Indian deep-tech startup Alt Carbon has secured a multi-year carbon dioxide removal (CDR) offtake agreement with Microsoft to permanently remove up to 36,920 metric tonnes of CO2. The contract represents Microsoft’s first purchase of Enhanced Rock Weathering (ERW) carbon credits within Asia.
The agreement also grants Microsoft the option to purchase additional credit volumes from Alt Carbon in the future, subject to the successful completion of subsequent operational and verification milestones.
The verified CDR credits will be generated via the Darjeeling Revival Project (DRP) in West Bengal, India. The initiative deploys ERW technology across more than 80,000 acres of agricultural land, including heritage tea estates and regional rice paddies, partnering with over 35,000 local farmers.
The underlying ERW process utilises crushed basalt rock, a byproduct sourced from industrial waste, which is spread over agricultural fields. The basalt reacts chemically with dissolved carbon dioxide in rainwater, trapping the gas permanently as stable bicarbonate ions. These ions eventually drain through river networks into the ocean, where they settle safely as calcium carbonate (CaCO3) in marine ecosystems for over 1,000 years.
Agronomically, the application of basalt dust alters soil chemistry by neutralizing pH levels, delivering trace nutrients, and improving crop yields. To date, Alt Carbon has successfully issued 9,566 carbon credits via the independent registry Isometric.
To support its measurement, reporting, and verification (MRV) requirements, the investor-backed startup operates specialised earth science facilities:
- Shonku Labs: Conducts core research and development at Alt Carbon’s Bangalore headquarters, located within the Indian Institute of Science (IISc).
- Darjeeling Climate Action Lab (D-CAL): Located at the Kamala Tea Estate, this facility processes agricultural soil and water samples to track carbon fluxes.
D-CAL has analysed more than 20,000 samples to date and is scaling its infrastructure to process up to 100,000 samples annually by the end of 2026. The expansion of laboratory throughput is designed to reduce overall MRV costs, thereby lowering the pricing of high-integrity carbon credits over time. Under the Microsoft agreement, Alt Carbon will publish its soil, porewater, and crop uptake datasets to advance the scientific scaling of ERW deployments across tropical agricultural systems in the Global South.
Shrey Agarwal, CEO and Co-founder of Alt Carbon, commented, “Our deal with Microsoft is built upon years of work building high-integrity carbon removal infrastructure in India. 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 covering an area roughly twice the size of Manhattan.”
Sparsh Agarwal, President and Co-founder of Alt Carbon, added, “ERW is emerging as a scalable and rigorous pathway for Carbon Removal technologies globally. Global South suppliers now account for 26% of CDR issuances, up from under 2% in 2022. This transformation is driven by the combination of favourable geologies, lower costs, and a new generation of science-first developers.”
Phil Goodman, Program Director for Carbon Removal at Microsoft, stated, “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.”
