Alt Carbon, a Darjeeling-born climate tech company, has secured a $12 million seed round led by Lachy Groom, co-founder of Physical Intelligence.
The funding will help the startup expand its enhanced rock weathering operations across India. Founded by siblings Shrey and Sparsh Agarwal, Alt Carbon transforms waste basalt into a carbon removal solution that supports local farming communities while locking away CO₂ for millennia.
From tea estate to climate innovation
The idea for Alt Carbon emerged in 2020 when the Agarwal brothers returned to their family’s failing tea estate. Instead of selling, they began experimenting with carbon credits and discovered the potential of enhanced rock weathering. By late 2023, Alt Carbon officially launched, piloting their technology across 500 acres of tea farmland.
Today, they’re scaling across North Bengal to include rice and bamboo farms, with a target of reaching 500,000 hectares and removing 5 million tons of CO₂ by 2030.
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The science behind the solution
Alt Carbon spreads waste basalt rock dust—sourced from India’s Rajmahal Traps—on farmland. When this dust interacts with rainwater, it removes CO₂ from the atmosphere and enriches the soil. The reaction creates stable bicarbonates that ultimately lock carbon into ocean sediment as calcium carbonate for over 10,000 years.
The startup’s proprietary blend, “Hari Maati” (meaning “green soil”), combines basalt with organic additives to improve adoption among farmers.
Building for scalability and impact
Alt Carbon’s carbon credits are currently priced at $270/ton, much cheaper than alternatives like direct air capture. With the new funding, the company plans to reduce costs even further within the next 3–4 years. Their multi-layered monitoring approach includes soil, groundwater, and river analysis, supported by reactive transport models and machine learning to ensure accurate carbon removal measurements.
The startup operates labs in Darjeeling and Bengaluru, employs 25 people including 8–10 PhDs, and is planning a hardware studio for real-time soil monitoring.
Strategic traction and global buyers
Alt Carbon previously secured a $500K pre-purchase from Frontier and is backed by Stripe, Alphabet, Meta, Shopify, and McKinsey through a $1B advanced market commitment. It also signed an offtake agreement with Japan’s MOL Group for 10,000 tons of credits.
The company will deliver its first carbon credits within a month via Isometric and has also aligned with registries like Puro.earth and SBTi.
Alt Carbon’s mission reflects the growing potential for climate solutions deeply tied to local ecosystems and global carbon markets.
