The Influence of Co-product Handling Methodology on Greenhouse Gas Savings of Biofuels in the European Context

Abstract

The handling of multi-output systems presents a crucial aspect of greenhouse gas (GHG) emission calculation as well as the certification of biofuels, and finding a robust and applicable method that accounts for distinctive characteristics of and benefits generated by all products is a challenge. In this work, GHG emission savings of 11 biofuel production concepts are assessed and the implications of methodological assumptions are discussed by applying the methodology defined by the Renewable Energy Directive (RED), allocation based on physical parameters, two hybrid approaches, as well as six variants of substitution. GHG emission savings according to RED methodology range from 35 to 57 %. Sugar beet-based ethanol shows highest savings. Results reveal that GHG savings according to the RED methodology present, in sum, a relatively good approximation of emission savings occurring due to substitution effects under given assumptions. An introduction of credits for products that are barely or not considered by the RED methodology due to allocation based on the lower heating value (LHV), i.e. fertilizers and wet feed co-products, reduces the difference between RED results and results based on substitution. If displacement mechanisms are considered by substitution, sugar beet-based ethanol, ethanol production by wet milling of wheat and sunflower biodiesel result in highest emission savings under given assumptions if oil that needs to be supplied due to occurring displacement mechanisms stems from rapeseed. The implementation of a method that supports concepts with high emission saving potential, e.g. allocation based the lower heating value of dry material, could promote emission reductions from biofuel provision.