Microsoft taps Alt Carbon for enhanced rock weathering in Asia

Microsoft has signed a three-year agreement to buy carbon-removal credits—verified units of carbon dioxide removed from the atmosphere—from Alt Carbon, an Indian startup. 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. The transaction marks Microsoft’s first agreement in Asia for enhanced rock weathering, a technique involving spreading crushed basalt on farmland to store carbon. The deal follows reports suggesting that Microsoft — the world’s largest buyer of carbon-removal credits — had paused parts of its carbon-removal procurement program. Microsoft rejected those claims, stating it remains committed to its climate goals.

Discussions between the Bengaluru-based startup and Microsoft began in early 2025. According to Sparsh Agarwal, co-founder and president of Alt Carbon, the agreement required additional monitoring, reporting, and verification (MRV) measures beyond standard registry requirements. Alt Carbon has issued nearly 10,000 carbon-removal credits to date, which Agarwal attributes as the world’s largest issuance of enhanced rock weathering credits. The startup expects to issue another 15,000 credits by the end of the year. It operates two projects in North Bengal, including one for Japanese shipping giant Mitsui OSK Lines, and has expanded its operations to work with more than 35,000 farmers across about 80,000 acres of farmland. Credits under the Microsoft agreement will be issued through Isometric, a carbon-removal registry.

The agreement highlights a broader shift toward developers in the Global South, who now account for about 26% of carbon-removal credit issuances, up from roughly 2% in 2022, according to Agarwal. This growth comes as buyers seek verified supply in a crowded but unproven market. “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.

The agreement is not Microsoft’s first carbon-removal investment in India; in January, the tech giant signed an agreement with another Indian startup, Varaha, to purchase more than 100,000 tonnes of carbon dioxide removal credits. Alt Carbon, which raised $12 million in a seed funding round, plans to expand its deployment footprint roughly fivefold over the next four to five years. Microsoft joins other buyers of Alt Carbon’s credits, including procurement coalitions Frontier and NextGen.

Why it matters

The deal marks Microsoft’s first enhanced rock weathering agreement in Asia and highlights the growing role of emerging-market suppliers in the carbon removal market.