Review of sustainable energy carriers for aviation: Benefits, challenges, and future viability

Sustainability has recently been identified as the greatest challenge facing the modern aviation field. Given the extreme power and energy characteristics of transport-class aircraft today,achieving sustainability goals across the aviation sector is a tremendous challenge when compared to other modes of transportation. Several key energy carriers have emerged, promising an environmentally sustainable aviation future. Those considered here include bio-jet fuel pathways for synthetic kerosene, power-to-liquid pathways for synthetic kerosene, liquid hydrogen, ammonia, liquid natural gas, ethanol, methanol, and battery electric systems, all of which are compared to conventional fossil-derived aviation turbine fuel. However, these alternate energy carriers bring forward significant technoeconomic considerations that must be addressed before such approaches can be viably implemented. These factors include material properties impacting aircraft performance and fuel handling, emissions, cost and scalability, resource and land requirements, and social impacts. The purpose of this review is to provide a summary of current approaches to alternative aviation energy carriers, which includes a discussion of key advantages, challenges, and implications determining the future viability of each approach. It is found that bio-jet fuels, power-to-liquid synthetic kerosene, liquid natural gas, and liquid hydrogen all have technical feasibility and can contribute to improved environmental outcomes. However, hydrocarbon fuels and non-renewable production pathways for carbon-free energy carriers are not viable permanent solutions for a fully sustainable aviation ecosystem. As a result, potential transition scenarios from fossil-derived aviation turbine fuel to synthetic kerosene, with simultaneous development for adoption of liquid hydrogen and battery-electric systems, are recommended.