United and Honeywell has announced a joint multimillion-dollar investment in Alder Fuels – a cleantech company that is pioneering first-of-its-kind technologies for producing sustainable aviation fuel (SAF) at scale by converting abundant biomass, such as forest and crop waste, into sustainable low-carbon, drop-in replacement crude oil that can be used to produce aviation fuel.

In a statement, United said 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 today's jet fuel. The goal of the technologies is to produce fuel that is a 100% 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.

United's 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. 

United said its purchase agreement with Alder also surpasses the previous record set by the airline in 2015 through its investment in Fulcrum BioEnergy with its option to purchase up to 900 million gallons of SAF. 

"Since announcing our 100% green commitment in 2020, United has stayed focused on decarbonizing 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 CEO Scott Kirby.

"United has come further than any other airline making sustainable travel a reality by using SAF to power flights," he added.

"As a pioneer of the SAF market with UOP Ecofining™ technology, our work with United and Alder on this new technology will help transform the industry and support the growth of a zero-carbon economy," said Darius Adamczyk, Honeywell chairman and chief executive officer.

"This solution will not only advance United's SAF commitment but can help the aviation industry meet its commitments to decouple increases in carbon emissions from growth in passengers."

Commercialization is expected by 2025. 

United's joint investment in Alder is the latest by United Airlines Ventures, a venture fund launched earlier this year that focuses on startups, upcoming technologies, and sustainability concepts that will complement United's goal of net zero emissions by 2050 -- without relying on traditional carbon offsets.

In 2020, United became the first airline to announce a commitment to invest in carbon capture and sequestration and has since followed with investments in electric vertical takeoff and landing aircraft and 19-seat electric aircraft that have the potential to fly customers up to 250 miles before the decade's end.