Sustainable Aviation Fuels: an analysis of carbon intensity estimates derived from LCA studies

The aviation industry is a significant contributor to global greenhouse gas (GHG) emissions, primarily due to its reliance on fossil-based jet fuels. To mitigate its environmental impact and align with international climate goals, Sustainable Aviation Fuels (SAF) have emerged as a promising alternative. This dissertation critically analyzes the life cycle carbon intensity (LCCI) of various SAF pathways using a systematic review of recent Life Cycle Assessment (LCA) studies. The analysis compares the environmental performance of key SAF production technologies, including Hydroprocessed Esters and Fatty Acids (HEFA), Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK), Power-to-Liquid (PtL), and Bioenergy with Carbon Capture and Storage (BECCS). The findings indicate that while all SAF pathways offer substantial reductions in life cycle GHG emissions compared to conventional jet fuel (87.5 gCO₂eq/MJ), their sustainability varies based on feedstock availability, process efficiency, and integration with carbon capture technologies. BECCS-based SAF exhibits the highest mitigation potential, achieving net-negative emissions (-121.83 gCO₂eq/MJ) when CO₂ capture is fully integrated. PtL SAF, powered by renewable electricity, can achieve emissions as low as 14.1 gCO₂eq/MJ but remains highly energy-intensive and economically constrained. Lignocellulosic SAF, derived from forestry residues, shows low emissions (0.6 - 1.5 gCO₂eq/MJ), while gasification-based SAF has moderate emissions reductions (5 - 25 gCO₂eq/MJ), depending on syngas cleanup efficiency and CCS adoption. Despite these environmental benefits, SAF deployment faces significant economic, technological, and policy challenges, including high production costs, limited scalability, and feedstock constraints.