Microsoft has signed a three-year agreement to buy 36,920 metric tons of carbon dioxide removal credits from Alt Carbon, marking the company’s first enhanced rock weathering deal in Asia.
The credits will come from Alt Carbon’s Darjeeling Revival Project in eastern India and are expected to be delivered by 2029. Microsoft also has an option to buy additional volumes if Alt Carbon meets delivery and verification milestones.
Alt Carbon Secures Microsoft Deal
Alt Carbon announced the agreement through its official press release page. The Bengaluru-based startup was founded in 2023 and focuses on carbon removal projects, including enhanced rock weathering.
The deal follows reports that Microsoft had paused parts of its carbon removal procurement program. Microsoft rejected those claims and said it remained committed to its climate goals while refining its sustainability strategy.
How The Project Removes Carbon
Enhanced rock weathering involves spreading crushed basalt and other silicate rocks on farmland. The process speeds up natural chemical reactions that help store carbon dioxide.
Alt Carbon sources basalt from the Rajmahal Traps in eastern India and applies it across farmland in West Bengal. The rock reacts with rainwater and atmospheric carbon dioxide to form stable bicarbonates.
Credits under the Microsoft agreement will be issued through Isometric, a carbon removal registry that developed an enhanced rock weathering methodology.
Verification Was A Key Part Of The Deal
Alt Carbon co-founder and president Sparsh Agarwal told TechCrunch that discussions with Microsoft began in early 2025. The deal was completed more than a year later after scientific review, due diligence, and contract negotiations.
Agarwal said Microsoft required additional monitoring, reporting, and verification measures beyond registry requirements. Those measures included expanded data sharing and carbon quantification protocols.
Alt Carbon has issued nearly 10,000 carbon removal credits through enhanced rock weathering to date, according to Agarwal. The startup expects to issue another 15,000 credits by the end of the year.
Carbon Removal Supply Remains Limited
The deal comes as buyers look for verified carbon removal projects in a market where commercial supply remains limited. Agarwal said many suppliers exist, but few have delivered verified credits.
Alt Carbon operates two carbon removal projects in North Bengal. One is dedicated to Japanese shipping company Mitsui OSK Lines, while the larger program will supply Microsoft’s credits.
The startup has expanded beyond tea estates into rice-growing areas. It now works with more than 35,000 farmers across about 80,000 acres.
Alt Carbon plans to expand its deployment footprint roughly fivefold over the next four to five years. The company raised $12 million in seed funding last year in a round led by tech investor Lachy Groom.
Featured image credits: Wikimedia Commons
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