Greenhouse gas life cycle assessment of canola-derived HEFA biojet fuel in Western Canada

Abstract

Biojet fuel represents the best short-term option for reducing greenhouse gas (GHG) emissions from the aviation industry. In the near term, biojet fuel is most likely to be produced via the hydroprocessed esters and fatty acids (HEFA) pathway. Canola is one of the most readily available feedstocks for HEFA fuel production in Canada, and interest has been shown in developing a domestic supply chain for biojet fuel. However, there is substantial variation in the reported emissions reductions that HEFA biojet from crop-based feedstocks can offer. The primary concern surrounds the inconsistent inclusion of land use change emissions. In addition to infrequently including land use change emissions, previous life cycle assessments (LCAs) of canola biojet fuel have not used Canadian production data, or have failed to examine the sensitivity of calculated emissions intensity to variation in many LCA parameters. In this thesis, the emissions intensity of canola biojet was calculated across four co-product allocation methods both with and without land use change emissions. Land use change emissions from potential grassland conversion on the Canadian Prairies were estimated using a soil carbon model. Finally, a sensitivity analysis on life cycle inputs and co-product allocation parameters was performed. Results suggested that without land use change, canola biojet fuel may provide emissions reductions of 35% to 54% compared to petroleum jet fuel. Land use change has an overwhelming influence on biojet fuel emissions intensity, and its inclusion results in negative reductions in most cases. Emissions intensity and the sensitivity to parameter changes varied across allocation methods. This research points to the importance of standardized LCA methodology, and to the development of advanced biojet fuel production pathways that do not compete for arable land.