Microsoft secures 37,000-tonne carbon removal deal with Indian startup Alt Carbon

Microsoft has entered a three-year agreement to purchase nearly 37,000 metric tons of carbon removal credits from Indian startup Alt Carbon, marking the tech giant’s first enhanced-rock weathering transaction in Asia. Under the terms of the deal, Alt Carbon will deliver 36,920 tons of carbon dioxide removal credits by 2029 from its Darjeeling Revival Project in West Bengal. Microsoft retains an option to purchase additional volumes contingent on the startup meeting specific delivery and verification milestones.

The agreement follows more than a year of scientific review and due diligence, during which Microsoft mandated additional monitoring, reporting, and verification measures beyond standard registry requirements. According to Alt Carbon co-founder and President Sparsh Agarwal, the process involved expanded data-sharing and carbon quantification protocols to ensure the integrity of the credits. The credits will be issued through Isometric, a carbon-removal registry that developed a specific methodology for enhanced rock weathering.

Alt Carbon sources basalt from the Rajmahal Traps and deploys it across farmland in West Bengal, where the rock reacts with rainwater and atmospheric carbon dioxide to form stable bicarbonates. The startup currently works with over 35,000 farmers across approximately 80,000 acres, having expanded its operations from tea estates into rice-growing areas. Alt Carbon has built its own monitoring infrastructure, including laboratories in Bengaluru and Darjeeling for soil and water sample analysis, to quantify carbon removal and lower measurement costs.

The deal comes as the carbon-removal market faces a scarcity of verified supply. Agarwal noted that while hundreds of startups have emerged promising to remove carbon dioxide, only a small fraction have delivered verified credits at commercial scale. Alt Carbon has issued nearly 10,000 carbon-removal credits through enhanced rock weathering to date, claiming this is the world’s largest issuance of such credits, with an expectation to issue another 15,000 by the end of the year.

This transaction highlights a broader shift in the market, with developers from the Global South now accounting for approximately 26% of carbon-removal credit issuances, up from roughly 2% in 2022. The agreement follows reports that Microsoft had paused parts of its carbon-removal procurement program, claims the company has rejected, asserting its continued commitment to climate goals. Microsoft previously signed an agreement in January with another Indian startup, Varaha, for over 100,000 tonnes of biochar-based credits.

Alt Carbon’s buyer roster includes procurement coalitions such as Frontier, which features members like Google, Stripe, and Shopify, and NextGen, backed by UBS, Swiss Re, and Boston Consulting Group. The startup, which raised $12 million in a seed funding round led by tech investor Lachy Groom last year, plans to expand its deployment footprint roughly fivefold over the next four to five years as demand for verified credits grows.