And the XPrize Carbon Removal winners are . . .

Carbon removal is a divisive issue. Critics say removing carbon dioxide from the atmosphere is unproven and distracts from reducing fossil fuel use; supporters argue it is necessary to limit the worst effects of climate change. One thing experts agree on: carbon removal technologies will need to be low cost, sustainable, and scalable if they are to be implemented worldwide.

The XPrize Carbon Removal contest was launched in 2021 with the goal of identifying such solutions. The global competition—with $100 million in prize money from the Musk foundation—drew 1,300 contestants. And now, the results are in.

Mati Carbon, which has operations in India and offices in the US, is the $50 million grand prize winner. The first runner-up, French start-up NetZero, will receive $15 million, while second and third runners-up Vaulted Deep in the US and Undo Carbon in the UK will be awarded $8 million and $5 million, respectively. Canada-based Planetary Technologies and Oman-based Project Hajar received a recognition award of $1 million each.

The 20 finalists had to demonstrate the removal of 1,000 metric tons (t) of CO₂ over the past 12 months and show the potential for removing 1 billion t per year by 2050. The contest included four carbon removal approaches: direct air capture, mineralization, biochar, and direct ocean capture.

The top four winners are all pursuing mineralization or biochar. “Some pathways are more easily deployable in the short term than others, and the winners sort of represent those pathways,” says Michael Leitch, senior technical lead at XPrize Carbon Removal.

Mati and Undo use enhanced rock weathering (ERW), which involves grinding silicate rock such as basalt to a fine powder and spreading it on land. The silicate minerals react with CO₂ and water to form bicarbonates, which travel via groundwater to oceans, where they stay long term. NetZero converts agricultural waste to carbon-rich biochar for use as soil amendment, and Vaulted Deep injects organic waste slurry deep underground to lock away CO₂.

Direct air capture and direct ocean capture are promising techniques but may be expensive and unproven at large scale. Crushing rocks and pyrolyzing agricultural waste use standard industrial equipment and are far less complex operationally, Leitch says.

Mati has a record of partnering with small farmers in India, Tanzania, and Zambia, which gave it an edge over other ERW competitors, says chief science officer Jake Jordan. The rock weathering process releases nutrients such as calcium and magnesium into soil, improving crop yield by up to 20%. So, besides addressing climate change, Mati’s technology—mati is the Hindi word for soil—improves food security “for people who are some of the most affected by climate change, while being the least responsible [for it],” he says.

As for scalability, CEO Shantanu Agarwal says that basalt is the most common rock in the world and that just a fraction of the roughly 0.5 million km³ of basalt deposits in West Central India can remove all anthropogenic CO₂.

But the prospect of bettering marginalized farmers’ lives is what truly drives him, Agarwal says. “We feel this prize money is essentially money for the smallholder farmers we work with. We now have the responsibility to build it into a planet-scale solution which can help us reach our grand goal of helping 100 million smaller farmers.”