Life Cycle Analysis Perspective on Greenhouse Gas Savings

This chapter explores total greenhouse gas emissions associated with biofuel production and their subsequent net savings relative to the production and combustion of conventional liquid transport fuels. Biofuels are defined and their general potential is outlined. Life cycle assessment, as the basis for greenhouse gas emissions calculations, is introduced and the main features of official calculation methodologies are summarized. The debate over net energy balances for biofuels is considered briefly. However, the key concerns relate to total greenhouse gas emissions, which can vary substantially as a consequence of a number of different effects. These effects, which are examined systematically, include the type of biofuel; the biomass feedstock from which it is derived; the details of biomass feedstock cultivation, such as direct and indirect land use change and soil emissions; sources of processing energy; and, not least, the features of the calculation methodologies, especially their treatment of coproducts.