Microsoft has signed a carbon removal agreement with enhanced rock weathering firm Alt Carbon to support the removal of almost 37,000 tons of CO2 in Darjeeling, India.

As per the agreement, Microsoft will receive 36,920 tons of carbon removal credits from the Darjeeling Revival Project (DRP). The DRP is Alt Carbon’s flagship initiative, in which the company applies ERW at tea estates in the region. The project targets Darjeeling's tea industry, which Alt Carbon claims is under pressure from climate-related impacts, including shorter harvests, droughts, forest fires, and soil degradation, affecting the region's 180-year-old tea gardens.

The company argues the project serves a dual purpose, not only by generating carbon removal credits but also by supporting increased crop yields. Alt Carbon claims that the project has already delivered Asia’s largest verified ERW credits, removing nearly 10,000 tons to date. The project aims to cover 500,000 hectares in the region by 2030.

ERW removes CO2 from the atmosphere via a chemical reaction called carbonation, in which CO2 trapped in rainwater reacts with carbonic acid in silicate-bearing rocks, such as Basalt. When rainwater interacts with rocks, the CO2 it carries mineralizes and is stored as solid carbonate. The natural process currently removes one billion tons of CO2 every year, but through ERW, it can be accelerated.

The Microsoft deal will support Alt Carbon in expanding its field trials, conducting deep soil and porewater monitoring, collecting crop uptake measurements, and committing to public data-sharing to advance the field. Through this, the company argues, it can significantly reduce the cost of Measurement, Reporting, and Verification (MRV), thereby lowering the overall cost of carbon removal.

“Alt Carbon is dedicated to undertaking frontier research to map out our planet. Our deal with Microsoft is built upon years of work building high-integrity carbon removal infrastructure in India,” said Shrey Agarwal, CEO and co-founder of Alt Carbon.

"From laboratory capabilities to field operations and farmer networks, we have focused on advancing the science of rock weathering globally. Over the past few years, we have measured and indexed thousands of soil and water samples across land parcels totaling roughly twice the area of Manhattan. Climate Change remains one of the most significant civilizational challenges we face, and India can be a global leader in tech-based carbon removal."

Microsoft will retain the option to purchase additional volumes of credits, subject to successful delivery and verification milestones.

“Our contract with Alt Carbon for high-quality carbon removal uses field deployments to collect primary and secondary quantification methods for carbon quantification, while using a high standard to safeguard against environmental impacts. We are encouraged by Alt's efforts to build durable carbon removal capacity in India given their past success in delivering carbon credits,” said Phil Goodman, program director, Carbon Removal, Microsoft.

Microsoft has signed several ERW-linked carbon removal agreements. In October of last year, Microsoft signed its third deal in the space with Undo, for 28,900 tons of carbon removal credits. This was built on a previous deal between the two companies, with Microsoft committing to purchase 5,000 credits back in 2024.

Microsoft has also completed a 12,000-ton deal with US firm Terradot, an 8,000-ton deal with Eion, and an 11,400-ton deal with Lithos Carbon.