life cycle assessment of electricity generation
TRANSCRIPT
November 2011
Life Cycle Assessment of Electricity Generation
The Union of the Electricity Industry–EURELECTRIC is the sector association representing the common interests of
the electricity industry at pan‐European level, plus its affiliates and associates on several other continents.
In line with its mission, EURELECTRIC seeks to contribute to the competitiveness of the electricity industry, to
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Dépôt légal: D/2011/12.105/53
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Life Cycle Assessment of Electricity Generation ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ WG Environmental Management & Economics Philippe BAUDUIN (Electricité de France‐FR), Chair Chris ANASTASI (International Power‐GB), Inga ANDERSSON (E.ON Sverige‐SE), Helena AZEVEDO (Redes Energéticas Nacionais, SGPS, S.A. ‐ REN‐PT), Klaus BRUCHERSEIFER (Société Électrique de l'Our SA (SEO)‐LU), David CORREGIDOR SANZ (ENDESA‐ES), Gaye DEMIRHAN BASBILEN (ARTI Wind & Alternative Energy Systems‐TR), Gabor HOHOL (TPP AES Tisza‐HU), Radovan HOLOD (Elektrovod Holding a.s.‐SK), Drazen LOVRIC (HEP D.D.‐HR), Pavel NECHVATAL (CEZ, a.s.‐CZ), Miroslaw NIEWIADOMSKI (PGE Mining&Power sa (BELCHATOW)‐PL), Flavia PASAREANU (S.C. Complexul Energetic Rovinari S.A.‐RO), Alida REJEC (SENG D.O.O. NOVA GORICA‐SI), Wilhelm A. RITTER (Energie AG Oberösterreich‐AT), Walter RUIJGROK (Energie‐Nederland‐NL), Geir TAUGBOL (Energi Norge‐NO), Tanja UTESCHER‐DABITZ (BDEW‐DE), Alexis van DAMME (GDF SUEZ Energy Europe & International‐BE), Roberto VENAFRO (Edison‐IT), Members
Contact: Helene LAVRAY, Advisor Environment & Sustainable Development Policy Unit ([email protected])
This report is part of the EURELECTRIC Renewables Action Plan (RESAP).
The electricity industry is an important investor in renewable energy sources (RES) in Europe. For instance, it is responsible for 40% of all wind onshore investments. RES generation already represents a substantial share in the power mix and will continue to increase in the coming years.
EURELECTRIC’s Renewables Action Plan (RESAP) was launched in spring 2010 to develop a comprehensive industry strategy on renewables development in Europe.
RESAP addresses the following key challenges in promoting RES generation:
• the need for a system approach to flexibility and back‐up, • the need for a market‐driven approach, • the need for a European approach to RES development.
RESAP consists of 13 task forces, including for example demand side management, market design, load and storage. The purpose of RESAP is to develop, through a series of reports and a final synopsis report, sound analysis with key recommendations for policymakers and industry experts.
For additional information on RESAP please contact:
John Scowcroft [email protected]
Susanne Nies [email protected]
Life Cycle Assessment of Electricity Generation
1. Background ....................................................................................... 3
1.1. Life Cycle Assessment (LCA) ............................................................................................ 3
1.2. Other analytical frameworks .......................................................................................... 4
1.3. Shortcomings........................................................................................................................ 5
2. Impacts of electricity generation...................................................... 7
2.1. “Carbon footprint” of electricity generation ............................................................. 8
2.2. Air pollution ....................................................................................................................... 10
2.3. Health impacts .................................................................................................................. 12
2.4. Water use ........................................................................................................................... 12
2.5. Land use .............................................................................................................................. 14
2.6. Biodiversity ........................................................................................................................ 14
2.7. Raw materials.................................................................................................................... 16
2.8. Energy payback................................................................................................................. 17
3. Concluding remarks ........................................................................ 18
4. References....................................................................................... 20
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As part of EURELECTRIC’s Renewables Action Plan (RESAP), the WG Environmental
Management and Economics was tasked with an evaluation, based on existing
literature, of the sustainability of RES technologies over their whole life cycle (task
4.4).
It was agreed that the scope of the work should encompass other generation
technologies as well.
1. Background
1.1. Life Cycle Assessment (LCA) Life Cycle Assessment aims at evaluating all environmental impacts associated with a
given product or service at all stages of its lifetime from “cradle to grave”: from
resource extraction and processing, through construction, manufacturing and retail,
distribution and use, repair and maintenance, disposal/decommissioning and
reuse/recycling.
LCA procedures are usually based on environmental management standards ISO
14040:2006 and 14044:2006 and are carried out in four steps:
1. Goal and scope definition
The goal and scope of the LCA must be clearly defined. The system to be
analysed, its boundaries, the functional unit (what is studied precisely and
what are the services/products delivered in order to provide a reference for
the inputs and outputs) and the procedure are determined. This step must
include the context of the analysis, the future use of the LCA results, the
addressees of the results, assumptions and limitations, the methods chosen
to allocate the impacts of a shared process and the impact categories.
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2. Life Cycle Inventory (LCI)
For this stage, every input (raw material, fuel, water, etc.) and every output
(product, emissions to air, water and soil, waste, etc.) of the functional unit
defined in the first step is recorded and quantified. The inventory can gather
data for hundreds of flows, depending on the system boundaries. First, all
necessary data must be collected. This requires in‐depth qualitative and
quantitative knowledge of all the related inputs, which must be expressed in
a common unit. Then the inventory results have to be calculated based on
the data collected, according to the chosen methodologies and assumptions.
3. Life Cycle Impact Assessment (LCIA)
All the outputs of the LCI are analysed to determine their impact on the
environment. Impact categories can include use of resources, GHG/CO2
emissions, toxicity, acidification, eutrophication, land use, etc.
4. Interpretation
The results of the LCI and LCIA are summarised and presented, identifying the
significant issues. The study’s completeness, sensitivities and consistencies
are evaluated. The objective is to propose conclusions and recommendations
for decision‐making.
1.2. Other analytical frameworks LCA is now a well‐established framework, based on internationally agreed
environmental management standards, and increasingly used to compare various
generation technologies and in particular RES or low‐carbon technologies with fossil
fuel based generation technologies.
Some studies have attempted to go beyond the assessment of the environmental
impacts. For instance they have tried to take into consideration changes in the
energy system, most notably as a result of an increasing share of intermittent RES. A
newly developed methodology, “consequential LCA” (as opposed to the traditional
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“attributional” LCA), attempts to consider the impact that the implementation of a
certain technology has on other technologies and market dynamics. However, this
concerns a minority of LCA studies and is not without its own challenges.
At the EU level, the European Commission launched ExternE (Externalities of Energy
1991‐1997, updated in 2005), a project whose ambition was to combine LCA with
the “impact pathway approach”. In this bottom‐up‐approach environmental benefits
and costs are estimated by following the pathway from source emissions through
quality changes of air, soil and water to physical impacts, before being expressed in
monetary benefits and costs.
In 2008, another project, NEEDS (New Energy Externalities Developments for
Sustainability) was initiated, with the ambition to evaluate the full costs and benefits
(direct and external) of energy policies and of future energy systems, both at the
level of individual countries and for the enlarged EU as a whole. Its results did not
have the same impact as ExternE, whose results were used, for instance, in the Clean
Air for Europe (CAFE) programme or in the IPPC Directive (cost/benefit analysis
aimed at contributing to the selection of Best Available Techniques). In addition to
severe limitations (no inclusion of hydro or wind onshore in the scope of the work),
debates in the final stages of NEEDS and conclusions after the final workshop
stopped short of proposing a technology ranking.
1.3. Shortcomings LCA and other analytical frameworks often present a number of limitations and
uncertainties.
• Given the importance of GHG, LCA tends to focus exclusively on those and
even on the LCI step of an LCA.
• As pointed out above, LCA rarely takes into consideration the fact that the
site which serves as a basis for the analysis is connected to a whole energy
system (increased share of intermittent RES, electricity grid, market, etc.).
LCA also does not take into account a number of important criteria such as
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social aspects, acceptability or security of supply that will have to be taken
into consideration at a later stage. To foster such aspects in the LCA, UNEP
developed guidelines for Social Life Cycle Assessment of products in 2009.
Attempts to incorporate those elements in turn lead to other limitations and
uncertainties.
• Analysis results are influenced by the assumptions made or the methodology
chosen (e.g. choice of LCA technique, impact pathway, system boundary, risk
of double counting) and the concepts introduced and/or used (e.g.: “Value of
a Life Year Lost”).
• For electricity generation technologies, the results of an analysis will be
influenced by the specific characteristics of the site chosen compared to
others in its category, the manufacturing and design characteristics, the
lifetime and the operating conditions. It is therefore difficult to transfer
results from one country to another or one generation unit to another, as
most major environmental impacts, with the exception of climate change, are
heavily site‐dependent. In the case of an LCA for gas, there will also be large
differences depending on the mode of transport (e.g. pipeline, LNG; distance)
and on the source (conventional gas, shale gas).
• LCA is often considered a long and onerous process and focuses on existing
installations. As a result out‐dated values are often used that fail to reflect
evolutions in the power sector. Although it is possible to conduct “fast� LCA
results will be imprecise and have a limited reach. LCA can also be
prospective. What matters is transparency in the first stage of the analysis
while defining the goal and scope. Other LCAs may include future scenarios
(e.g. NEEDS).
• Results of studies can be the result of a vast scope of studies undertaken by
different teams.
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• Uncertainties and limitations of various methodologies may be acknowledged
by the authors of the studies but are rarely taken into account when results
(or only some of them) are used by policymakers.
2. Impacts of electricity generation
In May 2011, the Intergovernmental Panel on Climate Change (IPCC) published a
Special Report on Renewable Energy Sources and Climate Change Mitigation
(SRREN). Although no study was conducted for this report, its scope covers a review
of existing literature on life cycle assessment. Efforts were made to cover the
different technologies for electricity generation and not only RES. The methodology
is described in “Annex II‐Methodology” of the report. It covers the financial
assessment of technologies over a project lifetime, the primary energy accounting
and LCA and risk analysis. For the review of LCAs of electricity generation
technologies, the US National Renewable Energy Laboratory (NREL) carried out a
review of published LCAs. Out of 2,165 references collected, they kept 296 that
passed screens. The review followed guidelines for systematic review but for the
studies that passed the screens there was no assessment of the accuracy of
estimates or validity of assumptions, identification of outliers. The estimates used
are the ones published.
It is also important to bear in mind that the scope of this analysis is international and
covers both developed and developing countries.
In addition to the ubiquitous greenhouse gas emissions, the SRREN also attempted
to give indications of other impact categories (air pollution, water use, raw materials,
accidents, etc.).
The following sections rely on the findings of the SRREN which represent an
extensive and recent evaluation of studies in this field.
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2.1. “Carbon footprint” of electricity generation Given the crucial importance of climate change, the focus, in terms of impact
category from LCA, is clearly on GHG emissions. Often, a study will only focus on that
aspect. It must be noted that a synthesis of those different evaluations is a field of
study in itself.
Figure 1 shows the lifecycle greenhouse gas emissions (in g CO₂ eq/kWh) for
different electricity generation technologies, including single estimates for CCS (see
number in brackets for the number of studies). Land‐use related net changes in
carbon stocks (mainly applicable to biopower and hydropower from reservoirs) and
land management impacts are excluded. Negative estimates for biopower are based
on assumptions about avoided emissions from residues and waste in landfill
disposals and co‐product.
The carbon footprint accounts for the total quantity of greenhouse gases emitted
over the life cycle of a product or a process.
All electricity generation technologies emit greenhouse gases at some point in their
life cycle and all have a carbon footprint. Fossil‐fuelled electricity generation has the
highest carbon footprint and most emissions are produced during plant operation.
CCS technologies could reduce those emissions significantly but have not yet
developed at a large scale. GHG reduction costs could be much lower by using CCS
compared to many RES technologies. By contrast, renewable and nuclear generation
have a low carbon footprint and most emissions are caused indirectly, for instance
during the construction phase. Emissions from biomass can be higher than for other
RES and nuclear. CO₂ emissions from biomass plants are sometimes not considered
during their lifetime because the CO₂ emitted is equal to the CO₂ absorbed in the
biomass growth stages. However not all studies take avoided emissions into account.
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Figure 1: Estimates of life cycle GHG emissions (g CO2eq/kWh) for categories of electricity generation technologies,
including some technologies integrated with CCS, SRREN (2011).
Solar Values Bio‐
power
PV CSP
Geo‐
thermal
Hydropower Ocean
Wind Nuclear Natural
Gas
Oil Coal
Minimum ‐633 5 7 6 0 2 2 1 290 510 675
25th
percentile
360 29 14 20 3 6 8 8 422 722 877
50th
percentile
18 46 22 45 4 8 12 16 469 840 1001
75th
percentile
37 80 32 57 7 9 20 45 548 907 1130
Maximum 75 217 89 79 43 23 81 220 930 1170 1689
CCS min ‐1368 65 98
CCS max ‐594 245 396
Table 1: Aggregated results of literature review of LCAs of GHG emissions from electricity generation as displayed in Figure 1,
SRREN (2011)
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2.2. Air pollution SRREN included data on selected air pollutants with the greatest impact on human
health (according to the WHO). Those pollutants are dispersed into the atmosphere
at both local and regional levels. However their real impact on the environment and
health varies according to a number of factors, so the data from life cycle inventories
must be interpreted carefully. Furthermore the climate effects of certain pollutants
such as black carbons and aerosols are still under investigation. Black carbon
abatement for instance appears to be an effective way of tackling both climate
change and air pollution. The removal of reflective aerosols through air pollution
control measures may accelerate the impact of global warming. Those
considerations will apply differently according to countries/regions.
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Figure 2: Cumulative life cycle emissions of a) NOx and SO2 and b) NMVOC and PM2.5 per unit of energy generated
for current heat and electricity supply technologies, SRREN (2011)
The results show that non‐combustion RES and nuclear emit comparatively few air
pollutants and comparatively little during the upstream and downstream processes.
For electricity production based on fossil fuel and biomass, most emissions occur
during the combustion stage. The transport stage might become more important in
the case of long‐distance transport of the fuel.
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The results do not take into consideration potentially higher emissions linked to a
more flexible operation of fossil fuel and biomass‐based electricity generation to
support the increasing share of intermittent RES in the system.
At the EU level emissions from the power sector have consistently and significantly
decreased over the past decades in spite of an increase in electricity production. In
some cases (PM, NOx), the power sector is a minor contributor compared to other
sectors such as transport. While electricity generation increased by 75% between
1980 and 2007 in the EU‐27, electricity‐related SO₂ and NOx emissions fell by 76%
and 57% respectively in the same period.
2.3. Health impacts Most health impacts are related to the emission of air pollutants from fossil fuel and
biomass‐based electricity generation. The legislative framework at the EU level has
allowed for a significant reduction in emissions. Focus is progressively shifting to
small combustion installations and household emissions. There are also some health
concerns associated with RES (e.g. noise from wind power; direct or indirect impact
of certain agricultural practices linked to biomass).
2.4. Water use Water is a crucial element for most electricity generating technologies. Its
availability, in particular in a changing climate, will influence the choice of location,
design and operation of a site. From a life cycle perspective there is little literature
available on that aspect.
On the operational level, it is important to note what while some electricity
generation technologies may have high water withdrawal rates (water removed from
the ground or diverted from the source), the consumption level (water lost mainly
through evaporation) is much lower but still important, in particular where water is
scarce. Once‐through‐cooling withdraws large volumes of water but consumes little
whereas closed‐loop‐cooling withdraws less but consumes more. Those different
technologies also affect plant efficiency and costs (e.g. dry cooling). The IPCC study
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also states that more research on the net effect of reservoir construction on
evaporation in a specific watershed is needed, since the high evaporation values
shown for hydropower in this graph are not considered representative. It also does
not account for the positive impacts hydropower can have on a river (filtering waste
material, slowing down the flow rate, stabilising the water level, etc.).
Figure 3: Ranges of rates of operational water consumption by thermal and non‐thermal electricity‐generating
technologies based on a review of available literature (m³/MWh), SRREN (2011)
As shown in Figure 3, water consumption varies greatly within and between cooling
technologies. With the exception of coal and CSP, the number of estimates used is
low.
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2.5. Land use There is little available literature related to life cycle estimates for land use of energy
generation technologies. For fossil fuel and nuclear, the impact is mainly upstream
(mining, extraction, supply and transport) and downstream (waste disposal). In
contrast, and with the notable exception of biomass, land use requirements are
largest for RES during the operational stage (e.g. PV plant, CSP, wind including
landscape issues). Run‐of‐river hydropower has low life cycle land use but this may
be very different for reservoirs, not least because of population displacement –
although in the case of multi‐purpose reservoirs such effects cannot be attributed to
electricity generation alone.
An increasing share of RES will also affect land use for electricity transmission and
distribution.
2.6. Biodiversity
Impacts on biodiversity are not part of LCA. While there is large operational
experience associated with fossil fuel and nuclear generation technologies, this is
usually not the case with RES technologies, with the exception of hydropower and
increasingly wind farms or solar panels. The impact of bioenergy is also strongly
disputed but here the impact is mainly upstream, linked to land use and agriculture
management practices (water, pesticides, etc.). The impacts of exploiting and
transporting fossil fuels, in particular oil, can also be damaging, in particular in case
of accidents. Regarding hydropower, conventional hydropower plants create a new
ecological system. The building of a new hydropower plant at a heavily modified
water body (HMWB) could actually improve the water body: monitoring reports
have shown that in the area of a fish way, there is a recovery in the population of
threatened species.
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Table 2: Overview of potential negative impacts and concerns regarding ecosystems and biodiversity related to RES
technologies, SRREN (2011)
Fossil‐fuel Impact of mining, extraction, infrastructures for transport and supply on habitats, wildlife and water
Air and water pollution (impact on wildlife, habitats and ecosystems)
Landfill of CCP (soil degradation)
Nuclear Impact of mining, extraction, infrastructures for transport and supply on habitats, wildlife and water
Water pollution (impact on wildlife, habitats and ecosystems)
Impact of disposal sites (see land use and associated effect on wildlife and habitats)
Table 3: Overview of potential negative impacts and concerns regarding ecosystems and biodiversity related to fossil fuel and
nuclear technologies, EURELECTRIC.
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2.7. Raw materials Scarcity of fossil fuels is well documented. Estimates vary but, while coal scarcity is
not a major issue for the time being, proven conventional reserves of oil and gas are
expected to be depleted in the next 40 to 60 years. These estimates are influenced
by the rate of economic growth, in particular in developing countries, and access to
non‐conventional sources (e.g. oil sands). For both depleted conventional reserves
and non‐conventional sources, extraction costs are increasing together with energy
input and life cycle carbon emissions. Security of supply is also an issue of concern.
In addition, Table 3 shows that RES rely on a number of raw materials for which
access and price volatility should also be taken into consideration. Demand for
precious rare earth and speciality metals is projected to increase. In some cases
substitution is not possible.
In its February 2011 strategy, the Commission identified 14 critical raw materials:
antimony, beryllium, cobalt, fluorspar, gallium, germanium, graphite, indium,
magnesium, niobium, platinum group metals, rare earths, tatalum, tungsten.
Table 3: critical raw materials content of renewable resources technologies, SRREN, 2011.
The setting up of effective recycling schemes appears essential.
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2.8. Energy payback The energy payback ratio is the ratio of total energy produced during the lifetime of
a technology divided by the energy needed to build, fuel, maintain and
decommission it. The higher the ratio, the better the environmental performance. A
payback ratio between 1 and 1.5 implies that the energy consumed is almost as
much as the energy produced.
Energy payback time is the time required for a generation technology to generate
the amount of energy that was required to build, fuel, maintain and decommission
it. The energy payback time is closely linked to the energy payback ratio and depends
on assumptions made on the lifetime of a technology.
In the case of combustion, the energy content of the fuel itself is not taken into
consideration.
The notion of energy payback is commonly used but the methodology is disputed
(the notion is not clearly defined, MJ electric and MJ heat are aggregated, etc.).
Table 4: Energy payback times and energy ratios of electricity‐generating technologies, SRREN (2011). Electricity from
biomass is excluded, as the literature almost exclusively documents GHG instead of energy balances for this technology,
and mostly covers the bio fuel cycle only.
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The main reasons for variations in Table 4 are fuel characteristics (e.g. moisture
content), cooling method, ambient and cooling water; temperatures and load
fluctuations (coal and gas); uranium ore grades and enrichment technology
(nuclear); crystalline or amorphous silicone materials (PV solar cells); economies of
scale in terms of power rating (wind); and storage capacity and design (concentrating
solar).
For some RES technologies, for example wind and PV, energy payback times have
decreased because of economies of scale and technological progress. However, the
location‐specific capacity factor has a major influence on the energy payback time in
particular for intermittent RES.
In the case of fossil fuel and nuclear power technologies, the impact of fuel
extraction and procession may increase in parallel with the decline in conventional
fuel and rise in unconventional fuel.
3. Concluding remarks
• LCAs for electricity generation indicate that life cycle emissions of GHG from
RES are, in general, considerably lower than those associated with fossil fuels.
Nuclear is in the same range and performs better than biomass. Among fossil
fuels, gas performs significantly better. The impact of CCS, although
promising, has yet to be demonstrated on a large scale.
• LCA or comparisons based on life cycle inventories such as life cycle GHG
emissions fail to take into consideration the intermittent nature of some RES
and the impact they will have on other generation technologies that will have
to be more flexible to accommodate them. This will result in an evolution in
the operational phase most notably in terms of emissions of CO₂ and air
pollutants. There are suggestions that, to account for the intermittency of
some RES, different generation technologies could be analysed in clusters.
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• Similarly, the energy system is often not seen as a whole. The electricity grid
and market issues are poorly taken into consideration.
• For some aspects (air pollution, water use, biodiversity) reliable global
indicators are lacking and the evaluation of the impacts highly depends on
local circumstances: identical plants will have different impacts according to
their location.
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4. References
Canadian Energy Research Institute (CERI), Comparative Life Cycle Assessment
(LCA) of base load electricity generation in Ontario, Prepared for the Canadian
Nuclear Association, October 2008,
http://www.cna.ca/english/pdf/studies/ceri/CERI‐ComparativeLCA.pdf
Denholm (P.), Kulcinski (G.P.), Holloway (T.), Emissions and energy efficiency
assessment of baseload wind energy systems, Environmental Science and
Technology, 2005, pp. 1903‐1911.
European Commission, Externalities for Energy (ExternE), The ExternE project
series
European Commission, New Energy Externalities Development for Sustainability,
NEEDS, 2008, NEEDS project
European Commission, Communication “Tackling challenges in the commodity
markets and on raw materials”, COM(2011)25, 02 February 2011.
Gagnon (L.), Greenhouse gas emissions from power generation options, January
2003, http://www.hydroquebec.com/sustainable‐
development/documentation/pdf/options_energetiques/pop_01_06.pdf
Gagnon (L.), Energy payback ratio of electricity generation options based on life‐
cycle assessments, July 2005, http://www.hydroquebec.com/sustainable‐
development/documentation/pdf/options_energetiques/rendement_investisse
ment.pdf
IPPC, Special Report on Renewable Energy Sources and Climate Change
Mitigation (SRREN), 2011, Special Report on Renewable Energy Sources and
Climate Change Mitigation — SRREN
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International Organisation for Standardisation (ISO), ISO 14040 (2006):
Environmental management – Life cycle assessment – Principles and framework,
and ISO 14044 (2006): Environmental management – Life cycle assessment –
Requirements and guidelines.
Parliamentary Office of Science and Technology (POST), Houses of Parliament
(UK), Carbon footprint of electricity generation, Number 268, October 2006,
http://www.parliament.uk/documents/post/postpn268.pdf
Parliamentary Office of Science and Technology (POST), Houses of Parliament
(UK), Carbon footprint of electricity generation, Number 383, June 2011,
http://www.parliament.uk/documents/post/postpn_383‐carbon‐footprint‐
electricity‐generation.pdf
Vattenfall, Vattenfall’s life‐cycle studies of electricity, 1999,
http://www.barsebackkraft.se/files/lifecycle_studies.pdf
Vattenfall, Life‐cycle assessment. Vattenfall’s electricity in Sweden, 2005,
http://www.vattenfall.com/en/file/2005‐LifeCycleAssessment_8459810.pdf
Weber (Ch.), Jaramillo (P.), Marriott (J.), Samaras (C.), Life‐cycle assessment and
grid electricity: what do we know and what can we know?, Environmental
Science and Technology (2010), pp 1895‐1901,
World Energy Council (a special report to the), Comparison of energy systems
using life cycle assessment, July 2004,
http://www.worldenergy.org/documents/lca2.pdf
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