Boeing has signed a deal with startup Charm Industrial to remove 100,000 metric tons of carbon from the atmosphere.

Charm collects agricultural and forestry waste and uses heat to turn it into a product it calls “bio-oil,” a messy jumble of hydrocarbons that it injects underground, including into former oil wells. Once sequestered, Charm can sell carbon removal credits to companies. Axios first reported on the startup’s deal with Boeing.

Aviation has made little progress on cutting its carbon emissions. That has left companies in the sector searching for alternatives. Carbon removal has emerged as a contender given that it has the potential to cost less than transitioning to sustainable aviation fuels.

By 2050, one study found that the aviation industry will need to spend at least $60 billion on carbon offsets to reach net zero emissions.

Charm can also produce biochar, a substance that when applied to farm fields can help boost soil productivity, though those efforts are still in their infancy, according to data from carbon removal registry Isometric.

Financial terms of the deal were not disclosed. Two years ago, Charm sold 112,000 carbon removal credits to Frontier, the advanced market commitment, for $53 million, or about $470 per metric ton. Charm has said it wants to bring the cost down to about $50 per metric ton.