United and Honeywell have announced a joint investment in Alder Fuels, a company that is pioneering first-of-its-kind technologies for producing sustainable aviation fuel (SAF) at scale.

Its technology seeks to covert abundant biomass, such as forest and crop waste, into a sustainable low-carbon, drop-in replacement crude oil that can be used to produce aviation fuel.

When used together across the fuel lifecycle, the Alder technologies, coupled with Honeywell’s Ecofining process, “could have” the ability to produce a carbon-negative fuel at spec with jet fuel.

The goal of the technologies is to produce fuel that is a 100 per cent drop-in replacement for petroleum jet fuel.

As part of the agreement, United is committing to purchase 1.5 billion gallons of SAF from Alder when produced to United’s requirements.

The purchase agreement, which is one and a half times the size of the known purchase commitments of all global airlines combined, makes this easily the largest publicly announced SAF agreement in aviation history.

“Since announcing our 100 per cent green commitment in 2020, United has stayed focused on decarbonising without relying on the use of traditional carbon offsets.

“Part of that commitment means increasing SAF usage and availability since it’s the fastest way to reduce emissions across our fleet.

“However, to scale SAF as quickly as necessary, we need to look beyond existing solutions and invest in research and development for new pathways like the one Alder is developing,” said United chief executive, Scott Kirby.

According to the United States Department of Energy, forestry and agricultural residues alone could provide enough biomass energy to generate more than 17 billion gallons of jet fuel and displace 75 per cent of domestic aviation fuel consumption.