What started as an emotional farewell to a failing family tea estate in Darjeeling has blossomed into a groundbreaking climate tech startup now backed by a $12 million seed round. Alt Carbon, co-founded by brothers Shrey and Sparsh Agarwal, is harnessing the power of enhanced rock weathering to lock away carbon dioxide for thousands of years—transforming the very soil of South Asia into a frontline climate solution.
Turning Tea Fields into Climate Assets
The journey began in 2020 when the Agarwals returned to Salem Hill, their family’s struggling tea estate nestled in the Himalayan foothills. Their intent was closure, but instead, they uncovered an opportunity. By 2023, Alt Carbon was born—not just to revive tea estates but to introduce a scalable carbon removal method to South Asia’s farmlands.
Their approach leverages waste basalt rock dust—a byproduct from the Rajmahal Traps mining region—and spreads it across farmlands where it reacts with CO₂ in rainwater to form stable bicarbonates. These compounds flow through the soil, into rivers, and ultimately settle in the ocean as calcium carbonate, a stable form of carbon sequestration that lasts over 10,000 years.
Alt Carbon adds value to this process with a proprietary blend called Hari Maati (Hindi for “green soil”)—a mix of basalt dust and organic inputs—encouraging farmer adoption while boosting soil fertility and crop yields. The startup’s first pilot on 500 acres near Darjeeling has now scaled to include rice and bamboo farms across North Bengal, with ambitions to cover 500,000 hectares and remove 5 million tons of CO₂ by 2030.
AI, Soil Science, and Strategic Scaling
To validate its climate impact, Alt Carbon has built a rigorous three-layered measurement system. It tracks weathering through soil and groundwater sampling, river monitoring, and AI-powered transport modeling to calculate carbon removed. Its system complies with standards from Isometric, Puro.earth, and intergovernmental bodies like SBTi, ICVCM, and CORSIA.
The startup is staffed with 25 people, including 8–10 PhDs across labs in Darjeeling and Bengaluru. It plans to scale data collection through a hardware studio and deploy sensors and remote sensing tools for real-time insights at reduced costs.
This rapid growth is now supported by a $12M seed round led by Lachy Groom, co-founder of robotics AI firm Physical Intelligence, with participation from climate backers like Frontier, which previously provided a $500K pre-purchase. Alt Carbon is also tied to a $1B advance market commitment from Stripe, Alphabet, Meta, Shopify, and McKinsey.
They’ve inked partnerships with major carbon credit buyers such as NextGen (a coalition by South Pole and Mitsubishi), which includes BCG, Swiss RE, LGT, and UBS. Just last month, they finalized an offtake agreement with Japan’s MOL Group for 10,000 tons of credits. Their first credits will be delivered within a month via Isometric, marking a milestone in their journey from family estate revival to carbon credit delivery.
Sparsh reflects on the improbable rise: “When we started, we saw poor-quality, avoidance-based credits flooding the Indian market. We wanted to change that narrative. Now we’re building not just climate tech, but a new economic opportunity for farmers.”
