Microsoft taps Alt Carbon in sign of India’s growing role in carbon removal

Microsoft has signed a three-year agreement to buy nearly 37,000 metric tons of carbon removal credits from Indian startup Alt Carbon, marking the tech giant’s first enhanced rock weathering deal in Asia.

Under the agreement, Alt Carbon will deliver 36,920 metric tons of carbon dioxide removal credits by 2029 from its Darjeeling Revival Project in eastern India. Microsoft also has an option to purchase additional volumes if the startup meets delivery and verification milestones.

The deal follows reports that suggested Microsoft — the world’s largest buyer of carbon-removal credits — had paused parts of its carbon-removal procurement program. The company rejected those claims, saying it remained committed to its climate goals even as it refined its sustainability strategy.

The agreement is a potential boon for Alt Carbon, a Bengaluru-based startup founded in 2023 that is focused on carbon removal projects, including enhanced rock weathering. This technique involves spreading crushed basalt and other silicate rocks on farmland to speed up natural chemical reactions that help store carbon dioxide. Alt Carbon sources basalt from the Rajmahal Traps in eastern India and deploys it across farmland in West Bengal, where the rock reacts with rainwater and atmospheric carbon dioxide to form stable bicarbonates.

Discussions with Microsoft began in early 2025 and culminated more than a year later after extensive scientific review, due diligence, and contract negotiations, Alt Carbon co-founder and president Sparsh Agarwal told TechCrunch. Microsoft also required additional monitoring, reporting, and verification (MRV) measures beyond registry requirements, including expanded data-sharing and carbon quantification protocols, he said.

The deal comes as buyers increasingly look for proven carbon-removal projects in a market where verified supply remains scarce. Hundreds of startups have emerged promising to remove carbon dioxide from the atmosphere. However, only a small fraction have delivered verified credits at commercial scale.

“The problem that exists right now is that there are a lot of suppliers, but there are very few verified deliveries out there,” Agarwal said. “When companies are able to deliver, everyone wants to ensure that they get a part of the supply.”

Alt Carbon has issued nearly 10,000 carbon-removal credits through enhanced rock weathering to date, making it the world’s largest issuance of such credits, according to Agarwal. The startup expects to issue another 15,000 credits by the end of the year.

Alt Carbon operates two carbon-removal proj