The fuel needed to launch a rocket into space creates a whole lot of emissions. In fact, each SpaceX launch is estimated to emit 715 tons of CO2, which is roughly as much as 10 cross-country flights on a 747. As spaceflights become more common, there is a need for a more sustainable source of fuel.

A New York City-based startup might have just the solution. The startup, which goes by the name Air Company, launched in 2019 to produce carbon-negative vodka using captured carbon. But while producing the vodka, the startup accidentally found out that it could also produce rocket fuel efficiently.

“We were running our systems at higher temperatures than normal, under some conditions that we don’t typically do, and found out that we could very efficiently make these fuel molecules,’ said Stafford Sheehan, an electrochemist and cofounder of the startup.

What the startup figured out is that they can produce liquid methane—the fuel used by SpaceX rockets—using captured CO2 rather than natural gas. By doing so, the net carbon footprint of each flight can be eliminated.

As described in Fast Company, the fuel also solves a second challenge; Assuming reusable rockets make it to Mars, they’ll need to refuel for the flight home, and the fuel could be made using materials found on the planet. “[On] Mars, you have water,” Sheehan says. “It’s frozen, but you can unfreeze it if you have enough energy to do that, and you do have energy in the form of solar energy. And you have an abundance of carbon dioxide because the atmosphere is 95% CO2.”

Moving forward, Air Company will start working closely with the space industry to scale up their technologies and build a refueling station.