The three year, 36,920 ton offtake from Bengaluru startup Alt Carbon comes with verification clauses that go beyond what the registry requires, a quiet signal of how thin the pool of delivery ready suppliers has become.
Microsoft just signed a three-year agreement to buy 36,920 metric tons of carbon-removal credits from Bengaluru startup Alt Carbon by 2029. The deal is being framed as proof that India is becoming a serious carbon-removal geography. The more durable story is what the contract required the seller to prove before Microsoft would write the check.
The offtake is Microsoft's first enhanced-rock-weathering (ERW) deal in Asia, TechCrunch reported on Wednesday. Credits will come from Alt Carbon's Darjeeling Revival Project, where crushed basalt from the Rajmahal Traps is spread on West Bengal farmland. Rainwater and atmospheric CO2 react with the rock to form stable bicarbonates, locking carbon away on geochemical timescales, at least in theory. Alt Carbon describes the mechanism in detail on its corporate site.
What makes this contract different is not the geography. It is the verification layer. Discussions between the two companies began in early 2025 and closed only after more than a year of scientific review, due diligence, and additional measurement, reporting, and verification (MRV) measures beyond what Isometric, the registry issuing the credits, requires. Those add-ons include expanded data-sharing and carbon quantification protocols, language the typical registry framework does not mandate.
The MRV step-up is the most telling clause in the deal. It signals that Microsoft does not trust the standard registry bar to sort delivery-ready suppliers from announced ones. The carbon-removal market has long been bifurcated: a small number of suppliers who can move verified tonnes to a buyer, and a long tail of announced projects that have not. Microsoft's purchase terms quietly move that line harder.
Alt Carbon is a 2023 startup and says it is the world's largest ERW issuer by volume, with 9,566 tonnes of credits issued to date and roughly 15,000 more expected by year-end. The company raised a $12 million seed round in May 2025 led by Lachy Groom, according to TechCrunch, and works with more than 35,000 farmers across about 80,000 acres in North Bengal, first on tea estates, now expanding into rice. The larger of Alt Carbon's two ERW projects supplies Microsoft; the other is dedicated to Mitsui OSK Lines.
Co-founder and President Sparsh Agarwal framed the market shift in an interview with TechCrunch: when Alt Carbon launched, international buyers were skeptical of Indian CDR projects. Two years later, Global South developers account for roughly 26% of carbon-dioxide-removal credit issuances, up from about 2% in 2022, a founder-cited datapoint rather than an audited registry aggregate, but a useful proxy for how fast the geography has rotated.
The supply-scarcity dynamic is visible in the buy list. Alt Carbon's other customers include Frontier (the Stripe, Google, Shopify, and Match Group effort run through Watershed), the NextGen CDR facility backed by UBS, Swiss Re, BCG, South Pole, and Mitsubishi, and the marketplace CEEZER. "Everyone wants to ensure they get a part of the supply," Agarwal told TechCrunch. The phrase captures the buyer's problem: the verified-ton pipeline is thin, and capital is concentrating on the suppliers who can actually move it.
The deal also lands in an awkward political window. Weeks earlier, Heatmap reported that Microsoft was pausing parts of its carbon-removal procurement. Microsoft publicly rejected that framing in April, telling Bloomberg it remained committed to its climate goals while refining its sustainability strategy. The Alt Carbon offtake is the clearest counter-evidence Microsoft has offered since, a multi-year, six-figure-tonne contract with a startup that did not exist two years ago.
Still, 36,920 tonnes over three years is modest. TechCrunch describes Microsoft as the world's largest buyer of carbon-removal credits, and the company is publicly committed to becoming carbon-negative by 2030. Its total greenhouse-gas emissions rose 23.4% in fiscal 2024 versus a 2020 baseline, driven by cloud and AI value-chain emissions. Fiscal 2025 numbers are not yet public. The Alt Carbon volume moves the needle on the supplier side. It does not, on its own, move the needle on Microsoft's overall removal gap.
It is also Microsoft's second Asia-first durable CDR offtake in five months. In January, the company signed with Indian biochar startup Varaha for more than 100,000 tonnes of removal credits through 2029, drawn from work with roughly 40,000 to 45,000 smallholder farmers in Maharashtra. The pattern, India, durable removal, multi-year volume, bespoke MRV, is now visible in two consecutive contracts.
What to watch next: whether the optional additional volumes in the Alt Carbon contract get exercised, whether Isometric's methodology evolves to absorb the MRV add-ons Microsoft is now requiring, and whether Alt Carbon can scale its deployment footprint roughly fivefold over the next four to five years, the path to its stated 2030 mission of five million tonnes of removed CO2.