The path from family tea business to climate tech startup is not particularly well-trodden. Yet that's exactly the trajectory Shrey and Sparsh Agarwal followed when they founded Alt Carbon in 2023, discovering—somewhat serendipitously, by their telling—that their ancestral tea estate in Darjeeling might be ideal terrain for atmospheric carbon removal.
Two years later, the Bengaluru-based company closed a $12 million seed round in May 2025, led by Lachy Groom, the former Stripe executive who co-founded Physical Intelligence. The financing, which included participation from existing investors Shastra VC and ACT Capital Foundation alongside a roster of angels (Jason Zhao of PIP Labs, Pixxel's Awais Ahmed, and DeHaat's Amarendra Singh), arrived roughly 18 months after Alt Carbon's $550,000 pre-seed—also led by Shastra.
It's a notable bet on enhanced rock weathering, a carbon removal approach that until recently lived mostly in academic papers and pilot programs. The timing, though, may be deliberate. ERW is having something of a moment.
Basalt Dust, Bicarbonate, and the Bet on Northeast India
Alt Carbon's method is conceptually straightforward, if operationally complex. The company sources waste basalt from the Rajmahal Traps in eastern India—ancient volcanic formations that produce silicate-rich rock dust as a byproduct of mining and quarrying. That material gets spread across agricultural land, where natural chemical weathering reacts with rainfall and atmospheric CO₂, gradually mineralizing carbon dioxide as bicarbonate and carbonate. Eventually, those compounds wash into rivers and oceans, where they're stored for millennia.
The startup packages this amendment with organic inputs under the brand "Hari Mati," positioning it not merely as a climate intervention but as a soil enhancer. Alt Carbon claims the treatment delivers yield improvements alongside carbon removal—a dual value proposition meant to appeal to farmers who might otherwise be skeptical of climate-first pitches.
The $12 million seed round is earmarked for what the company calls its Darjeeling Revival Project: a plan to deploy enhanced rock weathering across 500,000 hectares in northeast India's tea belt. If executed, Alt Carbon says it could remove five million metric tons of CO₂ annually by 2030. That's an ambitious target, and one that will require not just capital but buy-in from hundreds of agricultural landowners across North Bengal and the Terai region.
Sparsh Agarwal, the Oxford-trained climate lawyer among the sibling duo, appears to have steered much of the regulatory and verification strategy. The company's measurement infrastructure includes what it brands as the "FELUDA" planetary dashboard—a nod, perhaps more whimsical than corporate, to the fictional Bengali detective created by Satyajit Ray—alongside lab facilities it calls D-CAL. There's land and water monitoring, river chemistry analysis, the usual apparatus of rigorous carbon accounting.
From Frontier to MOL: Validation Through Prepurchases
Alt Carbon moved quickly after the seed round to translate buyer interest into verified deliveries, a critical milestone for any early-stage carbon removal company navigating skeptical markets and evolving verification standards.
In September 2024, Frontier—the advance market commitment fund backed by Stripe, Alphabet, Shopify, Meta, and McKinsey—committed $500,000 for prepurchased credits, making Alt Carbon the first India-headquartered company selected by the initiative. Two months later, NextGen, the joint venture between South Pole and Mitsubishi Corporation, inked a deal for ERW credits sourced from Indian tea plantations. Mitsubishi formalized a broader partnership with Alt Carbon in March 2025 to scale the technology across South Asia.
But the most concrete proof point came from Mitsui O.S.K. Lines. In April 2025, the Japanese shipping conglomerate agreed to purchase 10,000 tons of carbon removal credits from Alt Carbon over multiple years. By January 14, 2026, the company had delivered its first tranche: 216.923 Isometric-certified credits to MOL. A larger delivery followed on April 24—2,500 credits, which Alt Carbon described at the time as the largest-ever batch of Isometric-certified ERW credits delivered to date.
Those deliveries leaned on an Isometric validation report dated November 12, 2025, covering a crediting period stretching from October 2024 through October 2029, with on-site audits conducted on August 26 and September 11, 2025. Isometric, for context, is among the more rigorous third-party verifiers in the carbon removal space—its certification carries weight with corporate buyers wary of greenwashing accusations.
Still, it's worth noting that Alt Carbon's claims around yield improvements (a reported 30 percent average increase in crop productivity) and job creation (more than eight local jobs per 1,000 tons of carbon removal) are company-reported and lack independent verification by agricultural economists or development agencies.
A Suddenly Crowded Field
Alt Carbon's seed round landed as enhanced rock weathering began attracting serious capital and attention from the largest corporate carbon buyers. The technology, long considered promising but unproven at scale, is now being tested across continents with meaningful money behind it.
In March 2025, Frontier buyers committed $33 million to purchase 78,707 tons of ERW removals from Eion, a U.S.-based startup, with delivery windows between 2027 and 2030. Less than a year later, in a move that surprised some observers, Terradot—backed by Google, Microsoft, John Doerr, and Sheryl Sandberg—acquired Eion outright. The consolidation signals both confidence in the method and, perhaps, impatience among deep-pocketed buyers who'd rather own the technology than simply contract for its output.
Elsewhere, InPlanet secured a Microsoft agreement in December 2025 to deliver more than 28,500 tons of CO₂ removal between 2026 and 2028. And in India specifically, Varaha—a broader carbon project developer—raised $20 million in February 2026 to scale removal initiatives across the Global South, with Microsoft signing a separate offtake for over 100,000 tons.
The landscape, in other words, is getting crowded fast. Alt Carbon will need to execute not just on the science but on the operational complexity of working with hundreds of tea estates, rice paddies, and bamboo farms—many of them small-holder operations with limited infrastructure and varying degrees of interest in climate markets.
What the Aggarwals Are Betting On
The company, which had between 11 and 50 employees as of mid-2026 according to its LinkedIn profile, now faces the challenge of deploying $12 million efficiently enough to hit its 500,000-hectare footprint and five-million-ton annual removal target by 2030.
That timeline is aggressive. It assumes continued cooperation from landowners, stable basalt supply chains, favorable monsoon patterns (since weathering rates depend heavily on rainfall), and sustained corporate demand for ERW credits even as competing removal pathways—direct air capture, ocean alkalinity enhancement, biochar—vie for the same buyers.
But if Alt Carbon succeeds, it aims to demonstrate something valuable beyond carbon removal: that agricultural communities in the Global South can participate meaningfully in climate markets, not as passive recipients of offset payments but as active operators of scalable removal infrastructure. That's the pitch, anyway. Whether the Darjeeling tea estates become a model or a cautionary tale will depend on what happens over the next four years.
For now, the Agarwal siblings are betting that the rocks beneath their family's tea bushes hold an answer—or at least part of one—to a problem far larger than any single farm.
