To mitigate the worst impacts of climate change, it's crucial to pull carbon dioxide out of the atmosphere. It's a challenge startups are tackling with approaches like Direct Air Capture, which uses machines to harvest carbon from the air -- a technology that is extremely expensive and difficult to scale.
But a small startup in Houston, Texas has a radical plan that aims to eventually pull 100 million tonnes of CO2 out of the air in a way that's cheap, easy to scale up and is already helping the 20,000 subsistence farmers it works with bring home more cash -- which helped it land the $50 million grand prize in XPRIZE's carbon removal competition in 2025.
Founded in 2022 by Indian-born climate tech entrepreneur Shantanu Agarwal, Mati Carbon's carbon removal solution is decidedly low tech: convincing farmers to spread basalt, the most common type of volcanic rock in the Earth's crust, over their land plots.
When mixed with rainwater, finely crushed basalt dissolves into chemicals including magnesium, silicon and calcium that react with carbon from the atmosphere to form bicarbonate, a naturally occurring substance that will eventually be washed into the sea through rivers and streams, where it will remain for thousands of years. Those same chemicals enrich the soil as the basalt dissolves slowly over four or five years, increasing crop yields by an average of 20% and giving hand-to-mouth farmers a much needed cash boost.
Agarwal, a chemical engineer, previously was the cofounder and CEO of Sustaera, which has raised some $10 million from investors like Breakthrough Energy to develop devices to remove carbon from the atmosphere. But approximately one year into the venture, Agarwal realized that the huge amount of energy required to operate on a large scale made the concept a difficult proposition. "It is not going to scale this decade because we need energy for other things," Agarwal told Forbes.
After visiting some small-scale farmers in India that year who were in a "very desperate situation," Agarwal came to the conclusion that he needed to focus on a solution that would both remove carbon from the atmosphere and "help people survive the effects of climate change." He established Mati Carbon as a public benefit corporation under a nonprofit holding entity to advance that mission.
Called "enhanced rock weathering," the basalt technique does not negatively impact the environment because it replicates the geological carbon cycle, a natural process by which carbon moves through Earth's crust, oceans and atmosphere over millions of years. At $20 to $30 per ton, basalt is low cost and with more than 2 billion people involved in sustenance farming worldwide, according to the Food and Agriculture Organization, the land area where this carbon removal solution could be applied is virtually endless.
"They have a really compelling, low cost and scalable carbon removal solution with high derivability, meaning it can store carbon away for long periods of time," said Nikki Batchelor, the Executive Director for the XPRIZE Carbon Removal competition and a board member of the Carbon Business Council industry group. Mati Carbon's concept beat out over 1,300 teams from 112 countries that competed in the carbon removal XPRIZE.
The company's main revenue source is selling carbon credits based on the amount of carbon it is able to capture. In January, Mati Carbon signed a deal to sell 5,000 tonnes worth of carbon credits to Shopify, its biggest sale to date.
Mati Carbon has so far trained over 130 technicians who spread basalt in fields at no cost to farmers, then regularly collect water and soil samples that are analyzed in a network of labs, which includes six facilities in India and two in Africa. Computer models determine how much carbon has been absorbed, with all the results recorded in a blockchain system to ensure traceability. The data is verified by outside bodies, including Puro.earth, a leading crediting platform for engineered carbon removal that certifies that Mati Carbon's carbon removal credits are durable, meaning the carbon is stored away for millenia.
To fuel its growth, Mati Carbon has raised additional debt to expand in India, Tanzania and Zambia and start operations in Southeast Asia. "We don't want to take equity money because if we do that we would need to make money for investors. Instead, we have stayed philanthropically funded, customer funded and debt funded," Agarwal said.
While the company is not yet turning a profit, this funding model will allow Mati Carbon to donate future profits to farmers who are among the least responsible for and most vulnerable to the impacts of climate change.
The climate crisis is eroding agricultural soils in Mati Carbon's target countries. Higher temperatures and erratic rainfall cause droughts that reduce soil moisture, which often leads to shorter growing seasons. As a result, farmers with less than half an acre of land are harvesting smaller crops, which is increasing food insecurity.
That's certainly the case in Zambia, where corn farmer Virginia Mweemba Wachata lives in Mukuni, a village in the country's Southern Province. She told Forbes the basalt spread by Mati Carbon in July 2024 has boosted her degraded soil. "The year before we had a really bad drought and even though it did not rain much last season my crop was better than I had expected and that's because the soil is holding moisture for longer," she told Forbes.
The heat in Zambia actually helped boost the basalt’s fertilizing properties and led to more carbon absorption and crop yield, Agarwal said.
"We did not go to these countries for the hotter weather but the heat is actually beneficial to do enhanced rock weathering at a scale. Temperatures are expected to continue increasing in India and Africa and that means we're in the right places but for the wrong reasons," Agarwal said.
Mati Carbon said it is on track to recruit an additional 10,000 farmers in the three countries where it operates by the end of 2025.
But convincing farmers to take part in the program is no easy task -- at least until they see how much basalt can impact yields for themselves. Dharmendra Patle and Heeralal Baghel, two farmers in the village of Janamkhari, in the Indian state of Madhya Pradesh, said that when the startup first spread basalt over their fields in the spring of 2024, they were skeptical.
At the end of the crop season, their rice paddies were still green while neighboring fields withered, and they brought in higher yields. "Other farmers saw the results and now everyone wants to join the program," they told Forbes.
Despite recent successes, Mati Carbon is still in its infancy, having sold just 12,500 tonnes worth of carbon credits, well below its target of removing 100 million tonnes by 2040. Agarwal told Forbes that he is in "conversations with multiple other buyers for large contracts."
The social enterprise's next challenge will be to replicate its model "a hundred fold in lots of different communities, which will lead to more data collection, more awards, and more business and partners which could create a snowball effect," Batchelor said.
"I think they have a huge opportunity if they start landing big contracts to sell carbon credits. The banks want to see big off-take deals in order to give larger financing which would allow them to scale their operations," she told Forbes.
But signing big deals is difficult because the carbon credit market is underdeveloped, with only a small number of players making the bulk of high-quality carbon credit purchases. Microsoft alone bought 80% of all high durability carbon credits in 2024, according to a March 2025 report by the Circular Carbon Network, a data initiative run by XPRIZE.
Meanwhile, most carbon removal solutions only exist at pilot or early-commercial stage level and face substantial challenges to raise funds to scale up their operations. Growth in investments in "circular carbon" companies, which include startups developing a wide variety of technologies to remove carbon from the atmosphere or the oceans, has slowed dramatically from a peak of 384% between 2020 and 2021 to 25% between 2023 and 2024 according to the March report.
That's in line with a broader slowdown in climate tech investments but Batchelor thinks Mati Carbon's ability to scale quickly will help it grow even without massive funding (by contrast Climeworks a prominent Direct Air Capture carbon removal company has raised over $1 billion in funding).
"One of the advantages of their approach is that they need to develop a lot of decentralized projects. That means they don't need to raise hundreds of million dollars in one go in order to scale to their next size because they can grow iteratively and that kind of works in their favor," Batchelor said.