Comparative life cycle assessment of two biofuels ethanol from sugar beet and rapeseed methyl ester

Background, Aims and Scope. To all Member States, the European Union has imposed a minimum percentage of 2% of biofuels in the fuels consumed for road transport since 2005. This percentage is expected to reach 5.75% in 2010, and probably 10% in 2020. In this context, investments are made everywhere in Europe in local productions of biofuels. In Belgium, ethanol from sugar beet and rapeseed methyl ester (RME) ate generally supposed to be two of the more valuable possibilities. As these industries are growing, it is important to evaluate the environmental impacts of these productions and to highlight the main sources of these impacts using Life Cycle Assessment methodology. This evaluation will also lead to propositions of improvements of the environmental performances. A comparison with the impacts of the related fossil fuels (petrol and diesel) should also be conducted. Even if these fuels are different and used in different types of engines, it is important to determine which one offers the best environmental performances, as both require arable land, which is the limiting parameter in biofuel production. Methods. The system boundaries include cultivation, extraction, processing and final use of the biofuels. The system has been expanded to take into account valorization of by-products in substitution of animal feed (rapeseed meat or pulps from sugar beet) or chemicals (glycerin). No economical, mass or energetic allocation was made. The yields and fertilizer consumptions of the crops are those of the Belgian conditions. Simapro 7.1 databases and the Eco-Indicator 99 method have been used for the Life Cycle Impact Assessment. The functional unit was road transport over 100 km. Results. The results show that, without valorization of the by-products, the impacts of the two biofuels over their whole life cycle are not significantly lower than those of the related fossil fuels. However, the credits accorded thanks to the valorization of by-products lead to improvements of the environmental performances in comparison to fossil fuels, especially for RME. Discussion. The impacts of agriculture and production of the fertilizers are more important in the case of RME, because the yield per hectare is lower than in the production of ethanol from sugar beet. However, the extraction of the sugar from the beet, fermentation, purification of the ethanol and drying of the pulps and slops consume much more energy than extraction and esterification of rapeseed oil. Moreover, the by-products of RME (rapeseed meal and glycerin) are more valuable than those of ethanol from sugar beet (pulps). This induces a more important environmental benefit in the production of RME. These parameters lead to a global environmental impact that is higher for the production of ethanol than for RME. Conclusions. Life Cycle Assessment methodology has been successfully applied to two of the major ways of production of biofuels in Belgium using specific local data. The assessment of the environmental impacts reveals that rapeseed methyl ester allows a considerable improvement of the environmental performances compared to fossil diesel, while ethanol from sugar beet offers a more limited benefit compared to petrol. Recommendations. Arable land is a limited resource, especially in West-European countries like Belgium. Therefore, choices must be made to have the most valuable environmental benefit. Soil quality and crop rotations should also be taken into account before making a decision.