Microsoft has signed a substantial three-year agreement to purchase almost 37,000 tonnes of carbon removal credits from the Indian startup Alt Carbon. This landmark deal represents the tech giant's inaugural enhanced-rock weathering project in Asia, underscoring the expanding contribution of Indian firms to global climate change mitigation efforts. The credits, totalling 36,920 metric tonnes of carbon dioxide removal, are slated for delivery by 2029 from Alt Carbon's Darjeeling Revival Project in eastern India.
The agreement is a significant boost for Alt Carbon, a Bengaluru-based company established in 2023. The startup specialises in carbon removal techniques, particularly enhanced rock weathering. This method involves spreading crushed basalt and other silicate rocks on agricultural land to accelerate natural chemical reactions that capture and store atmospheric carbon dioxide. Alt Carbon sources basalt from the Rajmahal Traps in eastern India and distributes it across farmland in West Bengal, where it reacts with rainwater and atmospheric CO2 to form stable bicarbonates, effectively removing carbon from the air.
Discussions between Microsoft and Alt Carbon commenced in early 2025, culminating over a year later after extensive scientific review, rigorous due diligence, and detailed contract negotiations. According to Sparsh Agarwal, co-founder and President of Alt Carbon, Microsoft imposed additional monitoring, reporting, and verification (MRV) measures beyond standard registry requirements. These included expanded data-sharing and more stringent carbon quantification protocols, reflecting a growing demand from buyers for robustly verified carbon removal projects in a market where proven supply remains scarce.
This deal arrives at a crucial time for the carbon removal market, where hundreds of startups are emerging with promises to extract carbon dioxide from the atmosphere, yet only a fraction have successfully delivered verified credits at a commercial scale. Alt Carbon has already issued nearly 10,000 carbon removal credits through enhanced rock weathering, reportedly the largest issuance of its kind globally, with another 15,000 credits expected by the end of the year. The credits for the Microsoft agreement will be issued via Isometric, a carbon-removal registry that developed a specific methodology for enhanced rock weathering.
Furthermore, the agreement highlights the increasing significance of emerging market suppliers in the carbon removal landscape. Developers from the Global South now account for approximately 26% of carbon removal credit issuances, a notable increase from roughly 2% in 2022. Agarwal noted that while international buyers were initially sceptical of Indian carbon projects when Alt Carbon launched, rising issuance volumes and stricter verification standards have fostered greater confidence in the market. This marks Microsoft's second carbon removal investment in India, following a January agreement with Varaha for over 100,000 tonnes of biochar-generated credits.