Bengaluru: For Subhonanda Singha, a third-generation farmer in Dubanochi village, Darjeeling, rocks were something you cleared out of a field, not something you brought in by the truckload. But for the last three cropping seasons, Singha has been spreading a thin layer of grey basalt powder over his paddy fields.
The basalt dust disappears once a tractor folds it into the soil. In Singha’s field, it looks like soil treatment. But in a corporate climate report generated thousands of kilometres away, it is logged as carbon removal.
Singha’s improved yield after spreading the basalt dust, called Hari Mati, is not part of any government programme. The material is supplied free of cost by Bengaluru-based climate tech startup Alt Carbon, which sources it from quarry and mining waste in eastern India and distributes it to nearby farms.
Each verified tonne of CO2 removed from a field like Singha’s becomes a carbon credit, which global corporations currently buy for roughly $150 to $600 per tonne, depending on durability and technology. In a way, carbon credits are financial instruments designed to channel capital from developed economies that are responsible for a larger share of historical emissions into developing countries that are often more exposed to climate impacts. Such credits allow companies to offset emissions by funding verified environmental projects. One carbon credit is roughly equivalent to the emissions caused from burning about 430 litres of petrol or a round-trip flight between Delhi and Singapore. It can sometimes take more than a year for a carbon credit to be issued. Startups are now emerging to organize this long chain of geology, farming and carbon accounting.
Alt Carbon was founded in 2023 by Sparsh Agarwal and his brother Shrey, who saw an unusual opportunity in India’s geology and climate. “If durable carbon removal is going to scale, it has to work in places where agricultural land and minerals are abundant, with ideal weather conditions,” says Agarwal, who is the chief executive of Alt Carbon.
For farmers like Singha, the effects are more visible and immediate. A few seasons ago, his land yielded 1,600-1,700kg of paddy per acre. After three crop cycles using basalt blended with organic manure, his production has risen to around 2,600kg per acre from the same field. His family is among nearly 500 in the village who now participate in the programme.
This small agronomic tweak is part of a much larger experiment of turning millions of small farms in the Global South into distributed carbon removal infrastructure, where the physical work will happen in muddy fields and the financial instrument will travel halfway around the world.
Powerhouse in the making
Many of the world’s largest corporations, including Amazon, Microsoft, Google and Unilever, have pledged to reach “net zero” emissions between 2030 and 2040.
For companies that run vast data centres, shipping fleets or global supply chains, annual emissions can run into millions of tonnes. Net zero means completely negating the amount of emissions, either by reducing them or implementing methods to absorb carbon dioxide from the atmosphere.
For nearly a decade or so, carbon markets have relied on carbon avoidance projects that prevented deforestation or funded cleaner energy elsewhere. But concerns over credibility have pushed corporate buyers toward carbon removal projects that physically take carbon dioxide out of the atmosphere and store it for decades or longer.
This shift is why the Global South is being viewed as the next big hub for carbon removal. Large-scale carbon removal requires resources such as land, minerals and agricultural networks, which are concentrated in countries across the Global South.
“India, in particular, looks like a powerhouse in the making,” says Allister Furey, chief executive of Sylvera, a carbon data and rating platform, pointing out the country’s advantages, including faster tropical weathering rates, abundant agricultural waste and lower operating costs.
Nearly 50 carbon removal projects are now registered in India, collectively generating over 214,000 verified removal credits. This number is still modest compared to the 262 million credits that India has retired in carbon avoidance projects or even against the world’s 40 billion tonne annual emissions, but it is significant for a market that barely existed in the country four years ago.
Startups at the forefront
At the centre of this emerging supply chain is a clutch of Indian climate startups, including Alt Carbon, Varaha and Mitti Labs, each taking a different scientific pathway to generate tradable carbon credits. India’s agricultural landscape stretches from tea estates in the hills to waterlogged rice fields in the plains. The startups have begun tailoring different carbon removal methods to different crops, soils and regions.
In 2025, Google agreed to purchase 100,000 tonnes of biochar (a carbon-rich form of charcoal produced by heating agricultural waste) credits from Varaha in one of the largest such offtake deals to date, to be delivered by 2030. Microsoft followed with a separate three-year agreement for more than 100,000 tonnes.
“The category is still very young, but the interest from global buyers shows where this market is headed,” says Varaha chief executive Madhur Jain, adding that the contracts have supported the rollout of 18 reactors with projected lifetime removals exceeding 2 million tonnes of CO2 across India’s cotton belt.
Alt Carbon has signed a multi-year agreement with Japan’s Mitsui O.S.K. Lines through its Darjeeling Revival Project to remove 10,000 tonnes of CO2, issuing its first verified enhanced rock weathering (ERW) credits within eight months. The project has also secured offtake from Google, Stripe, Shopify and the NextGen Buyers Coalition. The company now operates across roughly 60,000 acres and aims to issue up to 100,000 credits annually from 2026.
Mitti Labs, founded by Harvard Business School alumni Devdut Dalal and Xavier Laguarta Soler along with Google scholar Nathan Torbick, works with rice farmers to reduce methane emissions. It currently operates on roughly 70,000 hectares of farmland with 40,000 farmers across six states, and shares about half of the carbon revenue with them.
Varaha reported revenue of $6.1 million in the year ending March 2025, according to data shared by Tracxn. Based on current market prices, Alt Carbon’s 10,000-tonne deal with Mitsui O.S.K. Lines could be worth roughly $2-3 million over multiple years, though revenue is realized only after credits are verified and issued.
How it works
In each carbon removal model, the farm becomes the starting point of a longer accounting process. For instance, in ERW, which Alt Carbon does with farmers in West Bengal, the journey to a tradable carbon credit begins long before the farmer spreads basalt powder in the farmlands and ends much after he sees the yield.
Companies first collect soil samples, spread crushed basalt and then test soil and water again after the monsoon to track chemical changes. The process involves quarry sourcing, mineral testing, soil and water sampling and lab analysis. The method and end result are reviewed by independent auditors and registries before a tonne is certified as a carbon credit and sold to a corporate buyer.
In the cotton farms of Vidarbha, most farmers currently burn the crop residue. It is a quick and cheap approach, but also the one that releases carbon instantly. “87% of farmers in that region burn the residue because it’s the easiest way to get rid of it,” says Varaha’s Jain.
Varaha’s biochar programme provides an alternative. Instead of open burning, the company collects the biomass, pays farmers for it and transports it to rural reactors. The biomass is then heated in these reactors in the absence of oxygen, converting it into biochar. This char is then returned to farmers as a soil amendment, where it can stay locked in the soil for decades.
Varaha’s strength lies in its logistics. Jain says that the company operates across nine states and has installed seven reactors across these states. Before announcing the Microsoft deal, he added that it had already delivered more than 130,000 removal credits, processing nearly 300,000 tonnes of agricultural residue.
The cycle is long and it takes months to secure contracts, months to install reactors and then 18-20 months before the first credits are delivered. “It’s like a lesson in supply chain management,” Jain says.
For farmers, the benefits are more immediate—they receive payment for residue that once had no value. They also save on labour and get free biochar, and in some cases, a share of the carbon revenue. Jain estimates the farmer’s overall net income gains at 7% to 25%, depending on the crop and region.
The gas you cannot see
In waterlogged rice fields across Telangana and Andhra Pradesh, where paddy fields remain continuously flooded, oxygen disappears from the soil and microbes produce methane, a greenhouse gas far more potent than carbon dioxide in the short term.
“Rice farming contributes roughly 15% of the global methane stack,” says Mitti Labs co-founder Dalal. “In total greenhouse gas terms, it’s about 2% of global emissions, roughly equivalent to the aviation industry.”
Mitti Labs’ intervention comes at the behavioural level of farmers. It promotes the irrigation technique of alternate wetting and drying (AWD) where instead of flooding fields continuously, irrigation pumps are shut and the soil is allowed to dry. By interrupting water stagnation, methane emissions can fall by 40-50% in some regions, says Dalal. For farmers, the pitch begins with water savings in regions where groundwater tables are falling and a share in the carbon credit revenue.
Karunakar, a farmer in Warangal who has signed up to follow the AWD method with Mitti labs, says he now keeps water levels low and shuts irrigation entirely for about five days twice in a three-month season. He says his yield has risen from about 35 bags per acre to roughly 40 bags and pest incidence has fallen, reducing pesticide use.
Because he is pumping less frequently, Karunakar is able to use the same amount of water now across all five acres. In previous years when summer groundwater ran short, he remembers struggling to irrigate his entire field. Now, he is able to manage all five acres more reliably.
The asset in farms like Karunakar’s is avoided methane. By stopping it before it forms, Mitti labs generates CO2 equivalent credits that plug directly into global carbon markets.
Karunakar does not follow the mechanics of carbon markets. What he does understand more clearly is that the weather is no longer predictable. Rains arrive late while seasons no longer follow familiar patterns. “Because of climate pollution our yields have become more uncertain, and new crop diseases appear more frequently,” he says, adding that he is happy to be a part of the programme.
The integrity question
The most important and critical event of the life cycle of a carbon credit is producing proof that the farmland activities involving soil, smoke and irrigation cycles actually resulted in carbon removal. “Anyone can put basalt on a field,” says Alt Carbon’s Agarwal. “The question is, can you prove what happened after?”
For instance, ERW is increasingly viewed as a durable form of carbon removal. But measuring how much carbon dioxide has actually been converted into stable minerals is a complex process.
“The chemistry isn’t new,” Agarwal says. “We’re just speeding up a natural process.” What surprised him was not the fieldwork but the burden of proof—of measuring, modelling and verifying how much CO2 has been removed and how long it will remain stored. This requires repeated sampling, modelling and lab analysis considering that soil chemistry varies and rainfall fluctuates.
Alt Carbon has built a 15,000 sq. ft earth science laboratory in Darjeeling to run mass spectrometry tests on soil and water samples and works with researchers, including those at the Indian Institute of Science, to refine its modelling and verification protocols.
“The view is shifting toward engineered removals as the gold standard for permanence,” says Sylvera’s Furey. But credits can only be as credible as the monitoring, reporting and verification behind them, he adds.
Biochar and methane reduction projects face their own scrutiny. The feedstock for biochar must truly be waste and sustainably sourced and life cycle emissions must be counted accurately. For methane reduction projects, the challenge is proving that farmers actually changed how they irrigate.
It is for solving these hard problems that these startups are now able to attract investors and global customers.
“They are solving the real bottleneck, which is scalable verification,” says Hemant Mohapatra, partner at Lightspeed Ventures, an investor in Mitti Labs. “In rice decarbonization, the constraint is not farmer willingness but the cost of high quality operations and complexity of MRV.”
India’s advantages
Varaha’s Jain points out that most demand for this work comes from countries that industrialized early and that are now taking the lead in building the market.
Alt Carbon’s Agarwal points out that a lower price point helps that flow. “Enhanced rock weathering credits from India are currently trading below $300 per tonne, less than half the roughly $700 average often seen across engineered removal markets globally,” he says.
If verification holds and early contracts translate into consistent delivery, Indian farmland could emerge as a serious exporter of durable carbon removal.
In Dubanochi, Subhonanda Singha is less concerned with carbon markets than with the coming monsoon. He will spread the grey dust again this season, unaware that somewhere, far from his field, a tonne of carbon bearing his name may be balancing someone else’s ledger.