Sustainable energy for aviation

Scientists and industry leaders worldwide are seeking to make aviation sustainable by 2050 and choosing a viable sustainable aviation fuel (SAF) is a challenge. Phil Ansell, aerospace engineer at the University of Illinois Urbana-Champaign, reviewed more than 300 research projects across industry sectors to help find a solution.

According to Ansell, several key energy carriers emerged, including 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. He compared each to conventional fossil-derived aviation turbine fuel, determining how their material properties impact aircraft performance and fuel handling, emissions, cost and scalability, and resource and land requirements, as well as difficult-to-measure social impacts.

“If we want to do this at scale, we need all three pillars of the environmental, economic, and societal contributions, to make that energy carrier sustainable,” Ansell says. “Because the production and infrastructure costs required to adopt an alternative fuel source are significant, people think we can only pick one, the biggest contenders being bio jet fuel and hydrogen. But the choice doesn’t have to be mutually exclusive. For example, we can use hydrogen to produce synthetic aviation fuels like the power-to-liquid pathway or use biomass to produce hydrogen.”

Ansell examined numerous options to produce biofuel from anything, from municipal waste to seaweed and algae.

“Anything you can burn, create energy from, decompose, can be turned into jet fuel. We’ve been using corn to produce ethanol. But if you take corn, ferment it, then turn that ethanol into jet fuel, you lose the ability to feed people or animals that corn.”

People are trying to use the stover, the parts of a corn plant left on the ground after harvesting to make fuel. Corn stover is full of sugar but it’s difficult to extract.

Ansell stresses that countries may need different strategies, different rates of implementation, and adoption of renewables, based on their own resources.

“The U.S. has one of the world’s largest agricultural sectors. We may have more land than Europe that can be allocated to feedstock development, which can be used for a variety of bio jet fuels or hydrogen production pathways. In contrast, Europe has an extensive network of clean energy, and is doing a lot of work in electrolytic hydrogen production.

“It’s important that the aviation community understands where the challenges exist,” Ansell says. “With a goal of net zero CO₂ by 2050, I want the aviation community to recognize how big of a task this is.”