Emerging technologies for the production of biojet fuels from wood—can greenhouse gas emission reductions meet policy requirements?

Abstract

The transition from fossil jet fuel to biojet fuel is an important step towards reducing greenhouse gas (GHG) emissions from aviation. To enable such a fuel shift, the Swedish Government introduced a GHG emission reduction mandate of 27% by 2030 for aviation fuel sold in Sweden, forcing fuel suppliers to blend in biojet fuel in fossil jet fuel. A similar policy instrument is being discussed within the EU. Biojet fuels with life cycle GHG emissions 90% lower than those for fossil jet fuel are projected to be available by 2025, which by far exceeds the requirement of 65% lower emissions in the EU Renewable Energy Directive. The purpose of this study was to carry out life cycle assessments for a number of wood-fuel-based production chains near commercialization and to determine whether they meet the Swedish projection and the EU requirement. The study illustrates what can be achieved in a region with high availability of wood fuels and access to heat and power with low GHG emissions. The production chains studied include the production of hydrocarbon intermediates via (i) fast pyrolysis, (ii) hydrothermal liquefaction, (iii) thermal gasification followed by Fischer–Tropsch-synthesis, and (iv) cellulosic ethanol fermentation followed by upgrading of these four intermediates to biojet fuel and other liquid biofuels. The results show that all the production chains studied can deliver biojet fuels with 89–91% lower GHG emissions than fossil jet fuels. Non-fossil hydrogen is required to achieve low emissions in the upgrading of intermediates from fast pyrolysis and hydrothermal liquefaction.