Forging a sustainable sky: Unveiling the pillars of aviation e-fuel production for carbon emission circularity.

In 2021, airplanes consumed nearly 250 million tons of fuel, equivalent to almost 10.75 exajoules. Anticipated growth in air travel suggests increasing fuel consumption. In January 2022, demand surged by 82.3%, as per the International Air Transport Association. In tackling aviation emissions, governments promote synthetic e-fuels to cut carbon. Sustainable aviation fuel (SAF) production increased from 1.9 million to 15.8 million gallons in six years. Although cost of kerosene produced with carbon dioxide from direct air capture (DAC) is several times higher than the cost of conventional jet fuel, its projected production cost is expected to decrease from $104-$124/MWh in 2030 to $60-$69/MWh in 2050. Advances in DAC technology, decreasing cost of renewable electricity, and improvements in FT technology are reasons to believe that the cost of e-kerosene will decline. This review describes major e-kerosene synthesis methods, incorporating DAC, hydrogen from water electrolysis, and hydrocarbon synthesis via the Fischer-Tropsch process. The importance of integrating e-fuel production with renewable energy sources and sustainable feedstock utilization cannot be overstated in achieving carbon emission circularity. The paper explores the concept of power-to-liquid (PtL) pathways, where renewable energy is used to convert renewable feedstocks into e-fuels. In addition to these technological improvements, carbon pricing, government subsidies, and public procurement are several policy initiatives that could help to reduce the cost of e-kerosene. Our review provides a comprehensive guide to the production pathways, technological advancements, and carbon emission circularity aspects of aviation e-fuels. It will provide a valuable resource for researchers, policymakers, industry stakeholders, and the general public interested in transitioning to a sustainable aviation industry.