1720r 2010 American Chemical Society pubs.acs.org/EF

Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432gPublished on Web 02/24/2010

Can Rape Seed Biodiesel Meet the European Union Sustainability Criteria for Biofuels?

T. Thamsiriroj†,‡ and J. D. Murphy*,†,‡

†Department of Civil and Environmental Engineering, University College Cork, Cork, Ireland, and‡Environmental Research Institute, University College Cork, Cork, Ireland

Received November 24, 2009. Revised Manuscript Received February 8, 2010

The European Union (EU) Renewable Energy Directive stipulates that only biofuel systems that achievegreenhouse gas emission savings of 60% will be eligible to be considered for the 2020 target of 10%renewable energy in transport. Rape seed biodiesel is a very popular indigenous European biofuel;however, this 60% target is very challenging for the biofuel produced. Tropical biofuels such as palm oilbiodiesel tend to be sustainable, due to use of residues and byproduct to satisfy parasitic energy demands.This paper explores, through life cycle assessment methodologies, the whole rape seed system and thepotential to improve sustainability. Allocation by energy content attributes almost half the greenhouse gasemissions to rape cake (a coproduct). Indeed rape cake as animal feed displaces imported soybean fromLatin America and potential destruction to rain forests. Together with use of glycerol as a source of heat,greenhouse gas savings of 75% maybe attained, indicating a sustainable system. Furthermore use of rapestraw pellets in lieu of the environmentally unsound practice of using peat produced from Irish Bogs as asource of domestic heating can lead to a 135% savings on diesel. Interestingly, rape cake as a source ofbiomethane greatly improves the energy balance of the system but is of little benefit to emissions.

1. Introduction

1.1. Biofuels and Biodiesel in the European Union (EU) andIreland. The EU has set a target of 10% renewable energy intransport by 2020.1 Ireland responded with the introductionof biofuels obligation2 with an obligation level of 4% renew-able energy (measured by volume) by 2010. Rape seed oil isthe only energy crop in Ireland used to produce biodiesel.Previous work by the authors indicated that 1% of agricul-tural land is required to satisfy 1% substitution of transportfuel by rape seed biodiesel.3 Over 90% of Irish agriculturalland is under grass; less than 10% is arable and available toproduction of energy crops.4 Conversion of permanentgrassland to arable land is not an option. It has been shownthat if grassland was converted to arable land growingoilseed rape, it would take about 49 years for the greenhousegas (GHG) saving from substitution of diesel by rape seed

biodiesel to offset the carbon released by ploughing of thegrassland.5,6

There has been a 4-fold increase in land growing oilseedrape in Ireland as an energy crop between 2004 and 2007(2.2-8.2 kha).7 This has been encouraged by the premiumfunded to farmers under the Energy Crop Scheme andBioenergy Scheme.8 The limited arable land in Ireland isalready fully employed; allowing for the fact that oilseed rapeis a crop rotated 1 year in 4 or 5; its maximum extent is of theorder of 2% of agricultural land providing 2% of energy intransport.3 Biofuels produced in Ireland only replaced 0.5%of transport fuels in 2007, with rape seed biodiesel as one ofthe primary biofuels. To achieve the renewable energy targetof 10%, importing biofuels or ready blended biofuels isalmost certainly unavoidable.

The recently published EU Renewable Energy Directive1

includes sustainability criteria for biofuels. For a biofuel to becounted toward national targets it must effect a minimumGHG reduction in comparison to the fuel it replaces of 35%post 2010 rising to 60% post 2017. The Directive provides adefault value of 38% for rape seed biodiesel. The biofuelproducer will therefore need to ensure that the 60% reductionmaybe effectedbefore investing in abiofuel production facility.

Previous work by the authors suggested that rape seedbiodiesel was inferior to palm oil biodiesel when consideredunder two parameters: energy production per hectare andGHG savings.3 Furthermore, a GHG saving of only 28%was calculated for the rape seed biodiesel system using a no-allocation methodology

*Towhomcorrespondence should be addressed. Telephone:þ 353 21490 2286. E-mail: jerry.murphy@ucc.ie.(1) Official J. Eur. Union Directive 2009/28/EC of the European Parlia-

ment and of the Council of 23April on the promotion of the use of energy fromrenewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC. June 5, 2009, http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:140:0016:0062:EN:PDF (accessed July 2009.(2) Department of Communications, Energy and Natural Resources.

Government White Paper: Delivering a Sustainable Energy Future forIreland, March 2007. http://www.dcmnr.gov.ie/NR/rdonlyres/54C78A1E-4E96-4E28-A77A-3226220DF2FC/27356/EnergyWhitePaper12March2007.pdf (accessed June 2009).(3) Thamsiriroj, T.; Murphy, J. D. Is it better to import palm oil from

Thailand to produce biodiesel in Ireland than to produce biodiesel fromindigenous Irish rape seed? Appl. Energy 2009, 86, 595–604.(4) Murphy, J. D.; Power, N. M. An argument for using biomethane

generated from grass as a biofuel in Ireland.Biomass Bioenergy 2009, 33,504–512.(5) CONCAWE, EUCAR. Well-to-wheels analysis of future auto-

motive fuels and powertrains in the European context. EuropeanCommission. Well-to-tank Report, version 2b; May 2006.(6) Stephenson, A. L.; Dennis, J. S.; Scott, S. A. Improving the

sustainability of the production of biodiesel from oilseed rape in theUK. Process Saf. Environ. Prot. 2008, 86, 427–440.

(7) Central Statistics Office Ireland (CSO). http://www.cso.ie(accessed June 2009).

(8) Department of Communications,Marine andNatural Resources.Report on measures taken to promote the use of biofuels or otherrenewable fuels to replace diesel or petrol: Compliance with Directive2003/30/EC (Article 4); July 2005, http://ec.europa.eu/energy/res/legisla-tion/doc/biofuels/member_states/2005_rapports/2003_30_ie_report_en.pdf(accessed June 2009).

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

1.2. Life Cycle Analysis. Life cycle analysis has become anessential tool in assessing the sustainability of biofuel sys-tems. In a life cycle analysis, the goal, scope, and functionalunit are initially defined followed by a definition of thesystem boundary.9 Of issue and a driver for this paper isthe wide range of results, which may be produced from thesame defined biofuel system. This is primarily due to theallocation methodology and the methodology employedwhen considering coproducts, byproduct, and residues inthe system.10 There are a number of allocation approachesthatmay be applied to the life cycle analysis. In general, theseinclude the no-allocation approach, allocation by physicalrelationship (e.g., mass, volume, energy content), allocationby economic value, substitution approach, and the mixedapproach.11,12 Many works on biofuel systems recently havefocused on the substitution approach.12-17 The method isclaimed to be the most appropriate, especially when theimpact from a specific change in the total fuel productionsystem to end uses is of interest.17

A study of the literature reveals a number of studies ofrape seed biodiesel systems utilizing different allocationmethods.3,6,17-19 The results depend significantly on alloca-tion methodology employed and on what substitutions areapplied to rape cake, glycerol, and rape straw. For example,Bernesson et al., when investigating a large-scale rape seedbiodiesel system, showed that calculated GHG emissionsdiffer by 30% using the substitution approach as opposed toallocation by energy content.17 Stephenson et al. whenassessing a small-scale system showed that the GHG emis-sions may change by 92% if rape cake is used for combinedheat and power production (CHP) rather than for use asanimal feed.6

1.3. Calculation Method for GHG Emissions from Biofuel

Systems. The EU Renewable Energy Directive provides a

methodology (eq 1) to calculate the GHG emissions frombiofuel systems in the Annex V Part C of the Directive.1 Thefunctional unit is specified in grams of CO2-eq MJfuel

-1. Theequation allows for the global warming potential (GWP) ofCO2, CH4, N2O.

EB ¼ eec þ el þ ep þ etd þ eu - esca - eccs - eccr - eee ð1Þwhere, EB is the total emissions from the biofuel; eec is theemissions from the cultivation of raw materials; el is theemissions from the land use change; ep is the emissions fromprocessing; etd is the emissions from the transport anddistribution; eu is the emissions from the biofuel in use; escais the emission saving via the improved agricultural manage-ment; eccs is the emission saving from the carbon capture andgeological storage; eccr is the emission saving from the carboncapture and replacement; and eee is the emission saving fromexcess electricity from cogeneration burning of agriculturalcrop residues.

In order to assess the sustainability of the biofuel, thecalculated GHG emissions are converted to the GHG savingcompared to fossil fuels. The Saving is calculated using eq 2.

Saving ¼ ðEF - EBÞ=EF ð2Þwhere,EB is the total emissions from the biofuel andEF is thetotal emissions from the fossil fuel comparator.

The highlight of the methodology is that it allows for boththe allocation by energy content and the substitution ap-proach to be included. Parameters including eec, ep, and etdare allocated to the main product, coproducts, and bypro-duct based on their lower heating values. The substitutionapproach is allowed through the parameter eccr when appliedto the use of coproducts, byproduct, and residues from thebiofuel system.

1.4. Objective of Paper. This paper has an objective inascertaining whether rape seed biodiesel may be classified asa biofuel in the EU after 2017. Two clauses exist in the EURenewable Energy Directive relating to sustainability. Thefirst relates to the aforementioned GHG savings. Thesecond clause states that no damagemaybe done to sensitiveeco-systems in growing biofuels (such as conversion ofgrassland to arable land to grow biofuels). In this paper itis not proposed to grow rape seed outside the existing arableland base in Ireland; thus damage to sensitivity ecosystems isnot associated with the rape seed crop. The life cycle assess-ment (LCA)methodology used in this paper thus follows theapproach suggested in the Directive and is primarily con-cerned with GHG savings. In particular this paper focuseson applications of coproducts, byproduct, and residuesfrom the rape seed biodiesel system, which will allowimprovement in the energy balance and the sustainabilityof the whole system. The analysis takes into account theenergy and emission credits from rape cake, glycerol, andrape straw.

2. Rape Seed Biodiesel Scenarios

2.1. Rape Seed Biodiesel Facility: Base Case.A small-scalebiodiesel plant with a capacity less than 1 million tonnes perannum is considered; this is a typical size for a farm-cooperative scheme in Ireland and was used in a previouspaper by the authors3 comparing palm oil to rape seed as asource of biodiesel. The harvested rape seed is treated locally;the oil press (cold press) and biodiesel plant are combined.Rape seed oil obtained from the oil press is directly mixed

(9) Guin�ee, J. B. Handbook on Life Cycle Assessment: OperationalGuide to the ISO Standards. Eco-Efficiency in Industry and Science, Vol. 7,Kluwer Academic Publishers: Dordrecht, The Netherlands, 2002.(10) Singh, A.; Pant, D.; Korres, N. E.; Nizami, A. S.; Prasad, S.;

Murphy J. D. Key issues in life cycle assessment of ethanol productionfrom lignocellulosic biomass: Challenges and perspectives. Bioresour.Technol. 2009, DOI: 10.1016/j.biortech.2009.11.062.(11) Roundtable on Sustainable Biofuels. Annex 1 to Paper 3: Pros

and cons of substitution and allocation. EPFL Energy Center, May 16,2008, http://cgse.epfl.ch/webdav/site/cgse/users/171495/public/Paper3_An-nex1_Pros%20and%20cons.pdf (accessed July 2009).(12) Thamsiriroj, T.; Murphy, J. D. The impact of the life cycle

analysis methodology on whether biodiesel produced from residuescan meet the EU Sustainability Criteria for biofuel facilities constructedafter 2017? Submitted to Renewable Energy, July 2009.(13) Smyth, B. M.; Murphy, J. D.; O’ Brien, C. What is the energy

balance of grass biomethane in Ireland and other temperate northernEuropean climates? Renewable Sustainable Energy Rev. 2009, 13 (9),2349–2360.(14) Murphy, J. D.; Power, N. M. How can we improve the energy

balance of ethanol production from wheat? Fuel 2008, 87, 1799–1806.(15) Liska, A. J.; Yang, H. S.; Bremer, V. R.; Klopfenstein, T. J.;

Walters, D. T.; Erickson, G. E.; Cassman, K. G. Improvements in lifecycle energy efficiency and greenhouse gas emissions of corn-ethanol.Res. Anal. 2008. DOI: .(16) (S&T)2 Consultants Inc. An examination of the potential for

improving carbon/energy balance of bioethanol. IEA Task 39 ReportT39-TR1, February 2009.(17) Bernesson, S.; Nilsson, D.; Hansson, P. A. A limited LCA

comparing large- and small-scale production of rape methyl ester(RME) under Swedish conditions.Biomass Bioenergy 2004, 26, 545–559.(18) Kaltschmitt, M.; Reinhardt, G. A.; Stelzer, T. Life cycle analysis

of biofuels under different environmental aspects. Biomass Bioenergy1997, 12, 121–134.(19) Reijnders, L.; Huijbregts, M. A. J. Biogenic greenhouse gas

emissions linked to the life cycles of biodiesel derived from Europeanrape seed and Brazilian soybeans. J. Cleaner Prod. 2008, 16, 1943–1948.

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

with methanol in the biodiesel processing unit. The energyrequirement of a small-scale biodiesel plant based on rapeseed oil is considered low, as the oil does not need pretreat-ment and biodiesel separates from glycerol through densitydifferential.

2.2. Scenarios. Five scenarios are assumed in this study asindicated in Table 1 and Figure 1. While rape seed oil is usedfor biodiesel production, there are choices for the uses of rapecake, glycerol, and rape straw.

Base Case Scenario. This considers only one energy out-put: biodiesel production. The calculation of net energy andGHG emissions are based on no-allocation. None of theGHG saving credits from coproducts or byproduct isconsidered. The cradle of the system is the cultivation ofoilseed rape in the field. The grave of the system is biodieselfuelling cars. The processes considered include agriculture,transport of rape seed to oil press, oil pressing process,biodiesel production, and biodiesel distribution to custo-mers.

Scenario 1. This differs from the base scenario in thatrape cake is used for animal feed and glycerol is com-busted in a boiler to produce heat for an industrial use.(The glycerol produced in a rape seed biodiesel facility inCork, Ireland, is used in a boiler specially made forglycerol feed to provide thermal energy). Scenario 1 isthe expected typical rape seed system in Ireland. Thecalculation of net energy and GHG emissions are basedon allocation by energy content method. GHG savingcredits from rape cake and glycerol are accounted for viathe parameters eccr in eq 1. The cradle for rape cake isdefined as the cultivation of oilseed rape (parasitic de-mands and emissions are allocated between biodiesel andrape cake in proportion to oil production for biodiesel andcake production for feed; refer Table 2); the grave for rapecake is its use as animal feed. For glycerol (considered aresidue), the cradle is the collection of glycerol from thebiodiesel plant; the grave is the combustion of glycerol inan industrial boiler.

Scenario 2. This differs from scenario 1 in the use of rapestraw to produce pellets for heat. It is assumed that the pelletproduction facilities are located close to the biodiesel plant.Parameters eccr and eccs are applied to rape straw. Normally,rape straw in Ireland is ploughed back to the land providingcarbon sequestration to the soil (eccs). The use of rape strawfor pellets production removes this GHG saving credit butadds the credit of replacement of fossil fuel heating (eccr) tothe system instead. The cradle for rape straw is the collectionof straw from the field. The grave is combustion of pellets forheat production.

Scenario 3. In scenario 3, rape cake and glycerol are usedfor biomethane production through an anaerobic digestionprocess. It is assumed that a nearby anaerobic digestionfacility complete with upgrading facilities is in place alreadydigesting other feedstocks. The biomethane is used as atransport fuel. The GHG saving credit (for displaced fossilvehicular fuel) is included via the parameter eccr. The cradlefor biomethane is defined as the cultivation of oilseed rape inthe case of rape cake and the collection of glycerol from thebiodiesel plant in the case of glycerol. The grave is the use ofbiomethane as a transport fuel.

Scenario 4. This scenario adds an option of rape straw forpellet production to scenario 3. The calculation of theemission saving credit for rape straw is as explained inscenario 2.

2.3. Functional Units Used to Compare Scenarios. Energy-related figures are denoted as GJ ha-1 a-1; GHG emissionsas kg of CO2-eq GJbiodiesel

-1. An important issue for thefunctional unit is the denominator of the emissions. Thus, forexample, when biomethane (from rape cake and glycerol) isproduced and the energy production increases, the energy inthe biomethane product is accounted for in the term eccr only.In effect, the functional unit is directly proportional to kg ofCO2-eq ha

-1 a-1.

Table 1. Scenarios Considered in the Study

rape seedto

biodiesel

rape caketo

animal feed

glyceroltoheat

rape cake,glycerol tobiomethane

rape strawto

pellets

base case Xscenario 1 X X Xscenario 2 X X X Xscenario 3 X Xscenario 4 X X X

Figure 1. Processes involved with different scenarios in this study;units of inputs and outputs are per hectare per day.

Table 2. Allocation Factors to Rape Seed Oil and Rape Cake

productLHV

(GJ t-1)yield of product(t ha-1a-1)

total energy(GJ ha-1a-1)

allocation(%)

rape seed oil 37.0a 1.23 45.51 51.87rape cake 14.82b 2.85 42.24 48.13

total 100

aFrom the EU Directive 2009/28/EC.1 bOn the basis of the ultimateanalysis of compositions by the authors, estimated using Sheng’sformula.20

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

3. Experiments Carried Out

To support the analysis a number of experiments were carriedout. The experiments and the rationale for the experiments areexplained in the following sections.

3.1. Anaerobic Digestion of Rape Cake and Glycerol. Scena-rios 3 and 4 include digestion of rape cake and glycerol. A batchanaerobic digestion experiment was performed using rape cakeand glycerol as feedstock sourced from the same biodiesel plantin Cork, Ireland. The anaerobic digestion unit was an ArmfieldW8 anaerobic digester, which was modified to work with a highsolids content feed. A mixer was installed and connected to amotor with a rotational speed of 60 rpm. Feedstock was fed tothe 5 L reactor tank once and left to be digested for a 25 dayperiod. The amount of feed was in the range 3-5 g of volatilesolids (VS) liter-1 of reactor volume to avoid pH adjustment.Inoculums were nongranulated sludge taken from the Camphillanaerobic digestion plant in Kilkenny, Ireland. This digesteruses cow manure and food waste as the main feeds. Gascompositions were analyzed for CH4 andCO2 using the infraredportable gas detector, model PGD3-IR, supplied by StatusScientific Controls Ltd. Three subexperiments were performedincluding digestion of rape cake-only, glycerol-only, and amixture of rape cake and glycerol. The mixture was 94.7% rapecake and 5.3%glycerol, which corresponds to the ratio of actualproduction (i.e., 2.85 t ha-1 a-1 for rape cake and 0.157 t ha-1

a-1 for glycerol). Each subexperiment was duplicated threetimes in order to calculate the average and variance (Table 3).The digestion occurred rapidly with up to 100% of biogasproduced in the first 15 days in most cases. The retention timefor energy crop digesters is of the order of 60 days,13 thusaddition to energy crop digesters should result in full contribu-tion from the biodiesel byproduct.

3.2. Carbon Released When Rape Straw Is Combusted. Sce-narios 2 and 4 involve combustion of straw. The yield ofharvested rape straw surveyed in Ireland varies significantlybetween 1.5 and 7 t of dry solids (DS) ha-1 a-1, with a meanvalue of 4.2 t of DS ha-1 a-1.21 Straw samples were collectedlocally (Cork, Ireland). The moisture content of the sampledstrawwas found to be 15%.Anultimate analysis was carried outboth on fresh straw and the ash after combustion. The carboncontent in the fresh straw was 45.57% ofDS; that in the ash was0.18% of DS. Thus, (1) carbon losses in combustion 1.9 t of Cha-1 a-1 ((4.2 t of DS ha-1 a-1)(45.39%C)); (2) global warmingpotential of 7 t of CO2-eq ha

-1 a-1 (1.9 t of C ha-1 a-1/0.273 t ofC t-1 of CO2-eq); (3) 156 kg of CO2-eq GJbiodiesel

-1 (7 t of CO2-eq

ha-1 a-1/44.87 GJ ha-1 a-1). This carbon dioxide will be

released to the atmosphere if straw is combusted as a fuel inlieu of ploughing back to the land.

3.3. Glycerol for Heat Production. Scenarios 1 and 2 involvecombustion of glycerin. Crude glycerol obtained from biodieselplants can vary in composition and energy content. An ultimateanalysis test was performed by the authors on a glycerol samplefrom a rape seed oil biodiesel plant in Cork. The lower heatingvalue was estimated using Channiwala’s formula22 as 19.2 GJt-1. The glycerol sample contained 16% methanol, whichindicated some fossil-derived CO2 emissions released from thecombustion of glycerol. The estimation of the fossil-derivedCO2

from glycerol according to Thamsiriroj and Murphy3 is 0.77 kgof CO2-eq GJbiodiesel

-1. Glycerol is assumed in the analysis to beused for heat production replacing light oil, which has a primaryenergy of 41.8MJ L-1 and emission factor of 75.19 kg of CO2-eq

GJ-1 primary energy.

4. Rape Seed Oil for Biodiesel Production (All Scenarios)

4.1. Previous Work. The authors previously comparedpalm oil biodiesel with rape seed biodiesel.3 The energybalance and GHG saving were based on the no-allocationapproach. The results suggested that theGHGsaving of rapeseed biodiesel was 28.8%. In that study, lime application tosoil was not included.3 However, in many parts of the U.K.and Ireland, soil conditions are acidic, necessitating pHadjustment through the use of lime. Thus, in this paper limeis considered. This results in a reduced net energy productionper hectare and a reduction in GHG savings.

4.2. Effect of Lime. The base case scenario in this paper isbased on the data from the authors’ previous work with theaddition of lime input to the system. In Munster (a provinceof Ireland) lime requirement was surveyed to be an averageof 1.8 t ha-1 a-1 (7.3 t ha-1 over 4 years between 1993 and1997).23 However, this is the mean figure that includesgrassland and arable land, with different soil pH. OptimumpH for grassland is 6.3, for cereal crops is 6.5, and for oilseedrape is 7.0.24 Farmers in Cork, (Munster, Ireland) apply limeat about 2 t ha-1 a-1. Lime requirement can be widelyvariable depending on soil conditions, farming practice,and crop rotation in specific areas. This study will assumethe lime application to the analysis as follows: (1) 2 t ha-1 a-1

of lime for rape seed production and (2) 1.6 t ha-1 a-1 of limefor barley production (rape cake used as a substitute forbarley in cattle feed)

In addition to the large quantity of lime applied, the GHGemissions released from lime are also very high. Lime reducessoil acidity by changing some of the hydrogen ions in soilsinto water and CO2. The pH increases because the hydrogenion concentration reduces. A tonne of agricultural lime(ground limestone) releases 440 kg ofCO2-eq based on stoichio-metry. In this study, the emission factor for lime is dividedin two: 432 kg of CO2-eq t

-1 from the chemical reaction and

Table 3. Result of the Batch Experiment for Anaerobic Digestion of

Rape Cake and Glycerol

methane yield

feed typem3 of CH4 kg

-1

wwbm3 of CH4 kg

-1 ofVSadded

c

rape cake 0.243( 0.048 0.289( 0.041glycerola 0.384( 0.044 0.445( 0.05194.7% rape cake þ5.3% glycerol

0.284( 0.004 0.336( 0.005

a 0.27( 0.031 L of CH4 g-1 CODremoved. In experiments it was noted

that 1.42 kg of COD is produced per kilogram of glycerol. Thus,methane yields of 0.384 ( 0.044 m3 CH4 kg

-1 ww. bww is wet weight.cVSadded is volatile solids added.

(20) Sheng, C.; Azevedo, J. L. T. Estimating the higher heating valueof biomass fuels from basic analysis data. Biomass Bioenergy 2005, 28,499–507.(21) Keogh, B.; Shalloo, L. Forage crops to reduce winter feed costs.

In Moorepark’ 09, Moorepark Dairy Production Research Centre, 2009http://www.teagasc.ie/publications/2009/20090618/MooreparkBook2009.pdf (accessed July 2009).

(22) Channiwala, S. A.; Parikh, P. P. A unified correlation forestimating HHV of solid, liquid and gaseous fuels. Fuel 2002, 81,1051–1063.

(23) Coulter, B. S.; McDonald, E.; Murphy, W. E.; Lee, J. Visualenvironmental data on soils and landuse. End of ProjectReportARMIS4496, Teagasc, Johnstown Castle Research Centre: Wexford, Ireland,May 1999; http://www.teagasc.ie/research/reports/environment/4496/eopr-4496.asp (accessed August 2009).

(24) Coulter, B. S.; Lalor, S. Major & micro nutrient advice forproductive agricultural crops. Teagasc, Johnstown Castle EnvironmentResearch Centre: Wexford, Ireland, April 2008.

(25) Mitchell, C. C. Soil acidity and liming (Overview). Homepage ofthe Department of Entomology, Soils and Plant Sciences, ClemsonUniversityExtension Service, http://hubcap.clemson.edu/∼blpprt/acid-ity2_review.html (accessed July 2009).

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

43 kg of CO2-eq t-1 from transportation yielding 475 kg ofCO2-eq t-1 of lime. The emission factor for the chemicalreaction is slightly less than the stoichiometric value as pureCaCO3 product is not generally available.

With the no-allocation approach included for lime appli-cation, the net energy is calculated as 22.95 GJ ha-1 a-1 andGHGemissions are 83.42 kg ofCO2-eqGJbiodiesel

-1 (Table 4).The previous work3 indicated the net energy and GHGemissions using the no-allocation approach (without lime)as 25.29 GJ ha-1 a-1 and 58.35 kg of CO2-eq GJbiodiesel

-1,respectively. In terms of greenhouse gases, the increase is 25 kgof CO2-eq GJbiodiesel

-1, equivalent to an increase of 43%.Lime is thus a very significant factor to the GHG life cyclestudy of rape seed biodiesel. When considering the produc-tion of 87.3 kg of CO2-eq GJdiesel

-1 on a whole life cycle offossil diesel,3 the green house gas saving for the biodieselsystem with lime addition is 4.4%.

4.3. AllocationMethodology.Allocation by energy contentdifferentiates rape seed oil from rape cake based on the lowerheating value (LHV) and yield of the products. The alloca-tion factors are estimated to be 51.87% and 48.13% for rapeseed oil and rape cake, respectively (Table 2). As such, theparasitic energy and related greenhouse gases in processesincluding oilseed rape cultivation, transport of rape seed,and oil pressing are allocated to the two products.

5. Rape Cake for Animal Feed (Scenarios 1 and 2)

5.1. Rape Cake and Concentrate Animal Feed. Rape cakeextracted by cold press comprises 35-38% of crude protein(CP) in the dry matter (DM).26-28 Because of the highprotein content, rape cake is used as an ingredient inconcentrate feed production. It is also used as the proteinsource in farm-mixed feed rations. In Ireland, animal rationsare required in the early spring and late summer when grass

production cannot fully support the herd and throughout thewinter period when housed.29 Soybean meal is the mostfrequently used supplementary protein source among arange of sources (such as distillers grains, corn gluten,brewers grains, cottonseed, copra, and rape seed).30 There-fore, the use of local rape cake to feed animals reduces theimportation of soybean meal and earns the carbon captureand replacement credit (eccr).

5.2. Rape Cake As a Substitute for Soybean and Barley.

This study focuses on rape cake to be used as a farm-mixedfeed. One of the ration mixes recommended is 90% barleygrains mixing with 10% soybean meal, which gives approxi-mately 13% crude protein in the feed. An alternative to thisration is 85%barley grains and 15% rape cake providing thesimilar crude protein content (Table 5).31 As a result, 1 kg ofrape cakemay replace 0.67 kg of soybeanmeal and 0.33 kg ofbarley grains. Barley is commonly grown on arable land inIreland, but the domestic production is not adequate andimportation is required. Soybean, on the other hand, cannotbe grown in Ireland, but there is a large demand for soybeanmeal in the livestock feed industry. Around 89 172 t of barleyand byproduct were imported to Ireland as opposed 607 367 tof soybean in 2007.33 Brazil and Argentina are the mainexporters of soybean to the EU countries. About 60% ofimports are in the form of soybean meal, with the remainderas raw soybean to be crushed in the EU.34 The analysis in thisstudy is based on barley grains produced in Ireland andsoybean meal imported from Brazil. Parasitic energy in theproduction of barley is estimated as 3.01 GJ t-1 grains, andgreenhouse gases are 500 kg of CO2-eq t

-1 grains (Table 6).

Table 4. Energy Balance and Greenhouse Gases from Rape Seed

Biodiesel with No-Allocation Approach and Lime Application In-

cluded (Adapted from Reference 3)

energybalance

(GJ ha-1a-1)

greenhousegases

(kg CO2-eq GJbiodiesel-1)

gross value from combustionof biodiesel 46.5 3.81

Parasitic Demandscultivation of oilseed rape(excluding lime)

14.15 49.05

lime 2.34 21.25transport of rape seed tooil press

0.1 0.17

oil extraction (cold press) 2.32 3.65transesterification 0.95 1.45methanol usage 3.49 3.87NaOH catalyst usage 0.16 0.11biodiesel distribution 0.04 0.06total parasitic demands 23.55 79.61

net value from life cycle ofbiodiesel

22.95 83.42

Table 5. Crude Protein in the Two Feed Options

ration 1: barley

and soybean meal

ration 2: barley

and rape cake

barley grains, 99 g of CP kg-1 fresha 90% 85%

soybean meal, 469 g of CP kg-1 fresha 10%

rape cake, 320 g of CP kg-1 freshb 15%

total crude protein (CP) 13.6% 13.2%

aFrom Keane.32 bFrom personal communication with Gro-oil Ltd.,Ireland.27

(26) Ferchau, E. Equipment for decentralised cold pressing of oilseeds. Folkecenter for Renewable Energy, November 2000.(27) Rape cake composition factsheet. Personal communication with

Gro-oil Ltd. Bandon, Cork, Ireland, 2007.(28) Huuskonen, A. The effect of cereal type (barley versus oats) and

rape seed meal supplementation on the performance of growing andfinishing dairy bulls offered grass silage-based diets.Livestock Sci. 2009,122, 53–62.

(29) Casey, J. W.; Holden, N. M. Analysis of greenhouse gas emis-sions from the average Irish milk production system. Agric. Syst. 2005,86, 97–114.

(30) Stacey, P.; O’Kiely, P.; Rice, B.; O’Mara, F. P. Experiment 2.5: Anote on the on-farmmoist grain storage and feeding practices in Ireland.InBeef Production fromFeedstuffs ConservedUsingNewTechnologies toReduce Negative Environmental Impacts. Beef Production Series, No. 82;Teagasc: Wexford, Ireland, December 2007.

(31) Fitzgerald, L. Cattle farm management notes: April 11, 2008:Looking at feed value in beef rations. Agriculture and Food Develop-ment Authority (Teagasc), 2008.

(32) Keane,M.G.Comparison of barley and sugar beet pulpwith andwithout added protein as supplements for weanling steers. In Beef andsheep production research, Research Report 2004; Teagasc: Wexford, Ire-land, 2004

(33) O’Callaghan, M. The transition to GM-free meat and dairyproduction in Ireland - The food island. Presentation to the SecondInternational Non-GMOSoy Summit, Brussels, Belgium,October 7-9,2008, http://www.gmfreeireland.org/feed/documents/SoySummit2/GMFI-SoySummit2008.pdf (accessed June 2009).

(34) van Gelder, J. W.; Kammeraat, K.; Kroes, H. Soy consumptionfor feed and fuel in the European Union. A research paper prepared forMilieudefensie (Friends of the Earth Netherlands). Final version Octo-ber 28, 2008.

(35) Rice, B. How the farmers’ world will change - new problems,new crops, new opportunities. In Before the Wells Run Dry: Ireland’sTransition to Renewable Energy; The Foundation for the Economics ofSustainability: Dublin, Ireland, 2003.

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

5.3. Soybean and Associated GHG Emissions. Soybean isproduced on a large scale in the Central West (Cerrado) andSouth of Brazil; these areas produce approximately 90% ofall vegetable oils in Brazil.40 The Cerrado region produces75% of soybean in Brazil.38 The expansion of export-oriented soybean cultivation is one of the principle reasonsfor deforestation in Latin America.41 As such, the green-house gases related to the conversion of forest and/or pastureland to arable land is necessary to be included in the analysis.The figure of 65 t of CO2-eq ha

-1 is estimated for greenhousegases from the clearing of Cerrado pasture land to cultiva-tion of soy.42 Considering a common plantation period of25 years,19 the greenhouse gases may be assessed as 2.6 t ofCO2-eq ha-1 a-1. The parasitic energy in the production ofsoybean meal is estimated as 4.65 GJ t-1 soybean meal andthe greenhouse gases are 1092 kg of CO2-eq t

-1 soybean meal(Table 6). It is noted that the allocation between soybean oiland soybean meal are based on the energy content, with theallocation factors of 36.1% and 63.9% for soybean oil andsoybean meal, respectively. The production yield of soybeanoil is 510 kg ha-1 a-1, and that of soybean meal is 2300 kgha-1 a-1.38 Nitrous oxide emissions (N2O) are an important

factor in agriculture that influences the result of greenhousegases calculation due to its high global warming potential.However, soybean is categorized as a nitrogen-fixing crop.As acommon practice in Cerrado, the application of N fertilizer isnot required.38DirectN2Oemissions is thereforeomitted in thisstudy. Indirect N2O emissions (soil N2O emissions) are beyondthe scope of this paper. However the discussion examines thesensitivity of N2O on the results obtained.

5.4. GHG Saving Associated with Rape Cake As a Feed-

stock. As previously noted 1 kg of rape cake substitutes for0.67 kg of soybean meal and 0.33 kg of barley grains. Thusthe greenhouse gases substituted by 1 t of rape cake are896 kg of CO2-eq ([(0.67 tmeal)(1092 kg of CO2-eq tmeal

-1)] þ[(0.33 tgrains)(500 kg of CO2-eq tgrains

-1)]).From Table 2, 2.85 t of rape cake is produced in one

hectare, thus the saving may be expressed as 2.55 t of CO2-eq

ha-1 a-1. This hectare also produces 44.7 GJ of biodiesel;thus the savings may be expressed as 57 kg of CO2-eq

GJbiodiesel-1 (Table 9).

6. Rape Cake and Glycerol for Biomethane Production

(Scenarios 3 and 4)

6.1. Model of Biogas Facilities.Rape cake and glycerol areassumed to be fed to a two-stage continuously stirred tankreactor (CSTR) as a codigested feed. The dry solids content

Table 6. Energy Demand and Greenhouse Gases from Barley Grains, Soybean Meal, and Rape Seed Productions

barley grains soybean meal rape seede

processprocess energy(GJ tgrains

-1)GHG emissions

(kg of CO2-eq tgrains-1)

process energyd

(GJ tmeal-1)

GHG emissions(kg of CO2-eq tmeal

-1)process energy(GJ tseed

-1)GHG emissions

(kg of CO2-eq tseed-1)

agriculture (total) 2.94 494.49 1.3 840.32 4.01 786.1direct (fuel use) 0.65a 48.67 0.71 53.3 1.0 72.92indirect (fertilizer and lime) 2.29b 329.99 0.59 64.35 3.01 584.96N2O from fertilizer use 115.83c 128.22

conversion of vegetationland to arable land

722.67

raw material processing 0.71 53.3transportation (total) 0.07 5.47 2.64 198.32 0.02 1.87

raw material 0.05 3.95product 0.07 5.47 2.59 194.37 0.02 1.87

grand total 3.01 500 4.65 1092 4.03 787.97

aOn the basis of an energy demand of 4.1GJ ha-1 a-1.35 bOn the basis of the average fertilization of 140 kgN ha-1 a-1, 28 kg P ha-1 a-1, and 63 kgKha-1 a-1 (adapted from Coulter et al.36) and lime application of 1.6 t ha-1 a-1. cOn the basis of the N2O emission factor of 5.24 kg of CO2-eq kg

-1 Nfertilized (adapted fromAbdalla et al.37) dProcess energy adapted fromCavalett and Ortega38 for the Cerrado region, Brazil, and transportation modeladapted fromLehuger et al.39 eAdapted fromThamsiriroj andMurphy3with a lime application of 2 t ha-1 a-1 included and rape seed transported to theoil press.

Figure 2. Daily mass balance of anaerobic digestion.

(36) Coulter, B. S.; Murphy, W. E.; Culleton, N.; Quinlan, G.;Connolly, L. A survey of fertilizer use from 2001-2003 for grasslandand arable crops; Teagasc: Wexford, Ireland, July 2005.(37) Abdalla, M.; Wattenbach, M.; Smith, P.; Ambus, P.; Jones, M.;

Williams, M. Application of the DNDC model to predict emissions ofN2O from Irish agriculture. Geoderma 2009, 151, 327–337.(38) Cavalett, O.; Ortega, E. Energy, nutrients balance, and economic

assessment of soybean production and industrialization in Brazil.J. Cleaner Prod. 2009, 17, 762–771.(39) Lehuger, S.; Gabrielle, B.; Gagnaire, N. Environmental impact

of the substitution of imported soybeanmeal with locally-produced rapeseed meal in dairy cow feed. J. Cleaner Prod. 2009, 17, 616–624.(40) Stattman, S. L.; Bindraban, P. S.; Hospes, O. Exploring biodiesel

production in Brazil: A study on configurational patterns in anevolving policy domain, Report 199, Plant Research International B.V.:Wageningen, The Netherlands, August 2008.(41) Upham, P.; Thornley, P.; Tomei, J.; Boucher, P. Substitutable

biodiesel feedstocks for the UK: a review of sustainability issues withreference to the UK RTFO. J. Cleaner Prod. 2009. DOI: 10.1016/j.jclepro.2009.04.014.(42) Bringezu, S.; Sch€utz, H.; Arnold, K.; Merten, F.; Kabasci, S.;

Borelbach, P.; Michels, C.; Reinhardt, G. A.; Rettenmaier, N. Globalimplications of biomass and biofuel use in Germany - Recent trendsand future scenarios for domestic and foreign agricultural land use andresulting GHG emissions. J. Cleaner Prod. 2009. DOI: 10.1016/j.jcle-pro.2009.03.007.

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

in the reactor is below 12%, recirculation of liquid from thesecond tank back to the first tank facilitates control of solidscontent. Biogas production is assumed to be 80% and 20%from the first and second tanks, respectively. The figure of0.284m3 of CH4 kg

-1 ww (wet weight), which corresponds to0.336 m3 of CH4 kg

-1 VS added obtained from the labora-tory experiment (Table 3) is considered as the methane yieldfrom the biodiesel byproduct in the digester. A mass balanceof the modeled facility is outlined in Figure 2, adapted fromSmyth et al.13 The total methane produced is 2.215 m3 ofCH4 ha

-1 d-1 (808 m3 of CH4 ha-1 a-1).

Electricity demand in the biogas plant is assumed to befrom the electricity grid, and thermal demand is met bynatural gas from the gas network. Electricity demand in anae-robic digestion includes 10 kWeh t-1 slurry for mixing13,43

and 0.694 kWeh t-1 circulated liquid for pumping.13,44 Heatdemand is required to raise the temperature by 28 �C onaverage. A boiler efficiency of 85% is assumed; heat loss of15% from the digester is assumed.13 Emission factors forelectricity and natural gas are given as 538 kg of CO2-eq

MWeh-1 and 205.6 kg of CO2-eq MWh-1 natural gas, res-

pectively.45,46 The electricity generation efficiency in Irelandis on average 45%.47 Biogas losses are kept to a minimumusing extended digestion periods in the second reactor; lossesof 2% are assumed. This is a conservative analysis; theconsiderable benefits of digestate as a substitute for mineralfertilizer are not considered in this analysis.

6.2. Biomethane for Transport. It is assumed that biogas isupgraded to biomethane (g97% methane) on site, and thebiomethane is injected to the natural gas network andused asa transport fuel. Compressed natural gas service stationsalong the gas grid are used to dispense the biomethane(compressed to 250 bar). Diesel is the fossil fuel displaced.

Upgrading of biogas to biomethane requires 0.35 kWehm-3 of biomethane.13,14,48 Compressing and fuelling pro-cesses demand for 0.61 kWeh m-3 of biomethane.5 Methanelosses in upgrading and compressing are in the range0.2-2%;49 1.5% is chosen in this study.13,48 Methane lossesin the gas grid are negligible;50 energy required for gasdistribution is also negligible as compression provides fordistribution.5

In Table 7, it is calculated that rape cake and glycerolcould produce 804 m3 ha-1 a-1 of biomethane equivalent to

804 L of diesel. It is assumed that 1 m3 of biomethanedisplaces 1 L of diesel. This may be supported analyticallyby noting that biomethane at 97% CH4 has an energy valueof 36.6MJm-3 ((0.97)(37.78MJm-3)) and that diesel has anenergy value of 36 MJ L-1.

7. Rape Straw for Heat Production (Scenarios 2 and 4)

7.1. Rape Straw Use and Implications for Carbon. Rapestraw has a relatively high lignin content when compared tograss and cereal straw (rape straw 19-22%; grass 3-7%;cereal straw 6-21%).51,52 Therefore, it is a good source ofthermal energy. In Ireland, cereal straws are commonly usedfor bedding; however, rape straw is ploughed back to theland. If rape straw is utilized for thermal energy, the carbonsequestration benefit from ploughing into soil is removed.Carbon losses from arable soil in Europe average 0.84 t of Cha-1 a-1 (3.08 t of CO2-eq ha

-1 a-1).53 However, allocationof carbon losses from soil to specific crops is difficult toascertain particularly as arable land is rotated.19 Accordingto Schulze and co-workers,54 the balance for all greenhousegases across Europe’s terrestrial biosphere is near neutral as

Table 7. Energy Balance and Greenhouse Gases from Biomethane As

Transport Fuel

quantitya

m3 ha-1 a-1energy

GJ ha-1 a-1

greenhousegases kg of

CO2-eq ha-1 a-1

gross value frombiomethane

833.3 30.54

Parasitic Demandsheat demand for anaerobicdigestion

3.11 177.68

electricity demand foranaerobic digestion

0.85 57.25

biogas losses in anaerobicdigestionb

16.7 0.61 265.44

electricity demand forbiomethane upgrading

1.03 69.2

methane losses inupgrading

12.2 0.45 195.1

energy demand forbiomethane distribution

methane losses inbiomethane distribution

electricity demand forcompression/fuelling

1.77 119

methane losses incompression/fuelling

included included

total parasitic demands 28.9 7.82 883.67

net value from biomethane 804.4 22.72 883.67

aQuantity of biomethane at 97% CH4 ha-1 a-1. bBiogas losses are

calculated as follows: 1 kg of CH4 dissipated produces 23 kg of CO2-eq.The density of CH4 is 0.714 kg m

-3; thus, 1 m3 of CH4 generates 16.4 kgof CO2-eq. Biomethane is 97% CH4.

(43) Murphy, J. D.; McKeogh, E.; Kiely, G. Technical/economic/environmental analysis of biogas utilisation.Appl. Energy 2004, 77, 407–427.(44) Berglund, M.; B€orjesson, P. Assessment of energy performance

in the life-cycle of biogas utilisation. Biomass Bioenergy 2006, 30, 254–266.(45) The Commission for Energy Regulation. Fuel mix and CO2

emission factors disclosure 2007. November 7, 2008, http://cer.ie.(46) Homepage of Sustainable Energy Ireland. http://www.sei.ie/

Publications/Statistics_Publications/Emission_Factors/ (accessed July2009).(47) Dennehy, E.; �O Gallach�oir, B.; Howley, M. Energy efficiency in

Ireland. Sustainable Energy Ireland, May 2009, http://www.sei.ie/Publications/Statistics_Publications/EPSSU_Publications/Energy_Efficiency_in_Ireland_2009/ (accessed June 2009).(48) Murphy, J. D.; Power, N. Technical and economic analysis of

biogas production in Ireland utilising three different crop rotations.Appl. Energy 2009, 86, 25–36.(49) B€orjesson, P.; Berglund, M. Environmental systems analysis of

biogas systems-Part II: The environmental impact of replacing variousreference systems. Biomass Bioenergy 2007, 31, 326–344.(50) McGettigan, M.; Duffy, P.; Connolly, N.; O’Brien, P. Ireland:

National inventory report 2006. Greenhouse gas emissions 1990-2004,Reported to the United Nations Framework convention on ClimateChange. Environmental Protection Agency: Wexford, Ireland, http://coe.epa.ie/ghg/nirs/NIR_2006_IE.pdf (accessed August 2009).

(51) Kamm, B.; Kamm, M.; Schmidt, M.; Hirth, T.; Schulze, M.Lignocellulose-based chemical products and product family trees. In-Biorefineries-Industrial Processes and Products: Status Quo and FutureDirections, Vol. 2, Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim,Germany, 2006; pp 97-149.

(52) Gill,M.; Beever, D. E.; Osbourn,D. F. The feeding value of grassand grass products. In Grass-Its Production and Utilisation; BlackwellScientific Publications: Oxford, U.K., 1989; pp 89-129.

(53) Vleeshouwers, L.M.; Verhagen, A. Carbon emission and seques-tration by agricultural land use: a model study for Europe. GlobalChange Biol. 2002, 8, 519–530.

(54) Schulze, E. D.; Luyssaert, S.; Ciais, P.; Freibauer, A.; Janssens, I.A.; et al. Importance of methane and nitrous oxide for Europe’sterrestrial greenhouse-gas balance. Nat. Geosci. 2009, 2, 842–850.

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

the CH4 emissions from feedstock and N2O emissions fromarable agriculture are fully compensated for by the CO2 sinkprovided by forests and grasslands. In Ireland, carbondensity in arable soil has not changed significantly overdecades. Comparing 1970 to 2000, the carbon density to adepth of 30 cmwas 42.9 Tg C (1970) as opposed to 43.6 Tg C(2000); for a depth to 100 cm, the carbon density was 64.4 TgC (1970) as compared to 65.4 Tg C.55 As a result, thetraditional system in which rape straw is ploughed backcould be referred to as a carbon neutral system, providing netzero CO2 emissions to the atmosphere. Therefore, the use ofrape straw to produce pellets gains the emission saving fromthe replacement (eccr) but removes the emission saving fromthe carbon capture and geological storage (eccs). Pelletsproduced from rape straw are assumed to be used in fire-places and boilers, replacing solid fuels, i.e., coal, sod peat,and peat briquettes. Section 3.2 deals with the carbon releasewhen rape straw is combusted.

7.2. Substitution of PeatwithRape StrawPellets.The pelletproduction plant is assumed to be installed near the oil pressand biodiesel plant. Fuels used for straw handling (includingwindrowing, baling, storage, and transport) were estimatedas 6.5 L t-1 straw.56 Straw can be pelletized without majordifficulties. Straw is ground in two steps: first a scarifyingprocess and then a fine-chopping into smaller particles.Generally, straw is delivered with a moisture content below20%, bypassing the drying stage, which is the most energy-consuming stage. The same pellet mills can be used for strawand wood pelleting, producing straw pellets with the LHV ofaround 15.5 GJ t-1.57 Energy demand for the productionvaries with scale. For a medium scale of about 2200 t pelletsa-1, the electricity demand is 128.5 kWh t-1 pellet for rawmaterial grinding and pellet milling processes.58

In Ireland, solid fossil fuels used for residential heatinginclude coal, sod peat, and peat briquettes. The energyconsumption of such fuels in 2007 was 208, 186, and 85 ktoe,respectively (1 ktoe = 41.9 GJ).59 The energy content ofstraw pellets (15.5 GJ t-1) is similar to that of peat but

different to that of coal (Table 8). Thus straw is proposed as areplacement for sod peat and peat briquettes for open fires,stoves, and boilers. Peat (which will be substituted) is de-scribed in this paper as a combination of sod and briquettesin proportion to use in 2007 (sod 186 ktoe; briquettes 85 ktoe).This generates a LHV of 14.43 GJ t-1 and an emission factorof 103.4 kg of CO2-eq GJLHV

-1.The full life cycle of the peatmust be taken into account. In

terms of energy (including for fuel extraction, processing,and transport) the rise is relatively small; from 14.43 GJLHV

t-1 to 14.88GJprimary energy t-1 (adapted fromCleary et al.61).

However for GHG emissions, the rise is significant; 103.4 kgof CO2-eq GJLHV

-1 to 136.9 kg of CO2-eq GJprimary energy-1

(adapted from Styles and Jones62).Rape straw produces 4.45 t ha-1 a-1 of pellets (4.2 t DS ha-1

a-1 are produced at 15%moisture content, which is equivalentto 4.94 t ha-1 a-1 “as is”; 10% losses occur in baling andpelletting) and 68.9GJ ha-1 a-1 ((4.45 t ha-1 a-1)(15.5 GJ t-1)of pellets). Peat substitution is 4.8 t ha-1 a-1 (68.9GJ ha-1 a-1/14.43 GJLHV t-1). Thus, the emission credit eccr is calculated tobe 9.7 t ofCO2-eq ha

-1 a-1 [(4.8 t ha-1 a-1)(14.88GJprimary energy

t-1)(136.9 kg CO2-eq GJprimary energy-1)]. With allowance for

44.7 GJbiodiesel a-1, this equates to 217.7 kg of CO2-eq

GJbiodiesel-1.

8. Results

8.1. Energy Balance.The results of net energy balances areshown in Figure 3. For scenarios (base without lime, basewith lime, 1, 2, 3, 4), the net energies are 25.3, 23.0, 38.0,102.9, 48.8, and 113.7 GJ ha-1 a-1, respectively. From anenergy perspective, it is better to use rape cake and glycerol toproduce biomethane for transport than to use rape cake foranimal feed and glycerol for heat (scenario 1 vs scenario 3).The net energy benefit is 16.7 GJ ha-1 a-1 (scenario 3,biomethane) as compared to 5.9 GJ ha-1 a-1 (scenario 1,feed and heat).

Use of rape straw for thermal energy is extremely advan-tageous in comparison to ploughing back to the land. Thebenefit is 64.9 GJ ha-1 a-1 of net energy; this is where themajority of energy lies. The net energy from straw is morethan twice the net energy from biodiesel. It is thus considered

Table 8. Energy Content and Emissions of Solid Fuels

emission factor for combustion

fuel typesLHV

(GJ t-1)kg of

CO2-eq kg-1

kg ofCO2-eq GJLHV

-1

coal 27a 2.55b 94.6c

sod peat 13.1b 1.377b 105.1d

peat briquettes 18.6b 1.852b 99.8d

aCalculated from emission factors in kg ofCO2-eq kg-1 andkg ofCO2-

eq GJLHV-1 in this table. bFrom Kenny and Gray.60 cFrom SEI home-

page.46 dCalculated from LHV and emission factor in kg of CO2-eq kg-1

in this table.

Figure 3. Net energy result of different scenarios.

(55) Eaton, J. M.; McGoff, N. M.; Byrne, K. A.; Leahy, P.; Kiely, G.Land cover change and soil organic carbon stocks in the Republic ofIreland 1851-2000. Climate Change 2008. DOI: 10.1007/s10584-008-9412-2.(56) Nilsson, D. Energy, exergy and emergy analysis of using straw as

fuel in district heating plants. Biomass Bioenergy. 1997, 13, 63–73.(57) Passalacqua, F.; Zaetta, C. Pellets in Southern Europe. The state

of the art of pellets utilisation in Southern Europe. New perspectives ofpellets from agri-residues, 2nd World Conference on Biomass forenergy, Industry and Climate Protection, Rome, Italy, May 10-14,2004.(58) Thek, G.; Obernberger, I. Wood pellet production costs under

Austrian and in comparison to Swedish framework conditions.BiomassBioenergy 2004, 27, 671–693.(59) Homepage of Sustainable Energy Ireland. http://www.sei.ie/

Publications/Statistics_Publications/Energy_Balance/ (accessed July2009).

(60) Kenny, T.; Gray, N. F. Comparative performance of six carbonfootprint models for use in Ireland. Environ. Impact Assess. Rev. 2009,29, 1–6.

(61) Cleary, J.; Roulet, N. T.;Moore, T.R.Greenhouse gas emissionsfromCanadian peat extraction, 1990-2000: A life-cycle analysis.Ambio2005, 34, 456–461.

(62) Styles, D.; Jones, M. B. Energy crops in Ireland: Quantifying thepotential life-cycle greenhouse gas reductions of energy-crop electricity.Biomass Bioenergy 2007, 31, 759–772.

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Energy Fuels 2010, 24, 1720–1730 : DOI:10.1021/ef901432g Thamsiriroj and Murphy

as the major factor that improves the sustainability of therape seed system.

8.2. GHGEmissions. Biodiesel in the Allocation Approach.Rape seed biodiesel, with the allocation of GHG emissionsby proportion to rape cake and biodiesel, is responsible for47.74 kg of CO2-eq GJbiodiesel

-1 (Table 9).RapeCake andGlycerol.TheGHGanalysis yields a totally

different viewpoint on rape cake and glycerol use to theenergy analysis. Rape cake used for animal feed coupledwithglycerol for heat provides aGHG saving of 26.2 kg of CO2-eq

GJbiodiesel-1, while rape cake and glycerol for biomethane

production provide a saving of only 1.1 kg of CO2-eq

GJbiodiesel-1 (Table 9).

Rape Straw. The GHG analysis agrees with the energyanalysis on the benefits of the use of rape straw to producepellets for thermal energy. This provides the highest GHGsavingamong theoptions, offeringa savingof 51.9kgofCO2-eq

GJbiodiesel-1. The system is greatly enhanced by the displace-

ment of the environmentally unsound practice of producingpeat from bogs for combustion; eccr is 40% greater than eccs.

8.3. GHG Saving. GHG savings from different scenariosare summarized in Figure 4. The GHG savings are deter-mined from eq 2, using the fossil fuel comparator figure of87.3 kg of CO2-eq GJdiesel

-1.3 (1) The base case scenariowithout lime and the base case with lime provide the lowestGHGsaving at 28.0%and 4.4%, respectively. (2) Scenario 1,base case with lime plus rape cake for animal feed andglycerol for heat production, generates a GHG saving of75.3%. (3) Scenario 2, scenario 1 plus straw for thermalenergy, generates a GHG saving of 134.8%; this is the bestoption. (4) Scenario 3, base case with lime plus rape cake andglycerol for biomethane, provides a GHG saving of 46.6%.

(5) Scenario 4, scenario 3 plus straw for thermal energy,provides a GHG saving of 106.0%.

9. Discussion

9.1. Lime. In a previous paper,3 the authors evaluated theGHG savings of rape seed biodiesel using a no-allocationapproach and found a 28% savings as compared to diesel.The savings are reduced to 4.4% when lime application toacidic land is included in the analysis. The effect of lime onthe energy balance and GHG emissions is significant. Interms of crop production, it is responsible for 14% of energyand 30% of GHG emissions (Table 4).

9.2. Allocation. Allocation by energy content (from bio-diesel to coproducts, in particular rape cake) while ignoringcredits (rape cake to animal feed, straw to thermal energy)improves the GHG emissions savings to 45% (Figure 4).GHG savings from European rape seed biodiesel systemsusing an allocation by an economic value yielded results of32-33%.6,19 Bernesson and co-workers17 arrived at a figureof 54% GHG savings based on an allocation by energycontent; using a no-allocation approach they arrived at a 0%GHG savings, very similar to the result here of 4%

9.3. Nitrous Oxide. A review of the literature on N2Oemissions is complicated and contradictory due to sitespecific characteristics, management practices and environ-mental conditions. Indirect N2O emissions in relation to thebiological nitrogen (N2) fixation by grain legumes (i.e.,soybean) are not well understood.63 N2 fixation by legumesas a source of N2O emissions has been excluded from thenational inventory calculations due to lack of sufficientevidence.64 The use of grain legumes in crop rotation in-creases soil fertility and crop yields.65 In such a case, N2Oemissions fromN2 fixation should be allocated to other cropsin rotation. Crutzen and co-workers66 in a recent publication

Table 9. GHG Emissions (kg of CO2-eq GJbiodiesel-1) from Different Components in the Integrated Rape Seed System

rape seed tobiodiesela

rape cake toanimal feed

glycerol toheat

rape cake and glycerolto biomethane

rape straw topellets

released emissionscultivation, eec 36.46 33.83 33.83processing, ep 7.32 1.76 21.53 9.14transport, etd 0.15 0.33 0.01 0.08 0.39fuel in use, eu 3.81 0.77

total released emissions 47.74 35.92 0.78 55.44 9.53

emission savingsd

geological storage, eccs 156.32replacement, eccr -57.02b -5.88 -56.54 -217.75

total emission savings -57.02 -5.88 -56.54 -61.43

net released emissionsc 47.74 -21.1 -5.1 -1.1 -51.9

aGreenhouse gases are allocated to rape seed biodiesel based on the energy content (see Table 4 for full GHG figures). bA total of 10.62 kg of CO2-eq

GJbiodiesel-1 from barley and 46.4 kg of CO2-eq GJbiodiesel

-1 from soybean meal. cNet released greenhouse gases = total released - total saving.dNegative sign represents the GHG saving, while positive sign represents the GHG released.

Figure 4. GHG saving from different scenarios.

(63) Zhong, Z.; Lemke, R.; Nelson, L. M. Nitrous oxide emissionsassociated with nitrogen fixation by grain legumes. Soil Biol. Biochem.2009, 41, 2283–2291.

(64) IPCC. IPCC guidelines for national greenhouse gas inventories.In Agriculture, Forestry and Other LandUse, Prepared by the NationalGreenhouse Gas Inventories Programme, Vol. 4; IGES: Kanagawa,Japan, 2006.

(65) Lupwayi,N.Z.;Kennedy,A.C.Grain legumes in northernGreatPlains: impacts on selected biological soil processes. Agron. J. 2007, 99,1700–1709.

(66) Crutzen, P. J.; Mosier, A. R.; Smith, K. A.; Winiwarter, W. N2Orelease from agro-biofuel production negates global warming reductionby replacing fossil fuels. Atmos. Chem. Phys. 2008, 8, 389–395.

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highlighted the reduction in GHG savings associated withN2O release from agro-biofuel production. However, it wasargued that they did not conduct a life cycle study and a lifecycle study is needed to properly account for relevantfactors.67 Kim and Dale68 examined the regional variationsin GHG emissions associated with soybean in the UnitedStates. They concluded that even though a very smallquantity of nitrogen fertilizer was applied during soybeancultivation, N2O emissions from soil were one of the largestGHG sources because of nitrogen fixation during soybeancultivation. Metay and co-workers69 indicated that the con-version of native ecosystems of Cerrado to agricultural usesalso increased N2O emissions.

9.4. Carbon Stocks. Bayer and co-workers70 showed thatwith a no-till system, carbon stocks in Brazilian Cerradosoils increased with a mean rate of carbon sequestration of1.28 t of CO2-eq ha

-1 a-1 when compared to tillage. This isconfirmed by Metay and co-workers.71 However Metayand co-workers69 stated that N2O emissions from soilsalso increased as a result of no-till. This effect reduced thecarbon sequestration balance to around 1.17 t of CO2-eq

ha-1 a-1. This does not reduce the magnitude of GHGemissions resulting from the conversion of Cerrado pastureland to arable land (65 t of CO2-eq ha

-1 in this study; section5.3).

9.5. Land Use Change. Dalgaard et al.72 estimated GHGemissions associated with soybean meal from Argentina as721 kg of CO2-eq tmeal

-1. This did not include for deforesta-tion. GHG emissions increased to 5700 kg of CO2-eq tmeal

-1

when the deforestation effects were included.72 Our valueconsidering conversion of grassland to arable land generatesa figure of 1092 kg of CO2-eq tmeal

-1. This highlights theimportance of land use change. A variation in magnitude ofGHG emissions due to conversion of grassland to arableland is found in the literature. Reijnders and Huijbregts19

reported a range between 92 and 103 t of CO2-eq ha-1

compared to 65 t of CO2-eq ha-1 (Bringezu et al.42) used in

our study.Rapeseed is presently grown in a 4 year rotation on arable

land in Ireland. It is used as a break crop in a cycle whichincludes wheat and barley. The authors do not envisageecosystem or habitat destruction as it is not proposed toconvert pasture land or forestry to arable land.

9.6. Sensitivity. The Irish biodiesel system is benefitingfrom reduced habitat destruction in Latin America. This isa controversial argument, which must be included under

land use change. The displaced importation of soybean byrape cake as a feedstock is beneficial when GHG emissionsand reductions in C sequestration due to conversion ofpastureland are taken into consideration. If the factorassociated with indirect N2O emissions were to be includedin the life cycle analysis, the GHG saving for rape cakereplacing soybeanwould be of a higher magnitude. Nobre73

measured an increase in N2O emissions up to 1.2 g ofN2O-Nha-1 d-1 within the first 100 days of crop establish-ment probably due to an increase of biologicalN fixation bythe crop. If the figure was applied to our analysis, the GHGsaving for rape cake replacing soybean meal could increaseby 11%. On the other hand, if the GHG emissions asso-ciated with conversion of pastureland were omitted fromthe analysis, then the benefit of GHG saving from thereplacement would be entirely removed and it would thenbe better to produce biomethane from rape cake andglycerol.

9.7. Biomethane. It was expected by the authors in advanceof the work that biomethane would be a very favorableoption. This was proved true from an energy perspective(scenarios 3 and 4, Figure 3) but not so from a GHGperspective. The reason for the low GHG saving in thebiomethane scenario is the high energy input associated withrape cake as a proportion of energy output. In the allocationmethodology, rape cake is responsible for 33.83 kg of CO2-eq

GJbiodiesel-1. The GHG saving for the biomethane system is

from displaced diesel. Approximately 804 L of diesel isdisplaced (30 GJ ha-1 a-1). Attributing GHG emissions of87.3 kg ofCO2-eqGJdiesel

-1,5 the savings are 56.5 kg ofCO2-eq

GJbiodiesel-1. Thus the emissions associated with the rape

cake are 60% of the emission savings.9.8. Straw Substitution for Peat. The greatest source of

energy and GHG savings is associated with use of straw as athermal energy source. In particular, the substitution of peatbriquettes as a source of thermal energy in Ireland pushes theGHG savings over 100%. Again the biodiesel system isbenefiting from reduced habitat destruction

9.9. Can Rape Seed Biodiesel Meet the EU Sustainability

Criteria for Biofuels? To comply with the GHG saving limitafter 2017 of 60%, the rape seed biodiesel system should at aminimum include rape cake for animal feed (allowing fordisplaced soy importation with associated habitat destruc-tion in Brazil) and glycerol for heat production. For anoptimum system, rape seed biodiesel should include combus-tion of rape straw as a source of thermal energy substitutingfor peat.

10. Conclusions

This paper highlights the importance of allocation metho-dology and substitution effects on a rape seed biodieselsystem. In a no-allocation approach, the rape seed biodieselsystem including lime only affects a 4.4% savings in GHGemissions as compared to diesel. However allocation byenergy content (distributed between biodiesel and rape cake)softened this detrimental effect. In particular the use of rapecake as a feed stock for animals, reducing imports from LatinAmerica of soybean meal, is a significant plus to the system,especially when land use change is associatedwith the produc-tion of soybean. Together with use of glycerol as a source of

(67) Dale, B. Calculation of Direct and Indirect N2O emissions andother Procedures in the EPA Draft Regulatory Impact Analysis: ACritical Evaluation, http://www.ncga.com/files/pdf/N2OemissionsinE-PAdraftreport_dale.pdf.(68) Kim, S.; Dale, B. E. Regional variations in greenhouse gas

emissions of biobased products in the United States-corn-based ethanoland soybean oil. Int. J. Life Cycle Assess. 2009, 14, 540–546.(69) Metay, A.; Oliver, R.; Scopel, E.; Douzet, J. M.; Moreira, J. A.

A.;Maraux, F.; Feigl, B. J.; Feller, C.N2O andCH4 emissions from soilsunder conventional and no-till management practices in Goiania(Cerrados, Brazil). Geoderma 2007, 141, 78–88.(70) Bayer,C.;Martin-Neto, L.;Mielniczuk, J; Pavinato,A.;Dieckow,

J. Carbon sequestration in two Brazilian Cerrado soils under no-till. SoilTillage Res. 2006, 86, 237–245.(71) Metay, A.; Bernoux, M.; Boyer, T.; Douzet, J. M.; Feigl, B.;

Feller, C.;Maraux, F.;Oliver,R. Storage and forms of organic carbon ina no-tillage under cover crops system on clayey Oxisol in dryland riceproduction (Cerrados, Brazil). Soil Tillage Res. 2007, 94, 122–132.(72) Dalgaard, R.; Schmidt, J.; Halberg, N.; Christensen, P.; Thrane,

M.; Pengue,W. A. LCA for food products: Case study: LCAof soybeanmeal. Int. J. LCA 2008, 13, 240–254.

(73) Nobre, A. D. Nitrous oxide emissions from tropical soils. Ph.D.Dissertation, University of New Hampshire, Durham, NH, 1994.

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heat, this is now a sustainable system resulting in GHGemission savings of 75%. Use of straw pellets to substitutefor the environmentally unsound practice of producing peatfrom bogs also greatly enhances the system; coupled with useof rape cake as a substitute for soybean the GHG savings are135%.

Acknowledgment. The authors acknowledgeTheHigher Edu-cation Authority (HEA) under the HEA PRTLI Cycle 4 ERI

program for funding the research. Nicholas Korres, Anoop

Singh, Beatrice Smyth, Abdul Sattar Nizami, John Buckley,

Richard Kearney, and Brian Nixon are acknowledged for their

advice, brainstorming sessions, conversations, and critiques.