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Additional Reviewers

Lukas Zach

Valeriu Prepelita

Ioannis Gonos

Shahram Javadi

Metin Demiralp

Valeri Mladenov

Dimitris Iracleous

Nikos Doukas

Filippo Neri

Nikos Karadimas

Aida Bulucea

Keffala Mohamed Rochdi

Mihaiela Iliescu

George Tsekouras

Nikos Bardis

Milan Stork

Vassiliki T. Kontargyri


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Knowledge Management Innovation For SustainableDevelopment in the Context of the Economic Crisis

Adrian IOANA/University Politehnica of Bucharest

Science and Engineering Materials FacultyUPB-SIM

Bucharest, [email protected]

Augustin SEMENESCU/University Politehnica of

Bucharest


Bucharest, Romania

Cezar Florin PREDA/University Politehnica of Bucharest


Bucharest, Romania

Abstract The trade (qualitative and quantitative level of

trade) can promote the concept of sustainable development. The

concept of Sustainable Development involves the implementation

of theoretical and practical components for making decisions in

any situation in which features a man-type medium, be it the

environment, economic or social. The goals of sustainable

development include the harmonization of the economic, social

and environmental targets. This paper presents the main types of

the correlations: Trade Sustainable Development Economic

Crisis. The Sustainable Development (SD) concept is alsoanalyzed in direct correlation with the Corporate Social

Responsibility (CSR) concept. The SD concept involves the

implementation of theoretical and practical components for

making decisions in any situation in which a man-type medium,

be it the environment, economic or social features. The

Corporations (qualitative and quantitative level of trade) can

promote the concept of sustainable development. The goals of

sustainable development include the harmonization of the

economic, social and environmental targets. This paper presents

the main research on the main types of the correlations:

Corporate Social Responsibility (including trade) Sustainable

Development Economic Crisis.

Keywords Management Innovation, Sustainable

Development, Economic Crisis

I. INTRODUCTION

The world must quickly design strategies that will allownations to move from their current, often destructive, processesof growth and development to sustainable development paths.This will require policy changes in all countries, with respect toboth to their own development and to the impact on othernations' development possibilities (Ammann, 2002, Ioana,1998).

The concept of sustainable development designates allforms and methods of socio-economic development, whosefoundation is primarily to ensure a balance between thesesystems and socio-economic elements of natural capital.

Development is sustainable when it addresses the problemof the large number of people who live in absolute poverty -that is, who are unable to satisfy even the most basic of theirneeds.

Poverty reduces people's capacity to use resources in asustainable manner (it intensifies pressure on the environment).

Most such absolute poverty is present in developingcountries (it has been worsened by the economic stagnation ofthe 1980s).

A necessary but not a sufficient condition for theelimination of absolute poverty is the relatively rapid rise ofper capita incomes in the Third World. It is therefore essentialthat the stagnant or declining growth trends of this decade arereversed.

Growth must be revived in developing countries becausethat is where the links between economic growth, thealleviation of poverty, and environmental conditions operatemost directly. Yet developing countries are part of aninterdependent world economy; their prospects also depend onthe levels and patterns of growth in industrialized nations.

Such growth rates could be environmentally sustainable ifindustrialized nations can continue the recent shifts in thecontent of their growth towards less material- and energy-intensive activities and the improvement of their efficiency inusing materials and energy.


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Sustainable Development involves achieving the currentneed without compromising the ability of future generations tomeet their own needs.

The standard theory of economic development involvesboth quantitative change (increase in Gross Domestic Product)and qualitative change (shift from pre-capitalist economy basedon agriculture to industrial capitalist economy (1, 3].

The theory of sustainable development involves both acritique of quantitative measure of GDP and a different visionof qualitative transformation. The goals of sustainabledevelopment include the harmonization of the economic, socialand environmental targets.

The concept of sustainable development was born 37 yearsago, as a response to the emergence of environmental andnatural resources crisis, especially those related to energy. TheConference on the Environment in Stockholm in 1972 marksthe moment when it is recognized for the first time that humanactivities contribute to environmental deterioration, whichthreatens the future of the planet [7, 11, 12].

Sustainable development has become an objective of theEuropean Union since 1997, when it was included in theMaastricht Treaty, and in 2001, the Summit at Goteborgadopted the Strategy for Sustainable Development of theEuropean Union, which was added an external dimension atBarcelona in 2002.

Risk management in banking designates the entire set ofrisk management processes and models allowing banks toimplement risk based policies and practices. They cover alltechniques and management tools required for measuring,monitoring and controlling risks. The spectrum of models andprocesses extends to all risks: credit risk, market risk, interestrate risk, liquidity risk, operational risk and country risk.

II. ABOUT THE TRADE FOR SUSTAINABLE DEVELOPMENT

The most known definition of sustainable development is

given by the World Commission on Environment andDevelopment (WCED) report Our Common Future, alsoknown as the Brundtland Report [9]:

"Sustainable development is development which aims to meetthe needs of present without compromising the ability offuture generations to meet their own needs.

The concept of Sustainable Development involves theimplementation of theoretical and practical components formaking decisions in any situation which features a man-type

environment, be it the environment, economic or social.In the human-environment correlation (more precisely the

human-environments correlation), the trade is of particularimportance [2, 5, 6]. This importance is that the trade may

affect (positively or negatively) all three types of environment(the environment/ ambient, economic and social environment).Figure schematically presents the importance of the trade forthe human-environments correlation.

Fig. 1. The importance of the trade for the human-

environments correlation.AM Environment (Ambient Environment);EM Economical Environment; SM Social Environment.

The importance of trade in human-environmentsrelationship is revealed by the central position of the trade.

The double correlations trade-man and trade-environments is also highlighting the importance of trade inthis relationship.

For the detailing of the human-environment relationship

schematically presented in figure 1, we may define twospecific types of trade:

Ecological Trade (Green Trade) in directcorrelation with the environment (ambient). TheEcological Trade-Environment correlation consistsof: the trade that applies and extends therequirements as to the protection of the environment

positively influences the latter ( ). Implicitly, underthese circumstances, the ecological trade is thesustainable development generator (figure 2).

Social trade, in direct correlation with the socialenvironment. This correlation suggests that a tradethat puts the forefront of continually optimizing theprice/quality ratio in terms of customer (that is theincrease of this report without being affected quality)is a trade positively affecting ( ) the socialenvironment.

The multiple correlation human (society) trade environment sustainable development is schematically in

figure 3.

HUMAN

(SOCIETY)

TRADE

ENVIRONMENT

(AM; EM;SM)


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Fig. 2. Ecological Trade Environment Sustainable Development correlation

Fig. 3. The multiple correlation Human (Society) Trade Environment Sustainable Development

HUMAN(SOCIETY) TRADE

ECONOMICALENVIRONMENT

ECOLOGICAL

TRADE

SUSTAINABLEDEVELOPMENT

SOCIALTRADE

ENVIRONMENT

SOCIALENVIRONMENT

ECOLOGICALTRADE

ENVIRONMENT SUSTAINABLEDEVELOPMENT


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The following positive influences (favorable, , ) areidentified:

Positive influence ( ) of the ecological trade onenvironment.

Positive influence ( ) of the social trade on

social environment.

Clear positive influence ( ) of environmenton sustainable development.

I. The negative influence ( ) of economic crisis on the trade(decrease of the sales volume).II. The negative influence ( ) of economic crisis onsustainable development.III. The positive influence ( ) of trade (ecological trade) onsustainable development

IV.THE COMMERCE,NONPERFORMING LOANS ANDELEMENTS OF RISK MANAGEMENT

III. ABOUT CORRELATION:TRADESUSTAINABLEDEVELOPMENTECONOMIC CRISIS

The main types of the correlations Trade (C) - SustainableDevelopment (SD) Economic Crisis (EC) are presentedbelow (figure no. 4).

Fig. 4. The main types of the correlations Trade (C) Sustainable Development (SD) Economic Crisis (EC)

There are three types of correlations:

The nonperforming loans (NPL) are those loans for whichprincipal or interest is due and left unpaid for 90 days or more(this period may vary by jurisdiction).

The NPL portfolio, along with the banks collection ratioand the level of provisions recorded illustrate the quality of theentire portfolio and the overall credit policy of the bank [4, 8,10].

There are various reasons why the quality of bank loanportfolios deteriorate and research reveals that most reasonsrelate to the nature of the banks credit culture. Below are listedthe most usual drivers of loan portfolio deterioration:

Self dealing refers to an overextension of creditsto directors and large shareholders, whilecompromising sound credit principles under thepressure from related parties.

Compromise of credit principles refer to thegranting with full knowledge of loans underunsatisfactory risk terms.

Anxiety over income outweighs the soundness oflending decisions, underscored by the hope thatthe risk will not materialize.

Incomplete credit information concerns loansgranted without proper appraisal or borrowercreditworthiness.

Complacency is typically manifested in a lack ofadequate supervision of old, familiar borrowers,based on an optimistic interpretation of knowncredit weaknesses because of survival in distressedsituations in the past.

Technical incompetence and poor selection of

risks include a lack of ability among credit officersto analyze financial statements and obtain andevaluate pertinent credit information.

Measures to counteract credit risks normally compriseclearly defined policies that express the banks credit riskmanagement philosophy and the parameters within whichcredit risk is to be controlled.

Among the policies targeted at limiting the credit risk canbe mentioned: policies on concentration and large exposures,adequate diversification, lending to connected parties or over-exposures.

C

SD

EC

(I)

(II)

(III)


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Bank regulators have paid close attention to riskconcentration by banks, the objective being to prevent banksfrom relying excessively on a large borrower or group ofborrowers.

Modern prudential regulations usually stipulate that a bankshould not make investments, grant large loans, or extend othercredit facilities to any individual entity or related group ofentities in excess of an amount that represents a prescribedpercentage of the banks capital and reserves.

According to international practice, a single client is anindividual, a legal person or a connected group to which a bankis exposed.

Single clients are mutually associated or control (directly orindirectly) other clients, usually through a voting right of atleast 15-20 percent, a dominant shareholding or the capacity toexercise a controlling influence on policy making andmanagement. These clients cumulative exposure mayrepresent a singular risk to a bank if financial interdependenceexists and their expected source of repayment is the same.

The second set of credit risk policies consist of the assetclassification method, which employs a periodic evaluation ofthe collectability of the loan portfolio.

The general rule is that all assets for which a bank is takinga risk should be classified, including loans and advances,accounts receivable, investments, equity participations andcontingent liabilities.

Asset classification, by means of which assets are classifiedat the time of origination and then reviewed and reclassified asnecessary (according to the degree of credit risk) a few timesper year, is a key risk management tool.

The periodical review considers loan service performanceand the borrowers financial condition. Assets classified asstandard or specially mentioned are typically reviewedtwice per year, while critical assets are reviewed at least eachquarter.

Banks determine classifications by themselves, but followstandards that are normally set by regulatory authorities.Standard rules for asset classification that are currently used arelisted below:

Standard (pass) are loans for which the debtservice capacity is considered to be beyond anydoubt.

In general, fully secured loans by cash or cash substitutes

(bank deposits, certificates, treasury bills etc) are usuallyclassified in this category.

Specially mentioned (watch) are assets withpotential weaknesses that may, if not checked orcorrected, to weaken the asset as a whole or

jeopardize the borrowers repayment capacity inthe future.

In this category are included, for example, credits giventhrough inadequate loan agreements, lack of control over thecollateral, lack of proper documentation.

Loans to borrowers operating under economic or marketconditions that may negatively affect the borrower in the futureare also included in this category.

Substandard regard well defined creditweaknesses that jeopardize debt service capacity,in particular when the primary sources forrepayment are insufficient and the bank must lookto secondary sources for repayment, such ascollateral, the sale of a fixed asset or refinancing.In this category can be included term credits toborrowers whose cash flow may not be enough tomeet currently maturing debts, as well as shortterm loans and advances to borrowers for whichthe inventory-to-cash cycle is insufficient to repaythe debt at maturity.

Doubtful are assets having the same weaknessesas substandard assets, but their collection in full isquestionable on the basic of existing facts.

The possibility of loss is present, but certain factors thatmay strengthen the asset exist as well.

Loss regard assets that are considereduncollectible and of such little value that thecontinued definition as bankable assets is notwarranted.

The inclusion in this category does not mean that the assethas absolutely no recovery or salvage value, but rather that it isneither practical nor desirable to defer the process of writing itoff, even though partial recovery may be possible in the future.

The third set of credit risk management policies are policiesregarding loss provisioning, by means of which allowances areset up at an adequate level as to absorb anticipated loss.

Asset classification is the one providing a basis fordetermining an adequate level of provisions for possible loanlosses. The aggregate level of provisions, together with generalloss reserves, indicates the capacity of a bank to effectivelyaccommodate credit risk.

In determining an adequate reserve, all significant factorsthat affect the collectability of the loan portfolio should beconsidered.

These factors include the quality of credit policies andprocedures, prior loss experiences loan growth, quality ofmanagement in the lending area, loan collection and recoverypractices, changes in national and local economic and businessconditions, and general economic trends.

Assessments of asset value should be performedsystematically, consistently over time and in conformity withobjective criteria.

Policies on loan-loss provisioning range from mandated todiscretionary, depending on the banking system. In manycountries, in particular those with fragile economies, regulatorshave established mandatory levels of provisions which arerelated to asset classification.


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V. CONCLUSION

The concept of sustainable development designates allforms and methods of socio-economic development, whosefoundation is primarily to ensure a balance between thesesystems and socio-economic elements of natural capital.

Many correlations may be identified among trade,sustainable development and economic crisis. Of these

correlations the following are most important: Positive influence ( ) of the ecological trade on

environment.

The negative influence ( ) of the economic crisison sustainable development.

Obvious positive influence ( ) of environmenton sustainable development.

The satisfaction of human needs and aspirations is themajor objective of development.

The essential needs of a large number of people indeveloping countries (for food, clothing, shelter, jobs) are not

being met yet, and beyond their basic needs these people havelegitimate aspirations for an improved quality of life.

A world in which poverty and inequity are endemic willalways be prone to ecological and other crises.

Sustainable development requires meeting the basic needsof all people and extending to everybody the opportunity tosatisfy their aspirations for a better life.

The level of commerce depends on the specific creditresource. There are three sets of policies specific to credit riskmanagement: policies aimed at limiting or reducing the creditrisk, policies of asset classification and policies concerning lossprovisioning.

In determining an adequate reserve, all significant factorsthat affect the collectability of the loan portfolio should beconsidered.

These factors include the quality of credit policies andprocedures, prior loss experiences loan growth, quality ofmanagement in the lending area, loan collection and recoverypractices, changes in national and local economic and businessconditions, and general economic trends.

Assessments of asset value should be performedsystematically, consistently over time and in conformity withobjective criteria.

The main types of the triple correlation Commerce Sustainable Development Risk Management reflect theleading position of Sustainable Development concept.

In this context, Commerce must realize the balance

between the requirements of Sustainable Development andRisk Management.

REFERENCES

[1] Ammann, M., Credit Risk Valuation: methods, models andapplication, Springer Publishing House, Berlin, 2012, pp. 11-123.

[2] Cooper, G., The Origin of Financial Crises, Vintage Editure, USA,2008, pp. 25-73.

[3] Hodorogel, Roxana Gabriela, The Economic Crisis and its Effects onSMEs, Theoretical and Applied Economics Review, ISSN 1841-8678,No 5/2009 (534), Bucharest, 2009, pp. 31-38.

[4] Ioana, A., Managementul activitii financiar-contabile si analizeeconomice. Teorie i Aplicaii., Ed. Politehnica Press, Bucureti,

2009, pp. 17-83.[5] Ioana, A., Marketing Elements Mix in the Materials Industry,

Proceedings of the International Conference European Integration -New Challenges for the Romanian Economy, 4th Edition, May, 30-31.2008, Oradea, 2008, pp. 51-54.

[6] Ioana, A. (2007) Managementul produciei n industria materialelormetalice. Teorie i aplicaii., Editura PRINTECH Bucureti, ISBN978-973-758-1232, 232 pg., Bucureti.

[7] Ioana, A. (1998) The Electric Arc Furnaces (EAF) Functional andTechnological Performances with the Preheating of the Load andPowder Blowing Optimization for the High Quality Steel Processing,PhD Thesis, University Politehnica of Bucharest, 1998, pp. .

[8] Ioana, A., Mirea, V., Blescu, C. (2009) Analysis of Service QualityManagement in the Materials Industry Using the BCG Matrix Method,Amphitheater Economic Review, Vol. XI, Nr. 26, June, Bucharest.

[9] Ioana, A., Nicolae, A., Blescu, C. (2009) Elements of MetallurgicalMarketing Mix (MMM), Metalurgia Review, ISSN 0461-9579, No78/2009, Bucharest.

[10] Ioana, A., Semenescu, A., Preda, C.F. (2012) Management Strategic.Teorie i Aplicaii. Editura Matrix Rom, Bucureti, ISBN 978-973-755-8268, 204 pg, Bucureti.

[11] * * *, http://www.earthpolicy.com

[12] * * *, http://evado.ro


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Anaerobic degradation of dairy wastewater in

intermittent UASB reactors: influence of effluent

recirculation

A. Silva, C. Couras, I. Capela, L. Arroja, H. Nadais*CESAM & Environmental and Planning Department

University of Aveiro

3810-193-Aveiro, Portugal

[email protected]

Abstract This work studied the influence of effluent

recirculation upon the kinetics of anaerobic degradation of dairy

wastewater in intermittent UASB (Upflow Anaerobic SludgeBed) reactors. Several laboratory-scale tests were performed with

different organic loads in a UASB reactor inoculated with

flocculent sludge from an industrial wastewater treatment plant.

The data obtained were used for determination of specific

substrate removal rates and specific methane production rates

and adjusted to kinetic models. A high initial substrate removal

was observed in all tests due to adsorption of organic matter onto

the anaerobic biomass which was not accompanied by biological

substrate degradation as measured by methane production.

Initial methane production was about 45% of initial soluble and

colloidal substrate removal rate. This discrepancy was observed

mainly in the first day of all experiments and was attenuated in

the second day. Effluent recirculation raised significantly the rate

of removal of soluble and colloidal substrate and methane

productivity as compared to literature results for batch assayswithout recirculation.

Keywords UASB reactor; dairy wastewater; feedless period;effluent recirculation; kinetics

I. INTRODUCTION (Heading 1)

Presently Upflow Anaerobic Sludge Bed (UASB) reactors

face significant challenges in what concerns their applicability

for the treatment of complex lipid-rich wastewater of which

dairy wastewater is an example. As an option to overcome

operating problems verified in continuous systems studies

have been developed on the intermittent operation of UASB

reactors used for treating dairy wastewater [1, 2] or for

treating proteinaceous wastewater [3], slaughterhousewastewater [4], domestic wastewater [5] or olive mill

wastewater [6]. The beneficial effects of discontinuous

feeding of fatty substrates on anaerobic systems have also

been confirmed by Palatsi et al. [7]. The intermittent operation

is composed of a succession of feed and feedless periods

where a feed period followed by a feedless period forms anintermittent cycle. During the feed periods high substrate

removal rates are achieved which are not accompanied by the

expected methane production, leading to heavy non degraded

substrate accumulation onto the biological biomass that

constitutes the UASB sludge bed. The feedless period is

crucial for the degradation of the complex substrates (fats andlong chain fatty acids LCFA) that accumulate in the biomass

during the feed period, mainly by adsorption mechanisms [1,

2, 6]. During the feed periods the intermittent UASB reactorworks as a continuous reactor and during the feedless periods

it works as a batch reactor. It has been shown that effluent

recirculation during the feedless periods of intermittent

operation are very beneficial for reactor performance

especially in terms of methane production [8].Insights on what happens during the feedless periods are

important to understand the functioning of the intermittentUASB systems. Literature presents several results for thedegradation of dairy wastewater in batch reactors. Yet if

effluent recirculation is applied during the feedless periods thehydrodynamic conditions may significantly alter the COD(Chemical Oxygen Demand) removal mechanisms andsubsequent biological degradation observed in feedless periodsof intermittent systems. The importance of the hydrodynamicconditions is related to mass transfer mechanisms [9] and toadsorption phenomena responsible for the major percentage ofinitial COD removal from complex wastewaters in anaerobicsystems [10, 11]. In this framework this investigation aimed atevaluating the influence of effluent recirculation on the kineticsof dairy wastewater degradation in the feedless periods ofintermittent UASB operation.

II. MATERIALS AND METHODS

In this work a lab-scale UASB reactor was used with a

working volume of 6 litres topped with a gas-solid-liquid

separator and operated at mesophilic temperature (351 C) bymeans of a water jacket connected to a thermostatic bath. The

UASB reactor is shown in Fig. 1. At the beginning of each test

the reactor was seeded with approximately 4 litres of

flocculent biomass adapted to dairy wastewater from an

industrial wastewater treatment plant.


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Fig. 1. Laboratory-scale UASB reactor used in this work.

The feed was prepared from dilution of semi-skimmed milk

and supplementing with nutrients and alkalinity [1]. Table I

presents the composition of the milk used for preparing the

feed.

TABLE I. CHARACTERIZATION OF THE MILK USED FOR FEED

Parameter (g/L) Value

Proteins 32

Carbon hydrates 48

Total lipids 16

Saturated lipids 10

Calcium 1.2

COD 147.47COD = Chemical Oxygen Demand.

The reactor was operated in a discontinuous mode wherethe feed was pumped into the reactor and then the producedeffluent was recirculated, without any extra feeding, atvolumetric flow of 0.5 L/h. Table II presents the experimentalconditions for the five tests performed in this work.

TABLE II. EXPERIMENTAL SET-UP

Test Organic load

(g COD/L)

Biomass

(gVSS/L)

1 0.333 4.763

2 0.666 4.7633 4.460 4.456

4 8.910 5.127

5 17.270 4.317

After recirculation started the monitoring plan was

implemented consisting of daily analysis of total COD, paper

filtered COD (CODpf), membrane filtered COD (CODmf),

total and volatile suspended solids (TSS and VSS), pH andvolatile fatty acids (VFA). Paper filtered COD samples

(CODpf) were prepared using paper filters with a pore

diameter of 1,2 m (Whatman Inc. Reeve Angel, grade 403,

4,7 cm). Membrane filtered COD samples (CODmf) were

prepared with membrane filters with a pore diameter of 0,45

m (Schleicher & Schuel Purabind, 4,7 cm). Membrane

filtered COD represents the soluble COD fraction whilst the

paper filtered COD represents the soluble and colloidal COD

fraction [4].

The produced biogas was measured by a waterdisplacement system. Methane content in biogas wasmonitored using a gas chromatograph Shimadzu GC 9a,equipped with a Supleco Molcular Sieve 5 A column and aThermal Conductivity Detector (T=100C). Injectiontemperature was 45C and Helium was used as carrier gas(P=4.4 kg/cm

2). Volatile fatty acids determination was carried

out in a gas chromatograph Chrompack CP 9001 equipped witha Chrompack CP sil5 CB column and a Flame IonizationDetector (T=300C). The injection temperature was 270 C andHelium was used as carrier gas with a volumetric flow of 8ml/min.

III. RESULTS AND DISCUSSION

The profiles of CODpf, cumulative methane production,

removal of CODpf and methanization of removed CODpf

were obtained for all the tests performed. Figs. 2 to 5 present

results for the two higher loads tested (8.91 g/L and 17.27 g

COD/L).

0

20

40

60

80

100

120

140

0

1

2

3

4

5

6

7

8

9

10

0 2 4 6 8 10

4()

+(/)

()

(/)

+ (/)

4 ()

Fig. 2. COD and CH4profile for test 4 (8.91 g COD/L).


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0

50

100

150

200

250

0

2

4

6

8

10

12

14

16

18

20

0 5 10

4()

(/)

()

(/)

+ (/)

4 ()

Fig. 3. COD and CH4profile for test 5 (17.27 g COD/L).

For all the organic loads tested a significant decrease inCODpf was observed during the first day of the tests with 75%

- 90% CODpf removal for all the tests except the higher load

(only 43% CODpf removal in the first day). From the second

day onwards the CODpf values are approximately constant intime except for the test with the higher load (17.27 g

COD/L.d) in which an important decrease of CODpf was

observed in the second day (Fig. 3). The values of volumetric

methane production present a tendency towards stabilization

only from the third day onwards for all the tests except for the

lower load (0.33 g COD/L.d, data not shown). With this lowerload the tendency to diminish the methane production was

observed only from the fifth day of the test (data not shown).

0

20

40

60

80

100

0 5 10

(%)

()

Fig. 4. COD removal and methanization efficiencies for test 4 (8.91 g

COD/L).

0

20

40

60

80

100

0 5 10

(%)

()

Fig. 5. COD removal and methanization efficiencies for test 5 (17.27 g

COD/L).

The evolution of the CODpf removal as a function of the

applied load (Fig. 6) shows that in the first and second days

the COD removal is very similar with exception of the higher

load. The additional COD removal in the second day is very

small in comparison with what was observed in the first day.

For the higher load by comparing the percentage removal

attained in the first and the second days it is possible to seethat not all the substrate is removed in the first day.

0

10

20

30

40

5060

70

80

90

100

0 5 10 15 20

(%)

( /)

(1)

(1+2)

Fig. 6. Evolution of COD removal with applied load..

A linear relation was found between the applied load and the

volumetric methane production obtained in the first day (Fig.

7) except for the higher load were a decrease in the relation

CH4/load was observed. This discrepancy is due to the fact

that not all the organic matter is available for the

microorganisms to degrade since it is adsorbed onto the

biomass particles, causing a lower methane production than

would be expected from the observed COD removal. Theseresults confirm the rapid adsorption of organic substrate onto

the biological sludge reported by Hwu [10] and by Nadais et


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i

s

max

K

S

S

K1

qq

++

=

SKs +=

maxqq

al. [11]. Yet when correlating the total volume of CH4

produced in the first and second days with the applied loads a

linear correlation is observed. Fig. 8 presents the values of

methanization percentage of the removed CODpf attained in

the first and in the second days of the tests as functions of the

applied loads. The differences observed in the methanization

of the removed substrate between the first and the second days

indicate that a part of the COD removed during the first day is

methanized only in the second day. This result is inaccordance of the proposed duration of two days for the

feedless period of intermittent operation of UASB reactors

treating dairy wastewater [1].

0

10

20

30

40

50

60

70

0 5 10 15 20

4()

(/)

4 (1)

4 (1+2)

Fig. 7. Correlation between applied load and methane production .

0

10

20

30

40

50

60

7080

90

100

0 5 10 15 20

(%)

( /)

(1)

(1+2)

Fig. 8. Evolution of methane production with applied load.

The methane content in the produced biogas varied from 50%

to 90% for all the tests being higher by the end of each test.

The soluble COD fraction (CODmf) is the fraction available

for microorganism metabolism and is around 20% to 40% of

the CODpf (colloidal + soluble COD) in the beginning of tests

(see Figs. 2 and 3). In all the tests the average pH values

varied between 7 and 8 the lowest value reached being 6.5.The VFA concentrations determined in all the tests never

surpassed 2 mg HAc/L, always being under the threshold

toxicity limit of 3 g HAc/L suggested by Malina and Pohland

[12]. As an example Fig. 9 presents the VFA profile for test 4

(load of 8.91 g COD/L), where it can be seen that a significant

percentage of the produced VFA is butyric acid, an

intermediate substrate related to the degradation of fatty

matter and LCFA in anaerobic systems [13].

0

100

200

300

400

500

600

700

800

900

1000

1 2 3 6 7 8

(/)

()

Fig. 9. VFA profile for test 4.

The specific CODcolloidal+soluble removal rates (qCODpf)

and the specific methane production rates (qCH4) wereobtained by the initial velocity method (t = 1 day) and were

adjusted to the Monod model (1) and to the uncompetitive

inhibition model or Haldane model (2), both described in [14].

The least squares method was applied and commercial

software, Scientist version 2.0 1994, was used, with an

integration method based on the Powell algorithm and initial

values search by the double simplex method. The quality ofthe fitting was assessed by the coefficient of determination r

2,

see Fig. 10 and Table III.

(1)

(2)

where: q is the specific substrate removal rate (g COD/g

VSS.d); qmax is the maximum substrate specific removal rate(g COD/g VSS.d); Ksis the half-velocity constant (g/L), Kiis

the Haldane inhibition constant (g/L) and S is the substrate

concentration (g/L).

According to the values of r2the model that provided a better

fit of the experimental data was the Monod model. The

specific rate of methane production (qCH4) is approximately

45% of the specific CODpf removal rate (see Fig. 11) which is


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justified by the fact that this rates were calculated using the

initial velocity method (t = 1 day) and there is a lag betweeninitial COD removal and methane production.

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

0 5 10 15 20

(/.

)

(/)

4 () ()

4

Fig. 10.Fitting of experimental data to the Monod model.

0,4518 + 0,0053

0,9899

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 0,5 1 1,5 2

4(/

.

)

+ (/.)

Fig. 11.Relation between specific COD removal rate and specific methane

production rate..

TABLE III. KINETIC PARAMETRES

Parameter CODpf CH4 CODpf

q ax 3.044 1.1750 2.4

Ks 9.9323 6.7140 9.6

r2 0.9941 0.9866 0.9974

1) This work; 2) Reference [15].Fig. 12 and Table III present a comparison of the specific

COD removal rates obtained in this work and those obtained

in batch reactors with no recirculation with a biomass content

of 5 g VSS/L [15]. It can be seen that for loads above 5 g

COD/L recirculation improves the COD removal rate in about

30% for tests performed with the same VSS content compared

to the results with no recirculation. This means that the

recirculation of the treated effluent and the hydrodynamic

conditions have a significant beneficial influence upon the

kinetics of the degradation process in discontinuous anaerobic

systems.

0,00

0,50

1,00

1,50

2,00

0 5 10 15 20 25

qCOD

(g/g.d

)

Load (g COD/L)

qCOD (this work)

qCOD (5 g VSS/L)[15]

Fig. 12.Comparison of data from this work and from literature [15].

Figs. 13 and 14 present the COD balances for tests 4 (organicload of 8.91 g COD/L) and for a test performed in similar

conditions but with no effluent recirculation performed with

an organic load of 9 g COD/L and 5 g VSS/L, [1].

Surprisingly it can be seen that methane production is more

rapid in the test with no recirculation. Yet initial adsorption(retained COD) is more pronounced in the test with effluent

recirculation probably due to a more complete contact

between the substrate and the biomass. Although initial

adsorption is higher with effluent recirculation also thesubstrate degradation is higher for this condition leading to

higher methanization efficiency.

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8

(%)

()

+

Fig. 13.COD balance for test 4 (8.91 g COD/L); coll = colloidal, SNA =

soluble not acidified.


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0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8

(%)

()

+

Fig. 14.COD balance for a batch test without recirculation with a load of 9 g

COD/L and 5 g VSS/L (adapted from [15]); coll = colloidal, SNA = soluble

not acidified.

These results are in agreement with what was reported

by Nadais et al. [8], that observed an improvement ofintermittent UASB reactor performance when effluent

recirculation was applied during the feedless periods.

(methanization raised to 95% as compared to 80-88% attained

with no effluent recirculation).

The results obtained in this work also suggest that fororganic loads above 10 g COD/L the feedless periods ofintermittent operation should be longer than the feed periods ashas been suggested by Coelho et al. [2]. On the other hand itwas observed that the monitoring of high rate reactors treatingcomplex fat containing wastewater based on the COD of the

produced effluent may be misleading in what concerns the real

biological degradation [16, 17].

IV. CONCLUSIONS

In laboratory experiments of UASB reactors with total effluent

recirculation treating dairy wastewater there is a rapid COD

removal in the first day of the tests, evidenced by the decrease

in CODcolloidal+soluble, which removal is not followed by a

biological degradation evidenced by CH4 production. This is

due to adsorption of the organic matter onto the surface of the

biological sludge since adsorption is faster than biological

degradation. The CH4 specific production rate, calculated by

the initial velocity method (t=1 day) was about 45% of thespecific CODcolloidal+soluble removal rate. This confirmsthat the monitoring of high rate reactors based on the COD of

the liquid phase may be misleading [16, 17]. The discrepancy

between the initial COD removal and the CH4production was

observed mostly in the first day of the tests fading on the

second day which suggests that a period for intermittency in

UASB reactors should be higher than one day and possibletwo days.

In what concerns the influence of the hydrodynamic

conditions upon the behavior of high rate reactors treating

milk wastewaters it can be said that effluent recirculation

during feedless periods improved significantly (up to 30%) the

specific CODcolloidal+soluble removal rate in comparison to

what was observed in classical batch reactors with no

recirculation. A more complete substrate degradation was also

observed with effluent recirculation.

ACKNOWLEDGMENT

This work was performed with funding from FCT-Fundao

para a Cincia e Tecnologia, Portugal(PTDC/AMB/65025/2006).

REFERENCES

[1] H. Nadais, I. Capela, L. Arroja, A. Duarte, Optimum cycle time forintermittent UASB reactors treating dairy wastewater, Water Research,vol. 39, no. 8, pp. 1511-1518, 2005.

[2] N. Coelho, A. Rodrigues, L. Arroja, I. Capela, Effect of non-feedingperiod length on the intermittent operation of UASB reactors treatingdairy effluents. Biotechnology Bioengineering, vol. 96, no 2, pp. 244249, 2007.

[3] M. Vias, C. Galain, M. Lois, Treatment of proteic wastewater incontinuous and intermittent UASB reactors,. VI InternationalSymposium on Anaerobic Digestion, So Paulo, Brazil, vol. 1, pp. 321-327, 1991.

[4] S. Sayed, Anaerobic treatment of slaughterhouse wastewater using theUASB process, Ph.D Thesis, Agricultural University of Wageningen,Wageningen, The Netherlands, 1987.

[5] S. Sayed, and M. Fergala, Two-stage UASB concept for treatment ofdomestic sewage including sludge stabilisation process, Water Scienceand Technology, vol. 32, no 11, pp. 5563, 1995.

[6] M.R. Gonalves, J.C. Costa, I.P. Marques, M.M. Alves, Strategies forlipids and phenolics degradation in the anaerobic treatment of olive millwastewater, Water Research, vol. 46, no 6, pp. 16841692, 2012.

[7] J. Palatsi, M. Laureni, M.V. Andrs, X. Flotats, H.B. Nielsen, I.Angelidaki, Recovery strategies from long-chain fatty acids inhibition

in anaerobic thermophilic digestion of manure, BioresourceTechnology, vol. 100, no 20, pp. 45884596, 2009.

[8] H. Nadais, I. Capela, L. Arroja, Intermittent vs continuous operation ofupflow anaerobic sludge bed reactors for dairy wastewater and relatedmicrobial changes, Water Sci. Technol., vol. 54, no 2, pp. 103109,2006.

[9] M.A. Pereira, O.C. Pires, M, Mota, M.M., Alves, Anaerobicbiodegradation of oleic and palmytic acids: evidence of mass transferlimitations caused by long chain fatty acid accumulation onto theanaerobic sludge. Biotechnol. Bioeng., vol. 92, no 1, 15-23, 2005.

[10] C.S. Hwu, Enhancing anaerobic treatment of wastewaters containingoleic acid, PhD thesis, Agricultural University of Wageningen,Wageningen, The Netherlands, 1997.

[11] H. Nadais, I. Capela, L. Arroja, A. Duarte, Biosorption of milksubstrates onto anaerobic flocculent and granular sludge, Biotechnol.Prog., vol. 19, pp. 10531055, 2003.

[12] J.E. Malina and F. Pohland, Design of anaerobic processes for thetreatment of industrial and municipal wastes, Technomic PublishingCompany, Inc. Lancaster, Pennsylvania, USA, 1992.

[13] G. Silvestre, A. Rodrguez-Abalde, B. Fernndez, X. Flotats, A.Bonmat, Biomass adaptation over anaerobic co-digestion of sewagesludge and trapped grease waste,Bioresource and Technology, vol. 102,pp. 68306836, 2011.

[14] B. Desjardins and P. Lessard, Modlisation du procd de digestionanarobie, Sciences et Techniques de L'eau, vol. 25, no 2, pp. 119-136,1992.

[15] H. Nadais, I. Capela, L. Arroja, A.. Duarte, Kinetic analysis ofanaerobic degradation of dairy wastewater, Proc. 9 th World Congress


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on Anaerobic Digestion-2001, Antwerp, Belgium, 2-5 September, 203-208, 2001.

[16] H. Nadais, Dairy wastewater treatment with intermittent UASBreactors, Ph.D Thesis, University of Aveiro, Aveiro, Portugal, 2002 (inportuguese).

[17] J. Jeganathan, G. Nakhla, A. Bassi, Long-term performance of high-rate anaerobic reactors for the treatment of oily wastewater, Environ.Sci. Technol., vol. 40, pp. 64666472, 2006


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Fuels: A Survey on Sources and Technologies

Farzaneh Kazemi Qale Joogh, Milad AsgarpourKhansary

Department of Chemical Engineering,

University of Mohaghegh Ardebili,

Ardebil, Iran.

Milad Asgarpour Khansary, Ashkan Hosseini, AhmadHallaji Sani

School of Chemical Engineering,

University of Tehran,

Tehran, Iran.

Navid ShabanZadeh

Petroleum Engineering,

Politecnico di Torino,

Torino, Italy.

Corresponding Author Email: [email protected]

Abstract Industry uses cheaply available fossil feed-stocks

such as petroleum, coal and natural gas based refineries to

produce a wide variety of products to meet the increasing

demand of the population such as fuel, fine chemicals,

pharmaceuticals, detergents, plastics, pesticides and fertilizers,

lubricants, solvent, waxes, asphalt, synthetics fibers, etc. Biomass,

an alternative renewable and carbon neutral source of fuel,

attracted significant interest in current researches. It ranks third

as an energy resource in the world, after coal and oil. About 14%

of the worlds annual energy consumption is provided by biomass

which is equivalent to 1250 million tons oil. Environmentally, use

of biomass fuels has substantial benefits. As biomass absorbs

carbon dioxide during growth and emits it during combustion, ithelps the atmospheric carbon dioxide recycling and does not

contribute to the greenhouse effect. In this paper fuels derived

from biomass, natural gas and oil are introduced and discussed.

Keywords biomass and fossil fuels; biomass conversion;

energy sources; greenhouse gas

I. INTRODUCTIONThe development of petroleum, coal, and natural gas based

refinery, the cheaply available fossil feed stocks, attracts mostresearch emphasis in twentieth century. These feed stocks tomeet the growing demand of the population are used to

produce various products such as fuel, fine chemicals,pharmaceuticals, detergents, synthetic fiber, plastics, pesticidesand fertilizers, lubricants, solvent, waxes, coke, asphalt, etc. inindustry [1, 2, 33].

Rising use of fossil fuels isnt sustainable as it increasesgreenhouse gas (GHG) emissions which consequently lead toenvironmental impact on global warming [3]. In addition, theindustrialized countries have agreed to reduce their emission ofgreenhouse gases, based on emission levels in 1990, by 5% by20082012 according to the Kyoto protocol. In order toachieve this goal, its essential to increase the efficiency in

energy use and to replace fossil fuels by biomass and otherrenewable energy sources. The European commissions white

paper for a community strategy and action plan sets out astrategy to double the share of renewable energy in grossdomestic energy consumption in the European union by 2010[4]. In 2003, 15% of Swedens energy use was provided by

biofuels and this figure is expected to rise [5, 33].

So it can be inferred that there is significant interest infinding alternative renewable sources of fuel that are

potentially carbon neutral, namely biomass [6-8], [3]. Biomass,compared to fossil fuels, is a widely available and renewable

fuel that has advantages such as low sulphur and ash content[9]. Biomass is the third energy resource in the world, aftercoal and oil [10]. It is the most important source of energy indeveloping countries and primary source of energy for morethan half the worlds population and provides about 14% of theworlds annual energy consumption equivalent to 1250 milliontons oil [11-15].

Use of biomass fuels has substantial benefits in view ofenvironmental concern [16]. Biomass helps the atmosphericcarbon dioxide recycling and does not contribute to thegreenhouse effect as it absorbs carbon dioxide during growth,and emits it during combustion. Therefore, biomass consumesthe same amount of CO2from the atmosphere during growth as

is released during combustion [17].which means combustion ofbiomass is carbon neutral. Biomass can be converted intoliquid, solid and gaseous fuels through some physical, chemicaland biological conversion processes, [11], [18, 19, 33]. In this

paper, fuels derived from biomass, natural gas and oil areintroduced and discussed.


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II. BIOMASSBiomass can be found all over the world. Almost any

organic material can be regarded as a potential energy source.Low value products such as sewage or other residues can betransformed to useful fuels. As the oil price rises, the interestfor alternative energy sources increases. Correctly managed,

biomass is a renewable and sustainable fuel that can reducesignificantly net carbon emissions when compared with fossil

fuels. Thus it can be assumed as an attractive cleandevelopment mechanism option for reducing greenhouse gas(GHG) emission [20, 33].

Biomass can be converted into liquid, solid and gaseousfuels with the help of some physical, chemical and biologicalconversion processes [18, 19]. A wide variety of biomassfeedstocks can be used to produce fuels such as; wood, short-rotation woody crops, agricultural wastes, short-rotationherbaceous species, wood wastes, bagasse, industrial residues,waste paper, municipal solid waste, sawdust, bio-solids, grass,waste from food processing, aquatic plants and algae animalwastes, and a host of other materials. Main current biomasstechnologies [21] are: destructive carbonization of woody

biomass to charcoal, gasification of biomass to gaseousproducts, pyrolysis of biomass and solid wastes to liquid, solidand gaseous products, supercritical fluid extractions of biomassto liquid products, liquefaction of biomass to liquid products,hydrolysis of biomass to sugars and ethanol, anaerobicdigestion of biomass to gaseous products, biomass power forgenerating electricity by direct combustion or gasification ,

pyrolysis, co-firing of biomass with coal, biological conversionof biomass and waste (biogas production, wastewatertreatment), biomass densification (briquetting, pelleting),domestic cook stoves and heating appliances of fuel wood,

biomass energy conservation in households and industry, solarphotovoltaic and biomass based rural electrification,

conversion of biomass to a pyro-lytic oil (biofuel) for vehiclefuel, and conversion of biomass to methanol and ethanol forinternal combustion engines.

A.FT-DieselFT-Diesel stands for Fisher-Tropsch-Diesel, a method of

manufacturing long hydrocarbon chains (-CH2-) from synthesisgas. The fuel is similar to petroleum diesel, but has much lowercontent of noxious substances in the emissions. The ratio

between hydrogen and carbon dioxide in synthesis gas iscrucial for a high efficiency in the following FT-synthesis [22].Table 1 shows a short summary of important properties of FT-Diesel.

In a FT-synthesis from synthesis gas, one mole CO reactswith two mole H2under the presence of a catalyst, often iron orcobalt, creating mainly long chains of -CH2- molecules(paraffin) and one mole H2O per carbon unit as shown in (1).Water gas shift reaction (WGS) can be used, if the presence ofhydrogen is too small which transforms carbon monoxide andwater into carbon dioxide and hydrogen as shown in (2).

22 2 2

CO H CH H O+ + (1)

2 2 2CO H O H CO+ + (2)

Several products such as hydrocarbons (C1-C4), gasoline (C5-

C11), diesel (C12-C20), and waxes (>C20) are generated in the

polymerization. There are two constrain which should be

reached before the synthesis gas is transported to the FT-

reactor; (i) the combined sulphur and particle amount has to be

less than 1 ppm and (ii) the combined presence of nitrogen,

carbon dioxide, and methane needs to be below 10%. There

are two technologies of FT-processes; low temperature-

Fischer-Tropsch, which is used to create greater polymer as

diesel, and high-temperature-Fischer-Tropsch to achieve a

high amount of lighter hydrocarbons.

The outcome of the process is controlled by the Anderson-Schultz-Flory distribution of hydrocarbons and is presented in(3). The propagation and termination rates are depending on

pressure, temperature, and how long the polymer chain hasbeen in the process. The output of the desired product can bemaximized by controlling these parameters. The highestexchange is achieved for methane but the highest exchangedfor a liquid fuel is diesel which motivates the production of

diesel instead of gasoline.2 1

(1 )n

W nn

= (3)

/ ( )K K Kp p t = + (4)

Wn, n, , Kpand Ktstand for weight fraction of Cn, carbonnumber, probability of chain growth, propagation rate andtermination rate, respectively.

The FT-process is exothermal, thus in order to receive thedesirable outcome it requires efficient cooling and temperaturecontrol. The gas which leaves the reactor is separated intomethane, ethane, ethene, and unreacted synthesis gas. Theunreacted gas can be reinserted in the reactor but commonly it

is burned.

The similarity to petro-diesel is a great advantage becausethe vehicle fleet and infrastructure already exist. FT-diesel isfully compatible with ordinary diesel engines and there is noneed for any modifications. As the product is sulphur free andonly contains low amount of other impurities the emission iscleaner than that of petro-diesel. But the production cost ishigher than that of petro-diesel which is the industrial term fordiesel produced from oil. Therefore FT-diesel requireseconomic assistance from the governments in order to make acommercial breakthrough [33].

TABLE I. SHORT SUMMARY OF MOST IMPORTANT PROPERTIES OF SOMEFUELS

Fuel

Properties

AliasLHV

(MJ/lit)a

Density

(kg/m3)aOctane

FT-diesel GTL, BTL, CTL 43.9 0.77-0.88 70-80

BiodieselFAME, RME,

SME, B10037-38b

0.88103b

51-58b

DME

Methoxymethane,

Wood Ether,

Dimethyl Ether

27.6 0.66103 >55

MethanolHydroxymethane,

Methyl Alcohol,19.9 0.79103

110-

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Fuel

Properties

AliasLHV

(MJ/lit)a

Density

(kg/m3)aOctane

Carbinol

Ethanol

Hydroxyethane,

Ethyl Alcohol,

Grain Alcohol

26.8 0.78103105-109

Hydrogen H2 120 0.09 106

Bio-methane

Biogas, CBM,CMG, SNG

45.4 0.72 >102

Gasoline Petrol, Gas 43.2 0.72-0.77 90-95

Diesel 43.4 0.82-0.84 45-53

a.All units are in SI. MJ/lit = mega joule per liter, kg/m3= kilogram per cubic meter.b.Values refer to RME andc.SME, respectively.

B.FT-DieselToday biodiesel is also known as fame (fatty acid methyl

ester) and can be divided into RME (rape seed oil methyl ester)or SME (sunflower oil methyl ester) as illustrated in Table 1.Biodiesel can be produced out of vegetable oils or animal

waste. The most common oils used to produce biodiesel arerape seed oil and sunflower oil.

Fatty acids methyl esters are one of two primary platformchemicals produced by the ole-chemical industry. Using cheap

base catalysts (NaOH or KOH) methanol at low temperatures(60

C to 80

C) and pressures (1.4 atm), methyl esters from

triglycerides can be produced in both batch and continuoussystems. The other major platform chemical, fatty acids, canalso be used to produce methyl esters. In one of two followingways fats are hydrolyzed to free fatty acids and glycerol.

(i) continuous, high pressure, counter current systems at 20to 60 bars and 250

C with or without catalysts, which are

typically zinc oxide, lime, or magnesium oxide added to water,

and (ii) countercurrent systems at atmospheric pressure withsmall amounts of sulfuric/sulfonic acids in steam.

Using sulfuric acid, strong mineral acids, or a sulfonatedion exchange resin, and methanol methyl esters are producedfrom fatty acids in counter current systems at 80

C to 85

C

under mild pressures. If a feedstock contains triglycerides andfree fatty acids, acid esterification is performed on the entirefeedstock first, followed by trans-esterification to convert theremaining triglycerides. To obtain high yields and low

processing problems, water should be managed correctly.

For all processes, generally, yields of glycerides and fattyacids to esters exceed 97% and with careful management of

equilibrium conditions can reach 99%. As temperatures andpressures increase, the trans-esterification reaction becomesauto-catalyzed. Henkle used this process with crude soy oil inthe 1970s. Conditions may not be supercritical for methanol

but may employ high enough temperatures and pressures toauto-catalyze the reaction [23]. In 1991 the first industrial plantfor producing biodiesel opened in Austria and by 1998, 21countries had commercial projects.

With only small modifications as gasket and filter changes,biodiesel can be used in conventional diesel engine. So a dieselvehicle, for a small amount of money, can be converted to run

on biodiesel which contributes with the advantageousenvironmental factors that is associated with biomass basedfuels. Biodiesel can also be used as a blender to petro-dieseland is then referred to as e.g. B80, where the numbercorresponds to the percentage of biodiesel present in the fuel.

C.DMEDME is the organic compound with the formula ch3och3, a

colorless gas that is a useful precursor to other organiccompounds and an aerosol propellant. Combusted, DME

produces minimal NOx and CO, though HC and soot formationis significant. DME can act as a clean fuel when burned inengines properly optimized for DME. Table 1 shows a shortsummary of important properties of dimethyl ether (DME).

DME is produced out of synthesis gas in the followingreaction chain.

3 32 3 3 2CO H CH OCH CO

+ + (4)

2 4 2 3 3 2CO H CH OCH H O+ + (5)

2 4 2 3CO H CH OH + (6)

23 3 3 2

CH OH CH OCH H O + (7)

2 2 2H O CO H CO+ + (8)

The DME synthesis (Eq. 4) can be separated into methanolsynthesis (Eq. 6) followed by the dehydration reaction (Eq. 7)and the shift reaction (Eq. 8). If the shift reaction is slow alsothe second DME synthesis (Eq. 5) is active. Reaction 5 can bedivided into Eq. 6 and 7. A more detailed description of the

production of DME is found in [24, 33].

DME is suitable for DICI-engines due to high octane rating.In order to make the engine compatible with DME, mainlymodifications of the fuel injector system is necessary. Asia hasthe highest growth in fuel usage where, the highest interest ofDME is found in there. With very low levels of NOx and soot,DME has exceptional emission properties. That is becausethere are no carbon-carbon bindings in the molecules and thehigh amount of oxygen (35%) which has fairly low burningtemperature. And this leads to the main contributor to the low

NOx formation. By using conventional methods, the emissionscan be reduced further, for example EGR which is highlysuitable for DME due to the lack of soot formation. But therelatively low energy density of DME and the fact that DME isa gas under normal conditions result in a bigger and

pressurized fuel tank which increases the retail price of the

vehicle and causes trouble for vehicles where space is limited.According to [25, 33] DME liquefies under 5 bars pressure

at 20C which compared to other gaseous fuels is low and

thereby a tank defined for DME is substantially cheaper andsmaller than tanks defined for methane or hydrogen.

D.MethanolMethanol, also known as methyl alcohol, wood alcohol,

wood naphtha or wood spirits, is a chemical with the formulaCH3OH (often abbreviated MeOH). It is the simplest alcohol,and is a light, volatile, colorless, flammable liquid with a


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distinctive odor very similar to, but slightly sweeter than,ethanol (drinking alcohol).at room temperature, it is a polarliquid, and is used as an antifreeze, solvent, fuel, and as adenaturant for ethanol. It is also used for producing biodieselvia trans-esterification reaction. Most important properties ofmethanol are shown in table 1.

Methanol is produced [24] from synthesis gas as presentedin reactions 9 to 11.

2 2 3H CO CH OH+ (9)

2 2 2CO H O H CO+ + (10)

32 2 3 2H CO CH OH H O

+ + (11)

First to help the upcoming reactions to occur, the synthesisgas is compressed. In the reaction chamber pellets of coppers isused as a catalyst causing the reactions shown above. After thereaction chamber the gas contains methanol, water andunreacted substances. By using methanol letdown, theunreacted substances are separated, a process where theunreacted gases rise to the top and are guided back to the

reaction chamber. The distillation is done in two phases, at firstall the substances that have a boiling point lower than methanolare removed by heating the mixture to a temperature just belowthe boiling point of methanol. In the second stage theremaining mixture is heated just above the boiling point ofmethanol. Methanol is drawn off the top and the water whichhas the highest boiling temperature at the bottom. Byproductsare drained in the middle.

Methanol can directly be used in a fuel cell referred to asDMFC (direct methanol fuel cells) which is still in adeveloping phase. Thus methanol usage is likely to increasedrastically if it is successful. The fuel can also be used incommon combustion engines and is a strong candidate for

replacing gasoline usage.

E.EthanolEthanol, best known as the type of alcohol found in

alcoholic beverages, also called ethyl alcohol, pure alcohol,grain alcohol, or drinking alcohol, is a volatile, flammable,colorless liquid. It is a psychoactive drug and one of the oldestrecreational drugs. It is also used in thermometers, as a solvent,and as a fuel. In common usage, it is often referred to simply asalcohol or spirits. A short summary of important properties ofethanol is shown in Table 1.

Here we only consider ethanol from cellulose. A more

detailed text about the production of ethanol from cellulose,starch or sugar can be found in [26].

There are three basic types of processes for production ofethanol from cellulose; acid hydrolysis, enzymatic hydrolysis,and thermochemical, with variations for each. The first is themost common. Virtually any acid can be used; however,sulfuric acid is most commonly used since it is usually the leastexpensive.

(i). Acid hydrolysis

Two basic types of acid processes are used: dilute acid andconcentrated acid, each with variations.

Dilute acid processes are carried out under hightemperature and pressure, and the reaction lasting in the rangeof seconds or minutes, which facilitates continuous processing.Most dilute acid processes are limited to a sugar recoveryefficiency of around 50%. The reason for this is that at leasttwo reactions are part of this process. Cellulosic materials areconverted to sugar in the first reaction and the second reactionconverts the sugars to other chemicals. Unfortunately theconditions that cause these two reactions to occur are the same.Thus, once the cellulosic molecules are broken apart, thereaction proceeds rapidly to break down the sugars into other

products. Not only does sugar degradation reduce sugar yield,but the furfural, a chemical used in the plastics industry, andother degradation products can be poisonous to thefermentation microorganisms.

The fast rate of reaction is the biggest advantage of diluteacid processes, which facilitates continuous processing. On theother hands, their low sugar yield is the biggest disadvantage.For rapid continuous processes, feed stocks must also bereduced in size so that the maximum particle dimension is inthe range of a few millimeters, in order to allow adequate acid

penetration

The concentrated acid process is carried out in relativelymild temperatures and the only pressures involved are usuallyonly those created by pumping materials from vessel to vessel.Usda developed one concentrated acid process first and furtherrefined by Purdue university and the Tennessee valleyauthority. Tva developed a concentrated acid process in whichcorn Stover is mixed with dilute sulfuric acid (10%), andheated to 100

C for 2 to 6 hours in the first (or hemicellulose)

hydrolysis reactor. The low temperatures and pressuresminimize the degradation of sugars. The hydrolyzed material in

the first reactor is soaked in water and drained several times inorder to recover the sugars. The solid residue from the firststage is then dewatered and soaked in a 30% to 40%concentration of sulfuric acid for 1 to 4 hr. as a pre-cellulosehydrolysis step. Then this material is dewatered and dried withthe effect that the acid concentration in the material isincreased to about 70%. After reacting in another vessel for 1to 4 hr. at 100

C, the reactor contents are filtered to remove

solids and recover the sugar and acid. To provide the acid forthe first stage hydrolysis, the sugar/acid solution from thesecond stage is recycled to the first stage. The sugars from thesecond stage hydrolysis are thus recovered in the liquid fromthe first stage hydrolysis [33].

The primary advantage of the concentrated process is thehigh sugar recovery efficiency (over 90% of bothhemicellulose and cellulose sugars). Relatively low costmaterials such as fiberglass tanks and piping can be used due tolow temperatures and pressures. Unfortunately, it is a relativelyslow process and needs cost effective acid recovery systems to

been develop which is difficult to achieve. Without acidrecovery, large quantities of lime must be used to neutralize theacid in the sugar solution. This neutralization forms largequantities of calcium sulfate, which requires disposal andcreates additional expense.


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(ii). Enzymatic hydrolysis

Another basic method of hydrolysis is enzymatichydrolysis. Enzymes are naturally occurring plant proteins thatcause certain chemical reactions to occur. However, forenzymes to work, they must obtain access to the molecules to

be hydrolyzed. For enzymatic processes to be effective, somekind of pretreatment process is thus needed to break thecrystalline structure of the lignocellulose and remove the ligninto expose the cellulose and hemicellulose molecules. Either

physical or chemical pretreatment methods may be useddepending on the biomass material. Physical methods may usehigh temperature and pressure, milling, radiation, or freezingwhich require high energy consumption. The chemical methoduses a solvent to break apart and dissolve the crystallinestructure.

The enzymes currently available require several days toachieve good results due to the tough crystalline structure.Long process times tie up reactor vessels for long periods, sothese vessels have to either be quite large or many of themmust be used. Currently the cost of enzymes is also too highand research is continuing to bring down the cost of enzymes.However, if less expensive enzymes can be developed,enzymatic processes hold several advantages: their efficiency isquite high and their byproduct production can be controlled,their mild process conditions do not require expensivematerials of construction, and their process energyrequirements are relatively low.

(iii). Thermochemical processes

There are two ethanol production processes that currentlyemploy thermochemical reactions in their processes.

In the first system biomass materials are first thermochemically gasified and the synthesis gas (a mixture ofhydrogen and carbon oxides) bubbled through speciallydesigned fermenters. A microorganism is introduced into thefermenters under specific process conditions, which is capableof converting the synthesis gas, to cause fermentation toethanol.

No microorganisms are used in second thermochemicalethanol production process. In this process, biomass materialsare first thermo-chemically gasified and the synthesis gas

passed through a reactor containing catalysts, which cause thegas to be converted into ethanol. Using synthesis gas-to-ethanol processes, ethanol yields up to 50% have beenobtained. Some processes that first produce methanol and thenuse catalytic shifts to produce ethanol have obtained ethanolyields in the range of 80%. Unfortunately, like the other

processes, finding a cost-effective all-thermochemical processhas been difficult.

The first industrial use of ethanol was in 1876, when it wasused in a combustion engine that worked in an Otto cycle. Theethanol driven automobiles grew strong until after the SecondWorld War when fuels from petroleum and natural gas becameavailable in large quantities and to a low cost. The profit in

producing fuel out of agriculture crops sank and many of theformer ethanol producing plants converted to the beveragealcohol industry. In the 1970s economic problems for Brazilcaused a new interest in ethanol. Brazil is a big sugar producer

which makes it suitable for the ethanol industry. Nowadays40% of the gasoline demand in Brazil is replaced with ethanol.

Ethanol production process can use any biologicalfeedstock that contains sugar or material that can be convertedinto sugar, such as starch or cellulose. Starch or sugarcontaining feedstock consists in the human food chain causes ahigh market price. Thus, using material containing cellulose,for example paper, cardboard, wood, and other fibrous plantmaterial, could reduce the price of ethanol.

Ethanol can be used as a blend in gasoline which is used toreduce emissions and increase the octane rating of the fuel.There are vehicles that can use gasoline, ethanol or any blendof them. The higher octane rating of ethanol compared togasoline allows a higher compression ratio of the engine thatleads to a higher efficiency. But on the other hand, gasolinelimits the compression ratio which leads to a higher fuelconsumption when using ethanol compared to a vehicle onlydedicated for ethanol usage.

F.HydrogenHydrogen gas (di-hydrogen or molecular hydrogen) is

highly flammable and will burn in air at a very wide range ofconcentrations between 4% and 75% by volume [27].Table 1summarize most important properties of hydrogen [33].

Although hydrogen is the most plentiful gas in the universeit does not exist naturally on earth. Hydrogen is almost alwayscombined with other elements such as carbon or oxygen

because of its likeliness to react with other molecules.it canhowever be produced in multiple ways using fossil fuels,

biomass, wind power etc. There are a substantial number ofpapers presenting production, usage and storage techniques. Sowe only mention them.

(i). Biological water splitting

Hydrogen produced by means of some photosyntheticmicrobes in their activities from water by using light energy.

(ii). Photo-electrochemical water splitting

Photovoltaic industry is being used for photo-electrochemical (PEC) light harvesting systems that generatessufficient voltage to split water and are stable in awater/electrolyte environment.

(iii). Reforming of biomass and wastes

Hydrogen is separated form synthesis gas produces throughpyrolysis or gasification of biomass.

(iv). Solar thermal methane splitting

Splitting methane into hydrogen and carbon needs hightemperature which is obtained from highly concentrated sunlight.

Hydrogen has the potential to be the fuel of the future dueto the clean burning, and as its emission is only water.Hydrogen, due to its volumetric low energy content at ambient

pressure and temperatures, is rarely used in vehicles. Whichmeans hydrogen must be liquefied or compressed duringtransportation. This, together with and the explosiveness of the


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hydrogen sets high standard to the containers and tanks, both invehicles and during transportation. Besides the great emission

properties hydrogen is interesting because it has the highestenergy content per weight unit of any known fuel.

G.Bio-methaneBio-methane is most often purified biogas and therefore it

is commonly referred to as biogas but in order to distinguishthem, purified biogas is consequently referred to as bio-methane. Table 1 illustrates some properties of bio-methane.

The primary task of the purification process, which isperformed by decreasing the amount of carbon dioxide, whichincreases the ratio of methane in the gas, is to extend its energycontent. The content of methane typically extends 97% in thefinished product. Traces of other substances must be removedin order to make it compatible with engines such as hydrogensulphur, water vapor, nitrogen, oxygen, particles, halogenatedhydrocarbons, ammonia, and organic silicon compounds. Often

bio-methane is odorized as a safety measure to detect leaks inthe systems in which it is being used. There is a way of

producing bio-methane with synthesis gas as an intermediateproduct. This process follows the same path as the productionof FT-diesel which is described before. Detailed description of

bio-methane production is collected in [28, 33].

The usage of bio-methane is yet small. The insufficiency offilling stations is one of the reasons that gas propelled vehicleshave not made a commercial breakthrough. But, this does notaffect local vehicle fleets as they most often stays in certainregions, always having relatively close to a filling station. Thefuture potential of bio-methane, regarding waste material asfeedstock, is discussed in the Finnish study, [29] which statesthat 20% of all traffic energy consumption in Finland can bereplaced by bio-methane.

III. NATURAL GASNatural gas is a clean and highly useful energy source. The

gas is generated in a similar way as oil. The

energy advances in environment

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