Alt Carbon has announced the generation of 9,566 tonnes of verified carbon dioxide removal (CDR) credits, establishing the firm as the largest Enhanced Rock Weathering (ERW) company globally by volume of issued credits.
The milestone marks the completion of third-party verified deliveries to a consortium of international buyers. These include the Frontier coalition (comprising Stripe, Google, Shopify, and Match Group via Watershed), the South Pole and Mitsubishi-led NextGen CDR coalition, and carbon marketplaces such as CEEZER.
The credits were issued on the Isometric Registry following independent verification by an accredited Validation and Verification Body (VVB). The underlying carbon removal operations were conducted across heritage tea estates, rice paddies, and agricultural networks throughout the Darjeeling and Terai regions of India, spanning multiple crop types, soil types, and growing seasons.
The volume of delivered carbon is roughly equivalent to the annual greenhouse gas emissions generated by a small artificial intelligence data centre operating continuously. The delivery addresses a persistent discrepancy in the voluntary carbon market between initial corporate offtake commitments and actual verified credit deliveries.
The ERW process involves distributing crushed waste basalt across agricultural land. The basalt reacts with carbon dioxide dissolved in rainwater, converting the gas into stable bicarbonate ions that eventually flow via river systems into the ocean, where the carbon remains sequestered as calcium carbonate for over 10,000 years. The chemical reaction also alters soil pH and introduces minerals that can improve agricultural yields.
Alt Carbon’s capacity to process and issue credits at this scale relies on two domestic facilities: Shonku Labs, located at the Indian Institute of Science (IISc) campus in Bangalore, and the 15,000-square-foot Darjeeling Climate Action Lab (D-CAL). Together, the facilities can process more than 100,000 samples annually and have analysed over 20,000 samples to date using inductively coupled plasma optical emission spectrometry (ICP-OES).
During an eight-week testing cycle for the recent harvest, the science team generated 12,000 analysed samples, with a percentage sent to external laboratories for cross-validation. The enterprise maintains ongoing research partnerships with IISc, North Bengal University, and Ashoka University to track long-term weathering rates.
Tom Sellers, Head of Registry Operations at Isometric, confirmed that the issuance from the Monsoon Harvest project represents the largest single enhanced weathering deployment certified by the registry to date, signalling a transition from pilot phases to commercial-scale delivery.
Mitch Selby, Sustainability Fund Lead at Shopify, and Lucas van Doorn, Sourcing and Supply Lead at CEEZER, both noted that the delivery of nearly 10,000 tonnes of verified removals indicates a broader shift in buyer demand towards open-system carbon removal projects supported by structured measurement and transparent monitoring frameworks.
