The aviation industry is notoriously difficult to decarbonize, in part because airplanes use a petroleum-based fuel to fly.

Alder Fuels wants to change that. The new cleantech company, headed by Bryan Sherbacow, is developing a low-carbon jet fuel that can be used as a 100 percent drop-in replacement for petroleum fuel, without needing to adapt existing aircraft or engines. That’s notable because the only commercially available sustainable aviation fuel (SAF) still requires a 50-50 blend with conventional fuel.

The technology has piqued the interest of the aviation industry. Alder Fuels said Thursday it has inked a multi-million dollar investment from aviation giants United and Honeywell – as well as a purchase agreement from United for 1.5 billion gallons of fuel, the largest known agreement for SAF in aviation history.

United consumes around 4 billion gallons of fuel per year, a company spokesperson told TechCrunch, so the purchase agreement would account for nearly 40% of the airlines overall annual fuel consumption.

Before the fuel starts powering United airplanes, it must meet specifications outlined by ASTM International, an international organization that sets the standards for a wide range of materials and products. From there, Alder and Honeywell expect to commercialize the technology by 2025.

Alder Fuels was formally launched earlier this year, but Sherbacow has been assessing the technology for around five years, he said in a recent interview with TechCrunch. It became clear through his previous work that the technology behind the low-carbon fuel – and especially the raw materials – needed to be scalable and widely available.

“What we’re all looking for is […] how do you access these carbon oil precursors, and efficiently convert them into something that works within the existing refining infrastructure?” Sherbacow said.

To solve that problem, he’s turned to carbon-rich woody biomass, like agricultural waste, which is turned into crude oil that can be used to make aviation fuel. The company uses a pyrolysis-based technology that transforms the biomass into a liquid and treats it in such a way that it can be put into existing refineries. Alder Fuels will initially use Honeywell’s proprietary “Ecofining” hydroprocessing technology. The ultimate aim is to make the new fuel compatible with all refining assets.

“There’s significant amount of [woody biomass] that’s already industrially aggregated, but has either no or very low economic value today,” Sherbacow explained. “But it’s a great opportunity for us because it’s a store of carbon that we can utilize.” It could even open up new markets for companies in forestry, agriculture, and even the paper industry, which are already generating plenty of bio-waste.

Alder Fuels’ research is supported by the U.S. Defense Logistics Agency and the Department of Energy, and Sherbacow stressed the importance of public-private partnerships to decarbonizing the aviation industry. Climate change has been of particular interest to President Joe Biden’s administration, and incentives for sustainable aviation fuel will likely end up in the $3.5 trillion spending bill currently being debated by Congress.

“That’s one of the roles of government, is to help the transition,” he said. “You need to incentivize the incumbents to change their behavior, or they’re going to resist a disruptive change.”