Lipid feedstocks for sustainable aviation fuel (SAF) production via hydroprocessed esters and fatty acids (HEFA) pathway: Current status and challenges in quality, sustainability, availability and cost

As the aviation industry faces an existential challenge from climate change, sustainable aviation fuel (SAF) has emerged as a critical solution for achieving net-zero emissions by mid-century. Currently, hydroprocessed esters and fatty acids (HEFA) technology represents the most established industrial process for SAF production. However, the quality and limited availability of sustainable lipid feedstocks pose a significant challenge to the decarbonization effort. This review provides a rigorous and prospective analysis of lipid feedstocks for SAF production, categorizing them into first, second, and third-generation sources. The compositional characteristics, including fatty acid profiles and other relevant components, and their implication for hydroprocessing and resulting fuel properties were examined. The review also critically assessed the environmental impacts, economic viability, technological challenges, and innovation potential associated with these feedstocks. First-generation feedstocks derived from edible oil crops demonstrate technical maturity but raise significant sustainability concerns due to land-use competition and food-energy conflicts. Second-generation feedstocks, including used cooking oils (UCO) and non-edible plant oils, alleviate these issues yet face challenges in supply chain fragmentation, compositional inconsistency, and inadequate production volumes to meet projected global SAF demand. Third-generation feedstocks, particularly microalgae, hold substantial promise due to their high oil content and minimal land-use requirements, though technological and economic barriers currently constrain their commercialization. This review highlights the urgent need for policy changes, ongoing research, and technological innovation to expand the use of diverse, sustainable feedstocks for scaling SAF production and enhancing long-term sustainability. • This review evaluates SAF production via HEFA from a feedstock perspective. • First-generation feedstock faces ILUC and food security concerns. • Second-generation waste feedstock faces quality inconsistencies and high impurities. • Third-generation feedstock has long-term potential pending advanced technology. • Feedstock-specific challenges and future opportunities for SAF are discussed.