted for

industrial scale-up. These include the ease with which the formed carbonated products can be separated from


other products or effluents, the level of impurities in the formed products which will affect its recoverable value,

and whether process additives and effluents can be recycled in a cost-effective way or must be disposed off.

Stage 4: System feasibility / scale-up

The decision as to whether the newly-developed process can be scaled up will be based on economic and

energetic considerations and how the multiple components of the process can be integrated together in existing

industrial processes.

Table 9 List of chemical additives used or mentioned in the published literature over the period 2008-

2010 (Torrontegui, 2010). Additive # Additive Chemical formula References

1 Acetic acid CH3COOH - Eloneva et al. (2008a)




- Bao et al. (2010)

2 Acidithiobacillus sp. Microbial catalyst to produce acid - Power et al. (2010)

3 Aluminium nitrate Al(NO3)3 - Eloneva et al. (2008b)

4 Aluminium sulfate Al2(SO4)3 - Eloneva et al. (2008b)

5 Aluminium acetate CH3COONH4 - Eloneva et al. (2008b)

6 Ammonium chloride NH4Cl - Doucet (unpublished data)


- Kodoma et al. (2008)


7 Ammonium di-hydrogen

phosphate

NH4H2PO4 - Eloneva et al. (2008b)

8 Ammonium hydroxide NH4OH - Fagerlund et al. (2009)

9 Ammonium nitrate NH4NO3 - Doucet (unpublished data)


10 Ammonium sulfate (NH4)2SO4 - Eloneva et al. (2008b)


- Power et al. (2010)

11 Calcium chloride CaCl2.2H2O - Power et al. (2010)

12 Citric acid C6H8O7 - Prigiobbe et al. (2009a)


13 Diammonium hydrogen

phosphate

(NH4)2HPO4 - Eloneva et al. (2008b)

14 Dipotassium phosphate K2HPO4 - Power et al. (2010)

15 EDTA C10H16N2O8 - Krevor and Lackner (2009)

16 Formic acid HCOOH - Fagerlund et al. (2009)

17 Hydrochloric acid HCl - Li et al. (2008)

- Nienczewski et al. (2008a)

- Nienczewski et al. (2008b)


- Li et al. (2009)





- Zhao et al. (2010)

18 Lithium hydroxide LiOH - Prigiobbe et al. (2009a)



19 Nitric acid HNO3 - Eloneva et al. (2008b)

- Doucet (2009a)

- Doucet (2010)



20 Potassium bicarbonate KHCO3 - Jarvis et al. (2009)

21 Propionic acid CH3CH2COOH - Eloneva et al. (2008b)

22 Rubidium bicarbonate RbHCO3 - Jarvis et al. (2009)

23 Sodium acetate CH3COONa - Krevor and Lackner (2009)

24 Sodium bicarbonate NaHCO3 - Andreani et al. (2009)


25 Sodium citrate C3H4OH(COOH)2COONa - Krevor and Lackner (2009)

26 Sodium chloride NaCl - Andreani et al. (2009)




- Li et al. (2009)

- Prigiobbe et al. (2009a)



27 Sodium hydroxide NaOH - Eloneva et al. (2008a)


- Li et al. (2008)

- Daval et al. (2009a)

- Daval et al. (2009b)

- Doucet (2009)


- Li et al. (2009)


28 Sodium nitrate NaNO3 - Prigiobbe et al. (2009a)



29 Sodium oxalate Na2(COO)2 - Krevor and Lackner (2009)

30 Succinic acid C4H6O4 - Baldyga et al. (2010)

31 Sulfuric acid H2SO4 - Eloneva et al. (2008a)

- Doucet (2009)


32 Tributyl phosphate (TBP) C12H27O4P - Eloneva et al. (2008a)

- Bao et al. (2010)

33 Urea (NH2)2CO - Eloneva et al. (2008a)


SELECTION, PRELIMINARY CHARACTERIZATION AND

ACTIVATION OF ALKALINE SOLID WASTES

DIRECT CARBONATION

SCHEME

INDIRECT CARBONATION

SCHEME

(1) (2)

POST-TREATMENT STEPS

SYSTEM FEASIBILITY / SCALE-UP Economic considerationsIntegration of components

Separation of carbonated product

Impurities level in carbonated product

Disposal / Recycling of process effluents

Recoverable values

Optimal particle size fractionTotal calcium / magnesium levels

Reactive calcium / magnesium levels Optimal physical activation

Mineral phase identification Optimal chemical activation

DIRECT GAS-SOLID

CARBONATION (dry process)

AQUEOUS DIRECT

CARBONATION (wet process)

Step 1: Extraction of calcium and

magnesium from wastes

Step 2: Purification of calcium- and

magnesium-rich solutions

Step 3: Carbonation reaction

Dissolution and carbonation reactions

combined in a single unit operation

Separate dissolution and

carbonation operations

Potential phase of reactive CO2 :

• gaseous

• liquid

• supercritical

SELECTION, PRELIMINARY CHARACTERIZATION AND

ACTIVATION OF ALKALINE SOLID WASTES

DIRECT CARBONATION

SCHEME

INDIRECT CARBONATION

SCHEME

(1) (2)

POST-TREATMENT STEPS

SYSTEM FEASIBILITY / SCALE-UP Economic considerationsIntegration of components

Separation of carbonated product

Impurities level in carbonated product

Disposal / Recycling of process effluents

Recoverable values

Optimal particle size fractionTotal calcium / magnesium levels

Reactive calcium / magnesium levels Optimal physical activation

Mineral phase identification Optimal chemical activation

DIRECT GAS-SOLID

CARBONATION (dry process)

AQUEOUS DIRECT

CARBONATION (wet process)

Step 1: Extraction of calcium and

magnesium from wastes

Step 2: Purification of calcium- and

magnesium-rich solutions

Step 3: Carbonation reaction

Dissolution and carbonation reactions

combined in a single unit operation

Separate dissolution and

carbonation operations

Potential phase of reactive CO2 :

• gaseous

• liquid

• supercritical

Figure 13 Critical issues to be considered in the design of optimal carbonation processes.


4. SCALE OF CURRENT AND PLANNED CCMC OPERATIONS

It is expected that when at maturity the overall cost of CCMC will be in the range 30-100 euros per ton of CO2, in

contrast to 30-45 euros per ton of CO2 for geological CCS in 2030 (60-90 euros per ton of CO2 in 2015)

(Priestnall, 2010).

Industries, governments, researchers, companies and investors are increasingly looking at feasibility and re-

evaluating economics. For instance:

- The UK-based Energy Technology Institute (ETI) has commissioned a £1m paper study on “mineralization

opportunities” which is run by British Geological Survey (BGS) in collaboration with Shell, Caterpillar and

CICCS. The study includes UK mineral distribution maps and a techno-economic study. The report will be

confidential and will be released to ETI later this year.

- Numerous commercial ventures using their respective proprietary CCMC process (detailed later on) have

come into existence over the last five years. Those include:

o Calera Corporation

o Cambridge Carbon Capture (UK)

o ICS

o Novacem (UK)

o Carbon8

o Calix

o Oxford Geo-Engineering

o Skyonic (USA)

4.1. Technological status and economic aspects

4.1.1. Ex situ

4.1.1.1. The Calera Process

Calera Corporation has developed the proprietary Carbonate Mineralization by Aqueous Precipitation (CMAP)

process. The technology may be suitable for a variety of facilities, including both retrofits and new plants. The

company has successfully retrofitted its technology at the pilot level to an existing 1,000-megawatt natural gas

powered electricity generation plant located in Moss Landing, California. According to Calera Corporation, its

CCMC technology is mature and ready for a demo scale project. The technology which can efficiently capture and convert CO2 post-combustion to mineral carbonate with alkaline solutions (e.g. seawater, certain minable

brines) and waste base sources and the generation of relatively fresh water suitable for desalination has been

tested at laboratory, small batch and large batch scales. At pilot scale, it was able to generate 5 tons of


supplementary cementitious material3 (SCM) capturing 2.5 tons of CO2 per day. Calera’s SCM is produced to

perform similarly to fly ash and can be used to replace cement in concrete mixtures. Its SCM can enhance the

strength of concrete and supplement a portion of the cement in concrete blends. At its pilot facility, capture rates

above 85% of CO2 and SO2 have been achieved for coal combustion.

As a result of the recent DOE funding received (DOE share: $19,895,553; Table 1), Calera has built a

demonstration plant capable of capturing 30,000 tons per year of CO2.

The flow diagram for the Calera process is illustrated in Figure 14. The primary materials used in the process include CO2-laden flue gas, coal-combustion fly ash, brines, waste water, and manufactured alkalinity (i.e.

NaOH) for locations where suitable brines are not readily available. A particularity of the process is its low

sensitivity to flue gas CO2 composition. The outputs to the process are a cleaner flue gas, green building

products and mineral carbonates. A key component of the integrated process seems to be its revolutionary

Alkalinity Based on Low Energy (ABLE) process (Figure 15) for the manufacture of the base, NaOH, which uses

an electrochemistry process to split salt (NaCl) to form an alkaline solution and acid (HCl) at one-third to one-fifth

of the energy of the current state-of-the-art. The process builds on advances in chlor-alkali and fuel cell design to

reduce the energy requirements for the process. The pilot scale system can currently produce 1 ton NaOH per

day. Interestingly, a CCMC process based on acetic acid for the carbonation of steel furnace slags was

developed by Åbo Akademi University, Finland but was abandoned owing to the elevated price of NaOH and the

difficulty in recycling it. The acetic acid may need to be revisited if the ABLE process can be integrated to it.

The Calera process provides pollution reduction beyond carbon capture. The absorption technology also

captures sulfur dioxide, as well as particulate materials, mercury, and other trace metals. For plants without flue

gas desulfurization (FGD) units, the Calera process is expected to provide SOx capture equivalent to the addition

of a state-of-the-art unit. Plants with FGD units will benefit from Calera technology through reduction in auxiliary

load associated with sulfur capture and/or higher levels of sulfur capture and a reduction in operating costs.

3 The US Concrete Institute defines a SCM as an “inorganic material such as fly ash, silica fume, metakaolin, or ground-granulated blast-furnace slag that reacts pozzolanically or hydraulically." A pozzolan is a material that reacts with by-products of the portland cement reaction to form additional binder material. SCMs are typically used to replace portland cement or to enhance the properties of concrete.


Figure 14 Flow diagram of the Calera process (Calera Corporation, 2009).

Figure 15 Schematic representation of the Calera ABLE process (http://www.calera.com).

A claim made by the company is that every ton of SCM or cement replacement produced by Calera avoids the

release of approximately a ton of CO2 that would otherwise be emitted by the traditional manufacturing of

Portland Cement (calcination). According to the US DOE, a normal U.S. Coal plant emits 0.9 metric tons of CO2


per MWh, while a gas plant emits 0.6 metric tons per MWh. When the carbon displaced by avoiding the

production of cement is considered, Calera’s process has a negative carbon intensity of -1.2 metric tons of CO2

per MWh. That is, for each MWh produced, Calera removes about 1.2 metric tons from the environment.

In most markets, revenues from the capture and sequestration of carbon dioxide, SOx, Mercury, other heavy

metals, and fly ash remediation, as well as sales of the building materials, will allow Calera to generate a profit,

while increasing the value of the carbon emitting plant.

Each point emitter site is different. Calera’s evaluation process assesses the optimal configuration and go-to-

market strategy for each location. This analysis determines the technology applied, the specific configuration,

and the best mix of products and services offered. In this regard, a study assessed the cost and economic

environment of different carbon capture and storage (CCS) technologies including the Calera CCMC process, in

order to make a decision regarding the best approach for capturing and then sequestering CO2 from the

emissions of a brown coal fired power plant in Southeastern Australia (Kolstad and Young, 2010). The Calera

process was found to be the most promising and to offer the most economically-viable opportunities.

Calera Corporation has recently entered the Chinese market. The company allied with China Huaneng Group

(the largest power generator in China) and Peabody Energy (the largest privately held coal producer) to develop

a 1,200-megawatt high-efficiency power plant and adjacent coal mine in the coal-rich Xilinguole region of Inner

Mongolia (Bulk Solids Handling, 2011; Kirkland, 2011). Calera’s mineral carbonation proprietary technology will

be deployed to convert some of the plant’s CO2 into solid carbonates which can be used as building materials

(ClimateWire, 2010). This may be a significant way forward for the development and deployment of CCMC since

China is considered the world’s largest and fastest growing coal market.

4.1.1.2. The ǺA process route for serpentinite

The three-step process route is illustrated by the three equations below and schematically given in Figure 16.

The reaction setup is depicted in Figures 17 and 18. This route has been tested on serpentinite rocks from Finland, Lithuania, Portugal and other locations (Romão et al., 2010; Stasiulaitiene et al., 2010).

a) Magnesium extraction: The first step involves the thermal solid-solid treatment of serpentinite

(Mg3Si2O5(OH)4) at ca. 400-500ºC and atmospheric pressure during 10-60 min, producing water-soluble

MgSO4 (Björklöf, 2010).

)(3)(2244244523 6523)(3)( gg NHOHSiOMgSOSONHOHOSiMg +++↔+

b) Mg(OH)2 production: Mg(OH)2 is precipitated from the previously formed MgSO4 using the NH3 released

during the thermal treatment in an aqueous solution, leaving behind unreacted mineral and insoluble

reaction products such as silica (Nduagu, 2008). The pH of the filtrate solution is raised stepwise to 8-9,

precipitating iron and calcium (extracted from the mineral) as FeOOH and Ca(OH)2 respectively, while

increasing the pH further to 10-11 precipitates Mg(OH)2.

At this stage, the recovery of solid (NH4)2SO4 from the aqueous form for reuse in step 1 incurs a

substantial energy penalty. There is therefore a need to develop an alternative route to Mg(OH)2 that bypasses the aqueous stage and/or a route in which MgSO4 is carbonated directly, e.g. using ammonium


(bi)carbonate produced from CO2 absorption in aqueous ammonia in an upstream scrubbing stage. Calcium

and iron oxides are selectively precipitated during sequential pH adjustment.

2)(424)(44 )()(2 OHMgSONHOHNHMgSO aqaq +↔+

c) Mg(OH)2 carbonation: The Mg(OH)2 produced in step 2 is converted into MgCO3 in a pressurized

fluidized bed (PFB) reactor at pressures greater than 20 bar and temperatures of 450-600ºC.

)(2)(3)(2)(2)( gsgs OHMgCOCOOHMg +↔+

Figure 16 Process overview of the ǺA process route (Fagerlund et al., 2010).

Figure 17 Fluidized-bed reactor setup at ǺA (Zevenhoven et al., 2010).


Figure 18 Photograph depicting the fluidized-bed reactor setup at ǺA (Zevenhoven et al., 2010).

The current status of this process is that extraction efficiencies of Mg from the rock seldom exceeds 60% of the

Mg content of the rock and carbonation efficiencies for a synthetic, commercial Mg(OH)2 in the PFB levels off at

50-55%. Although 1.2MJ/kg CO2 can be recovered as reaction heat from the carbonation step, the overall input requirements add up to 4 to 5 MJ/kg CO2, consuming about 3 ton of rock per ton of CO2 (Romão et al., 2010).

There is yet considerable route for improvement in the development of this process (Zevenhoven et al., 2010).

4.1.1.3. The Albany Research Center

4 (ARC) process

The Albany Research Center has conducted extensive research into aqueous mineral carbonation, favouring

olivine over serpentine due to a greater reactivity (O’Connor et al., 1999; Gerdemann et al., 2003). Today, the

ARC process is considered to be the most successful route for mineral carbonation. It entails the direct aqueous

mineral carbonation of olivine and/or serpentine in a 1M NaCl + 0.64M NaHCO3 solution at 155°C (for heat-

treated serpentine) or at 185°C (for olivine) and ca. 158.6 bars over 2 hours. The mixture of NaHCO3 + NaCl

was found to increase the reaction rate. NaHCO3 is an effective CO2 carrier (O’Connor et al., 2000), which

significantly increases the HCO3- concentration and the solution pH, both favouring carbonate precipitation. The

chlorine ions provided by NaCl are believed to enhance the solubility of Mg by creating soluble complexes

(MgCl2, MgCl3-, MgCl4

2-; Huijgen and Comans, 2003). Under these experimental conditions, the antigorite variety

of serpentine carbonated approximately 60% of the stoichiometrically available Mg, whilst the lizardite variety

only carbonated 40%. This was an indication that the structure of the starting material was of significance for the

carbonation reactions. Conversion of up to 94.9% was obtained when mineral particle size was reduced to

37µm, but the gain in conversion would not justify the energy penalty incurred by the required milling exercise.

The cost for CO2 sequestration would be 54 and 78 US$ per ton CO2 for olivine and serpentine respectively.

However, the reported carbonation rates were obtained only at a high energy cost: a 20% energy penalty for a

coal-fired power plant. Recently, further improvement was reported by using an aqueous solution containing

5.5M KHCO3 aimed at reducing the mineral pretreatment efforts and costs. Also, it must be kept in mind that the

reported process costs were overestimated, partly due to unrealistic calculations of energy efficiency and energy

costs. The costs of the process heat input were significantly overestimated when charged in the same way as

power input, giving a false impression of the overall process economics. It is important to make the distinction

4 The Albany Research Center is a U.S. Department of Energy laboratory and is now part of the National Energy

Technology Laboratory (NETL).


between power and heat and the temperature of the various heat streams of the process. For heating purposes,

it is not necessary, and even unwise, to use electric power, since it is enough to use heat of a sufficiently high

temperature, which should result in a much lower cost. At a power or steel plant, this would mean using process

waste heat instead of electricity (Zevenhoven, 2010).

The same process was recently tested on serpentines from Greece and surprisingly only 10% of Mg was converted to carbonates (Koukouzas et al., 2009).This showed that the ARC process will require optimization for

each serpentine variety, although maintaining the lowest possible reaction temperature and pressure is desired

for the technical and economic feasibility of the direct carbonation process. However, the carbonation reaction

product consists of essentially magnesite (60 wt %), free silica (25 wt %) and residual silicate (15 wt %).

Potential uses for the magnesite/silica product include soil amendments, replacing material such as lime (CaO),

limestone (CaCO3) and/or dolomite (Ca,Mg CO3). The hydrophilic nature of the free silica may also improve soil

water retention where necessary. In addition, the results from the studies suggest that the ARC process may be

an effective method for the remediation of asbestos wastes due to the apparent destruction of chrysotile by

combined heat treatment and direct carbonation. Future studies are intended to investigate various mineral

pretreatment options, alternative reactants, scale-up to a continuous process, and process economics.

4.1.1.4. Chemical and biological catalytic enhancement as novel carbon capture and

storage technology

Zhao and Park (2010) are developing a microbial and chemical enhancement scheme for in situ carbon

mineralization in geological formations in order to achieve long-term stability of injected CO2. However, it is

conceivable that a variant of this process may generate suitable reaction pathways for ex situ CCMC or for in

situ CCMC in basaltic rocks.

The ARC process proposed to suspend minerals in a NaHCO3 + NaCl solution where the chlorine ions are

believed to enhance Mg extraction. Zhao and Park took the ARC process one step further and speculated that mineral dissolution could be further enhanced using chemical catalysts in the form of Mg-targeting ligands (e.g.

sodium oxalate). Figure 19 shows a rapid and substantially improved Mg extraction from olivine when NaCl is

replaced by Na-oxalate in a dissolution process under atmospheric conditions. This can be explained in terms of

the higher stability constant of Mg-oxalate (2.55 M-1) compared to that of MgCl+ (0.34 M-1). Indeed, the higher the

stability constant, the more complex is formed in solution. Of all the chelating agents tested, Na-oxalate was by far the most effective in extracting Mg (Figure 20). This was further confirmed by another group (Bonfils et al.,

2010) who demonstrated that near 100% of Mg can be extracted from both olivine and serpentine at 120ºC and

20 bars (Figure 21). However, in the presence of Mg-oxalate in solution, there is a strong competition between

the formation of magnesite and glusbinskite (Figure 22) and the process parameters must be optimized for each

type of resource to prevent the preferential formation of glusbinskite over magnesite. The proposed reaction

model with Mg- and Si-targeting chelating agents is schematically represented in Figure 23 and the proposed

engineered mineral weathering process which makes use of carbonic anhydrase is shown in Figures 24 and 25

(Zhao and Park 2010).

The energy requirement for CCMC is significant, and thus the use of the formed products is important for the

future implementation of this CCS technology. The direct capture and storage of flue gas would further improve

the overall feasibility of the technology.


Figure 19 Effect of chemical additives on olivine dissolution kinetics (Park, 2010).

Figure 20 Effect of types of chelating agents (Park, 2010).


Figure 21 Mg extraction yield (%) for dissolution of olivine and serpentine in oxalate solution (T = 120ºC, P

= 20 bar, fine particles; Bonfils et al., 2010).

Figure 22 Speciation of precipitated Mg (Bonfils et al., 2010).


Figure 23 Proposed reaction model with Mg- and Si-targeting chelating agents (Park, 2010).

Figure 24 Schematics of the proposed engineered mineral weathering process (Park, 2010).


Figure 25 Use of carbonic anhydrase in the proposed engineered mineral weathering process (Park,

2010).

4.1.1.5. The ALCATRAP (Alkaline Carbon TRAPing) process

The author visited the ALCATRAP pilot plant near Nuremberg, Germany. This process is a direct aqueous

process whereby ash (lignite ash, biomass ash, wood ash) is dispersed in a suspension tank containing CO2-saturated water (Figure 26) to form calcite (Bauer et al., 2010). The carbonation reactor is placed in line with the

flue gas output from a biomass power plant. However, this process is fraught with difficulties. In the main, the

compositions of the flue gas and the ash are extremely variable owing to the variations in the biomass fed into

the power plant. This makes the optimization of process parameters very challenging. It would have been

preferable to integrate the process to a conventional power station where the by-products (flue gas and ash)

show similar properties and compositions over time. At this stage, no optimization of flux balancing, reaction pH

and retention times has been possible, costs have not been evaluated, energy and mass balances have not

been performed, and formed product properties have not been assessed.


Figure 26 Suspension tank (material of construction: PE-HD; 1.5m diameter; mixing unit: 3000rpm) in

which ash in dispersed in aqueous media.

4.1.2. In situ

4.1.2.1. The CarbFix project

The CarbFix project (http://www.carbfix.com) has been officially launched by Icelandic, French and American

scientists in 2007. The main partners in the project are Reykjavik Energy, University of Iceland, The Earth

Institute at Columbia University in New York, and the Centre National de la Recherche Scientifique / Université Paul Sabatier in France. It was created to develop and optimize practical and cost-effective technology for in situ

carbon mineralization in basalts. The project includes field scale injection of CO2-charged waters into basaltic

rocks, laboratory experiments, studies of natural analogues, and geochemical modelling.

In the lab, McGrail et al. (2006) showed that exposing basalt samples from the Columbia River Basalt (USA) to

CO2-saturated water yielded calcium carbonate mineral formation in four to six weeks and extensive

mineralization within several months. The CO2 mineralization rate in the field is unknown today. This is the main

motivation for the CarbFix project, to conduct the field injection experiment and to monitor the CO2 mineralization rate in situ. The injection site is located about 3 kms south of the Hellisheidi geothermal power plant in SW

Iceland. The test injection is currently injecting 0.07 kg/s of CO2 dissolved in 2 kg/s of water at 19ºC. This

amounts to 2.2 thousand tons of CO2 per year. The CO2 gas is pumped into the injection well at about 25 bar

total pressure and 350 m depth. The water stream carries CO2 down-well to more than 500 m depth where the

hydrostatic pressure is over 40 bars, ensuring complete dissolution of the CO2 before entering the aquifer.


Besides the CarbFix project in Iceland, the Big Sky Regional Partnership, one of the seven U.S. Department of

Energy partnerships for carbon capture and sequestration, is conducting a CO2 injection pilot test in the Columbia River Basalt in NW of the United States to study the in situ mineralization of CO2

(http://www.bigskyco2.org/).

4.1.2.2. CO2 Energy Reactor®

The following stages of development have been provided by Innovation Concepts B.V. :

- Laboratory scale:

Innovation Concepts B.V. has built a laboratory-scale version of the reactor which will simulate the time

and pressure conditions of the process. Experiments start in February 2011.

- Modelling:

Innovation Concepts B.V. is working on a computer simulation of the whole process, including the heat

exchange, the chemical reactions, particle bouncing effect, etc.

- Pilot scale:

It is estimated that a pilot scale process will be tested in about two years.

This concept is innovative and if successful will be able to make use of the natural hydrostatic pressure as well

as the geothermal heat combined to the heat generated by the carbonation process to activate the mineral

slurry. The result may be a cost-effective process designed to perform a direct aqueous carbonation pathway which is an ex situ route benefiting from in situ conditions. However, the idea relies very much on a design which

has been successfully applied to the treatment of organic effluents, but the extent to which it will successfully

carbonate mineral slurries is uncertain at this stage. In addition, the removal of SiO2-induced diffusion limiting

layer at the surface of mineral particles during the carbonation process must be controlled effectively to achieve

optimal conversion.

It is recommended that South Africa stays informed on the development of this concept.

4.2. Promising applications and markets

Calera’s formed products are probably a good example of what can be expected from a large-scale carbonation

process. Their products are tested to meet or exceed all of the applicable standards (including ASTM, ACI, EPA,

etc.) for the material. Typical testing for its SCM products includes ASTM C 1157 (Standard Performance

Specification for Hydraulic Cement). Figure 27 shows the compressive strength performance of Calera SCM.

The black bar is a 100% Portland cement mortar while the coloured bars represent replacement of Portland

cement by different SCMs currently being developed and tested by Calera. This testing (done in accordance with

ASTM C 109) data shows that the Calera SCM produces equivalent compressive strengths at up to a 20%

replacement of Portland cement.


Figure 27 Calera SCM compressive strength performance (http://www.calera.com).

There appears to be very large markets available today for Calera's building materials (Figure 28). For instance,

roadbed alone could consume all the aggregate and cement Calera could produce for the next 5-10 years. At

first, Calera will introduce its aggregate materials into applications such as pavements and road base course. It

will then aim at expanding their market and at introducing its SCM into applications such as pavers, non-

structural block, other miscellaneous precast products, sidewalks, and other similar applications.

Figure 28 Possible applications for carbonated products and other by-products generated by CCMC

(http://www.calera.com).

The U.S. market for mineral building materials totals well over 3.5 billion tons per year, and concrete is the most

widely used man-made material in the world. Concrete is made of roughly 80% aggregate (sand and gravel), 10-


15% cement, and the remainder air, water, and additives. The CMAP process is capable of permanently

mineralizing carbon in the form of either fine or coarse aggregates or a SCM that can be utilized in the built

environment and meet the growing green product market as a carbon-negative material (Figure 29). The

standard process for manufacturing Portland cement generates large amounts of CO2 both from the fuel used to

heat the raw materials (CaCO3, clays, etc.) as well as from the calcination process itself (the conversion of

CaCO3 to CaO, releasing CO2). Therefore, concrete made from Portland cement carries a CO2 footprint of

approximately 0.8-1.5 ton CO2/ton cement, translating to roughly 537 pounds of CO2/cubic yard of concrete. This

CO2 footprint can be reduced somewhat through the use of SCMs such as fly ash that displace portions of the

Portland cement used in a concrete mix.

Since Calera’s SCMs do not undergo the combustion or calcination processes of Portland cement, their

production does not release any CO2. Calera SCM both captures carbon from one source and avoids carbon

emissions from another. Concrete made with Calera’s fine and coarse aggregate, 20% cement replacement with

Calera SCM, and 20% cement replacement with fly ash would have carbon footprint of negative 1146 pounds of

CO2/cubic yard of concrete. This is a carbon savings of 1683 pounds of CO2/cubic yard of concrete compared to

standard concrete. With projected U.S. Portland cement consumption at nearly 200 million metric tons by 2020,

a 20% market penetration with a SCM replacement level of 50% would reduce CO2 emissions by 30 million

metric tons. An analysis of the South African markets for such products will be necessary to assess the full

potential of CCMC in this country.

Figure 29 Production of carbon-negative materials using the Calera process

(http://www.arb.ca.gov/cc/etaac/meetings/102909pubmeet/mtgmaterials102909/basicsofcaleraprocess.pdf).

Calera business model generates several revenues streams, including (1) building materials manufactured and

sold, (2) carbon monetization of CO2 sequestered and avoided, and (3) softened water for RO.

In summary, Calera has developed a line of carbon negative building materials being tested against existing

industry standards (Figure 30) and is expanding it to address a variety of large markets (Figure 31).


Figure 30 Carbon negative building materials generated by the Calera process and their market shares.

Figure 31 Product development time and possible markets for the products generated by the Calera

process.

As mentioned earlier, there are several other companies specializing in the development and deployment of

CCMC and the production of carbonated products:


− Cambridge Carbon Capture (UK) is a new venture which was created in 2010 (Priestnall, 2010). The company believes that CCMC can offer a highly profitable and fully-scalable approach to CCS for a ca. 1

trillion US$ / year market (global market for carbonate materials produced by CCMC process) and that the

technology is at least as proven as geological CCS. In addition, commercial deployment does not depend on

learning curves, carbon pricing or CO2 pipeline infrastructure. Their process generates carbonate mineral

precipitates that can be consolidated to building materials and aggregates and cementitious phases that can

replace high-value cements and displace additional CO2.

− Integrated Carbon Sequestration (ICS) Pty Ltd (Australia): In its simplest form, the ICS process integrates

two basic operations: in the first, an ammonia-rich aqueous solution of ammonium bicarbonate is used to

scrub CO2 from flue gases to form a solution enriched in CO2. In the second, pre-treated serpentinite or

other suitable ultramafic rock is blended directly into this rich solution prior to the mixture being held under

controlled conditions in a purpose-built reactor. There, via what is at first glance a double decomposition

reaction, the silicate minerals react with ammonium carbonate to form magnesium carbonate (magnesite)

and silica, thereby directly removing from solution the CO2 that was absorbed in the flue gas scrubbers, as

insoluble precipitates. By simply filtering or otherwise separating out the insoluble solids, the capture solution

is regenerated to the extent necessary for its recycle to the flue gas scrubbers. Under the correct conditions

ammonia has a catalytic role; it is not consumed in the process. Ammonia losses are restricted to residual

quantities accompanying the final carbonated mineral, and as ammonium sulphates and nitrate formed as a

consequence of the scrubbing of oxides of sulphur and nitrogen (SOx and NOx) in the raw flue gases. The

ICS process embraces optional further steps for recovering these residual quantities of ammonia, and plant

for keeping ammonia slip in the final flue gases below one part per million. Over the last couple of years, a

group of scientists from CSIRO (Australia's major national government research body, www.csiro.au)

contracted to ICS have been conducting autoclave trials at Lucas Heights south of Sydney. These trials

have demonstrated "proof of concept", notably the direct conversion of silicates to magnesite, and work

continues to establish optimum conditions for this reaction to allow a continuous pilot plant to be designed.

Their thermodynamic modelling has confirmed the energy efficiency of the process. Pre-feasibility studies into the application of the ICS process at large scale, e.g. retrofitting it to major existing coal-fired power

stations to capture at least 90% of their CO2 emissions, suggest a total cost of $50US to capture and store

each ton of the gas permanently and securely as mineral carbonate. Since most existing power stations may

normally be expected to lie some distance from suitable silicate rock deposits, such estimates must include

allowances for transporting the rock to the power stations and for the transport of the carbonated mineral.

The figure of $50US/ton includes an allowance for 200 kilometres of rock transport by rail, plus some final

carbonated mineral transport by slurry pipelines. The above summarises the position for existing power

stations. But since the tonnage of rock required for this mineralization process is six times the tonnage of

coal to be fired in the host power station, logic dictates that a new power station would be built nearer the

rock deposit than the coal field that furnishes its fuel. Under these conditions the cost of capturing and permanently storing by CCMC one ton of CO2 may reasonably be expected to fall below US $40/ton of the

gas. (All estimates, capital and operating, include contingencies.)

Significantly, the ultramafic rocks used in the ICS process tend also to host many important base metals

including nickel, chromium, platinum-group metals, copper-gold, and iron. The ICS process would convert many of these metals to more readily recoverable forms, e.g. iron to magnetite, and nickel and copper to

amines in solution. The potential revenue from the recovery of such metals as by-products could offset


partially, and at times fully, the cost of carbon capture and storage. By way of example, a typical serpentinite

may contain 10 per cent magnetite and 0.2 per cent nickel-equivalent (including cobalt). Since to capture

one ton of CO2 it takes three tons of serpentinite, with reasonable assumptions for recoveries we can

assume byproduct production of 250 kg of magnetite and 4 kg of nickel per ton of CO2 captured, which at $40US/ton and $10US/kg respectively, should yield gross revenues of $50US/ton of CO2 captured, i.e., a

sum sufficient to offset fully, the cost of capturing and storing that quantity of CO2. While the additional costs

involved in recovering these by-products in marketable form would need to be included in any particular total

project cost structure, these numbers do indicate the significance of likely base-metal credits. They promise

to have a major, positive impact on the economics of the first wave of installations of the ICS process, when

such revenues would be needed most.

− Novacem (UK) is a spin-out from Imperial College, London that has developed a new carbon-negative

cement. The company aims at offering a scalable, transformative alternative to current carbon intensive

cement production. It announced its first product, the Green Cement Bond, in July 2010, with Lafarge as first

subscriber. Novacem is currently operating an experimental batch pilot plant, which is currently being

upgraded to continuous operation. In 2011 it is planning a major funding round to build and operate a 25,000

ton semi-commercial Novacem Plant. The first commercial scale plants will follow from around 2015. Current

investors include the Royal Society Enterprise Fund, London Technology Fund and Imperial Innovations. Its

business model is process-licensing to allow widespread adoption of the technology. Anecdotally, the World

Economic Forum has named Novacem as one of its Technology Pioneers for 2011. Novacem’s

development is developed by an experienced international team which comprises international

multidisciplinary team of scientists and engineers, seasoned entrepreneurs, savvy industry non-execs, high-

calibre investors and major industry partners. Novacem has three fundamental differences in embodied

carbon compared to current cement production (Figure 32).

Novacem carbon negative cement is based on two technologies:

o Novel low-carbon MgO production process based on magnesium silicate raw materials;

o Novel cement composition based on MgO. Strength developed through the formation of

magnesium silicate hydrates (M-S-H) rather than carbonation with atmospheric CO2.

Overall Novacem can achieve energy demand which is 60-90% that of ordinary Portland cement. Its target is

profitable Novacem plants serving significant segments of the market within 5 years; significant further roll-

out within 10 years.

Novacem claims that it will not be a niche product; its objective is full cost and performance parity with

Portland Cement.


Figure 32 Embodied carbon: Novacem vs current cement production (Evans and Vlasopoulos, 2010).

Carbon8 (UK): the company utilizes an innovative, patented solution called Accelerated Carbonation Technology

(ACT) that is a rapid, cost-effective treatment suitable for soil and waste. ACT can be used in both on-site and

off-site operations and can be integrated into existing industrial processes. ACT is a controlled accelerated

version of the naturally occurring carbonation process, which results in an improvement in the chemical and

physical properties of the treated materials. The technology can utilize waste CO2 emissions from local sources,

capturing significant volumes of CO2. When carbonation is used in the recovery and recycling of waste, an end

product with real value is created. Some examples of wastes that have been successfully treated include slag

(from steel manufacture), MSWI ashes (bottom ash and APC residues), galligu (from soap manufacture), soils

contaminated with pyrotechnics waste, water treatment sludge, and quarry fines. No additional information on

their process was available at the time of writing.

− Calix (Australia): produces a green cement. No additional information could be found at the time of writing.

− Oxford Geo-Engineering Research (UK) has proposed a concept process for the sequestration of CO2, the

mitigation of ocean acidification and the production of biomass in arid environments. The process works by

thermally decomposing (calcining) limestone and adding the resulting calcium oxide to seawater, thereby

increasing the capacity of the oceans to act as a carbon sink, whilst at the same time mitigating ocean

acidification. The CO2 generated by the thermal decomposition (calcination) of limestone can be

sequestered, or utilized either as the starting point for the production of fuels, or to enable biomass to be

grown in arid environments, without the need for irrigation. The process thus addresses a number of

environmental and social problems: climate change, ocean acidification, food shortages, fuel shortages,

water shortages and soil salinification from excessive irrigation.

It seems counter-intuitive to attempt to counter climate change by heating limestone. For a start the process

is highly energy-intensive – to calcine limestone requires a temperature of 850°C and consumes 2.67GJ per

ton of limestone calcined. Also, when the limestone (CaCO3) decomposes it generates CO2:


So it is doubly damaging – the energy-intensive process results in CO2 production (assuming fossil fuels are

used to drive the reaction) and CO2 is emitted as a product of the process.

In order to derive pure CO2 from the calcination of limestone it will not be possible to use conventional lime

kilning processes as these co-fired fuel, air and limestone, resulting in a flue gas which contains large

quantities of nitrogen. Instead one of two novel techniques will need to be employed:

• Co-firing fuel, oxygen and limestone in a conventional kiln. (It may be necessary to dilute the fuel oxygen

mix with CO2, which will lower the burn temperature that would otherwise result – if the temperature is

too high, the calcium oxide generated will sinter)

• Separating the heating process from the calcining process. A fluid, potentially molten iron or water

vapour, is heated within a sealed vessel by the combustion of the fuel in air external to the sealed

vessel. The limestone is calcined in or on the heated fluid. The flue gases of the two processes

(combustion and calcination) are treated separately with the flue gas from combustion having a low CO2

content, whilst the flue gas from the calcination is pure CO2.

Stranded energy is energy that is remotely located, so it is not economically viable to exploit. For example, in

a desert there is plenty of energy available, but it would cost too much to transfer the energy to where

anyone wants it, so it never gets used. So, paradoxically, in a desert energy is abundant and cheap, but

worthless. Oxford Geo-Engineering Research states that this process can use that stranded energy.

− Skyonic is working on a project that can remove up to 99% of all pollutants from exhaust gases, including

SOx, NOx, mercury, and heavy metals. The company has begun the construction of a commercial carbon

capture plant next to Capital Aggregates Cement in San Antonio, Texas, that will incorporate both SkyMine

and SkyScraper technology. The plant should be finished before 2012. No information about the process

itself or its economics has been made available.

5. CARBON CAPTURE AND MINERAL CARBONATION IN SOUTH AFRICA

5.1. Availability of raw materials in South Africa

Figure 33 depicts Ca- and Mg-rich mineral occurrences in South Africa, with the legend showing the most

abundant minerals. South Africa is in a unique position since large volumes of mafic and ultramafic rocks

suitable for CCMC have already been mined and are present in the form of waste rocks in mine tailings from the

diamond, PGM, Cr2O3, P2O5 and asbestos sectors. These mine tailings are discussed in more details below.

South Africa has also accumulated sizeable dumps of steel furnace slags, phosphogypsum and coal-combustion

fly ash which are also suitable candidates for CCMC. Although these resources are available in small amounts in

comparison to mine tailings, they can sequester a significant portion of CO2 from the flue gas generated at their

mother plants and they are more reactive than natural minerals.


Figure 33 Ca- and Mg-rich mineral occurrences in South Africa.

5.1.1. Platinum Group Elements (PGE) mine tailings

A potential source of suitable material, and one virtually unique to South Africa, is that of mine tailings from the

primary beneficiation of Platinum Group Elements (PGE) ore bodies (Figure 34). This material is available in large quantities and is known to contain significant quantities of Ca-Mg bearing silicates (Vogeli et al.,

submitted). A definite beneficial characteristics of PGE tailings for the purpose of CCMC is the very fine grain

size (D(v,0.5) < 22-66 µm; D(v,0.9) = 164-209 µm) of their particulate constituents, which is the result of the

ultra-fine grinding required to liberate the valuable small (sub-30 µm) PGE grains from the ores (Schouwstra and

Kinloch, 2000; Rule, 2009). It is indeed generally accepted that the smaller the average particle size, the larger

the mineral surface area per unit mass and the higher the reactivity of the particles. In this instance, no

additional mechanical activation will be required, implying that no energy penalty will be incurred for further

milling.

Figure 35 shows the distribution of the Bushveld Complex mafic rocks which are rich in PGE. The mafic zone

shown in green in Figure 35 consists of norite, pyroxenite, anorthosite and gabbro, which are suitable for CCMC.

The ores can be subdivided into 3 broad types:


- Merensky Reef (shown in yellow in Figure 35, as well as a small portion south-west of Thabazimbi which is

too small to be shown):

The Reef is silicate-dominated (pyroxene, feldspar, olivine, chromite).

- UG2 Reef (it does not appear in Figure 35 because of its position in relation to the Merensky Reef. The UG2

Reef is located just below the Merensky Reef in the vicinity of Rustenburg:

The Reef is oxide-dominated (chromite, pyroxene, feldspar).

- Platreef (it does not appear in Figure 35 because of its size on a map of this scale. It is located on the inside

of the mafic rocks contour near Mokopane).

The Reef is silicate-dominated (pyroxene, feldspar, amphibole, carbonate).

The differences in mineral compositions between these three reefs mean that the optimum CCMC conditions

may be different for each reef, although this assumption will need to be tested.

Figure 34 Map of Platinum Group Metals (PGM) operations in the Bushveld Igneous Complex in South

Africa. The positions of BRPM and Northam platinum mines are highlighted with an asterisk, as well as the

position of Sasolburg, the local CO2 sequestered stream (Adapted from Northam Annual Report 2010).


Figure 35 The distribution of the Bushveld Complex mafic rocks.

Preliminary work has already been performed on Merensky Reef tailings in the context of CCMC (Vogeli et al.,

submitted), and the authors are currently surveying the other two types of tailings (Vogeli, personal

communication). Given the paucity of available data, this report will exclusively focus on discussing the potential

for mineral carbonation of Merensky Reef tailings.

Bulk Merensky tailings samples from BRPM and Northam Platinum Mines (Figure 34) were sourced and

characterized for their potential for CCMC. Their Mg and Ca contents are favourable for CCMC with MgO + CaO

approximating 27% (Northam) and 23% (BRPM) (Table 10). Their mineralogical compositions are depicted in

Table 11. The mine tailings contain several Mg silicate minerals, the most abundant being enstatite (30.6 to

41.9%), talc (11.1 to 12.4%), olivine (2.4 to 8.1%) and serpentine (0.7 to 3.7%). They also contain plagioclase

feldspar (13.6 to 32.2%), a solid solution series ranging from albite to anorthite endmembers (with respective

compositions NaAlSi3O8 to CaAl2Si2O8), where calcium and sodium atoms can substitute for each other in the

mineral's crystal lattice structure. Interestingly, enstatite was more abundant in the coarser size fraction (Figure

36).

To date, no carbonation experiment has been attempted on South African PGE mine tailings, although Jacques

Vogeli will come and run some preliminary tests in our batch reactor from 16 to 18 February 2011.


Table 10 Chemical composition (in weight %) of the Northam and BRPM tailings (Vogeli et al., submitted).

Mining Operation

Major Oxide Northam Merensky Tailings

BRPM Merensky Tailings

SiO2 47.8 49.9

TiO2 0.29 0.24 Al2O3 7.87 14.4 Fe2O3 13.1 8.85 MgO 21.9 14.6

CaO 4.97 8.73

Na2O 0.75 1.20 Cr2O3 2.25 0.87 NiO 0.13 0.08

Table 11 Bulk mineralogy of the Northam and BRPM tailings samples (adapted from Vogeli et al.,

submitted). The asterisk marks indicate sequestrable minerals.

Mining Operation

Modal Abundance (%) Northam Merensky Tailings BRPM Merensky Tailings

Pyrite FeS2 0.3 0.4

Quartz SiO2 0.9 1.3

Plagioclase Feldspar* NaAlSi3O8 to CaAl2Si2O8 series 13.6 32.2

Mica 0.4 0.5

Chlorite* 0.8 1.7

Olivine* (Mg,Fe)2SiO4 8.1 2.4

Diopside* CaMgSi2O6 1.8 2.1

Enstatite* MgSiO3 41.9 30.6

Amphibole 3.9 5.5

Epidote Ca2Fe3+2.25Al0.75(SiO4)3(OH) 0.8 2.1

Calcite CaCO3 0.1 0.1

Chromite Fe2+Cr2O4 5.6 1.9

Others 4.9 6.8

Talc* Mg3Si4O10(OH)2 12.4 11.1

Serpentine* Mg3Si2O5(OH)4 3.7 0.7

Total Sequesterable 82.3 80.8

Total Non-sequesterable 17.7 19.2


Figure 36 Size by size modal abundance for sequestrable minerals in the a) Northam and b) BRPM mine

tailings samples. Alteration minerals represent talc, chlorite and serpentine (Vogeli et al., submitted).

In the year June 2009 to June 2010, Northam (Northam Annual Report, 2010) and BRPM (Anglo Annual Report,

2010) generated 1.0-million tons of Merensky mine tailings each. Based on their elemental compositions and the

tonnages generated by each PGM operation, it was estimated that Northam and BRPM could theoretically sequester 387.56 and 269.72 kt of CO2 per annum for the Merensky tailings alone (Vogeli et al., submitted).


These two PGM operations are located at approximately 260 and 190 kms from Sasol’s Secunda coal-to-liquid

plant. It is therefore conceivable that CO2 from the plant could be transported to such mining sites for CCMC.

The above CO2-specific sequestration capacity refers only to two PGM mines. However, the South African PGM

industry generates vast volumes of Ca- and Mg-rich tailings annually. During the period June 2009 to June 2010,

the major “players” in the PGM industry (i.e. Anglo, Implats, Northam and Lonmin) produced 77.5 million tons of

Meresky, UG2 and Platreef tailings, which could theoretically sequester up to 13.9 million tons of CO2 per annum (Figure 37; Vogeli et al., submitted).This represents over 40% of the concentrated CO2 stream emitted annually

by Sasol’s coal-to-liquid plant in Secunda, and a volume of annual sequestrable CO2 which is about 4 times

larger than the current world’s largest geological storage site.

Figure 37 Estimated theoretical annual CO2-specific sequestration capacity of PGM tailings from the four

major players in South Africa. The annual milled tonnage and site-specific CO2 emissions are also shown. (Vogeli et al., submitted).

5.1.2. Findings from the Carmex research project about South African mine tailings

The Carmex research project is undertaken by a French consortium and aims at assessing the worldwide potential for ex situ mineral carbonation. To this effect, sites of interest for implementing ex situ mineral

carbonation were ranked by crossing two data sources, the world inventory of “Large and Superlarge Deposits” and CO2 emission sites, using arcGIS (Picot et al., 2010). For the purpose of this report, only results relevant to

South Africa are presented and discussed. The potentially carbonatable material of choice in terms of quantity

and quality is the waste from mining world-class deposits related to ultramafic (Ca,Mg,Fe > 40% by weight) and

mafic (Ca,Mg > 30-40%) rocks. However, the study used a number of selection criteria in their search, such as considering only Superlarge (those of Class 4) ore deposits related to ultramafic rocks (i.e. chromium, copper,

nickel, PGE), distance from CO2 emissions sites, and volume of CO2 released per annum. The negative effect of

their selection is the exclusion of PGE mine tailings from their short-list, although these materials are known to

be abundant and promising resources for CCMC (see section 5.1.1.). Nevertherless, the finding was that the

situation of the South African sites was very favourable in terms of the concentration of ore deposits related to

ultramafic rocks, very large amounts of mining waste (several billion tons), and the proximity of numerous CO2


emission sites (Figure 38). Table 12 (Picot et al., 2010) presents a list of African ore deposits whose

characteristics met all the proposed criteria, but fails to identify PGM tailings as a potentially important resource

(see Section 5.1.2 below). The ore deposit from Botswana was included in this report since South Africa may

have the opportunity to lead the development and deployment of CCTC on the African continent which is rich in

industrial commodities.

The work carried out by the Carmex project will need to be revisited in the specific context of South Africa by

modifying the selection criteria accordingly, for instance by taking into consideration that South Africa benefits

from the availability of a large volume of concentrated CO2 stream. Collecting a number of different short-lists of

potentially suitable materials, based on different selections of parameters, will guide South Africa in identifying

possible compromises to be made for specific raw materials.

It is mentioned by the authors that the use of the waste from the diamond mines is not possible because of

current or planned retreatment projects by the operating mining companies. However, this statement is in

contradiction with findings the author made at the ACEME conference where several scientists have mentioned

the shown interest of South African diamond companies in CCMC (see section 5.1.3.).

Figure 38 Map matching fixed CO2 sources with ore deposits related to ultramafic rocks (Picot et al.,

2010).


Table 12 Characteristics of the selected ore deposits related to ultramafic rocks (modified from Picot et

al., 2010).

Superlarge (Class 4) ultramafic ore deposits

Name Country Main commodity Rocks Estimated volume

of waste

Jwaneng Botswana diamond Sandstone, shale, basalt,

kimberlite, gneiss, granite

ca. 250 Mt

Premier South Africa diamond Kimberlite, quartzite,

sandstone, felsite, norite,

gabbro

> 1 bt

Bushveld Norite South Africa Cr2O3 Magnetite, pyroxenite,

diorite, anorthosite,

norite, chromite

> 1 bt

Phalaborwa South Africa P2O5 Pyroxenite, sovite,

foskorite, glimmerite,

granite, gneiss, regolith

> 1 bt

5.1.3. Diamond mine tailings

Diamond mine tailings are also abundant. For instance, Picot et al. (2010) identified a South African diamond

mine (Premier, at Cullinan, East of Pretoria) which has generated over a billion ton of mine tailings over the

years (Table 12). These tailings are likely to contain rocks such as gabbro and norite which are suitable for

CCMC. Figure 39 illustrates kimberlite mines and occurrences in South Africa. No quantification of the volume of

CO2 that could be sequestered in these tailings is currently available.

Interestingly, the author discovered at the ACEME-10 conference that a South African diamond company has

made some enquiries regarding the potential suitability of diamond mine tailing for CCMC. The company is

primarily interested in recovering additional diamonds from its tailings but the recovery process is currently not

economically viable. The company was interested in finding out whether an additional auxiliary process such as

CCMC of the tailings could permit further diamond recovery through extra incentives, such as CO2 sequestration

and the production and sale of formed aggregates which would offset the costs associated to further diamond

extraction.


Figure 39 Kimberlite mines and occurrences in South Africa.

5.1.4. Other mine tailings

5.1.4.1. Chromium and Phosphorus pentoxide mine tailings

Picot et al. (2010) showed that large deposits of Cr2O3 (Bushveld Norite) and P2O5 (Phalaborwa) are mined and

have generated over a billion ton of mine tailings each at these two sites alone over the years (Table 12). These

tailings are likely to contain significant amounts of Mg-rich rocks which are suitable for CCMC. No quantification

of the volume of CO2 that could be sequestered in these tailings is currently available.

5.1.4.2. Asbestos mine tailings

Although asbestos mining activities have ceased in South Africa, they have left a considerable legacy in the form

of numerous old mining dumps which remain hazardous to this day. For crocidolite asbestos alone, there are

over 80 dumps listed in the country. Whilst many sites were covered to prevent dust exposure as part of past

remediation programmes, numerous dumps have now been partially uncovered, which is indicative of the short-

term benefits of this method. Most of these are located at proximity of settlements where children use the

surroundings of the dumps as play-grounds. They are therefore exposed to variable amounts of asbestos dusts which are known to cause health respiratory problems and possibly fatalities (i.e. asbestosis followed by

mesothelioma) following long-exposure.


The problem of asbestos is not only limited to existing mine tailings. Numerous locations which contain useful

economic commodities are currently dismissed due to the presence of hazardous serpentine and/or amphibole

asbestos minerals. There is published evidence that asbestos tailings can be stabilised by CCMC with the

formation of products which are asbestos-free. CCMC may therefore be a potentially effective method for the

remediation of asbestos in mine tailing (Doria, 2005; Larachi et al., 2010).

Figure 40 shows the asbestos mines and occurrences in South Africa. These possible resources for CCMC have

not been quantified in the context of CO2 sequestration, but it is anticipated that data on the elemental and

mineralogical composition of the tailings are already available. A desktop study aimed at estimating the

theoretical CO2-specific sequestration capacity of existing dumps would be required to assess their possible

suitability for CCMC. The volume of CO2 that could be sequestered is probably limited in comparison to the total

emissions in South Africa, but it may bring the added benefits of remediating asbestos-contaminated land and

generating aggregates from the tailings.

Figure 40 Asbestos mines and occurrences in South Africa

5.1.5. In situ CCMC in South African basalts

It was discussed earlier (see section 4.1.2.1.) that practical and cost-effective technology for in situ carbon

mineralization in Icelandic (i.e. The CarbFix project), Californian and Indian basalts is currently under

development. The distribution of basaltic and andesitic rocks in South Africa is shown in Figure 41. Basalts are


also particularly abundant in the Lesotho (not shown). It is currently uncertain whether these rocks exhibit

suitable properties (e.g. composition, porosity, permeability, weathered state) for in situ CCMC. Their properties

are likely to be less favourable than those currently studied overseas, but they might nevertheless be suitable for in situ carbon mineralization under similar conditions than those currently investigated. Alternatively, there may

be CO2 injection strategies that are better suited for in situ carbon mineralization in South African basalts.

Figure 41 The distribution of basaltic and andesitic rocks in South Africa.

5.1.6. Industrial alkaline wastes

5.1.6.1. Steel furnace slags

Steel furnace slags are the most studied industrial alkaline wastes for the purpose of CCMC, owing to their high

Ca content and their elevated reactivity. Worldwide the iron and steel industry accounts for 6-7% of the total CO2

emissions (Kim and Worrell, 2002; House and van der Walle, 2007) whilst it generates about 350-million tons of

iron and steel slag per annum (Miklos, 2000). Admittedly, CO2 sequestration in steel slag is unlikely to have a

substantial impact on CO2 emissions on a global scale, but estimates suggest that electric arc (EAF) and basic

oxygen (BOF) furnace slags have the potential to sequester 35-45% and 6-11% of CO2 generated from EAF and BOF furnaces respectively (Lekakh et al., 2008). This would amount to a saving of about 170-million tons of CO2

per annum (Eloneva, 2008). CCMC has therefore the potential to provide substantial CO2 emissions reduction

for individual steel plants, assuming that economically-viable industrial carbonation processes can be developed.


The manufacture of steel generates various wastes in the form of slags; this includes blast furnace slag (BF),

basic oxygen furnace slag (BOF), electric arc furnace slag (EAF), ladle slag, and argon oxygen carbonisation

slag (AOD). Figure 42 illustrates part of the process of steel manufacture and highlights the steps at which the two most important steel furnace slags for CCMC (i.e. BOF and EAF slags) form. South African BF slag is not a

problem since it is already reused. Work on BOF and EAF slags has already started at the Council for

Geoscience (Doucet, 2008, 2009a, 2009b, 2010).

1

2a

2b

11

2a

2b

2a

2b

2a

2b

Figure 42 Schematic representation of the process of steel manufacture (Source: http://www.ec.gc.ca).

The bulk chemical composition of 3 BOF and 1 EAF steel slags from various steel plants in South Africa is

similar to that of equivalent slags generated in other countries (Table 13). The slags are rich in Ca (32-50 wt %

CaO), a result of the addition of limestone as a fluxing agent in the manufacturing process of steel for the removal of undesirable impurities (Huijgen et al., 2005). This compositional characteristic, coupled to their

elevated alkalinity (BOFSA: 11.9-12.4; EAFSA: 11.3), make them suitable candidates for the industrial

sequestration of CO2. The calculated ‘theoretical’ maximum CO2-specific sequestration capacity of the slags is

very high and ranges from 357 to 475 g of CO2/kg of steel slag (Table 14), which is in agreement with published

data (250-509 g of CO2 / kg of slag; Huijgen and Comans, 2005b; Huijgen et al., 2005). However, when the

annual production of these four wastes is taken into account, it is found that only up to 338kt of cumulated CO2

could in principle be sequestered in these four slags per annum, provided that an economically-viable industrial

mineral carbonation process is developed (Doucet, 2009a). This cumulative sequestration volume is estimated

on the basis of fresh slag production in a single year and does not include previously dumped material which can

be measured in millions of tons. Based on the total amount of the four slags which was generated over the last

ten years, an estimated 2,418kt of CO2 could theoretically be sequestered in existing slag dams. Since most Ca

and Mg in steel slag are tied up as silicates or in other poorly-soluble mineral phases (Table 15), it can be

assumed that little Ca or Mg contained in dumped material would have undergone extensive natural carbonation

or other forms of weathering over the last decade, although this assumption would need to be validated or

confirmed.


Table 13 Chemical composition of selected BOF and EAF steel slags generated in and outside South

Africa (Doucet, 2008, 2009a, 2009b).

Concentration (wt. %)

Waste group SiO2 CaO MgO Fetotal MnO P2O5 Al2O3 S

BOF slag

BOFSA1

BOFSA2

BOFSA3

EAF slag

EAFSA

USA*

China*

Japan*

Europe*

Finland*

South Africa

USA*

Japan*

Europe*

Finland*

Sweden*

Canada*

South Africa

10-15

9-15

13.8

12-18

13.9

18.8

16.9

13.9

19.4

19.0

10-17

26.6

34.0

14.6

18.0

40-50

34-48

44.3

42-55

43.6

41.2

49.9

38.1

32.1

38.0

25-40

40.8

47.0

32.8

32.3

5-10

2.5-10

6.4

<3-8

1.4

8.0

7.7

9.4

9.4

6.0

4-15

7.2

6.0

10.0

9.5

15-30

17-27

17.5

14-20

24.1

16.5

17.3

26.9

26.4

15.2

18-29

24.2

25.3

34.2

30.1

5-10

1.5-6

5.3

< 5

2.4

4.3

1.2

3.2

6.8

6.0

< 6

2.3

n.d.

2.5

4.5

1-3

0.9

n.d.

< 2

n.d.

1.3

0.3

1.0

n.d.

n.d.

< 1.5

n.d.

n.d.

0.3

0.6

2

0.9-2.8

1.5

< 3

1.8

3.4

2.0

7.5

8.6

7.0

4-7

8.4

2.3

5.1

5.5

n.d.

0.2

0.07

n.d.

0.09

n.d.

n.d.

n.d.

0.6

0.38

n.d.

0.09

n.d.

0.07

n.d.

n.d. = not disclosed

* data extracted from Fregeau-Wu et al., 1993; Okumura, 1993; Bi and Lin, 1999; Proctor et al., 2000; Motz and Geiesler,

2001; Moosberg-Bustnes, 2004; Teir et al., 2007; Bonenfant et al., 2008; Lekakh et al., 2008.


Table 14 ‘Theoretical’ CO2-specific sequestration capacity of selected steel slags generated in and

outside South Africa (Doucet, 2010).

Waste group CaO

(wt. %)

MgO

(wt. %)

SSCCO2(max)

(g/kg)

ASCCO2(max) (kt/y)

BOF slag

BOFSA1

BOFSA2

BOFSA3

EAF slag

EAFSA

USA*

China*

Japan*

Europe*

Finland*

South Africa

USA*

Japan*

Europe*

Finland*

Sweden*

South Africa

40-50

34-48

44.3

42-55

43.6

41.2

49.9

38.1

32.1

38.0

25-40

40.8

47.0

32.3

5-10

2.5-10

6.4

<3-8

1.4

8.0

7.7

9.4

9.4

6.0

4-15

7.2

6.0

9.5

369-501

294-486

417

<362-518

357

411

475

402

354

364

240-477

399

434

357

n.c.*

n.c.

n.c.

n.c.

n.c.

64

6

217

n.c.

n.c.

n.c.

n.c.

n.c.

51

Cumulated theoretical capacity for the four slags: 338kt CO2 per annum

Cumulated theoretical capacity for the four slags: 2,418kt CO2 for the last decade

* not calculated since the amount of waste generated in these countries was not reported in the published literature

Over the last two years, the author has conceptualized an integrated acid leach and mineral carbonation process

which involves (i) the recovery of valuable iron (Fe) from steel furnace slags (a landfilled waste from the steel

industry) and (ii) the production of carbonated green building aggregates (Figure 43). The volume of valuable Fe

lost at landfill sites per annum amounts to a staggering 240 000 tons of elemental Fe, which represents a loss of

up to 30% of the mined iron ore. Step 1 of the aforementioned integrated process involves an acid leach reaction

(i) which can currently recover up to 90% of Fe from the slags for further steel production and (ii) which

successfully extracts over 95% of the Ca contained in these same slags with minimum energy requirement.

Therefore, this Fe recovery process generates a Ca-rich effluent which represents an excellent source of Ca and

silicon (Si) for the production of green carbonated aggregates via mineral carbonation. This overall integrated

process offers the opportunity to recycle 3 industrial wastes (steel furnace slag, coal-combustion fly ash, and

CO2) into 2 products (steel, and building materials) with commercial value. Work required is the development of

Step 2 of the aforementioned process.


R1

Legend:

R1 Dissolution batch reactorR2 Carbonation batch reactor

Fe Furnace requirements:Fe > 65%

Al2O3 < 1.5%SiO2 < 3.5 %

K2O < 0.25 %Na2O < 0.05 %

P < 0.06 %F Blast or Steel furnace

Re This process will depend onadopted leachant (e.g.

electrodialysis for nitric acid)

Fe-rich BOF & EAFsteel furnace slags

Leachant

Solid-liquid

separator

Concentratedsolid Fe powder

Fe

Pelletization

Ca-rich

Leachate

F

R2

Carbonatedsuspension

Steel

e.g.

Building

industry

Industrial CO2 stream

Solid-liquid

separator

Syntheticcarbonated

aggregates

Leachant

recycling process

Ca-rich solution

Re

pH adjuster (e.g.

Fe-poor furnace steel slags, coal-combustion fly

ash)Effluent

recycling

Existing process

drying

3 sources of industrial wastes used as raw materials:

• Fe-rich BOF & EAF steel furnace slags• Fe-poor steel furnace slags or coal-combustion fly ash

• Industrial CO2 stream

R1

Legend:

R1 Dissolution batch reactorR2 Carbonation batch reactor

Fe Furnace requirements:Fe > 65%

Al2O3 < 1.5%SiO2 < 3.5 %

K2O < 0.25 %Na2O < 0.05 %

P < 0.06 %F Blast or Steel furnace

Re This process will depend onadopted leachant (e.g.

electrodialysis for nitric acid)

Fe-rich BOF & EAFsteel furnace slags

Leachant

Solid-liquid

separator

Concentratedsolid Fe powder

Fe

Pelletization

Ca-rich

Leachate

F

R2

Carbonatedsuspension

Steel

e.g.

Building

industry

Industrial CO2 stream

Solid-liquid

separator

Syntheticcarbonated

aggregates

Leachant

recycling process

Ca-rich solution

Re

pH adjuster (e.g.

Fe-poor furnace steel slags, coal-combustion fly

ash)Effluent

recycling

Existing process

drying

3 sources of industrial wastes used as raw materials:

• Fe-rich BOF & EAF steel furnace slags• Fe-poor steel furnace slags or coal-combustion fly ash

• Industrial CO2 stream Figure 43 Block diagram of conceptualized process: Fe-recovery combined to CO2 sequestration by

indirect mineral carbonation (Doucet, 2010).

5.1.6.2. Phosphogypsum

Phosphogypsum, a by-product chemical gypsum produced in the phosphate fertilizer industry, is produced in

large quantities in South Africa (Motalane and Strydom, 2004). Only a small portion of the overall

phosphogypsum produced is utilized by cement companies, such as LaFarge, as a set retarder in the pace of

natural gypsum. Another small portion is utilized in agriculture to combat alkalinity and salinity in solids that have

a high sodium concentration. The bulk of the phosphogypsums produced is transported to repositories on land

and stacked.

Phosphogypsum contains over 30% CaO, which makes it particularly suitable for CCMC. A possible CCMC

process, which is a variant of the Merseburg process, can be described as follows:

4243244 )()( SONHCaCOCOsaltNHCaSO +⇔++

where NH4 salt can be NH4NO3, NH4OH or NH4Cl.

The average particle size of phosphogypsum particles is low (< 30 µm), which suggests that the above reaction

may not be energy-intensive. In addition, the formed products may have ready markets; ammonium sulphate is a

fertilizer and CaCO3 may have properties suitable for e.g. the paper industry.

No clear estimate of the volumes of phosphogypsum dams is available at the time of writing. It is however known

that Sasol’s Phalaborwa generated ca. 900,000 tons per annum before its closure last year. Based on a content

of 30% CaO (not measured), the maximum theoretical amount of CO2 which could be sequestered in this

phosphogypsum is estimated at 236,000 tons of CO2 per million ton of phosphogypsum generated per annum.


This industrial waste will not sequester significant quantities of CO2 in comparison to annual emissions, but it can

serve a niche market where phosphogypsum causes problems for disposal but could instead sequester some

CO2 and generate useful products.

5.1.6.3. Coal-combustion fly ash

Coal-combustion fly ash (FA) is formed from the non-combustible portion of the coal. Over 36.4 Mt of FA are generated by the electricity production industry in South Africa per annum (Muriithi et al., 2010) with only about

5% of it being utilized while the remaining is disposed in ash dumps (Kruger, 2003). Whilst the quantities

generated are large, this raw material for CCMC suffers from a low CaO (< 10%) and MgO (< 3%) content

(Muriithi et al., 2010; Doucet, unpublished data) which limits the amount of CO2 that can be converted to

carbonates. For instance, the 20-150 µm fraction can sequester up to 71.84 kg of CO2 per ton of FA while the > 150 µm particle can only sequester 36.47 kg of CO2 per ton of FA (Muriithi et al., 2010). Assuming that all the Ca

and Mg of FA undergo carbonation, South African FA offers the potential of sequestering up to 1.9 million tons of

CO2 per annum. This option may however been considered if carbonated fly ash can find a suitable application,

for instance in agriculture. A characteristic of mineral carbonation for wastes such as fly ash is that the process

can help encapsulate harmful elements and thereby prevent their leaching in the natural environment.

5.1.6.4. Industrial brines

CCMC has also the potential of removing hard cations (e.g. Ca, Mg) from both natural (e.g. sea water) and

industrial brines to produce cleaner brines. It is conceivable that CO2-treated brine could then be fed into a

desalination plant where the process could be performed at lower cost than for untreated brines. The volume of

industrial brines currently generated in South Africa was unknown to the author at the time of writing.

5.1.7. Natural brines

During the injection of CO2 in deep saline formations, vast volumes of natural brines are displaced. Depending

on the geological formation, the pressure built-up during injection and displacement will vary. For good

containment to be ensured, the back-pressure exercised by the brine is beneficial. However, too high a back-

pressure could compromise the injectivity. This situation could happen if the formation has a fairly low

permeability or if the injection takes place in a reservoir contained at all sides by dolerites where displacement of the brine is not possible (e.g. the Karoo). In this instance, it is conceivable that the brine may be extracted back

to the surface, subjected to CCMC treatment for the removal of hard cations, following by its feeding into a

desalination plant for the production of freshwater. In addition to facilitate the injection of CO2 in geological

formations, this CCMC process would have the added advantage of producing freshwater in areas which are

often remote from main cities and where only small communities live. Whilst the volume of water generated

through this process is limited when compared to the overall cycle of freshwater in South Africa, it will be

significant for local communities which often suffer from poor infrastructure.


Table 15 Mineralogical composition of selected steel slags generated in South Africa (%)

Ca-containing phases identified Fe-containing phases

identified

Other

Waste

group

Larnite

ß-Ca2SiO4

Brownmillerite

(Mg,Si-exchanged)

Ca2Fe1.4Mg0.3Si0.3O5

Calcite

CaCO3

Lime

CaO

Portlandite

Ca(OH)2

Ca silicate

α- Ca2SiO4

Akermanite

Ca2Mg(Si2O7)

Katoite

Ca3Al2(OH)12

Gypsum

CaSO4.2H2O

Wustite

FeO

Magnetite

Fe3O4

Quartz

Si(OH)2

BOFSA1

BOFSA2

BOFSA3

EAFSA

13.8

44.2

37.8

18.2

14.5

14.2

2.6

14.1

23.4

8.7

-

2.2

5.9

4.5

-

-

3.9

7.3

-

-

-

-

-

2.5

-

-

2.6

18.7

-

-

11.8

-

-

-

4.2

-

24.3

16.6

35.5

38.3

4.2

4.4

5.6

6.0

10.1

0.2

-

-

- 72 -

5.2. South African studies

Institutions which are currently active in the field of CCMC include:

1) Council for Geoscience (CGS)

The author of this report is leading a R&D programme on CCMC which focuses on both technology

development and capacity building. Existing collaborations include the University of Pretoria (Dr Liezel van

der Merwe (Chemistry) and Prof Wlady Altermann (Geology)), The University of The Western Cape (Dr

Leslie Petrik, Chemistry), Vaal University of Technology (Prof Bobby Naiddo, Chemistry) and the CSIR (Ms

Marinda de Beer, senior scientist and PhD student), and he has regular contact with prominent international

experts in the field. Past and current students in CCMC include projects towards BHon (x1), MSc (x3) and

PhD (x3). He was the external examiner for Ms Grace Muriithi who completed an MSc on CCMC at The

University of Western Cape. He has also a strong networking relationship with the Departments of Geology

(Prof David Reid) and Chemical Engineering (Dr Jennifer Broadhurst) of the University of Cape Town and he

organized a mini-symposium on CCMC between CGS and UCT on 16 February 2010.

2) University of The Western Cape (UWC)

Dr Leslie Petrik supervised Ms Grace Muriithi on an MSc project on the mineral carbonation of fly ash and

brines. Dr Leslie Petrik and Dr Doucet (CGS) are now her PhD supervisor.

3) University of Cape Town (UCT)

Prof David Reid (Geology) and Dr Jennifer Broadhurst (Chemical Engineering) are interested in the

carbonation of PGE mine tailings and have an MSc student who is quantifying the volume of CO2 that could

theoretically be sequestered in the Merensky, Platreef and UG2 tailings.

4) Vaal University of Technology (VUT)

Dr Doucet (CGS) has one MTech student employed at the CGS who is registered at VUT.

5) CSIR

Ms Marinda de Beer is a senior scientist at the CSIR and approached Dr Doucet (CGS) to be her PhD

supervisor on a project aimed at production Precipitated Calcium Carbonate (PCC) via CCMC of industrial

wastes.

6) University of The Witswatsrand

Prof Nicola Wagner has currently an MSc project by teaching which involves a brief research component on

the reaction of CO2 with fly ash. The project is not strictly speaking on CCMC but includes some elements of

it.

5.3. Possible applications and markets in South Africa

Potentially available markets for CCMC include:

o Minerals and mining industry: recovery of high-value residual metals (e.g. Fe, Co, Ni, rare-earths,

precious metals, diamond); on-site clean electricity

o High-purity silica; bicarbonate chemicals

o Precipitated Calcium Carbonate (PCC; global market: 13Mt pa) and Ground Calcium Carbonate (GCC; ca. 65Mt pa)

o Remediation value from carbonation of landfill wastes, mine tailings and hazardous wastes

o Construction aggregates

- 73 -

o Cementitious phase carbonates to substitute Portland and pozzolanic cements

o Construction sector: low-embodied carbon building materials

o CO2 credits from displaced quarrying and cement processes

6. CONCLUSIONS

Thanks to its harmless end-products, CCMC has met with relatively wide public acceptance and should be

pursued as a complementary storage option. In addition to optimising the process parameters for the most

promising processes, further technical development should rapidly switch to a demonstration of the proof-of-

concept to permit a sound evaluation of the processes. This should include an energy balance incorporating any

preceding energy-intensive process steps, such as the milling of the mineral resources. An energy balance is

crucial to establishing the eligibility of CCMC as a storage option. In the context of South Africa, a promising

opportunity is to evaluate the use of mine tailings from the PGM and diamond industries, where pre-treatment via

milling is not required.

To make an informed choice between various CCMC processes, it is essential to have an objective,

commensurate life-cycle assessment (LCA) which takes into account all the activating and succeeding steps to

CCMC. This requires valid data, which for many processes do not exist for the types of resources available in

South Africa. Comparability of the assessments necessitates the precise determination of the system boundaries

of all the technological options, reflecting the variation in time horizons for CO2 storage.

Development and deployment of CCMC will require the combination of experts from necessary core disciplines,

including chemical process engineers, chemists, material scientists, geologists, environmental coordinators from relevant mining sectors (e.g. diamond, PGM, chromium), power plant personnel, building materials and

aggregates experts.

SUGGESTIONS FOR FURTHER STUDY:

1) Detailed evaluation and mapping of suitable mineral deposits for CCMC and correlating with past, current

and future mining activities, combined with theoretical estimates of their total CO2 storage capacity for each mining sector (e.g. PGM, diamond, Cr2O3, P2O5, asbestos).

2) Preliminary testing of reactivity of mine tailings using most promising CCMC processes (i.e. ARC process,

ǺA process route, CO2 Energy Reactor©, Chemical and biological catalytic enhancement; any commercial

process we can access (e.g. Calera)) for comparison purposes. This could include rate and extent of

carbonation, energy and mass balances, and analysis of formed products. Opportunities for recovery of high-value residual metals (e.g. Fe, Co, Ni, rare-earths, precious metals, diamond) should also be assessed.

The findings would provide a good foundation to select the most promising process which requires

optimization for each mine tailings.

3) Life Cycle Analysis applied to findings from 2)

4) Detailed evaluation and mapping of South African basaltic and andesitic rocks to assess their suitability for

in situ carbon mineralization.

5) Assessment of each small-scale commercial process (e.g. Calera, Cambridge Carbon Capture) regarding

their possible integration to South African plants from different sectors (e.g. power generation, cement

manufacture, steel manufacture, mining, petrochemical etc).

- 74 -

6) Fast-tracking of Fe recovery from and CCMC of steel furnace slags to reach pilot scale experiment within

three years.

7) Assessment of industrial alkaline wastes (coal-combustion fly ash, phosphogypsum, industrial brines) for

CCMC; this should include the elemental and mineralogical characterization of the wastes and estimates of

their total CO2 storage capacity for each industrial sector, and preliminary testing of their reactivity using

most promising CCMC processes.

8) Assessment of the potential for CCMC to be applied to the pre-treatment of extracted displaced natural

brines from deep saline reservoirs to the surface prior to desalination for the production of freshwater.

9) Desktop study of the South African markets for building materials and aggregates.

This R&D endeavour would preferably require the creation of a working team for each main raw material [e.g. (1)

PGM mine tailings, (2) Diamond mine tailings, (3) Asbestos mine tailings, (4) Cr2O3 and P2O5 mine tailings, (5)

industrial alkaline wastes (steel slags, phosphogypsum, fly ash, brines). The working teams would need to liaise

on a regular basis to share knowledge and experiences, and should include chemists, chemical and process

engineers, material scientists, geologists, and representatives from the relevant industrial sectors.

REFERENCES

1. Alexander G., Maroto-Valer M.M., Gafarova-Aksoy P. (2007) Evaluation of reaction variables in the

dissolution of serpentine for mineral carbonation. Fuel 86, 273-281.

2. Alfredsson H.A., Hardarson B.S., Franzson H., Gislason S.R. (2008) CO2 sequestration in basaltic rock at

the Hellisheidi site in SW Iceland: stratigraphy and chemical composition of the rocks at the injection site.

Mineral Mag 72, 1-5.

3. Andreani M., Luquot L., Gouze P., Godard M., Hoise E., Gibert B. (2009) Experimental study of carbon sequestration reactions controlled by the percolation of CO2-rich brine through peridotites. Environmental

Science & Technology 43, 1226-1231.

4. Assayag N., Matter J., Ader M., Goldberg D., Agrinier P. (2009) Water-rock interactions during a CO2 injection field-test: Implications on host rock dissolution and alteration effects. Chemical Geology 265, 227-

235.

5. Baciocchi R., Costa G., Marini C., Polettini A., Pomi R., Postorino P., Rocca S. (2008) Accelerated carbonation of RDF incineration bottom ash: CO2 storage potential and environmental behaviour. 2

nd

International Conference on Accelerated Carbonation for Environmental and Materials Engineering, Rome,

Italy, pp 201.210.

6. Baciocchi R., Costa G., Polettini A., Pomi R., Prigiobbe V. (2009a) Comparison of different reaction routes for carbonation of APC residues. Energy Procedia 1, 4851-4858.

7. Baciocchi R., Costa G., Polettini A., Pomi R. (2009b) Influence of particle size on the carbonation of

stainless steel slag for CO2 storage. Energy Procedia 1, 4859-4866.

8. Baciocchi R., Costa G., Di Bartolomeo E., Polettini A., Pomi R. (2010a) Comparison of different process

routes for stainless steel slag carbonation.

9. Baciocchi R., Costa G., Polettini A., Pomi R. (2010b) The influence of carbonation on major and trace

elements leaching from various types of stainless steel slag. 3rd

International Conference on Accelerated

Carbonation for Environmental and Materials Engineering, Turku, Finland, pp 215-226.

10. Baciocchi R., Costa G., Lombardi L., Verginelli I., Zingaretti D. (2010) Storage of carbon dioxide captured in

a pilot-scale biogas upgrading plant by accelerated carbonation of industrial residues. 3rd

International

- 75 -

Conference on Accelerated Carbonation for Environmental and Materials Engineering, Turku, Finland, pp

247-256.

11. Back M., Kuehn M., Stanjek H., Peiffer S. (2008) Reactivity of alkaline lignite fly ashes towards CO2 in water. Environmental Science & Technology 42, 4520-4526. 3

rd International Conference on Accelerated


12. Balaz P., Turianicova E., Fabian M., Kleiv R.A., Briancin J., Obut A. (2008) Structural changes in olivine (Mg,Fe)2SiO4 mechanically activated in high-energy mills. International Journal of Mineral Processing 88, 1-

6.

13. Baldyga J., Henczka M., Sokolnicka K. (2010) Utilization of carbon dioxide by chemically accelerated mineral carbonation. Materials Letters 64, 702-704.

14. Balucan R.D., Kennedy E.M., Mackie J.M., Dlugogorski B.Z. (2010) An optimized antigorite heat pre-treatment strategy for CO2 sequestration by mineral carbonation. 3

rd International Conference on

Accelerated Carbonation for Environmental and Materials Engineering, Turku, Finland, pp 53-62.

15. Bao W., Li H., Zhang Y. (2010) Selective leaching of steelmaking slag for indirect CO2 mineral sequestration. Industrial & Engineering Chemistry Research 49, 2055-2063.

16. Bauer M., Hopf N., Hofstetter E., Peiffer S. (2010) CO2 sequestration by alkaline waste in a wet scrubbing system: The Alcatrap pilot plant. 3rd

International Conference on Accelerated Carbonation for Environmental

and Materials Engineering, Turku, Finland, pp 313.

17. Beaudoin G., Hebert R., Constantin M., Duchesne J., Cecchi E., Huot F., Vigneau S. (2008) Spontaneous

carbonation of serpentine in milling and mining waste, southern Quebec and Italy. 2nd

International

Conference on Accelerated Carbonation for Environmental and Materials Engineering, Rome, Italy, pp 73-

82.

18. Berner R.A., Lasaga A.C., Garrels R.M. (1983) The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years. American Journal of Science 283, 641-683.

19. Bi L., Lin H. (1999) The comprehensive utilization of steel slag. Conservation and Utilization of Mineral

Resources, 1999, 3, 51-54.

20. Björklöf T. (2010) An energy efficiency study of carbon dioxide mineralization. MSc thesis, Ǻbo Akademi

University, Finland. 21. Boerrigter H. (2009) A process for preparing an activated mineral. Shell Internationale Research

Maatschappij B.V.

22. Bonenfant D., Kharoune L., Sauve S., Hausler R., Niquette P., Mimeault M., Kharoune M. (2008) CO2 sequestration potential of steel slags at ambient pressure and temperature. Industrial & Engineering

Chemistry Research 47, 7610-7616.

23. Bonfils B., Julcour C., Bourgeois F., Guyot F., Chiquet P. (2010) About the foundations of direct aqueous carbonation with dissolution enhancing organic salts. 3



24. Boschi C., Dini A., Dallai L., Gianelli G., Ruggieri G. (2008) Mineralogical sequestration of carbon dioxide: new insights from the malentrata magnesite deposit (Tuscany, Italy). 2

nd International Conference on

Accelerated Carbonation for Environmental and Materials Engineering, Rome, Italy, pp 55-62.

25. Boschi C., Dini A., Dallai L., Ruggieri G., Gianelli G. (2009) Enhanced CO2 mineral sequestration by cyclic

hydraulic fracturing and Si-rich infiltration into serpentinites at Malentrata (Tuscany, Italy). Chemical Geology

265, 209-226.

26. Brent G.F. (2008) Integrated chemical process. Orica Explosives Technology Pty Ltd.

27. Bulk Solids Handling http://www.bulk-solids-handling.com, China Huaneng, Peabody and Calera to Pursue

Clean Coal Project, 24 January 2011.

- 76 -

28. Calera Corporation (2009) Sequestering CO2 in the built environment. Slide presentations, 14th May 2009.

29. Clarens F., Grandia F., Meca S., Duro L., de Pablo J. (2010) Determination of CO2 sequestration capacity and stabilisation of MSWI fly ash through accelerated carbonation. 3



30. ClimateWire.net, 13 August 2010.

31. Cloete M. (2010) Atlas on Geological Storage of Carbon Dioxide in South Africa. Council for Geoscience.

32. Dalwai I., Smith C.L. (2009) Sequestration of CO2 by means of carbonation of mineral industrial tailings. 4th

Year Chemical Engineering dissertation, University of Cape Town, South Africa, pp.47.

33. Daval D., Martinez I., Corvisier J., Findling N., Goffe B., Guyot F. (2009a) Carbonation of Ca-bearing silicates, the case of wollastonite: Experimental investigations and kinetic modelling. Chemical Geology 265,

63-78.

34. Daval D., Martinez I., Guigner J.M., Hellmann R., Corvisier J., Findling N., Dominici C., Goffe B., Guyot F.

(2009) Mechanism of wollastonite carbonation deduced from micro- to nanometre length scale observations. American Mineralogist 94, 1707-1726.

35. Diener S., Andreas L., Brannvall E. (2010) Leaching properties of steel slags after ageing under laboratory

and field conditions. 3rd

International Conference on Accelerated Carbonation for Environmental and

Materials Engineering, Turku, Finland, pp 237-245.

36. Dipple G.M., Wilson S.A., Power I.M., Thom J.M., Raudsepp M., Southam G. (2008) Passive mineral carbonation in mine tailings. 2nd


Materials Engineering, Rome, Italy, pp 119-122.

37. Doria L.R. (2005) Belvidere asbestos mine: mine suitability for CO2 sequestration through mineral

carbonation. BHon thesis, Department of Geology, Middleburg College, USA, pp.60.

38. Doucet F.J. (2008) Carbon dioxide sequestration by industrial mineral carbonation: Evaluation of industrial

alkaline waste materials and their leachates – A South African perspective. Progress Report No 2008-0039,

Council for Geoscience, pp.39.

39. Doucet F.J. (2009a) Effective CO2-specific sequestration capacity of steel slags and variability in their

leaching behaviour in view of industrial mineral carbonation. Minerals Engineering 23, 262-269.

40. Doucet F.J. (2009b) Carbon dioxide sequestration by industrial mineral carbonation: Evaluation of industrial

alkaline waste materials and their leachates – A South African perspective. Progress Report No 2009-0044,

Council for Geoscience, pp.35.

41. Doucet F.J. (2010) Development and optimization of steel slag reprocessing technologies with implications

for the steel and cement manufacturing sectors and for long-term CO2 sequestration. Progress Report No

2010-0037, Council for Geoscience, pp.36.

42. Doucet F.J. (2011) Carbonate mineralization technologies: A for-profit approach to CO2 management. In:

Carbon Mitigation. Nova Science Publishers, Inc., New-York, USA (in preparation).

43. Dufaud F., Martinez I., Shilobreeva S. (2009) Experimental study of Mg-rich silicates carbonation at 400 and

500ºC and 1 kbar. Chemical Geology 265, 79-87.

44. Dunsmore H.E. (1992) A geological perspective on global warming and the possibility of carbon dioxide removal as calcium carbonate mineral. Energy Conversion and Management 33, 565-572.

45. Eloneva S. (2008) Co-utilisation of CO2 and steelmaking slags for precipitated calcium carbonate production,

Lic. Tech. thesis, Helsinki Univ. of Technology, Finland.

46. Eloneva S. Teir S., Salminen J., Fogelholm C.J., Zevenhoven R. (2008a) Fixation of CO2 by carbonating calcium derived from blast furnace slag. Energy 33, 1461-1467.

47. Eloneva S., Teir S., Salminen J., Revitzer H., Kontu K., Forsman A.M., Zevenhoven R., Fogelholm C.J. (2008b) Pure calcium carbonate product from the carbonation of a steelmaking slag. 2

nd International

- 77 -

Conference on Accelerated Carbonation for Environmental and Materials Engineering, Rome, Italy, pp 239-

248.

48. Eloneva S., Said A., Mannisto P., Fogelholm C.J., Zevenhoven R. (2010) Ammonium salt based steelmaking slag carbonation: precipitation of CaCO3. 3

rd International Conference on Accelerated Carbonation for

Environmental and Materials Engineering, Turku, Finland, pp 169-178.

49. Engelbrecht A., Golding A., Hietkamp S., Scholes B. (2004) The potential for sequestration of carbon dioxide

in South Africa. DME report 86DD/HT339, pp.54.

50. Evans S.M., Vlasopoulos D.N. (2010) Novacem: Carbon negative cement and the Green Cement Bond.

Presented at CSI Forum 2010, Varsaw, 14 September.

51. Fabian M., Shopska M., Paneva D., Kadinov G., Kostova N., Turianicova E., Briancin J., Mitov I., Kleiv R.A.,

Balaz P. (2010) The influence of attrition milling on carbon dioxide sequestration on magnesium-iron silicate. Minerals Engineering in press.

52. Fagerlund J., Teir S., Nduagu E., Zevenhoven R. (2009) Carbonation of magnesium silicate mineral using a pressurised gas/solid process. Energy Procedia 1, 4907-4914.

53. Fagerlund J., Nduagu E., Romão I., Zevenhoven R. (2010) A stepwise process for carbon dioxide

sequestration using magnesium silicates. Frontier in Chemical Engineering China 4, 133-141.

54. Fregeau-Wu E., Pignolet-Brandom S., Iwasaki I. (1993) Liberation analysis of slow-cooled steelmaking slags: implications for phosphorus removal. In: Proceedings of the 1

st International Conference on

Processing Materials for Properties. Minerals, Metals & Materials Society (TMS), pp. 153-156.

55. Gerdemann S.J., Dahlin D.C., O’Connor W.K., Penner L.R. (2003) Carbon dioxide sequestration by aqueous mineral carbonation of magnesium silicate minerals. DOE/ARC report 2003-018.

56. Gislason S.R., Wolff-Boenish D., Stefansson A., Oelkers E.H., Gunnlaugsson E., Sigurdardottir H.,

Sigfusson B., Broecker W.S., Matter J.M., Stute M., Axelsson G., Fridriksson T. (2010) Mineral sequestration of carbon dioxide in basalt: A pre-injection overview of the CarbFix project. International Journal of

Greenhouse Gas Control 4, 537-545.

57. Goldberg D.S., Kent D.V., Olsen P.E. (2010) Potential on-shore and off-shore reservoirs for CO2

sequestration in Central Atlantic magmatic province basalts. Proceedings of the National Academy of

Sciences 107, 1327-1332.

58. Grandia F., Meca S., Duro L., Clarens F., de Pablo J. (2010) Stabilization of cement kiln dust through

accelerated carbonation. 3rd



59. Ghoorah M., Balucan R.D., Kennedy E.M., Dlugogorski B.Z. (2010) Selection of acid for weak acid processing of Australian wollastonite for mineralization of CO2. 3



60. Gunning P.J., Hills C.D., Carey P.J. (2008) Production of lightweight aggregate from industrial waste and carbon dioxide. 2nd

International Conference on Accelerated Carbonation for Environmental and Materials

Engineering, Rome, Italy, pp 291-298.

61. Gunning P.J., Hills C.D., Carey P.J. (2010) Accelerated carbonation treatment of industrial wastes. Waste

Management 30, 1081-1090.

62. Haug T.A., Kleiv R.A., Munz I.A. (2008) Importance of particle size, specific surface area and crystallinity of

mechanically activated olivine for HCl dissolution. 2nd International Conference on Accelerated Carbonation

for Environmental and Materials Engineering, Rome, Italy, pp 83-92.

63. Haug T.A., Johansen H., Brandvoll O. (2010) The way forward for mineral carbonation – importance of

collaboration, experiments and modelling. 3rd

International Conference on Accelerated Carbonation for


- 78 -

64. Hitch M., Ballantyne S.M., Hindle S.R. (2010) Revaluing mine waste rock for carbon capture and storage.

International Journal of Mining, Reclamation and Environment 24, 64-79.

65. House M., van der Walle R. (2007) Is the steel industry the leading producer of CO2 emissions? Iron & Steel

Today, September/October, 14-15.

66. House, M. and van der Walle, R., Is the steel industry the leading producer of CO2 emissions? Iron & Steel

Today September/October, 2007, 14-15

67. Huijgen W.J.J., Comans, R. N. J. (2003) Carbon dioxide sequestration by mineral carbonation: Literature

review. ECN report ECN-C-03-016, Energy Research Centre of the Netherlands, pp. 52.

68. Huijgen W.J.J., Witkamp G.J., Comans R.N.J. (2004) Mineral CO2 sequestration in alkaline solid residues. Proceedings of the 7

th International Conference on Greenhouse Gas Control Technologies (GHGT-7),

Vancouver BC, Canada, 2415-2418.

69. Huijgen W. J. J., Comans, R. N. J. (2005a) Carbon dioxide sequestration by mineral carbonation: Literature

review update 2003-2004. ECN report ECN-C-05-022, Energy Research Centre of the Netherlands, pp. 37.

70. Huijgen W. J. J., Comans, R. N. J. (2005b) Mineral CO2 sequestration by carbonation of industrial residues:

Literature review and selection of residue. ECN report ECN-C-05-074, Energy Research Centre of the

Netherlands, pp.32.

71. Huijgen W.J.J., Witkamp G.J., Comans R.N.J. (2005) Mineral CO2 sequestration by steel slag carbonation. Environmental Science & Technology 39, 9676-9682.

72. Huitzinger D.N., Gierke J.S., Sutter L.L., Kawatra S.K., Eisele T.C. (2009) Mineral carbonation for carbon

sequestration in cement kiln dust from waste piles. Journal of Hazardous Materials 168, 31-37.

73. Infomine (2007) Mining intelligence & Technology/Mine sites,

http://www.infomine.com/minesite/minesiteall.asp.

74. IPPC (2005) IPCC special report on carbon dioxide capture and storage. Prepared by Working Group III of

the Intergovernmental Panel on Climate Change [Metz B., Davidson O., de Coninck H.C., Loos M., Meyer

L.A. (eds.)], Cambridge University Press. Cambridge, United Kingdom and New York, NY, USA.

75. Jamtveit B., Putnis C.V., Malthe-Sorenssen A. (2009) Reaction induced fracturing during replacement

processes. Contributions to Mineralogy and Petrology 157, 127-133.

76. Jarvis K., Carpenter R.W., Windman T., Youngchul K., Nunez R., Alawneh F. (2009) Reaction mechanisms for enhancing mineral sequestration of CO2. Environmental Science and Technology 43, 6314-6319.

77. Kawatra S.K., Eisele T.C., Simmons J.J. (2009) Capture and sequestration of carbon dioxide in flue gases,

Michigan Technological University. 78. Kelemen P.B., Matter J.R. (2008) In situ carbonation of peridotite for CO2 storage. Proceedings of the

National Academy of Sciences 105, 17295-17300.

79. Kim Y., Worrell E. (2002) International comparison of CO2 emission trends in the iron and steel industry. Energy Policy 30, 827-838.

80. Kirkland J. (2011) Peabody-Calera partnership could bring U.S. ‘Green Cement’ to China. The New York

Times, 21 January 2011.

81. Kodama S., Nishimoto T., Yamamoto N., Yogo K., Yamada K. (2008) Development of a new pH-swing CO2 mineralization process with a recyclable reaction solution. Energy 33, 776-784.

82. Kolstad C., Young D. (2010) Cost analysis of carbon capture and storage for the Latrobe Balley. Bren

School of Environmental Science and Management, University of California, Santa Barbara, USA, pp.35.

83. Koukouzas N., Gemeni V., Ziock H.J. (2009) Sequestration of CO2 in magnesium silicates in Western Macedonia, Greece. International Journal of Mineral Processing 93, 179-186.

84. Krevor S.C., Lackner K.S. (2009) Enhancing process kinetics for mineral carbon sequestration. Energy

Procedia 1, 4867-4871.

- 79 -

85. Kruger R.A. (2003) Fuel 76, 2537.

86. Kuusik R., Uibu M., Velts O., Trikkel A., Kallas J. (2010) CO2 trapping from flue gases by oil shale ash aqueous suspension: intensification and modeling of the process. 3



87. Kwak J.H., Hu J.Z., Hoyt D.W., Sears J.A., Wang C. Rosso K.M., Felmy A.R. (2010) Metal carbonation of

forsterite in supercritical CO2 and H2O using solid state 29Si, 13C NMR spectroscopy. The Journal of Physical

Chemistry C 114, 4126-4134.

88. Lackner K.S., Wendt C.H., Butt D.P., Edward L., Joyce J., Sharp D.H. (1995) Carbon dioxide disposal in

carbonate minerals. Energy 20, 1153-1170.

89. Lackner K.S., Butt D.P., Wendt C.H., Ziock H.J. (1998) Mineral carbonates as carbon dioxide sinks. Proceedings of the Advanced Coal-Based Power and Environmental Systems conference, Morhantown,

USA, July 21-23.

90. Lackner K.S. (2002) Carbonate chemistry for sequestering fossil carbon. Annual Review of Energy and The

Environment 27, 193-232.

91. Larachi F., Dardoul I. Beaudoin G. (2010) Fixation of CO2 by chrysotile in low-pressure dry and moist

carbonation: Ex-situ and in-situ characterizations. Geochimica et Cosmochimica Acta, DOI

S0016/j.gca.2010.03.007.

92. Lekakh S.N., Rawlins C.H., Robertson D.G.C., Richards V.L., Peaslee K.D. (2008) Kinetics of aqueous leaching and carbonization of steelmaking slag. Metallurgical and Materials Transactions B, 39B, 125-134.

93. Li P.C., Huang C.W., Hsiao C.T., Teng H. (2008) Magnesium hydroxide extracted from a magnesium-rich mineral for CO2 sequestration in a gas to solid system. Environmental Science & Technology 42, 2748-2752.

94. Li W., Li W., Li B., Bai Z. (2009) Electrolysis and heat pretreatment methods to promote CO2 sequestration

by mineral carbonation. Chemical Engineering Research and Design 87, 210-215.

95. Liu Z., Zhao J. (1999) Contribution of carbonate rock weathering to the atmospheric CO2 sink. Environmental

Geology 39, 1053-1058.

96. Machenbach I., Brandvoll O., Wihle J., Munz I.A., Johansen H. (2008) Development of an industrial process

concept for CO2 sequestration by mineral carbonation. 2nd

International Conference on Accelerated

Carbonation for Environmental and Materials Engineering, Rome, Italy, pp 459-461.

97. Mannesmann A.G. (1995) VerTech – Ein neues, umweltverträgliches und wirtschaftliches. Presentation

material, Düsseldorf, pp.17 (as cited in Giese L.B., Baba A., Pegdeger A. (2006) Thermal treatment of

wastewater from cheese production in Turkey. In: Wasterwater Reuse – Risk Assessment, Decision-Making

and Environmental Security (Ed: M.K. Zaidi), Springer, pp.348-355).

98. Matter J.M., Kelemen P.B. (2009) Permanent storage of carbon dioxide in geological reservoirs by mineral

carbonation. Nature Geoscience 2, 837-841.

99. Matter J.M., Broecker W.S., Stute M., Gislason S.R., Oelkers E.H., Stefansson A., Wolff-Boenisch D.,

Gunnlaugsson E., Axelsson G., Bjornsson G. (2009) Permanent carbon dioxide storage into basalt: The

CarbFix pilot project, Iceland. Energy Procedia 1, 3641-3646.

100. Mazumder D., Dikshit A.K. (2002) Applications of the deep-shaft activated sludge process in wastewater treatment. International Journal of Environmental Pollution 17, 266-272.

101. McGrail B.P., Schaef H.T., Ho A.M., Chien Y.J., Dooley J.J., Davidson C.L. (2006) Potential for carbon

dioxide sequestration in flood basalts. Journal of Geophysical Research 111, B12201.

102. Meima J.A., van der Weijden R.D., Eighmy T.T., Comans R.N.J. (2002) Carbonation processes in

municipal solid waste incinerator bottom ash and their effect on the leaching of copper and molybdenum.

Applied Geochemistry 17, 1503-1513.

- 80 -

103. Miklos P. (2000) The utilization of electric arc furnace slags in Denmark. In Proceedings of 2nd

European

Slag Conference. Düsseldorf, 2000.

104. MIT (2007) The future of coal.

105. Mlambo T.K., Doucet F.J., Van der Merwe E.M., Altermann W. (2010) The application of mineral

carbonation engineering principles to geological CO2 sequestration: A conceptual approach to improved

reservoir integrity. 3rd International Conference on Accelerated Carbonation for Environmental and Materials

Engineering, Turku, Finland, pp 131-137.

106. Montes-Hernandez G., Perez-Lopez R., Renard F., Nieto J.M., Charlet L. (2009) Mineral sequestration

of CO2 by aqueous carbonation of coal combustion fly-ash. Journal of Hazardous Materials 161, 1347-1354.

107. Moosberg-Bustnes H. (2004) Steel slag as filler material in concrete. In Proceedings of the VII

International Conference on Molten Slags Fluxes and Salts. The South African Institute of Mining and

Metallurgy.

108. Motalane M.P., Strydom C.A. (2004) Potential groundwater contamination by fluoride from two South African phosphogypsums. Water SA 30, 465-468.

109. Motz H., Motz, J., Geiesler, J. (2001) Products of steel slags an opportunity to save natural resources.

Waste Management 21, 285-293.

110. Munz I.A., Kihle J., Brandvoll O., Machenbach I., Carey J.W., Haug T.A., Johansen H., Eldrup N. (2009) A continuous process manufacture of magnesite and silica from olivine, CO2 and H2O. Energy Procedia 1,

4891-4898.

111. Muriithi G.N., Gitari M.W., Petrik L.F. (2009) Brine remediation using fly ash and accelerated carbonation. Abstracts of the International Mine Water Conference, Pretoria, South Africa, 19th – 23rd

October 2009, pp 671-679.

112. Muriithi G., Petrik L., Gitari W., Doucet F.J. (2010) Mineral carbonation of a fly ash / brine system. 3rd

International Conference on Accelerated Carbonation for Environmental and Materials Engineering, Turku,

Finland, pp 341-344.

113. Muriithi G.N., Gitari M.W., Petrik L.F., Ndungu P.G. (2011) Carbonation of brine impacted fractionated

coal fly ash: Implications for CO2 sequestration. Journal of Environmental Management 92, 655-664.

114. Murray C.N., Wilson T.R.S. (1997) Marine carbonate formations – their role in mediating long-term ocean-atmosphere carbon dioxide fluxes – a review. Energy Conversion and Management 38, S287-S294.

115. Nasir S., Al Sayigh A.R., Al Harthy A., Al-Khirbash S., Al-Jaaidi O., Musllam A., Al-Mishwat A., Al-

Bu’saidi S. (2007) Mineralogical and geochemical characterization of listwaenite from the Seail ophiolite, Oman. Chemie Der Erde Geochem. 67, 213-228.

116. Nduagu E. (2008) Mineral carbonation: preparation of magnesium hydroxide [Mg(OH)2] from serpentinite

rock. MSc thesis, Ǻbo Akademi University, Finland.

117. Nduagu E., Zevenhoven R. (2010) Production of magnesium hydroxide from magnesium silicate for the purpose of CO2 mineralisation or increasing ocean alkalinity: Effect of reaction parameters. 3rd

International


31-40.

118. Nienczewski J.R., Alves S.M.S., Costa G.S., Amaral L.C., Dullius J.E.L., Ligabue R.A., Ketzer J.M.,

Einloft S. (2008a) Improving the extraction of calcium and magnesium oxides of the steel slag aiming

carbonates for mitigation of climate change. 2nd


Environmental and Materials Engineering, Rome, Italy, pp 249-256.

119. Nienczewski J.R., Alves S.M.S., Costa G.S., Amaral L.C., Dullius J.E.L., Ligabue R.A., Ketzer J.M.,

Einloft S. (2008b) Analysis of the influence of the size of carbon steel slag particle on the carbonation

- 81 -

reaction. 2nd

International Conference on Accelerated Carbonation for Environmental and Materials


120. Northam, Northam F2010, www.northam.co.za

121. O’Connor W.K., Dahlin D.C., Turner P.C., Walters R. (1999) Carbon dioxide sequestration by ex-situ mineral carbonation. Proceedings of the Second Annual Dixy Lee Ray Memorial Symposium, American

Society of Mechanical Engineers, Washington D.C., August 29-September 2.

122. O’Connor W.K., Dahlin D.C., Nilsen D.C., Walters R.P., Turner P.C. (2000) Carbon dioxide sequestration by direct mineral carbonation with carbonic acid. Proceedings of the 25

th International

Technical Conference on Coal Utilization and Fuel Systems, Clearwater, F.L., Coal Technology Association,

March 6-9.

123. O’Connor W.K., Rush G.E., Dahlin D.C. (2003) Laboratory studies on the carbonation potential of basalt: applications to geological sequestration of CO2 in the Columbia River Basalt Group. AAPG Annual Meeting

Expanded Abstracts 12, 129-130.

124. O’Connor W.K., Rush G.E. (2005) Applications of mineral carbonation to geological sequestration of

CO2. DOE/ARC, Report number 2005-010.

125. Oelkers E.H., Gislason S.R., Matter J. (2008) Mineral carbonation of CO2. Elements 4, 331-335.

126. Okumura H. (1993) Recycling of iron- and steelmaking slags in Japan. In Proceedings of the 1st

International Conference on Processing Materials for Properties, Minerals, Metals & Materials Society

(TMS), pp. 803-806.

127. Park A.H.A., Fan L.S. (2004) CO2 mineral sequestration: physically activated dissolution of serpentine and pH swing process. Chemical Engineering Science 59, 5241-5247.

128. Park A.H.A. (2010) Microbial and chemical enhancement of carbon mineralization. Proceedings of the

3rd International Conference on Accelerated Carbonation for Enviromental and Materials Engineering.

129. Perez-Lopez R., Montes-Hernandez G., Nieto J.M., Renard F., Charlet L. (2008) Carbonation of alkaline paper mill waste to reduce CO2 greehouse gas emissions into the atmosphere. Applied Geochemistry 23,

2292-2300.

130. Picot J.C., Cassard D., Maldan F., Greffié C., Bodénan F. (2010) Worldwide potential for ex-situ mineral

carbonation. (Carmex project), in GHGT-10 – 10th International Conference on Greenhouse Gas Control

Technologies, Amsterdam, The Netherlands, 19-23 September.

131. Power I.M., Wilson S.A., Thom J.M., Dipple G.M., Gabites J.E., Southam G. (2009) The hydromagnesite playas of Atlin, British Columbia, Canada: A biogeochemical model for CO2 sequestration. Environmental

Science & Technology 44, 456-462.

132. Power I.M., Dipple G.M., Southam G. (2010) Bioleaching of ultramafic tailings by Acidithiobacillus spp.

for CO2 sequestration. Chemical Geology 260, 286-300.

133. Priestnall M. (2010) Carbon capture & storage – CO2 mineralisation via fuel cells. Presented at

Cleanpower 2010.

134. Prigiobbe V., Costa G., Baciocchi R., Hanchen M., Mazzotti M. (2009a) The effect of CO2 and salinity on olivine dissolution kinetics at 120°C. Chemical Engineering Science 64, 3510-3515.

135. Prigiobbe V., Hanchen M., Costa G., Baciocchi R., Mazzotti M. (2009b) Analysis of the effect of temperature, pH, CO2 pressure and salinity on the olivine dissolution kinetics. Energy Procedia 1, 4881-

4884.

136. Prigiobbe V., Hanchen M., Werner M., Baciocchi R., Mazzotti M. (2009c) Mineral carbonation process for CO2 sequestration. Energy Procedia 1, 4885-4890.

137. Prigiobbe V., Polettini A., Baciocchi R. (2009d) Gas-solid carbonation kinetics of air pollution control residues for CO2 storage. Chemical Engineering Journal 148, 270-278.

- 82 -

138. Proctor D.M., Fehling K.A., Shay E.C., Wittenborn J.L., Green J.J., Avent C., Bigham R.D., Connolly M.,

Lee B., Shepker T.O., Zak M.A. (2000) Physical and chemical characteristics of blast furnace, basic oxygen furnace and electric arc furnace steel industry slags. Environmental Science and Technology 34, 1576-1582

139. Purnell P., Farahi E., Short N.R. (2008) Super-critical carbonation of pressed lime-waste composites. 2nd


Italy, pp 299-304.

140. Quaghebeur M., Nielsen P., Laenen B., Harcouet-Menou V., Van Mechelen D., Nguyen E. (2010)

Carbstone: valorisation technology for fine grained steel slags and CO2 based on accelerated carbonation –

Control and prediction of the temperature during the carbonation process. 3rd International Conference on

Accelerated Carbonation for Environmental and Materials Engineering, Turku, Finland, pp 191.

141. Reddy K.J., Argyle M.D., Viswatej A. (2008) Capture and mineralization of flue gas carbon dioxide (CO2). 2

nd International Conference on Accelerated Carbonation for Environmental and Materials


142. Reddy K.J., John S., Weber H., Argyle M.D., Bhattacharyya P., Taylor D.T., Christensen M., Foulke T., Fahlsing P. (2010) Accelerated mineral carbonation (AMC) of flue gas carbon dioxide: Pilot scale study. 3rd



143. Reeder R. J. (1983) Crystal chemistry of the rhombohedral carbonates. In: Reeder, R. J. (Ed.), Carbonates: mineralogy and chemistry. Mineralogical Society of America, Chelsea, USA.

144. Regnault O., Lagneau V., Schneider H. (2009) Experimental measurement of portlandite carbonation kinetics with supercritical CO2. Chemical Geology 265, 113-121.

145. Ridgwell A., Zeebe R. (2005) The role of the global carbonate cycle in the regulation and evolution of the

Earth system. Earth and Planetary Science Letters 234, 299-315.

146. Romão I., Ferreira L.M.G., Fagerlund J., Zevenhoven R. (2010) CO2 sequestration with Portuguese serpentinite. 3

rd International Conference on Accelerated Carbonation for Environmental and Materials


147. Rudge J.F., Kelemen P.B., Spiegelman M. (2010) A simple model of reaction-induced cracking applied to serpentinization and carbonation of peridotite. Earth and Planetary Science Letters 291, 215-227.

148. Rule C.M. (2009) Energy considerations in the current PGM processing flowsheet utilizing new

technologies. The Journal of The Southern African Institute of Mining and Metallurgy 108, 39-46.

149. Said A., Eloneva S., Fogerholm C.J., Fagerlund J., Nduagu E., Zevenhoven R. (2010) Carbonation of Mg(OH)2 produced from serpentinite rock: integration for integrated gasification combined cycle. 3

rd



150. Sanchez M.A.M., Martinez M.M. (2010) Dry accelerated carbonation reaction studies for lime, hydrated lime and steel slag. 3

rd International Conference on Accelerated Carbonation for Environmental and


151. Santos A., Ajbary M., Morales-Florez V., Kherbeche A., Pinero M., Esquivias L. (2009) Larnite powders and larnite/silica aerogel composites as effective agents for CO2 sequestration by carbonation. Journal of

Hazardous Materials 168, 1397-1403.

152. Santos R., François D., Vandevelde E., Mertens G., Elsen J., Van Gerven T. (2010) Process intensification routes for mineral carbonation. 3rd



153. Schaef H.T., McGrail B.P., Owen A.T. (2009) Basalt-CO2-H2O interactions and variability in carbonate mineralization rates. Energy Procedia 1, 4899-4906.

- 83 -

154. Seifritz W. (1990) CO2 disposal by means of silicates. Nature 345, 486.

155. Sipilä J., Teir S., Zevenhoven R. (2008) Carbon dioxide sequestration by mineral carbonation –

Literature review update 2005-2007. Report No 2008-1, Heat Engineering Laboratory, Faculty of

Technology, Ǻbo Akademi University, pp. 52.

156. Sun J., Fernadez-Bertos M., Simons S.J.R. (2008) Kinetic study of accelerated carbonation of municipal

solid waste incinerator air pollution control residues for sequestration of flue gas CO2. Energy &

Environmental Science 1, 370-377.

157. Schaef H.T., McGrail B.P., Owen A.T. (2009) Basalt-CO2-H2O interactions and variability in carbonate

mineralization rates. Energy Procedia 1, 4899-4906.

158. Schouwstra R.P., Kinloch E.D. (2004) A short geological review of the Bushveld Complex. Platinum

Metals Reviews 44, 33-39.

159. Schramm B., Devey C., Gillis K.M., Lackschewitz K. (2005) Quantitative assessment of chemical and

mineralogical changes due to progressive low-temperature alteration of East Pacific Rice basalts from 0 to 9 MPa. Chemical Geology 218, 281-313.

160. Stasiulaitiene I., Fagerlund J., Nduagu E., Denagas G., Zevenhoven R. (2010) Carbonation of

serpentinite rock from Lithuania and Finland. Presented (as poster) at GHGT-10, Amsterdam (The Netherlands), 19-23 September (see Energia Procedia).

161. Sun J., Simons S.J.R. (2008) Accelerated carbonation of the nirex reference vault backfill. 2nd


Italy, pp 305-312.

162. Teir S., Eloneva S., Fogelholm C.J., Zevenhoven R. (2006) Stability of calcium carbonate and magnesium carbonate in rainwater and nitric acid solutions. Energy Conversion and Management 47, 3059-

3068.

163. Teir S., Eloneva S., Fogelholm C.J., Zevenhoven R. (2007) Dissolution of steelmaking slags in acetic acid for precipitated calcium carbonate production. Energy 32, 528-539.

164. Teir S., Eloneva S., Fogelholm C.J., Zevenhoven R. (2009) Fixation of carbon dioxide by producing

hydromagnesite from serpentinite. Applied Energy 86, 214-218.

165. Teir S., Kettle J., Harlin A., Sarlin J. (2010) Production of silica and calcium carbonate particles from silicate minerals for inkjet paper coating and filler purposes. 3



166. Torróntegui, M.D. (2010) Assessing the mineral carbonation science and technology. MSc thesis, ETH-

Zurich, Switzerland, pp. 51.

167. Turianicova E., Balaz P., Fabian M., Shopska M., Kostova N.G., Kadinov G. (2008) CO2 sequestration

on olivine activated in an industrially-scalable mill. 2nd International Conference on Accelerated Carbonation

for Environmental and Materials Engineering, Rome, Italy, pp 439-442.

168. Turianicova E., Balaz P. (2010) CO2 capture by mechanochemical carbonation of olivine. 3rd



169. Uibu M., Velts O., Trikkel A., Kallas J., Kuusik R. (2008) Developments in CO2 mineral carbonation by oil shale ash. 2

nd International Conference on Accelerated Carbonation for Environmental and Materials


170. Uibu M., Velts O., Kuusik R. (2010a) Developments in CO2 mineral carbonation of oil shale ash. Journal

of Hazardous Materials 174, 209-214.

- 84 -

171. Uibu M., Kuusik R. (2010b) Effect of ageing pre-treatment on performance of oil shale ash for CO2

sequestration in aqueous suspensions. 3rd



172. Uliasz-Bochenczyk A., Mokrzycki E., Piotrowski Z., Pomykala R. (2009) Estimation of CO2 sequestration potential via mineral carbonation in fly ash from lignite combustion in Poland. Energy Procedia 1, 4873-4879.

173. Ucurum A. (2000) Listwaenites in Turkey: perspectives on formation and precious metal concentration with reference to occurrences in East-Central Anatolia. Ofioloti 25, 15-29.

174. Van der Laan S.R., van Hoek C.J.G., van Zomeren A., Comans R.N.J., Kobesen J.B.A., Broersen P.G.J.

(2008) Chemical reduction of CO2 to carbon at ambient conditions during artificial weathering of converter steel slag while improving environmental properties. 2

nd International Conference on Accelerated

Carbonation for Environmental and Materials Engineering, Rome, Italy, pp 229-238.

175. Velts O., Kallas J., Kuusik R. (2010) Modeling of calcium leaching from lime-consisting oil shale

combustion ash. 3rd International Conference on Accelerated Carbonation for Environmental and Materials


176. Vogeli J., Reid D.L., Mathivha R., Becker M., Broadhurst J., Franzidis J.P. (2010) Scale of natural

carbonation occurring in mine wastes. 7th Inkaba yeAfrika Earth Sciences workshop, Potsdam, Germany.

177. Vogeli J., Reid D.L., Becker M., Broadhurst J., Franzidis J.P. (2011) Investigation of the potential for mineral carbonation of South African PGM tailings. Submitted to Minerals Engineering.

178. Wang X., Maroto-Valer M. (2010) Integrated CO2 capture and production of hydromagnesite from

serpentine by using recyclable ammonium salts. 3rd International Conference on Accelerated Carbonation for


179. Werner M., Mazzotti M. (2010) Direct flue gas CO2 mineralization using activated serpentine:

experiments and population balance modeling. 3rd International Conference on Accelerated Carbonation for

Environmental and Materials Engineering, Turku, Finland, pp 75.

180. Wilson S.A., Dipple G.M., Power I.M., Thom J.M., Anderson R.G., Raudsepp M., Gabites J.E., Southam

G. (2009) Carbon dioxide fixation within mine wastes of ultramafic-hosted ore deposits: Examples from the

Clinton Creek and Cassiar Chrysotile deposits, Canada. Economic Geology 104, 95-112.

181. Wolff-Boenisch D., Gislason S.R., Oelkers E.H. (2006) The effect of crystallinity on dissolution rates and CO2 consumption capacity of silicates. Geochimica et Cosmochimica Acta 70, 858-870.

182. Wu J.C.S., Sheen J.D., Chen S.Y., Fan Y.C. (2001) Feasibility of CO2 fixation via artificial rock weathering. Industrial and Engineering Chemistry Research 40, 3902-3905.

183. Yuan D. (1997) The carbon cycle in karst. Zeitschrift fur Geomorph Suppl-Bd.108, 91-102.

184. Zevenhoven R., Teir S., Eloneva S. (2008) Heat optimisation of a staged gas-solid mineral carbonation

process for long-term CO2 storage. Energy 33, 362-370.

185. Zevenhoven R., Björklöf T., Fagerlund J., Romão I., Highfield J., Jie B. (2010) Assessment & improvement of a stepwise magnesium silicate carbonation route via MgSO4 & Mg(OH)2. 3

rd International


41-49.

186. Zhao L., Sang L., Chen J., Ji J., Teng H.H. (2010) Aqueous carbonation of natural brucite: Relevance to CO2 sequestration. Environmental Science & Technology 44, 406-411.

- 85 -

APPENDICES

Appendix A – List of patents on CCMC (Torrontegui, 2010).

The patents are listed from the most recent to the earliest filings.

1) CAPTURE AND SEQUESTRATION OF CARBON DIOXIDE IN FLUE GASES Publication number(s): WO2009139813 (A3); US2009202410 (A1). Inventor(s): KAWATRA SURENDRA KOMAR; EISELE TIMOTHY C.; SIMMONS JOHN J. Assignee(s): MICHIGAN TECHNOLOGICAL UNIVERSITY [US/US].

2) A PROCESS FOR PREPARING AN ACTIVATED MINERAL Publication number(s): WO2009092718 (A1); WO2008142025 (A2) (A3); EP2158159 (A2); CA2687620 (A1); AU2008252987 (A1); CN101679060 (A). Inventor(s): BOERRIGTER HAROLD. Assignee(s): SHELL INERNATIONALE RESEARCH MAATSCHAPPIJ B.V. [NL/NL].

3) CARBON DIOXIDE SEPARATION VIA PARTIAL PRESSURE SWING CYCLIC CHEMICAL

REACTION Publication number(s): US2009162268 (A1); EP2072111 (A2); US2010040520 (A1); JP2009149507 (A); CN101468790 (A); CA2646385 (A1). Inventor(s): HUFTON JEFFREY RAYMOND; QUINN ROBERT; WHITE VINCENT; ALLAM RODNEY JOHN. Assignee(s): AIR PRODUCTS AND CHEMICALS INC [US] .

4) PROCESS FOR THE SEQUESTRATION OF CO2 BY REACTION WITH ALKALINE SOLID WASTES

Publication number(s): WO2009077358 (A1); EP2070578 (A1). Inventor(s): MONTES HERNANDEZ GERMAN; PEREZ LOPEZ RAFAEL; RENARD FRANCOIS; CHARLET LAURENT; NIETO JOSE MIGUEL. Assignee(s): UNIV. JOSEPH FOURIER [FR]; CENTRE NAT. RECH. SCIENT. [FR]; UNIV. HUELVA [ES].

5) INTEGRATED CHEMICAL PROCESS

Publication number(s): WO2008061305 (A1); US2009305378 (A1); MX2009005386 (A); KR20090102760 (A); EP2097164 (A1); CA2670299 (A1); AU2007324344 (A1). Inventor(s): BRENT GEOFFREY FREDERICK. Assignee(s): ORICA EXPLOSIVES TECHNOLOGIE PTY LTD [-/AU].

6) SYSTEM, APPARATUS AND METHOD FOR CARBON DIOXIDE SEQUESTRATION

Publication number(s): WO2008101293 (A1); US2010021362 (A1); KR20090125109 (A); EP2134449 (A1); CA2678800 (A1); AU2009250983 (A1). Inventor(s): HUNWICK RICHARD J. Assignee(s): HUNWICK RICHARD J.

7) A PROCESS FOR SEQUESTREATION OF CARBON DIOXIDE BY MINERAL CARBONATION

Publication number(s): WO2008142017 (A2) (A3); EP2158158 (A2); CA2687618 (A1); AU2008253068 (A1); US20070261947 (A1); CN101679059 (A). Inventor(s): GEERLINGS JACOBUS JOHANNES CORNELIS; WESKER EVERT; BOERRIGTER HAROLD. Assignee(s): SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.

8) PROCESS FOR SEQUESTRATION OF CARBON DIOXIDE

Publication number(s): WO2007071633 (A1); US2009010827 (A1); EP1966092 (A1); CN101331084 (A). Inventor(s): GEERLINGS JACOBUS JOHANNES CORNELIS; VAN MOSSEL GERARDUS ANTONIUS F.; IN T VEEN BERNARDUS CORNELIS M.

- 86 -

Assignee(s): SHELL INT RESEARCH [NL].

9) APPARATUS AND METHOD FOR SEQUESTERING FLUE GAS CO2

Publication number(s): WO2007081561 (A2) (A3); US2008267838 (A1). Inventor(s): REDDY KATTA J.; ARGYLE MORRIS D. Assignee(s): UNIVERSITY OF WYOMING [US/US].

10) METHOD FOR INDUSTRIAL MANUFACTURE OF PURE MgCO

3 FROM AN OLIVINE CONTAINING

SPECIES OF ROCK Publication number(s): WO2007069902 (A1); US2008299024 (A1); RU2008119911 (A); NO20082270 (A); EP1951622 (A1); CN101356118 (A). Inventor(s): GORSET ODDVAR; JOHANSEN HARALD; KIHLE JAN; MUNZ INGRID ANNE; RAAHEIM ARNE. Assignee(s): INSTITUTT FOR ENERGITEKNIKK [NO/NO].

11) PROCESS FOR PRODUCING CaCO

3 OR MgCO

3

Publication number(s): WO2006008242 (A1); CN1989073 (A); US2007202032 (A1). Inventor(s): GEERLINGS JACOBUS J.C.; VAN MOSSEL GERARDUS ANTONIUS F.; IN T VEEN BERNARDUS C.M. Assignee(s): SHELL OIL COMPANY.

12) HEAT TREATMENT PROCESS OF SERPENTINE AS RAW MATERIAL FOR MINERAL

CARBONATION BY REMOVING ADSORBED WATER MOLECULES, HYDROXYL GROUP AND ORGANIC FRACTION IN UNTREATED SERPENTINE Publication number(s): KR2006110119-A. Inventor(s): LEE JAE KEUN; KIM KI HYUNG; KIM DONG WHA; CHOI WEON KYUNG; CHO TAE HWAN; MOON SEUNG HYUN; HAN SANG SIK; KONG KI HOON; HWANG OK JUNG; KIM KYONG HOON; YOUN CHANG HWA. Assignee(s): KOREA ELECTRIC POWER CORPORATION.

13) METHOD FOR FIXING CARBON DIOXIDE

Publication number(s): JP 2005097072 (A). Inventor(s): YOGO KATSUNORI; TOU EIKOU; YASHIMA TATEAKI. Assignee(s): RESEARCH INSTITUTE OF INNOVATIVE TECHNOLOGY FOR THE EARTH.

14) METHOD FOR CARBON SEQUESTRATION IN THE FORM OF A MINERAL IN WHICH CARBON

HAS A +3 DEGREE OF OXYDATION Publication number(s): WO2005070521 (A1); FR2863911 (A1); US2008296146 (A1); RU2334547 (C2); PT1699545 (E); JP2007515283 (T). Inventor(s): TOULHOAT HERVE; ROPITAL FRANCOIS; DUVAL SEBASTIEN. Assignee(s): INST FRANCAIS DU PETROLE [FR].

15) CARBON DIOXIDE SEQUESTRATION USING ALKALINE EARTH METAL-BEARING MINERALS

Publication number(s): US2005180910 (A1). Inventor(s): PARK AH-HYUNG.; FAN LIANG-SHIH. Assignee(s): PARK AH-HYUNG; FAN LIANG-SHIH.

16) CARBON DIOXIDE CAPTURE AND MITIGATION OF CARBON DIOXIDE EMISSIONS

Publication number(s): WO2005108297 (A2) (A3); US2008031801 (A1); US2008138265 (AA); WO06009600 (A2) (A3). Inventor(s): LACKNER KLAUS; GRIMES PATRICK; KREVOR SAMUEL; ZEMAN FRANK. Assignee(s): COLUMBIA UNIVERSITY; THE TRUSTEES OF COLUMBIA UNIVERSITY IN THE CITY OF NEW YORK.

- 87 -

17) PROCESS FOR REMOVAL AND CAPTURE OF CARBON DIOXIDE FROM FLUE GASES Publication number(s): WO2004037391 (A1); US2004126293 (A1); JP2006503692 (T); DE60310594 (T2); CA2503096 (A1). Inventor(s): GEERLINGS JACOBUS JOHANNES CORNELIS; WESKER EVERT. Assignee(s): SHELL INTERNATIONALE REASEARCH MAATSCHAPPIJ B.V.

18) CARBONATION OF METAL SILICATES FOR LONG-TERM CO2 SEQUESTRATION

Publication number(s): WO2004094043 (A2) (A3); US2004213705 (A1); US2008112868 (A1); EP1617933 (A2); CA2523135 (A1). Inventor(s): BLENCOE JAMES G.; PALMER DONALD A.; ANOVITZ LAWRENCE M.; BEARD JAMES S. Assignee(s): UT BATTELLE LLC [US].

19) PROCESS FOR SEQUESTERING CARBON DIOXIDE AND SULFUR DIOXIDE

Publication number(s): WO2004098740 (A2) (A3); US2005002847 (A1); US7604787 (B2). Inventor(s): MAROTO-VALER M. MERCEDES; ZHANG YINZHI; KUCHTA MATTHEW E.; ANDRESEN JOHN M.; FAUTH DAN J. Assignee(s): PENN. STATE RES. FOUND [US].

20) SEQUESTRATION OF CARBON DIOXIDE

Publication number(s): US2004219090 (A1); US7132090 (B2). Inventor(s): DZIEDZIC DANIEL; GROSS KENNETH B.; GORSKI ROBERT A.; JOHNSON JOHN T. Assignee(s): GENERAL MOTORS CORPORATION.

21) PROCESS FOR MINERAL CARBONATION WITH CARBON DIOXIDE

Publication number(s): WO02085788 (A1); US2004131531 (A1); NO20034678 (A); JP2004525062 (T); DE60209492 (T2); CA2444576 (A1). Inventor(s): GEERLINGS JACOBUS JOHANNES CORNELIS; MESTERS CAROLUS MATTHIAS ANNA; OOSTERBEEK HEIKO. Assignee(s): SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.

22) EXTRACTION OF SILICA AND MAGNESIUM COMPOUNDS FROM OLIVINE

Publication number(s): WO0248036 (A1); EP1373139 (A1); AU2554202 (A). Inventor(s): HANSEN TORD; ZANDER BO. Assignee(s): SILICA TECH ANS [NO].

23) METHOD OF MANUFACTURING CARBONATION CURED COMPACT Publication number(s):

JP2002201085 (A). Inventor(s): INAGAKI KENJI; ISU NORIBUMI; TERAMURA TOSHIFUMI. Assignee(s): CLION CO LTD; KENZAI GIJUTSU KENKYUSHO KK.

24) METHOD FOR EXTRACTING AND SEQUESTERING CARBON DIOXIDE

Publication number(s): US2001022952 (A1); US6890497 (B2); WO0010691 (A1); US7655193 (B1); AU5568099 (A). Inventor(s): RAU GREGORY H.; CALDEIRA KENNETH G. Assignee(s): RAU GREGORY H.; CALDEIRA KENNETH G.; THE UNITED STATES OF AMERICA AS REPRESENTED BY THE UNITED STATES DEPARTMENT OF ENERGY.

25) CARBON DIOXIDE SEQUESTRATION BY COBALT (II) COMPLEXES

Publication number(s): WO0198313 (A1); GB2365428 (A); AU7424901 (A). Inventor(s): FREEMAN JONATHAN DUNCAN; WALTON PAUL HOWARD; PERUTZ ROBIN NOEL. Assignee(s): LATTICE INTELLECTUAL PROPERTY.

26) TREATMENT OF HYDRATED CALCIUM SILICATE AND TREATING APPARATUS

Publication number(s): JP6279017 (A). Inventor(s): AKIYAMA TADASHI; NOMURA MASARU. Assignee(s): ASAHI CHEMICAL IND.

- 88 -

Appendix B – Proceedings of ACEME-10 conference (see separate file)

ACKNOWLEDGEMENTS

• South African Centre for Carbon Capture and Storage

• Prof Ron Zevenhoven, Laboratory for Thermal and Flow Engineering, Åbo Akademi University, Finland

• Dr Harald Johansen, Dr Anette Haug, Dr Ǿyvind Brandvoll, Institute for Energy Technology (IFE), Norway

• Dr Markus Bauer, University of Bayreuth, Germany

• Dr Marcel Verduyn, Shell Global Solutions International B.V., The Netherlands

• Prof Bogdan Dlugogorski (Director) and Prof Eric Kennedy (Deputy Director, Assistant Dean), Priority

Research Centre for Energy, The University of Newcastle, Australia

• Mr Keesjan Rijnsburger and Mr Pol Knops, Innovation Concepts B.V., The Netherlands

• ACEME-10 delegates

• Manie Brynard and Shirley Tucker, Spatial Data Management Unit, CGS

scoping study on co2 mineralization technologies report · co 2 mineralization technologies report...

Documents