Life-Cycle Assessment of Biofuels

Publisher Summary The concerns about energy balances are related to both the life-cycle energy efficiency of biofuels and the saving of nonrenewable energy between biofuels and fossil fuels. The chapter considers wheat-based bioethanol production in Switzerland as a case study, with the aim of quantifying the variation in GHG (greenhouse gas) emissions and nonrenewable energy use depending on methodological choices. The results presented in this chapter show a large variation of the net GHG emissions of wheat-based ethanol for transportation with a high sensitivity to the following factors: the method used to allocate the impacts between coproducts, the type of reference systems, the type of land-use change, and the type of fuel blend. Depending on the allocation method (energy content, economy, dry mass or carbon content), the net GHG emissions of ethanol may vary by a factor of up to 2.6 (with carbon content being the most favorable and economy the least favorable). When substitution is applied, the net GHG emissions of ethanol may even be negative when both straw and DDGS are used as fuels, thereby making the difference even more significant. Depending on the land-use change situation, the net GHG emissions of ethanol may vary by a factor of up to 6.4. Similarly, the hypotheses regarding actual fuel blends and vehicle/fuel performance may result in a variation of net GHG emissions by a factor of 2.2. Depending on the combinations of methodological choices and land-use change situations, the variation of life-cycle GHG emissions with respect to gasoline may range from –112% to +120% for the same ethanol production pathway.

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