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Does the production of Belgian bioethanol fit with European requirements on GHG emissions? Case of wheat
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Does the production of Belgian bioethanol fit with European requirements on GHG emissions? Case of wheat Sandra Belboom a,*, Bernard Bodson b, Angelique Leonard a Department of Chemical Engineering, Processes and Sustainable Development, University of Liege, 3 Allee de la Chimie, 4000 Liege, Belgium b Department of Agronomic Sciences, Crop Science Unit, Gembloux Agro-Bio Tech, University of Liege, 2 Passage des Deportes, 5030 Gembloux, Belgium a
article info
abstract
Article history:
This paper undertakes an environmental evaluation of bioethanol production, using wheat
Received 9 July 2014
cultivated in Belgium. Cultivation steps are modelled using Belgian specific data. Wheat
Received in revised form
transformation in ethanol relies on industrial data. GHG emissions of the whole life cycle
5 January 2015
are calculated and compared with the default values given by the European Renewable
Accepted 6 January 2015
Energy Directive. Belgian wheat bioethanol achieves a 5% higher GHG reduction than the
Available online
one mentioned in the European directive but impact repartition is different with a higher importance of cultivation step in our case. Belgian wheat bioethanol complies with the
Keywords:
current sustainability criteria but is also able to conform to further ones. Sensitivity ana-
Bioethanol
lyses are performed on the importance of N fertilizers and associated emissions known as
Wheat
main important parameters. These analyses reveal non negligible variations and then a
Life cycle assessment (LCA)
range of available GHG reduction when using wheat bioethanol.
Renewable Energy Directive (RED)
© 2015 Elsevier Ltd. All rights reserved.
Greenhouse gas emissions (GHG)
1.
Introduction
The decrease of fossil fuels reserves and the consequences on energy security and supply are both main concerns of our century. In 2010, fossils fuels allow to reach 78.9% of the consumed primary energy in the world with 30% of them for transportation sector [1]. The increase of greenhouse gas emissions in the atmosphere through years can be linked to this consumption and their reduction has become an important issue for our generation.
* Corresponding author. Tel.: þ32 43664584; fax: þ32 43664435. E-mail address: [email protected] (S. Belboom). http://dx.doi.org/10.1016/j.biombioe.2015.01.005 0961-9534/© 2015 Elsevier Ltd. All rights reserved.
With its climate and energy package published in 2008, the European Council defined two key targets: ‘a reduction of at least 20% greenhouse gases (GHG) by 2020 and a 20% share of renewable energies in EU energy consumption by 2020’ [2]. The amount of renewable energy in the transport sector, mainly biofuels used as E5 in Europe, should reach 10% by 2020 [3]. To comply with the Renewable Energy Directive (RED), these biofuels must achieve a minimum of 35% GHG savings per unit of energy, through its whole life cycle assessment. By 2017, this reduction should reach at least 50% [3,4].
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Life cycle assessment is a common and useful methodology for the evaluation of the environmental impacts of a product, service or process, following four mandatory steps. The first step comprises the definition of the goal and scope of the study; the second one gathers information concerning the matter and energy balances involved in each unit process of the scenarios; the third step includes the conversion of the life cycle inventory into a measure of environmental impacts and the last step consists of the interpretation of these results. The environmental assessment of biofuels has been performed in several studies using the life cycle assessment methodology for several crops or locations. Cherubini and Strømman (2011) analysed a large portion of existing scientific literature related to LCA of bioenergy systems [5]. Gnansounou (2009) and von Blottnitz and Curran (2007) conducted reviews focussing on the use of bioethanol as transportation fuel [6,7]. Considering Belgium in particular, few studies were published to our knowledge. Halleux et al. (2008) focused on the production and use of biofuel using sugar beet and rapeseed [8] in a Belgian context. De Ruyck et al. (2006) assessed the environmental impact of Belgian biofuel production from rapeseed, wheat and sugar beet [9]. These studies are based on various assumptions using mainly non Belgian specific data for cultivation or transformation steps. They also use different allocation methodology making difficult the comparison of the results. The present study assesses environmental impacts of bioethanol production using wheat, cultivated in Belgium. It uses Belgian representative data for both cultivation and transformation steps and follows the methodology developed by the European Council through its RED. The aim of this study is to compare the representative values for Belgium with the generic ones given by the European directive or literature and to draw conclusions concerning sustainability of bioethanol production in Belgium.
2.
Materials and methods
2.1.
Goal definition
Environmental impacts of bioethanol production using wheat, grown and transformed in Belgium, are assessed using attributional LCA methodology classified as Situation C from the ILCD handbook [10]. They are calculated using both ILCD 2011 midpoint [11] and ReCiPe 2008 [12] methods. The first one is recommended by the ILCD handbook and regroups the most relevant methods to assess the environmental impact in each
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studied impact category. The last one regroups both midpoint and endpoint approaches and is relevant to evaluate separately the environmental impact of mineral and fossil fuel depletion which cannot be performed using the first method. This study is made in accordance with the ISO standards 14,040 [13] and 14,044 [14] and tends to answer these questions: “Does wheat Belgian bioethanol comply with the sustainability criteria of European Council?”, “Does the generic values of RED reflect the real environmental impacts of Belgian bioethanol?” and “What is the influence of modelling assumptions on environmental impacts of Belgian bioethanol?”.
2.2.
Scope definition
The functional unit of this study is defined as 1 MJ of biofuel, as recommended by the Annex V of the directive of the European Parliament [3]. Boundaries of system, presented in Fig. 1, include four main stages: (1) cultivation with production and application of fertilizers and pesticides, consumptions due to agricultural operations and use of land, (2) crops transportation from field to plant, (3) crops transformation into bioethanol, and finally (4) combustion.
2.3.
Life cycle inventory analysis
Inventory is based, as much as possible, on specific data for Belgium for both cultivation and transformation steps. Other data are obtained using scientific literature and modelled using ecoinvent database v2.2 [15].
2.3.1.
Cultivation of wheat
The cultivation of wheat in Belgium achieves yields which are among the highest observed within the European continent with an average, for the 2005e2010 period, of 8.6 t/ha. The average European yield for the same period reaches 3.6 t/ha [16]. Cultivation of this crop requires the use of fertilizers and pesticides. Table 1 presents the average applied quantities of each input, based on Belgian specific data. For wheat, K and P fertilizers are not directly applied on field. Crops cultivated before wheat on the same field, generally sugar beet, let the needed amount of K and P nutrients that can be used by the plant. To avoid allocation between wheat and the previous crop and to assess an average case, it is assumed that the required amount of K and P fertilizer is given by chemical fertilizers as shown in Table 1. Detailed data are available in the supporting information file [17e20].
Fig. 1 e Boundaries of wheat bioethanol scenario.
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Table 1 e Cultivation of wheat in Belgium e amount of applied fertilizers. Input
Unit
Amount
Fertilizer N Fertilizer K2O Fertilizer P2O5 Pesticides
kg/ha kg/ha kg/ha kg/ha
169 [17e20] 93 [17,18,20] 57 [17,18,20] 3.1 [18,20]
Emission factors related to the use of fertilizers are calculated for wheat, as an average of values mentioned in scientific literature [21e27]. These emissions are not measured in Belgium excepted for CO2 [28]. Measurements of N2O emissions are currently performed on field but no result is available up to now. These emissions are highly dependent on climate, crop, type and structure of soil, type of tillage, N or manure application rates [29,30]. The real range of emissions can be as broad as mentioned in literature (see Table 2) and is then a key point on which a sensitivity analysis is performed in paragraph 3.1.6. For wheat, the whole cultivated area is mechanically harvested. Average consumption of diesel for one hectare of wheat cultivation is equal to 79 L based on Belgian practices and modelled using ecoinvent database [15,20]. During crop cultivation, carbon dioxide from atmosphere is converted by the plant into biomass. In this study, we do not take this benefit into account as recommended by the Annex V of the RED [3] neither the emissions of biogenic CO2 released during combustion phase. No Land Use Change (LUC) effect is included in this study. Indeed, in Europe, no direct transformation of pastures or forests to crop land is allowed by the Common Agricultural Policy. We are aware of the possibility of indirect land use change, induced by the increase of bioethanol use but this effect, not yet taken into account by the RED, is subject to many uncertainties and is not the purpose of our study.
2.3.2.
Crop transportation from field to plant
A distance of 50 km, travelled for 75% by barge tanker and 25% by truck [31], between field and transformation plant is assumed for wheat, based on industrial data and in accordance with Gnansounou et al. (2009) [6].
2.3.3.
Wheat transformation and bioethanol production
Bioethanol production from wheat is modelled using Belgian industrial data. A schema of this industrial plant is provided at Fig. 2 and energy consumptions are presented in Table 3. The studied plant uses the wet milling technology with two main
Table 2 e Emission factors of pollutants due to application of fertilizers, expressed in weight percentage of the applied element. Pollutant
Air
Water
N 2O NOX NH3 Nitrates
Wheat Min
Max
Mean
0.5 [21,23] 1 [21] 2 [26] 17.1 [27]
1.96 [22] 4 [22] 10 [26] 29.3 [24]
1.17 2.5 6.7 23.2
specificities. First, wheat bran is recovered and used as fuel in a biomass furnace. This amount of energy is not enough for the global process needs but avoids an important amount of natural gas, used as supplemental energy. Secondly, recovered coproducts are composed of gluten and liquid feed. The production of 1000 L of bioethanol (99.7% vol.) requires 2.9 t of wheat, in accordance with literature mentioning between 340 [32] and 370 [33] L of bioethanol per t of wheat. Chemical and energy consumptions are based on technical reports published by the plant operator [34,35]. For 1000 L of bioethanol (99.7%) from wheat, 46.9 kg of gluten with a Lower Heating Value (LHV) of 15.64 MJ/kg [36] and 1158 kg of liquid feed with a LHV of 3.01 MJ/kg are produced [31]. As the main product is bioethanol, the global environmental impact of all previous steps must be divided between all coproducts. Several possibilities can be used as system expansion or physical relation. In our study, as recommended by ILCD guidelines, an allocation is used. As bioethanol will be used for its energy content, an energy allocation has been chosen to divide impacts between bioethanol and its coproducts. The worst case, when no allocation factor is used, and then all environmental impacts are associated with bioethanol production will also be taken into account in the results section.
2.3.4.
Combustion
Use of bioethanol can induce different exhaust emissions than the one obtained with pure gasoline. Few data are available concerning E5 combustion in Europe. For E85, used in Brazil, some results are available in literature which show some differences between pure gasoline and E85 for exhaust gases [37e42] but no clear trend can be found. They will then be assumed to be the same for both fuels, in accordance with Euro 5 requirements which give emission in terms of quantity per travelled distance [43]. This assumption can also be used for E5. Average car consumption is supposed to be of 6 L each 100 km which represents 1.92 MJ/km. Emissions reach for NOX, CO, VOC and PM, respectively 60, 1000, 100 and 5 mg/km. For CO2 emissions, zero value is used for bioethanol as explained before. For gasoline, the value mentioned in the RED is used. Environmental impacts of gasoline and bioethanol are compared on an energy basis, assuming that the same energy is needed to travel the same distance as advocated by Quirin et al. (2004) [44]. If exhaust emissions lead to a non-negligible impact on the global LCA of bioethanol or gasoline, a sensitivity analysis based on extreme values found in literature will be performed.
3.
Results and discussion
3.1.
Results
Fig. 3 presents a breakdown of the results for ILCD 2011 environmental impact categories of our study. It compares the environmental impact of 1 MJ of Belgian bioethanol from wheat and 1 MJ of gasoline. To model this latter, ecoinvent database is used with Euro 5 and RED exhaust emissions. Results relative to mineral and fossil fuel depletion categories modelled with ReCiPe 2008 method are added in Fig. 3.
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Fig. 2 e Detailed scheme of the industrial plant e wheat transformation into bioethanol.
Categories of ILCD 2011 method do not express directly the impact of fossil fuel consumption, which is an important factor for comparisons between fossil fuels and biofuels. Values of impacts for each category are presented in Table 4 and are commented in further paragraphs. The scenario achieving the highest score is not the same for all categories. For climate change, ozone depletion and fossil fuel depletion categories, gasoline obtains the highest score. As usually mentioned in literature [21,45,46], the use of bioethanol from wheat instead of gasoline allows a reduction of GHG emissions and fossil fuel consumptions. This trend is usually reverse when focussing on other impact categories. The main relevant categories are detailed in further paragraphs with the impact of each step described in paragraph 2.3. As bioethanol from wheat is produced to replace fossil fuel, special attention is given to climate change and fossil fuel depletion categories.
3.1.1.
Climate change category
The results for 1 MJ of bioethanol, presented in Table 5, show non-negligible differences between default data mentioned by the RED and our calculations relative to a specific Belgian case study. The impact of the Belgian wheat bioethanol, without allocation, is similar to the European one. With an energy allocation, the impact decreases and reaches 91% of the European one. Literature relative to European wheat bioethanol shows higher values than the calculated one. The JRC/EUCAR/
Table 3 e Energy consumptions for bioethanol production. Energy consumption
3.1.2. Wheat Mean
Electricity (kWh/1000 L bioethanol) Heat (MJ/1000 L bioethanol)
Concawe study (2011) shows the highest value with 58.4 g CO2eq per MJ [47] while Hoefnagels et al. (2011) obtains 47.3 g CO2eq which is close to our value [45]. The impact of wheat bioethanol can be divided in our four previous steps. The highest part of the impact is induced by the cultivation step with 68%, followed by the transformation step with 27% and finally the transportation step with 5%. For the RED, the cultivation of European wheat achieves a lower part in the global impact with 52%. The transformation of wheat into bioethanol leads to 43% of the global impact. Scientific literature mentions different repartition of the impact with 67.6% for cultivation, 28.8% for transformation and 3.6% for transportation in the JRC/EUCAR/Concawe (2011) [47] study or 51.1% for cultivation, 44.7% for transformation and 4.2% for transportation in Hoefnagels et al. (2011) [45]. The low impact of transformation in our case is explained by the specificities of our process with the use of bran as fuel and also with the use of wet milling instead of dry milling. This process allows the recovery of gluten which can be sold as a coproduct. This replacement permits to reduce GHG emissions calculated by the RED for wheat bioethanol using natural gas in cogeneration. The reduction of GHG when using bioethanol instead of gasoline, achieved by the Belgian wheat bioethanol without allocating the global impact, is lower than the RED one with 43% reduction. When taking into account energy allocation, with the valorisation of specific coproducts, gluten and liquid feed, this reduction increases to 52%. Belgian wheat bioethanol complies then with the current and further European sustainability criteria.
235 1800
Mineral, fossil and renewable resource depletion
Another important category concerns fossil fuel depletion. As the ultimate goal of bioethanol production is the replacement of fossil products, consumption of fossil fuels should be reduced when using energetic crops as raw material. In the ILCD 2011 method, this category takes into
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Fig. 3 e Comparison of the environmental impacts of wheat and gasoline scenarios using ILCD 2011 and ReCiPe 2008 midpoint categories.
account mineral and fossil fuel and shows that the production of bioethanol generates a consumption of these resources at least 5 times higher than the production of gasoline. This is due to small characterization factors associated to fossil fuels compared to those for mineral elements. A factor of 107 exists between fossil and mineral resources which explain such differences. Comparison between scenarios can be performed, using ReCiPe 2008 method at midpoint level [12], which separates mineral and fossil fuel consumptions in two categories. Results, presented in Table 4, show an important reduction of fossil fuel consumption equal to 65% when using bioethanol instead of gasoline. The reverse trend can be shown in Fig. 3 for mineral depletion with an impact 4.6 times higher for wheat bioethanol. The energy yield ratio meaning the amount of delivered energy compared to the fossil one needed, is about 2.2 for wheat which is higher than usually seen in literature [45,46]. This is due to the specificity of the wheat bioethanol production in our model which allows an important reduction of fossil fuel consumption, especially with the use of bran as fuel instead of natural gas.
3.1.3.
Acidification
Bioethanol production obtains, for this category, an impact at least 3 times higher than gasoline, as shown in Fig. 3. This category takes into account pollutants as NOX, SOX and NH3. For wheat, cultivation, with N application and its associated emissions, is the main contributor to this impact with 95%. The low amount of energy used during the transformation can explain this trend. Emissions factor due to fertilizer application is then a key point to analyse for this category.
3.1.4.
Terrestrial and freshwater eutrophication
The impact obtained by bioethanol, compared to gasoline for terrestrial and freshwater eutrophication, is atleast 5 times higher for wheat as presented in Fig. 3. Majority of these impacts is induced by cultivation step with more than 90%. More specifically, the production and use of P fertilizer is the main contributor for freshwater eutrophication category and impact in terrestrial eutrophication category is mainly due to N emissions associated with N fertilizer application. As for acidification category, emissions factor is then a highly influencing factor for this impact category.
Table 4 e Impact results at characterization stage for 9 categories e ILCD 2011 and ReCiPe 2008 methods. Method
Impact category
Unit
Wheat bioethanol (1 MJ)
Gasoline (1 MJ)
ILCD 2011
Climate change Particulate matter Acidification Terrestrial eutrophication Freshwater eutrophication Land use Mineral, fossil & ren resource depletion Mineral depletion Fossil fuel depletion
kg CO2 eq kg PM2.5 eq molc Hþ eq molc N eq molc P eq kg C deficit kg Sb eq kg Fe eq kg oil eq
4,00E-02 3,17E-05 6,78E-04 2,85E-03 1,51E-05 1,70Eþ00 4,21E-07 1,78E-03 1,04E-02
8,38E-02 1,67E-05 2,33E-04 3,41E-04 2,82E-06 2,44E-01 7,83E-08 3,87E-04 2,96E-02
ReCiPe 2008
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Table 5 e Climate change e impact of bioethanol steps and comparison with default values of the RED e percentages into brackets are relative to the RED values for each step. IPCC 2007 Belgian wheat bioethanol Belgian wheat bioethanol (without allocation) European wheat bioethanol
3.1.5.
Cultivation (g CO2eq/MJ)
Transportation (g CO2eq/MJ)
Transformation (g CO2eq/MJ)
Combustion (g CO2eq/MJ)
Total(g CO2eq/MJ)
27 (117%) 33 (143%)
2 (100%) 2 (100%)
11 (58%) 13 (68%)
0 0
40 (91%) 48 (109%)
23
2
19
0
44
Particulate matter formation
The bioethanol production doubles emissions of particulate matter compared to the production and use of gasoline as shown in Fig. 3. This impact is mainly generated by the cultivation step for wheat with 88%. Emissions are specifically related to the production and use of N fertilizer for wheat bioethanol. This can be explained by the consumption of fossil energy during the production of fertilizer which leads to the emissions of particulate matter. Furthermore, exhaust gas is negligible in this impact, leading to less than 0.02%. For gasoline, impact of exhaust gas reaches around 10% of the global impact.
3.1.6.
Sensitivity analysis e cultivation step
For wheat bioethanol, the main impacting step is cultivation with fertilizers use and associated emissions. In the main scenario, average values of Belgian data for fertilizers, shown in Table 1, are used. To assess the available range of variation induced by fertilizers, extreme values of Belgian specific literature are used. The same exercise is performed for emission factors using minimal and maximal values indicated in Table 2, relative to generic conditions and not Belgian ones due to unmeasured emissions. Fig. 4 presents the variation for relevant categories with ILCD 2011 and ReCiPe 2008 methods.
The variation of the amount of applied fertilizers and associated emission factors induces a high variation in several impact categories. This change reaches at least 8% and þ6% in fossil fuel depletion category with a maximum for terrestrial acidification where impact varies between 59% and þ50%. Knowledge improvement of specific emission factor for Belgium is then an important point to increase the accuracy of results for categories as acidification or eutrophication. For climate change category, the range of GHG emissions is situated between 32.5 g and 48.2 g CO2eq/MJ. This is associated with a reduction comprised between 42.5 and 61.2% in comparison with the whole life cycle of gasoline. Belgian wheat bioethanol production achieves at least the GHG reduction mentioned by the RED and seems to be able to comply with further criteria of sustainability for biofuels.
3.2.
General discussion
Production and use of bioethanol instead of gasoline show advantages for climate change and fossil fuel depletion categories. For other impact categories, impact induced by the production and use of bioethanol is higher than the one of gasoline. This shows then a shift in pollution between categories. Focussing on climate change category, wheat bioethanol complies with current sustainable criteria of RED with or
Fig. 4 e Importance on global impact of fertilizers consumptions and associated emissions during cultivation step e wheat bioethanol.
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without energy allocation. Transportation phase achieves the same value of CO2 emissions in the RED and our case. Thanks to the use of bran as fuel, the transformation of wheat into bioethanol consumes less fossil energy and obtains 60% of the impact of the transformation phase in the RED. Cultivation is the main step influencing the impact. Through literature [17e27], amount of applied fertilizers and associated emissions factors can vary in a broad range, with potential effects on the final results as already mentioned for acidification or terrestrial and freshwater eutrophication categories. Cultivation phase in the Belgian scenario achieves a higher value than in the RED despite the fact that Belgian wheat crop is well-known and managed and achieves among the highest yield in Europe. Even with the minimum scenario, emissions of GHG for the cultivation step in our scenario are increased by 17% compared to the RED and the maximum case allows an increase of more than 40% in emissions compared to RED value. No allocation has been used in our case for starch produced at the same time with wheat. This could explain the best value for wheat cultivation step in the RED and it could then be considered as the best scenario of GHG reduction. In contrast to available literature [6,7,9], this study shows a comparison between Belgian specific scenario of bioethanol production, using specific cultivation values and the RED which is considered as the reference in terms of CO2 emissions for biofuels. A range of CO2 emissions has been calculated, based on uncertainties linked to the crop cultivation, which is the main sensitive parameter in this field. Despite the non-availability of measured values for exhaust gases, this study has highlighted the non-significant influence of this parameter through the whole life cycle of bioethanol. Their impact reaches less than one percent in impact categories as particulate matter formation or acidification. This study shows the importance of the cultivation step for wheat and the variation induced by a modification of fertilizers or emission factors. This indicates the importance of calculating specific values to assess the sustainability of bioethanol for a specific country using a specific crop and a specific technology. Further measurements and research about emission factor due to fertilizers application could improve the accuracy of our results. For decision making, this specific approach should be performed, associated with a consequential approach to assess the environmental impact of change in the market, especially concerning coproducts use. This also implies to take into account the indirect land use change generated by the increase of crops demand for bioethanol production. All these topics should be addressed to get the most relevant answer before making any decision as recommended by the ILCD handbook [10].
4.
Conclusions
The life cycle assessment methodology, in accordance with the ISO standards, is applied to wheat used as energetic crop for bioethanol production, using Belgian specific data for both cultivation and transformation steps. Its environmental impacts are compared with gasoline and results show a
reduction of GHG emissions and fossil fuel consumption when replacing gasoline by bioethanol. For other impact categories, the reverse trend is obtained. Our results are compared to the default RED values for climate change and show non negligible variation, especially in the transformation step where the wet milling technology with the use of bran permits to highly reduce impact of this step. Sensitivity analysis is performed on amount of fertilizers and associated emission factors. Induced variations are high in that case with at least an 8% variation of the global impact of wheat bioethanol. Emissions of GHG using 1 MJ bioethanol instead of 1 MJ gasoline can be reduced between 42.5 and 61.2% for wheat. The range for wheat reaches at least similar amount of reduction given by the RED.
Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.biombioe.2015.01.005
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[30] Larson ED. A review of life-cycle analysis studies on liquid biofuel systems for the transport sector. Energy Sustain Dev 2006;10(2):109e26. [31] BioWanze S.A. [Internet]. CropEnergies bio.wanze. Available from: http://www.biowanze.be/fr/Homepage/. Cardona CA. Trends in biotechnological nchez OJ [32] Sa production of fuel ethanol from different feedstocks. Bioresour Technol 2008;99(13):5270e95. [33] Ballerini D, AlzarToux N. Les biocarburants: Etat des lieux, veloppement. Paris: Technip; perspectives et enjeux du de 2006. [34] Fluzin C. Projet BioWanze e usine de production de thanol (300 000 m3/an) sur le site de Wanze e Notice bioe ne rale. 2007. descriptive ge [35] Wanze Commune de. Permis unique : implanter et exploiter thanol, du gluten et une usine de production de bioe tails e Arre ^ te . 2005. d'aliments pour be 500 g. Available from: [36] MORGA AG [Internet]. Gluten de ble http://www.morga.ch/pages/fr/shop/viewArticle/28876/4239. html. [37] Hess P, Johnston M, Brown-Steiner B, Holloway T, de Andrade JB, Artaxo P. Air quality issues associated with biofuel production and use. Gummersbach, Germany. In: Howarth RW, Bringezu S, editors. Biofuels: environmental consequences and interactions with changing land use; 2009. p. 164e94. [38] Yanowitz J, McCormick RL. Effect of E85 on tailpipe emissions from light-duty vehicles. J Air Waste Manag Assoc 2009;59(2):172e82. [39] International Fuel Quality Center. Setting a quality standard for fuel ethanol. Dep Environ Herit 2004:9. sentation des [40] Luneau G, Fayet S. Les biocarburants, pre res et impacts environnementaux-qualite de principales filie se bibliographique pour AtmoPACA. Marseille: l’air. Synthe de l’Air; 2007. p. 1e23. Qualite [41] Vasudevan P, Sharma S, Kumar A. Liquid fuel from biomass: an overview. J Sci Industrial Res 2005;64(11):822e31. ziat JC, Morel S, Boch V, Rousseaux P. Life [42] Querini F, Be cycle assessment of automotive fuels: critical analysis and recommendations on the emissions inventory in the tank to wheels stage. Int J Life Cycle Assess 2011;16(5):454e64. [43] European Parliament and the Council REGLEMENT (CE) No 715/2007 DU PARLEMENT EUROPEEN ET DU CONSEIL du 20 la re ception des ve hicules a moteur au regard juin. relatif a missions des ve hicules particuliers et utilitaires le gers des e paration et (Euro 5 et Euro 6) et aux informations sur la re hicules. J off de l’Union Eur L171/12007 l’entretien des ve 2007:12. € rtner S, Pehnt M, Reinhardt GA. CO2 mitigation [44] Quirin M, Ga through biofuels in the transport sector e status and perspectives main report. Heidelberg: IFEU e Institut fu¨r Energie- und Umweltforschung Heidelberg GmbH; 2004. [45] Hoefnagels R, Smeets E, Faaij A. Greenhouse gas footprints of different biofuel production systems. Renew Sustain Energy Rev 2010;14(7):1661e94. [46] Bessou C, Ferchaud F, Gabrielle B, Mary B. Biofuels, greenhouse gases and climate change. A review. Agron Sustain Dev 2011;31(1):1e79. J-F, Be ziat JC. Well-to-wheels analysis of [47] Edwards R, Larive future automotive fuels and powertrains in the European context e version 3c. Well-to-tank report. Luxembourg: Concawe: European Commission and EUCAR; 2011.
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Does the production of Belgian bioethanol fit with European requirements on GHG emissions? Case of wheat Sandra Belboom a,*, Bernard Bodson b, Angelique Leonard a Department of Chemical Engineering, Processes and Sustainable Development, University of Liege, 3 Allee de la Chimie, 4000 Liege, Belgium b Department of Agronomic Sciences, Crop Science Unit, Gembloux Agro-Bio Tech, University of Liege, 2 Passage des Deportes, 5030 Gembloux, Belgium a
article info
abstract
Article history:
This paper undertakes an environmental evaluation of bioethanol production, using wheat
Received 9 July 2014
cultivated in Belgium. Cultivation steps are modelled using Belgian specific data. Wheat
Received in revised form
transformation in ethanol relies on industrial data. GHG emissions of the whole life cycle
5 January 2015
are calculated and compared with the default values given by the European Renewable
Accepted 6 January 2015
Energy Directive. Belgian wheat bioethanol achieves a 5% higher GHG reduction than the
Available online
one mentioned in the European directive but impact repartition is different with a higher importance of cultivation step in our case. Belgian wheat bioethanol complies with the
Keywords:
current sustainability criteria but is also able to conform to further ones. Sensitivity ana-
Bioethanol
lyses are performed on the importance of N fertilizers and associated emissions known as
Wheat
main important parameters. These analyses reveal non negligible variations and then a
Life cycle assessment (LCA)
range of available GHG reduction when using wheat bioethanol.
Renewable Energy Directive (RED)
© 2015 Elsevier Ltd. All rights reserved.
Greenhouse gas emissions (GHG)
1.
Introduction
The decrease of fossil fuels reserves and the consequences on energy security and supply are both main concerns of our century. In 2010, fossils fuels allow to reach 78.9% of the consumed primary energy in the world with 30% of them for transportation sector [1]. The increase of greenhouse gas emissions in the atmosphere through years can be linked to this consumption and their reduction has become an important issue for our generation.
* Corresponding author. Tel.: þ32 43664584; fax: þ32 43664435. E-mail address: [email protected] (S. Belboom). http://dx.doi.org/10.1016/j.biombioe.2015.01.005 0961-9534/© 2015 Elsevier Ltd. All rights reserved.
With its climate and energy package published in 2008, the European Council defined two key targets: ‘a reduction of at least 20% greenhouse gases (GHG) by 2020 and a 20% share of renewable energies in EU energy consumption by 2020’ [2]. The amount of renewable energy in the transport sector, mainly biofuels used as E5 in Europe, should reach 10% by 2020 [3]. To comply with the Renewable Energy Directive (RED), these biofuels must achieve a minimum of 35% GHG savings per unit of energy, through its whole life cycle assessment. By 2017, this reduction should reach at least 50% [3,4].
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Life cycle assessment is a common and useful methodology for the evaluation of the environmental impacts of a product, service or process, following four mandatory steps. The first step comprises the definition of the goal and scope of the study; the second one gathers information concerning the matter and energy balances involved in each unit process of the scenarios; the third step includes the conversion of the life cycle inventory into a measure of environmental impacts and the last step consists of the interpretation of these results. The environmental assessment of biofuels has been performed in several studies using the life cycle assessment methodology for several crops or locations. Cherubini and Strømman (2011) analysed a large portion of existing scientific literature related to LCA of bioenergy systems [5]. Gnansounou (2009) and von Blottnitz and Curran (2007) conducted reviews focussing on the use of bioethanol as transportation fuel [6,7]. Considering Belgium in particular, few studies were published to our knowledge. Halleux et al. (2008) focused on the production and use of biofuel using sugar beet and rapeseed [8] in a Belgian context. De Ruyck et al. (2006) assessed the environmental impact of Belgian biofuel production from rapeseed, wheat and sugar beet [9]. These studies are based on various assumptions using mainly non Belgian specific data for cultivation or transformation steps. They also use different allocation methodology making difficult the comparison of the results. The present study assesses environmental impacts of bioethanol production using wheat, cultivated in Belgium. It uses Belgian representative data for both cultivation and transformation steps and follows the methodology developed by the European Council through its RED. The aim of this study is to compare the representative values for Belgium with the generic ones given by the European directive or literature and to draw conclusions concerning sustainability of bioethanol production in Belgium.
2.
Materials and methods
2.1.
Goal definition
Environmental impacts of bioethanol production using wheat, grown and transformed in Belgium, are assessed using attributional LCA methodology classified as Situation C from the ILCD handbook [10]. They are calculated using both ILCD 2011 midpoint [11] and ReCiPe 2008 [12] methods. The first one is recommended by the ILCD handbook and regroups the most relevant methods to assess the environmental impact in each
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studied impact category. The last one regroups both midpoint and endpoint approaches and is relevant to evaluate separately the environmental impact of mineral and fossil fuel depletion which cannot be performed using the first method. This study is made in accordance with the ISO standards 14,040 [13] and 14,044 [14] and tends to answer these questions: “Does wheat Belgian bioethanol comply with the sustainability criteria of European Council?”, “Does the generic values of RED reflect the real environmental impacts of Belgian bioethanol?” and “What is the influence of modelling assumptions on environmental impacts of Belgian bioethanol?”.
2.2.
Scope definition
The functional unit of this study is defined as 1 MJ of biofuel, as recommended by the Annex V of the directive of the European Parliament [3]. Boundaries of system, presented in Fig. 1, include four main stages: (1) cultivation with production and application of fertilizers and pesticides, consumptions due to agricultural operations and use of land, (2) crops transportation from field to plant, (3) crops transformation into bioethanol, and finally (4) combustion.
2.3.
Life cycle inventory analysis
Inventory is based, as much as possible, on specific data for Belgium for both cultivation and transformation steps. Other data are obtained using scientific literature and modelled using ecoinvent database v2.2 [15].
2.3.1.
Cultivation of wheat
The cultivation of wheat in Belgium achieves yields which are among the highest observed within the European continent with an average, for the 2005e2010 period, of 8.6 t/ha. The average European yield for the same period reaches 3.6 t/ha [16]. Cultivation of this crop requires the use of fertilizers and pesticides. Table 1 presents the average applied quantities of each input, based on Belgian specific data. For wheat, K and P fertilizers are not directly applied on field. Crops cultivated before wheat on the same field, generally sugar beet, let the needed amount of K and P nutrients that can be used by the plant. To avoid allocation between wheat and the previous crop and to assess an average case, it is assumed that the required amount of K and P fertilizer is given by chemical fertilizers as shown in Table 1. Detailed data are available in the supporting information file [17e20].
Fig. 1 e Boundaries of wheat bioethanol scenario.
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Table 1 e Cultivation of wheat in Belgium e amount of applied fertilizers. Input
Unit
Amount
Fertilizer N Fertilizer K2O Fertilizer P2O5 Pesticides
kg/ha kg/ha kg/ha kg/ha
169 [17e20] 93 [17,18,20] 57 [17,18,20] 3.1 [18,20]
Emission factors related to the use of fertilizers are calculated for wheat, as an average of values mentioned in scientific literature [21e27]. These emissions are not measured in Belgium excepted for CO2 [28]. Measurements of N2O emissions are currently performed on field but no result is available up to now. These emissions are highly dependent on climate, crop, type and structure of soil, type of tillage, N or manure application rates [29,30]. The real range of emissions can be as broad as mentioned in literature (see Table 2) and is then a key point on which a sensitivity analysis is performed in paragraph 3.1.6. For wheat, the whole cultivated area is mechanically harvested. Average consumption of diesel for one hectare of wheat cultivation is equal to 79 L based on Belgian practices and modelled using ecoinvent database [15,20]. During crop cultivation, carbon dioxide from atmosphere is converted by the plant into biomass. In this study, we do not take this benefit into account as recommended by the Annex V of the RED [3] neither the emissions of biogenic CO2 released during combustion phase. No Land Use Change (LUC) effect is included in this study. Indeed, in Europe, no direct transformation of pastures or forests to crop land is allowed by the Common Agricultural Policy. We are aware of the possibility of indirect land use change, induced by the increase of bioethanol use but this effect, not yet taken into account by the RED, is subject to many uncertainties and is not the purpose of our study.
2.3.2.
Crop transportation from field to plant
A distance of 50 km, travelled for 75% by barge tanker and 25% by truck [31], between field and transformation plant is assumed for wheat, based on industrial data and in accordance with Gnansounou et al. (2009) [6].
2.3.3.
Wheat transformation and bioethanol production
Bioethanol production from wheat is modelled using Belgian industrial data. A schema of this industrial plant is provided at Fig. 2 and energy consumptions are presented in Table 3. The studied plant uses the wet milling technology with two main
Table 2 e Emission factors of pollutants due to application of fertilizers, expressed in weight percentage of the applied element. Pollutant
Air
Water
N 2O NOX NH3 Nitrates
Wheat Min
Max
Mean
0.5 [21,23] 1 [21] 2 [26] 17.1 [27]
1.96 [22] 4 [22] 10 [26] 29.3 [24]
1.17 2.5 6.7 23.2
specificities. First, wheat bran is recovered and used as fuel in a biomass furnace. This amount of energy is not enough for the global process needs but avoids an important amount of natural gas, used as supplemental energy. Secondly, recovered coproducts are composed of gluten and liquid feed. The production of 1000 L of bioethanol (99.7% vol.) requires 2.9 t of wheat, in accordance with literature mentioning between 340 [32] and 370 [33] L of bioethanol per t of wheat. Chemical and energy consumptions are based on technical reports published by the plant operator [34,35]. For 1000 L of bioethanol (99.7%) from wheat, 46.9 kg of gluten with a Lower Heating Value (LHV) of 15.64 MJ/kg [36] and 1158 kg of liquid feed with a LHV of 3.01 MJ/kg are produced [31]. As the main product is bioethanol, the global environmental impact of all previous steps must be divided between all coproducts. Several possibilities can be used as system expansion or physical relation. In our study, as recommended by ILCD guidelines, an allocation is used. As bioethanol will be used for its energy content, an energy allocation has been chosen to divide impacts between bioethanol and its coproducts. The worst case, when no allocation factor is used, and then all environmental impacts are associated with bioethanol production will also be taken into account in the results section.
2.3.4.
Combustion
Use of bioethanol can induce different exhaust emissions than the one obtained with pure gasoline. Few data are available concerning E5 combustion in Europe. For E85, used in Brazil, some results are available in literature which show some differences between pure gasoline and E85 for exhaust gases [37e42] but no clear trend can be found. They will then be assumed to be the same for both fuels, in accordance with Euro 5 requirements which give emission in terms of quantity per travelled distance [43]. This assumption can also be used for E5. Average car consumption is supposed to be of 6 L each 100 km which represents 1.92 MJ/km. Emissions reach for NOX, CO, VOC and PM, respectively 60, 1000, 100 and 5 mg/km. For CO2 emissions, zero value is used for bioethanol as explained before. For gasoline, the value mentioned in the RED is used. Environmental impacts of gasoline and bioethanol are compared on an energy basis, assuming that the same energy is needed to travel the same distance as advocated by Quirin et al. (2004) [44]. If exhaust emissions lead to a non-negligible impact on the global LCA of bioethanol or gasoline, a sensitivity analysis based on extreme values found in literature will be performed.
3.
Results and discussion
3.1.
Results
Fig. 3 presents a breakdown of the results for ILCD 2011 environmental impact categories of our study. It compares the environmental impact of 1 MJ of Belgian bioethanol from wheat and 1 MJ of gasoline. To model this latter, ecoinvent database is used with Euro 5 and RED exhaust emissions. Results relative to mineral and fossil fuel depletion categories modelled with ReCiPe 2008 method are added in Fig. 3.
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Fig. 2 e Detailed scheme of the industrial plant e wheat transformation into bioethanol.
Categories of ILCD 2011 method do not express directly the impact of fossil fuel consumption, which is an important factor for comparisons between fossil fuels and biofuels. Values of impacts for each category are presented in Table 4 and are commented in further paragraphs. The scenario achieving the highest score is not the same for all categories. For climate change, ozone depletion and fossil fuel depletion categories, gasoline obtains the highest score. As usually mentioned in literature [21,45,46], the use of bioethanol from wheat instead of gasoline allows a reduction of GHG emissions and fossil fuel consumptions. This trend is usually reverse when focussing on other impact categories. The main relevant categories are detailed in further paragraphs with the impact of each step described in paragraph 2.3. As bioethanol from wheat is produced to replace fossil fuel, special attention is given to climate change and fossil fuel depletion categories.
3.1.1.
Climate change category
The results for 1 MJ of bioethanol, presented in Table 5, show non-negligible differences between default data mentioned by the RED and our calculations relative to a specific Belgian case study. The impact of the Belgian wheat bioethanol, without allocation, is similar to the European one. With an energy allocation, the impact decreases and reaches 91% of the European one. Literature relative to European wheat bioethanol shows higher values than the calculated one. The JRC/EUCAR/
Table 3 e Energy consumptions for bioethanol production. Energy consumption
3.1.2. Wheat Mean
Electricity (kWh/1000 L bioethanol) Heat (MJ/1000 L bioethanol)
Concawe study (2011) shows the highest value with 58.4 g CO2eq per MJ [47] while Hoefnagels et al. (2011) obtains 47.3 g CO2eq which is close to our value [45]. The impact of wheat bioethanol can be divided in our four previous steps. The highest part of the impact is induced by the cultivation step with 68%, followed by the transformation step with 27% and finally the transportation step with 5%. For the RED, the cultivation of European wheat achieves a lower part in the global impact with 52%. The transformation of wheat into bioethanol leads to 43% of the global impact. Scientific literature mentions different repartition of the impact with 67.6% for cultivation, 28.8% for transformation and 3.6% for transportation in the JRC/EUCAR/Concawe (2011) [47] study or 51.1% for cultivation, 44.7% for transformation and 4.2% for transportation in Hoefnagels et al. (2011) [45]. The low impact of transformation in our case is explained by the specificities of our process with the use of bran as fuel and also with the use of wet milling instead of dry milling. This process allows the recovery of gluten which can be sold as a coproduct. This replacement permits to reduce GHG emissions calculated by the RED for wheat bioethanol using natural gas in cogeneration. The reduction of GHG when using bioethanol instead of gasoline, achieved by the Belgian wheat bioethanol without allocating the global impact, is lower than the RED one with 43% reduction. When taking into account energy allocation, with the valorisation of specific coproducts, gluten and liquid feed, this reduction increases to 52%. Belgian wheat bioethanol complies then with the current and further European sustainability criteria.
235 1800
Mineral, fossil and renewable resource depletion
Another important category concerns fossil fuel depletion. As the ultimate goal of bioethanol production is the replacement of fossil products, consumption of fossil fuels should be reduced when using energetic crops as raw material. In the ILCD 2011 method, this category takes into
62
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Fig. 3 e Comparison of the environmental impacts of wheat and gasoline scenarios using ILCD 2011 and ReCiPe 2008 midpoint categories.
account mineral and fossil fuel and shows that the production of bioethanol generates a consumption of these resources at least 5 times higher than the production of gasoline. This is due to small characterization factors associated to fossil fuels compared to those for mineral elements. A factor of 107 exists between fossil and mineral resources which explain such differences. Comparison between scenarios can be performed, using ReCiPe 2008 method at midpoint level [12], which separates mineral and fossil fuel consumptions in two categories. Results, presented in Table 4, show an important reduction of fossil fuel consumption equal to 65% when using bioethanol instead of gasoline. The reverse trend can be shown in Fig. 3 for mineral depletion with an impact 4.6 times higher for wheat bioethanol. The energy yield ratio meaning the amount of delivered energy compared to the fossil one needed, is about 2.2 for wheat which is higher than usually seen in literature [45,46]. This is due to the specificity of the wheat bioethanol production in our model which allows an important reduction of fossil fuel consumption, especially with the use of bran as fuel instead of natural gas.
3.1.3.
Acidification
Bioethanol production obtains, for this category, an impact at least 3 times higher than gasoline, as shown in Fig. 3. This category takes into account pollutants as NOX, SOX and NH3. For wheat, cultivation, with N application and its associated emissions, is the main contributor to this impact with 95%. The low amount of energy used during the transformation can explain this trend. Emissions factor due to fertilizer application is then a key point to analyse for this category.
3.1.4.
Terrestrial and freshwater eutrophication
The impact obtained by bioethanol, compared to gasoline for terrestrial and freshwater eutrophication, is atleast 5 times higher for wheat as presented in Fig. 3. Majority of these impacts is induced by cultivation step with more than 90%. More specifically, the production and use of P fertilizer is the main contributor for freshwater eutrophication category and impact in terrestrial eutrophication category is mainly due to N emissions associated with N fertilizer application. As for acidification category, emissions factor is then a highly influencing factor for this impact category.
Table 4 e Impact results at characterization stage for 9 categories e ILCD 2011 and ReCiPe 2008 methods. Method
Impact category
Unit
Wheat bioethanol (1 MJ)
Gasoline (1 MJ)
ILCD 2011
Climate change Particulate matter Acidification Terrestrial eutrophication Freshwater eutrophication Land use Mineral, fossil & ren resource depletion Mineral depletion Fossil fuel depletion
kg CO2 eq kg PM2.5 eq molc Hþ eq molc N eq molc P eq kg C deficit kg Sb eq kg Fe eq kg oil eq
4,00E-02 3,17E-05 6,78E-04 2,85E-03 1,51E-05 1,70Eþ00 4,21E-07 1,78E-03 1,04E-02
8,38E-02 1,67E-05 2,33E-04 3,41E-04 2,82E-06 2,44E-01 7,83E-08 3,87E-04 2,96E-02
ReCiPe 2008
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Table 5 e Climate change e impact of bioethanol steps and comparison with default values of the RED e percentages into brackets are relative to the RED values for each step. IPCC 2007 Belgian wheat bioethanol Belgian wheat bioethanol (without allocation) European wheat bioethanol
3.1.5.
Cultivation (g CO2eq/MJ)
Transportation (g CO2eq/MJ)
Transformation (g CO2eq/MJ)
Combustion (g CO2eq/MJ)
Total(g CO2eq/MJ)
27 (117%) 33 (143%)
2 (100%) 2 (100%)
11 (58%) 13 (68%)
0 0
40 (91%) 48 (109%)
23
2
19
0
44
Particulate matter formation
The bioethanol production doubles emissions of particulate matter compared to the production and use of gasoline as shown in Fig. 3. This impact is mainly generated by the cultivation step for wheat with 88%. Emissions are specifically related to the production and use of N fertilizer for wheat bioethanol. This can be explained by the consumption of fossil energy during the production of fertilizer which leads to the emissions of particulate matter. Furthermore, exhaust gas is negligible in this impact, leading to less than 0.02%. For gasoline, impact of exhaust gas reaches around 10% of the global impact.
3.1.6.
Sensitivity analysis e cultivation step
For wheat bioethanol, the main impacting step is cultivation with fertilizers use and associated emissions. In the main scenario, average values of Belgian data for fertilizers, shown in Table 1, are used. To assess the available range of variation induced by fertilizers, extreme values of Belgian specific literature are used. The same exercise is performed for emission factors using minimal and maximal values indicated in Table 2, relative to generic conditions and not Belgian ones due to unmeasured emissions. Fig. 4 presents the variation for relevant categories with ILCD 2011 and ReCiPe 2008 methods.
The variation of the amount of applied fertilizers and associated emission factors induces a high variation in several impact categories. This change reaches at least 8% and þ6% in fossil fuel depletion category with a maximum for terrestrial acidification where impact varies between 59% and þ50%. Knowledge improvement of specific emission factor for Belgium is then an important point to increase the accuracy of results for categories as acidification or eutrophication. For climate change category, the range of GHG emissions is situated between 32.5 g and 48.2 g CO2eq/MJ. This is associated with a reduction comprised between 42.5 and 61.2% in comparison with the whole life cycle of gasoline. Belgian wheat bioethanol production achieves at least the GHG reduction mentioned by the RED and seems to be able to comply with further criteria of sustainability for biofuels.
3.2.
General discussion
Production and use of bioethanol instead of gasoline show advantages for climate change and fossil fuel depletion categories. For other impact categories, impact induced by the production and use of bioethanol is higher than the one of gasoline. This shows then a shift in pollution between categories. Focussing on climate change category, wheat bioethanol complies with current sustainable criteria of RED with or
Fig. 4 e Importance on global impact of fertilizers consumptions and associated emissions during cultivation step e wheat bioethanol.
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without energy allocation. Transportation phase achieves the same value of CO2 emissions in the RED and our case. Thanks to the use of bran as fuel, the transformation of wheat into bioethanol consumes less fossil energy and obtains 60% of the impact of the transformation phase in the RED. Cultivation is the main step influencing the impact. Through literature [17e27], amount of applied fertilizers and associated emissions factors can vary in a broad range, with potential effects on the final results as already mentioned for acidification or terrestrial and freshwater eutrophication categories. Cultivation phase in the Belgian scenario achieves a higher value than in the RED despite the fact that Belgian wheat crop is well-known and managed and achieves among the highest yield in Europe. Even with the minimum scenario, emissions of GHG for the cultivation step in our scenario are increased by 17% compared to the RED and the maximum case allows an increase of more than 40% in emissions compared to RED value. No allocation has been used in our case for starch produced at the same time with wheat. This could explain the best value for wheat cultivation step in the RED and it could then be considered as the best scenario of GHG reduction. In contrast to available literature [6,7,9], this study shows a comparison between Belgian specific scenario of bioethanol production, using specific cultivation values and the RED which is considered as the reference in terms of CO2 emissions for biofuels. A range of CO2 emissions has been calculated, based on uncertainties linked to the crop cultivation, which is the main sensitive parameter in this field. Despite the non-availability of measured values for exhaust gases, this study has highlighted the non-significant influence of this parameter through the whole life cycle of bioethanol. Their impact reaches less than one percent in impact categories as particulate matter formation or acidification. This study shows the importance of the cultivation step for wheat and the variation induced by a modification of fertilizers or emission factors. This indicates the importance of calculating specific values to assess the sustainability of bioethanol for a specific country using a specific crop and a specific technology. Further measurements and research about emission factor due to fertilizers application could improve the accuracy of our results. For decision making, this specific approach should be performed, associated with a consequential approach to assess the environmental impact of change in the market, especially concerning coproducts use. This also implies to take into account the indirect land use change generated by the increase of crops demand for bioethanol production. All these topics should be addressed to get the most relevant answer before making any decision as recommended by the ILCD handbook [10].
4.
Conclusions
The life cycle assessment methodology, in accordance with the ISO standards, is applied to wheat used as energetic crop for bioethanol production, using Belgian specific data for both cultivation and transformation steps. Its environmental impacts are compared with gasoline and results show a
reduction of GHG emissions and fossil fuel consumption when replacing gasoline by bioethanol. For other impact categories, the reverse trend is obtained. Our results are compared to the default RED values for climate change and show non negligible variation, especially in the transformation step where the wet milling technology with the use of bran permits to highly reduce impact of this step. Sensitivity analysis is performed on amount of fertilizers and associated emission factors. Induced variations are high in that case with at least an 8% variation of the global impact of wheat bioethanol. Emissions of GHG using 1 MJ bioethanol instead of 1 MJ gasoline can be reduced between 42.5 and 61.2% for wheat. The range for wheat reaches at least similar amount of reduction given by the RED.
Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.biombioe.2015.01.005
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