GHG emission balances and prospects of hydrogen enhanced synthetic biofuels from solid biomass in the European context

The European Commission has proposed a minimum share of 3.6% for advanced biofuels in transport in 2030. Satisfying this target using synthetic biofuels would require 48-62 Mt/a of forest residue feedstock. If all biofuel plants were maximally enhanced with additional hydrogen input, the biomass demand would be reduced by 35 Mt to 16-24 Mt/a. As sustainable biomass is a limited resource, such drastic improvements in the efficiency of biomass use have a favourable impact on biomass availability. In this work we assume electrolysis of water as the source of hydrogen and investigate the GHG emission balances of hydrogen enhanced biofuels using the calculation method provided in the European Union's sustainability criteria for biofuels. The required 70% emission saving compared to fossil fuels is achieved when the carbon intensity of electricity remains under 84-110 gCO2/kWh, depending on the process configuration. In addition, we study the possibility that an emission factor could be allocated to the wood biomass, referring to recent discussions on climate impacts of forest bioenergy. Without hydrogen enhancement, the emission factor needs to remain below 13 gCO2/MJwood to meet the 70% requirement, while for hydrogen-enhanced configurations it could increase to 36 gCO2/MJwood, under the assumption of zero emission electricity.