In September 2024, a company barely a year old became the first India-headquartered firm to win a prepurchase from Frontier, the advance-market commitment for permanent carbon removal whose buyers include Stripe, Google, Shopify and Match. The cheque was small — $500,000 (about ₹4.8 crore) — but the buyers were not, and the sellers were two brothers who had just watched their family’s 300-acre Darjeeling tea estate slide toward bankruptcy.
Eighteen months later, in May 2026, that same company said it had issued 9,566 tonnes of independently verified carbon-removal credits — enough, on its own telling, to make it the largest enhanced-rock-weathering (ERW) company in the world by volume of credits issued. The business that started as a rescue plan for a failing tea garden had become, by that one metric, a global leader. This is how Alt Carbon got there, what is real in the story, and what is still unproven.
Quick facts
| Company | Alt Carbon Tech Private Limited (brand: Alt Carbon) |
| Founded | Incorporated 22 August 2023, ROC Kolkata (CIN U19109WB2023PTC264424) |
| Founders | Shrey Agarwal (co-founder & CEO) and Sparsh Agarwal (co-founder & President), brothers |
| Businesses | Carbon dioxide removal via enhanced rock weathering; sells verified, durable CDR credits |
| Latest FY revenue | Not publicly disclosed; MCA filings show only nominal paid-up capital of ₹1.25 lakh (as of July 2026, Tofler) |
| Latest FY profit/loss | Not publicly disclosed as audited absolute figures |
| Listed | Private (venture-funded) |
| Last funding | $12 million seed round announced 22 May 2025 (reported as India’s largest climate-tech seed round) |
| Key people / backers | Directors: Roma Agarwal, Sparsh Agarwal, Shrey Agarwal. Lead investor: Lachy Groom. Buyers: Frontier coalition, Microsoft, Mitsui O.S.K. Lines, NextGen |
What they do
Alt Carbon removes carbon dioxide from the air by speeding up a reaction that would otherwise take thousands of years. It sources crushed basalt — a silicate-rich volcanic rock — and spreads it across tea estates and neighbouring farmland in and around Darjeeling, West Bengal. In the region’s warm, wet, humid climate, rainwater reacts with the rock, pulling CO₂ from the air and locking it as stable bicarbonate that eventually washes to the ocean and can stay put for more than 10,000 years. The company brands its basalt blend “Hari Mati.”
- It sells the resulting removals as durable carbon-removal (CDR) credits, each independently verified.
- Credits are issued on the Isometric Registry under Isometric’s Enhanced Weathering Protocol, after review by an accredited validation and verification body (company-stated, May 2026).
- The buyers are corporates with net-zero targets, not retail offsetters — Microsoft, Frontier’s members, and Japanese shipping firms among them.
- A second, on-the-ground benefit is soil improvement: the basalt is pitched to tea and rice farmers as a way to lift degraded soils and yields.
The origin
The founding insight was personal before it was scientific. Shrey and Sparsh Agarwal are fourth-generation tea planters. Their family owns a roughly 300-acre estate in Darjeeling, and during the pandemic lockdown the brothers spent long stretches there. “We had fallen in love with the estate,” Sparsh told ThePrint. “We’d grown up around it, and the time that we spent there during the lockdown really made us feel that if we could revive this place, it would be a life well lived.”
The two brought different toolkits. Shrey leans technical, with interests in chemistry and engineering; Sparsh studied political philosophy and international law. The realisation that tied the estate’s survival to a global market was this: the same crushed rock that could restore tired Darjeeling soils could also be measured, verified and sold as permanent carbon removal to companies that were, by 2023, desperate for durable credits. A dying tea garden and a booming climate-finance market pointed at the same bag of basalt. They incorporated Alt Carbon Tech Private Limited in Kolkata on 22 August 2023.
The struggle years
The backdrop was an industry in decline, not a clean slate. Darjeeling’s tea estates have been squeezed for years, and the Agarwals’ own garden was among the casualties.
- Near-collapse post-pandemic: the family estate was, in the company’s own framing, “on the verge of bankruptcy and collapse” after the pandemic (company-stated).
- Structural rot in the trade: ThePrint’s reporting describes the pressures the estate faced — cheaper tea smuggled across the Nepal border, heavy dependence on middlemen, and mounting climate damage from hailstorms and forest fires.
- Family resistance: the idea itself was resisted at home. The brothers’ father objected to spreading crushed rock on the land, reportedly asking whether they meant to put “concrete on my farm” (ThePrint).
- Scientific credibility gap: ERW is measurement-heavy and easy to over-claim. To be sellable, every tonne had to survive third-party verification — a slow, technical hurdle for a first-time team with no prior CDR track record.
None of this was softened by an easy first customer. The company had to prove a scientific method, build measurement infrastructure and win over both farmers and fastidious corporate buyers at the same time.
The turning point
The turn came on 18 September 2024, when Alt Carbon became the first Indian company to secure a prepurchase from Frontier. The headline figure was modest — $500,000 (about ₹4.8 crore) — but the signal was outsized: the buyers standing behind that Frontier commitment were Stripe, Shopify, Google and Watershed (on behalf of Match).
Before the deal, Alt Carbon was an unproven rescue project on one estate. After it, the company had a validation stamp from the most scrutinising buyers’ club in carbon removal, and a reference that unlocked a fast run of larger agreements:
- 16 October 2024: NextGen — a South Pole and Mitsubishi Corporation joint venture — signed a deal to scale Asian CDR from India’s tea plantations.
- 17 October 2024: Alt Carbon launched the Darjeeling Climate Action Lab (D-CAL) to support gigatonne-scale ambitions.
- 12 March 2025: a Mitsubishi Corporation agreement to scale carbon removal in South Asia.
- 25 April 2025: Japan’s MOL Group signed an offtake to buy 10,000 tonnes of CDR credits.
The $500,000 that looked small in September 2024 was the hinge on which the rest of the story swung.
The money behind it
Alt Carbon is venture-funded and private. Its defining raise is a single large seed round.
- Seed round: $12 million (about ₹115 crore), announced 22 May 2025 and reported by multiple outlets as the largest climate-tech seed round in India to date.
- Lead investor: Lachy Groom, the tech investor and Physical Intelligence co-founder.
- Named participants: ACT Capital Foundation, Shastra VC, Jason Zhao (PIP Labs co-founder), Awais Ahmed (Pixxel co-founder), Amarendra Singh (DeHaat co-founder), plus existing investors (company-stated).
- What it changed: the capital funded scientific and measurement infrastructure, the D-CAL lab and IISc-linked lab work (Shonku Labs), and the field operation needed to move from one estate to tens of thousands of acres.
One caution on framing: the seed was raised in US dollars from a global buyer-and-investor base, so the rupee figures here are converted for context, not reported. International gloss uses one rate: $1 ≈ ₹96.0 as of 18 September 2026 (Trading Economics).
How it makes money
Alt Carbon’s product is a tonne of verified, durable carbon removal. The business model is a manufacturing-and-measurement chain rather than a software margin story. Money in comes from selling credits; costs sit in rock, logistics, field application and the heavy science of proving each tonne.
- Money in: corporate buyers pay for CDR credits, usually via multi-year offtake agreements or prepurchases that fund delivery ahead of issuance.
- The unit sold: one issued, verified tonne of CO₂ removed, listed on the Isometric Registry after independent verification.
- Where cost sits: sourcing and crushing basalt, transporting and spreading it across scattered smallholdings, and the measurement, reporting and verification (MRV) science that turns spread rock into a sellable, defensible tonne.
- The part people get wrong: the crushed rock also acts as a soil amendment for tea and rice farmers, so the same input serves two customers — the farmer who wants better soil and the corporate that wants a credit. The credit, not the rock, is the revenue line.
- Prepurchase economics: deals such as Frontier’s $500,000 and MOL’s 10,000-tonne offtake bring cash in before full delivery, which is how a young, capital-hungry CDR firm funds the multi-year gap between spreading rock and issuing credits.
The numbers
Alt Carbon is an early-stage private company incorporated in August 2023, and it has not published audited annual revenue or profit figures. MCA-linked filings show only a nominal capital structure — authorised capital of ₹15 lakh and paid-up capital of ₹1.25 lakh (Tofler, as of July 2026) — which reflects a venture-funded startup rather than a trading business with mature accounts. Rather than invent a profit-and-loss statement that does not exist in the public record, the honest scorecard here is traction: capital raised and contracted removal volumes, all of which are individually verifiable.
| Metric | Figure | Period / source |
| Seed capital raised | $12 million (≈ ₹115 crore) | Announced 22 May 2025 (company / press) |
| Frontier prepurchase | $500,000 (≈ ₹4.8 crore) | 18 September 2024 (company / GlobeNewswire) |
| MOL Group offtake | 10,000 tonnes CDR | Signed 25 April 2025 (company) |
| Microsoft deal | up to 36,920 tonnes CO₂, delivery by 2029 | Announced 11 June 2026 (company / TechCrunch) |
| Verified credits issued (cumulative) | 9,566 tonnes | As of 27 May 2026 (company / ESG Post) |
| Paid-up capital | ₹1.25 lakh (authorised ₹15 lakh) | As of July 2026 (Tofler) |
The trajectory of issued credits is the number that matters most: from zero at incorporation to 9,566 verified tonnes by May 2026, which the company says made it the world’s largest ERW issuer by volume. By the end of 2026 it expected to issue roughly another 15,000 credits (company-stated, via Carbon Herald).
Where the money comes from
The revenue base is corporate and international, and it has concentrated quickly around a handful of large, named buyers — a very different picture from the retail offset market.
- Frontier coalition (Stripe, Google, Shopify and Match via Watershed): the first buyer, September 2024.
- Microsoft: a multi-year, three-year agreement for up to 36,920 tonnes to be delivered by 2029 — reported as Microsoft’s first enhanced-rock-weathering purchase in Asia, with an option to buy more if milestones are met (June 2026).
- Mitsui O.S.K. Lines (MOL): a 10,000-tonne offtake signed April 2025; Alt Carbon then made what it called Asia’s largest verified enhanced-weathering issuance to MOL in November 2025, and a further delivery of 2,500 tonnes in April 2026 — a second delivery inside a year.
- NextGen (South Pole and Mitsubishi Corporation JV) and carbon marketplace CEEZER, both named among buyers taking delivery in the May 2026 issuance.
The surprise in the split is geographic: an Indian removal project earns most of its money from North American and Japanese corporates. The carbon is captured in West Bengal’s tea belt, but the demand — and the price discipline — comes from foreign net-zero commitments. On the ground, that money reaches a wide base: by June 2026 the company said it had onboarded more than 80,000 acres of agricultural land and worked with over 35,000 farmers across 60-plus gram panchayats in West Bengal, up from the single 300-acre estate where it began.
The risks
- Delivery and verification risk. Alt Carbon sells tonnes before it fully delivers them. The Microsoft deal is explicitly milestone-based, with additional volume contingent on Alt Carbon meeting delivery and verification targets. If measured removals fall short of models — a live scientific debate across all ERW — contracts can shrink and reputations with fastidious buyers can sour.
- Buyer concentration. Revenue leans on a small set of large corporates (Microsoft, MOL, Frontier members, NextGen). Losing or delaying any one deal moves the whole business, and voluntary corporate carbon budgets can be cut quickly when priorities shift.
- Method and market risk. ERW’s core uncertainty is measurement: proving exactly how much CO₂ a field of spread basalt has permanently removed is hard, and standards are still maturing. Any tightening of protocols, or public doubt about ERW’s real durability, would hit price per tonne and the pace of issuance directly.
- Operational and financial base. This is a young company with nominal paid-up capital and a single seed round funding a capital-intensive, logistics-heavy operation across scattered smallholdings. Scaling basalt supply, transport and field application across 80,000-plus acres — toward a stated 5 million tonnes a year by 2030 — is an execution challenge, not just a science one.
The takeaway
The transferable lesson from Alt Carbon is about sequencing credibility. The brothers did not lead with scale or a big raise; they led with the hardest-to-fake proof point available in their market — a Frontier prepurchase from buyers famous for saying no. That small, credible first cheque did more than $500,000 of work: it converted an unproven family rescue project into a company that global corporates would sign multi-year deals with, and the seed capital followed the credibility rather than the other way round. For any founder selling something buyers cannot easily verify, the order matters: earn the strictest validator first, and let the money and the scale chase the proof.
Frequently asked questions
What does Alt Carbon actually do?
It removes carbon dioxide from the atmosphere through enhanced rock weathering — spreading crushed basalt on tea estates and farmland around Darjeeling, where rainwater reacts with the rock to lock CO₂ as stable bicarbonate — and sells the verified removals as durable carbon-removal credits.
Who founded Alt Carbon and when?
Brothers Shrey Agarwal (co-founder and CEO) and Sparsh Agarwal (co-founder and President), fourth-generation Darjeeling tea planters. The legal entity, Alt Carbon Tech Private Limited, was incorporated on 22 August 2023 in Kolkata.
How much money has Alt Carbon raised?
It announced a $12 million seed round on 22 May 2025 — reported as India’s largest climate-tech seed round — led by Lachy Groom, with participation from ACT Capital Foundation, Shastra VC and several startup founders.
Why is the Microsoft deal significant?
Announced on 11 June 2026, the multi-year agreement covers up to 36,920 tonnes of CO₂ removal to be delivered by 2029 and was reported as Microsoft’s first enhanced-rock-weathering purchase anywhere in Asia, with an option for more volume if Alt Carbon meets its milestones.
Is Alt Carbon really the world’s largest rock-weathering company?
By its own claim in May 2026, yes — measured by the volume of verified ERW credits issued, which it put at 9,566 tonnes on the Isometric Registry. That is a specific, single metric of issued credits, not a claim about revenue, valuation or removal capacity.
Sources
Figures are as of September 2026. Currency converted at $1 ≈ ₹96.0 as of 18 September 2026 (Trading Economics).
- Alt Carbon press releases and project pages, altcarbon.com — September 2024 to June 2026
- GlobeNewswire / Yahoo Finance, “Alt Carbon makes history as the first Indian company to secure $500K prepurchase from Frontier” — September 2024
- ESG Today; Indian Startup News; FoundersToday, coverage of Alt Carbon’s $12 million seed round — May 2025
- ThePrint, “How a Darjeeling tea estate turned into one of India’s biggest carbon removal experiments” — 2026
- TechCrunch; ESG News; Data Center Dynamics; Carbon Herald, Microsoft-Alt Carbon 36,920-tonne ERW deal — June 2026
- Mitsui O.S.K. Lines (MOL) and ESG News, Asia’s largest verified enhanced-weathering issuance and 2,500-tonne delivery — November 2025 and April 2026
- ESG Post; Carbon Herald, “world’s largest ERW issuance / 9,566 tonnes” — May-June 2026
- S&P Global Commodity Insights, NextGen (South Pole / Mitsubishi Corporation JV) offtake — October 2024
- Tofler; The Company Check; IndiaFilings, Alt Carbon Tech Private Limited corporate filings (CIN U19109WB2023PTC264424) — accessed September 2026
- Trading Economics, USD/INR reference rate — September 2026
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