Liquid e-fuels for a sustainable future: A comprehensive review of production, regulation, and technological innovation

The decarbonization of sectors such as aviation, maritime transport, and heavy-duty mobility-where direct electrification is not yet feasible-requires alternative fuels with high energy density and compatibility with existing infrastructure. This review investigates the potential of liquid synthetic fuels, known as liquid electrofuels (or e-fuels), to replace fossil fuels in these hard-to-abate sectors. The objective is to provide a comprehensive, integrative assessment of liquid e-fuel development by analyzing production pathways, feedstock demands, regulatory frameworks, and industrial implementation trends. The study reviews three major production processes-Fischer-Tropsch synthesis, methanol synthesis, and the Haber-Bosch process-used to produce six key synthetic fuels: e-kerosene, e-diesel, e-methanol, e-dimethyl ether, e-gasoline, and e-ammonia. The methodology includes a systematic review of literature, life cycle assessments for water and energy demand, and analysis of over 30 large-scale projects worldwide in terms of plant capacity (10-200 MW), production volume, capital investment, and technology readiness level. Results show that process efficiencies range from 59 % to 89 %, with current production costs for synthetic kerosene and methanol varying between 1,200-4,200 /ton depending on the pathway and technology maturity. The study finds that polymer electrolyte membrane electrolysis and industrial point-source carbon dioxide capture are the most prevalent technologies among operational plants. Regulatory complexity, high capital expenditure, and the lack of harmonized sustainability criteria remain key barriers to commercial scaling. This review advances the scientific literature by presenting a novel, multi-dimensional framework that connects technical, environmental, and policy considerations, offering a strategic roadmap for accelerating the global deployment of liquid synthetic fuels.