Review of Energy Balances and Emissions Associated with Biomass-Based Transport Fuels Relevant to the United Kingdom Context

A numerical evaluation of the energy available from biomass-derived transport fuels, including biodiesel, bioethanol, and biomethane has been undertaken based on the available literature. The evaluation focuses on the energy balance, co-products, and tailpipe emissions of the fuels. Biomethane from the anaerobic digestion of crops was found to have a more favorable energy balance for the production of transport fuel than biodiesel or bioethanol (maximum 237 011 MJ/ha compared to 24 185 and 77 264 MJ/ha, respectively). Tailpipe emissions were superior for methane with lower emission levels of CO, CO2, and particulates and lower NO x levels than biodiesel but comparable to bioethanol. To make the most efficient use of the limited land available for production of biofuels, it is recommended that further development of gaseous biofuels, such as biomethane and biohydrogen, are encouraged. This conclusion will have significant implications for the formation of policy for the development of biofuels in the U.K.