Alt Carbon, a climate-tech startup, has successfully raised $12 million in a seed round to expand its carbon dioxide removal efforts in South Asia. The company, which utilizes enhanced rock weathering on farmlands to lock away carbon for thousands of years, received investment led by Lachy Groom, co-founder of Physical Intelligence. This funding will enable Alt Carbon to scale its innovative approach to combating climate change.

The journey of Alt Carbon began in May 2020, when siblings Shrey and Sparsh Agarwal returned to their family’s tea estate, Salem Hill, in Darjeeling, expecting to bid farewell to the struggling business. However, this visit planted the seeds for Alt Carbon, which was officially launched in late 2023. Initially, the siblings explored carbon markets as a means to revive their family business and support other tea estates in the region by generating supplementary income.

During their exploration, they discovered enhanced rock weathering as a approach that could transform Darjeeling’s legacy from being vulnerable to climate change impact to a frontier of climate action. Sparsh Agarwal noted, “Within carbon markets, our realization was that many projects in India, which are more avoidance-based, are of very low quality and produce junk credits.” This realization led them to focus on developing a high-quality carbon removal solution.

Alt Carbon initiated its pilot project around the Agarwals’ family tea estate, covering approximately 500 acres of land. The startup has since scaled up its operations in North Bengal, expanding its scope from tea farms to rice and bamboo farms. The company aims to expand its coverage to 500,000 hectares of land. By 2030, Alt Carbon plans to remove 5 million tons of carbon from the region, as stated by Sparsh Agarwal.

The startup’s approach involves deploying enhanced rock weathering using waste basalt rock dust from mines and quarries in Eastern India. The rock dust, a waste product from the construction industry, is spread on farm fields, where it reacts naturally with rainwater to remove carbon dioxide and add micronutrients to the soil, improving its fertility and health and enhancing crop yields.

When rainwater containing carbon dioxide interacts with basalt dust, it forms stable bicarbonate ions, which are stored in the soil and eventually flow through rivers to the ocean, where they settle as calcium carbonate, locking away carbon for over 10,000 years. To transport the specialized dust from source locations to farm fields, the startup relies on rails and diesel trucks, utilizing the tea industry’s freight transportation system to minimize emissions.

Instead of using basalt dust alone, Alt Carbon has developed a proprietary combination of basalt with other organic ingredients, called Hari Maati (green soil in Hindi), to convince farmers to spread it on their farmlands. The startup estimates its carbon credits at $270 per metric ton, significantly cheaper than direct air capture credits, which cost around $800 per ton. However, Sparsh Agarwal expects the startup to reduce costs within 36 to 48 months.

Alt Carbon employs a three-layer measurement approach to understand the weathering process and carbon removal. The startup uses machine learning-driven modeling to track carbon removal numbers and adheres to methodologies set by carbon removal registries, including Isometric and Puro.earth. The company has received approvals from intergovernmental organizations, such as SBTi, ICVCM, and CORSIA.

The startup operates labs in Darjeeling and Bengaluru, employing 8 to 10 PhDs, with an overall headcount of 25 employees. With the seed funding, Alt Carbon plans to scale its labs, expand its work, and set up a hardware studio for better data collection. The company also intends to deploy sensors on the ground to gather more insights at a lower cost and faster pace.

Last year, Alt Carbon secured a $500,000 pre-purchase from Frontier and a $1 billion advanced market commitment led by Stripe, Alphabet, Meta, Shopify, and McKinsey. The startup has also signed a strategic partnership with NextGen, a buyer coalition started by South Pole and Mitsubishi Corporation, to scale its enhanced rock weathering. Additionally, Alt Carbon signed an offtake agreement with Japan’s shipping company, MOL Group, to purchase 10,000 tons of carbon removal credits.

Alt Carbon will deliver its first carbon credits in less than a month through Isometric, according to Sparsh Agarwal. With its innovative approach and growing partnerships, the startup is poised to make a significant impact in the fight against climate change.