United Airlines has signed a 20-year deal with Cemvita, a Houston-based start-up that produces sustainable aviation fuel (SAF) from recycled carbon dioxide. Under the agreement, Cemvita will supply the carrier with 50 million gallons per year over the period.

Cemvita’s technology represents a potential solution to current SAF shortages as its production process uses microbes to synthetically recreate plant photosynthesis, converting carbon dioxide from other companies’ waste streams into non-fossil fuel, plastics, and chemicals.

The company claims sourcing and using carbon dioxide in this way would not only produce more SAF with far less land, water, and electricity requirements than traditional SAF production methods, but would also be more reliable and efficient than relying on crops.

Moji Karimi, co-founder of Cemvita along with his sister, Dr. Tara Karimi, said of the process: “If you think about it, in today’s refineries we’re using petroleum as a feeder stock and then we turn that into fuels and the process also creates emissions. In the biomanufacturing facilities of the future you could use carbon dioxide as a feeder stock and produce fuels that are low carbon, zero carbon or even carbon negative.”