From struggling home tea gardens to innovative climate risks, Alt Carbon plans to expand its carbon dioxide removal efforts in South Asian countries, raising $12 million in seed rounds. The climate technology startup locks in thousands of years of carbon by weathering rocks on farmland, attracting investments led by Lachy Groom, co-founder of Robotics AI Company Boody Intellionce.

The journey began in May 2020, with a bittersweet home return. Siblings Shrey and Sparsh Agarwal drove 16 hours from eastern Kolkata to Darjeeling - a city known for tea cultivation in the Himalayas, hoping to say goodbye to their family’s tea garden, Salem Hill. Instead, this farewell visit planted Alt Carbon seeds, which they officially launched in late 2023.

Initially, they explored the carbon market to restore their family business and support other teahouses in the region by generating supplementary income. But during the exploration, they discovered that enhanced rock weathering was a way to transform Darjeeling’s legacy from the risk of climate change impacts to the risk of climate action boundaries.

"In the carbon market, our realization that many projects in India are based on avoidance, they are of very low quality and generate spam credit," Sparsh said in an exclusive interview.

Last year, Alt Carbon started pilots around Agarwals’ home tea gardens on about 500 acres, and later they expanded their scale in North Bangladesh, thus expanding it from coffee tables to rice and bamboo. The startup aims to expand the land to 500,000 hectares.

Sparsh told TechCrunch that by 2030, the startup aims to remove 5 million tons of carbon from the region.

Alt Carbon uses waste basalt dust from mines and quarries to deploy enhanced rock weathering in the Rajmahal trap in the volcanic volcanic rock province in eastern India. Rock dust is a waste product in the construction industry that is spread on the farm on the farm, which naturally reacts with rainwater to remove carbon dioxide and add micronutrients to the soil to improve its fertility and health and improve crop yields. When rainwater containing carbon dioxide interacts with basalt dust, it forms stable bicarbonate ions. These are stored in the soil and eventually flow through rivers to the ocean, where they settled with calcium carbonate, locking carbon for more than 10,000 years.

To transport specialized dust from the source to farmland, the startup relies on railroads and diesel trucks and pays one-way fares as these sources are part of the tea freight transport system. The startup also avoids emissions from dedicated rock processing by relying on waste basalt from existing mining and crushing operations.

Instead of using basalt dust alone, the startup developed a proprietary combination of basalt with other organic ingredients, called Hari Maati (green soil in Hindi), convinced farmers to spread it on farmland.

Alt Carbon estimates its carbon credit of $270 per ton, which Sparsh says is much cheaper than direct air capture credit, which he believes is priced at about $800 per ton. However, he expects the startup to reduce costs within 36 to 48 months.

Shrey told TechCrunch that the startup relies on three layers of measurement to understand how much the rock is weathering and how much carbon is being removed. It begins with tracking measurements of weathering progress, then moving to water in the soil, groundwater sampling and river monitoring. The third layer uses a proprietary reactive transport model that helps track ions transported from soil to water. The startup also uses machine learning-driven modeling to get carbon removal numbers.

Alt Carbon said its model adheres to the method set by the carbon removal registry, including isometric and puro.earth. They also received approval from intergovernmental organizations, including SBTI, ICVCM and CORSIA.

The startup has labs in Darjeeling and Bangalore and has 8 to 10 PhDs with a total of 25 employees. Its purpose is to expand these laboratories by performing more soil sample analysis and even building hardware studios to use remote sensing on the ground, resulting in better high-quality data collection on the ground. The startup also plans to deploy sensors on the ground to gain more insights at lower costs and faster time. All of this will be through that seed led by the groom.

Last year, the startup received a $500,000 pre-purchase from Frontier and received a $1 billion premium market commitment, led by Stripe, Alphabet, Meta, Shopify and McKineyy. It also recently signed a strategic partnership with buyer alliance Nextgen, launched by South Pole and Mitsubishi to expand its enhanced rock weathering. The group also includes BCG Group, Swiss RE, LGT and UBS among its members. Last month, the startup signed a reception agreement with Japanese shipping company Mol Group to purchase 10,000 tons of carbon clearance credit.

Sparsh said Alt Carbon will provide its first carbon credits by isometric in less than a month.