Microsoft has signed a three-year agreement with Indian startup Alt Carbon to purchase nearly 37,000 metric tonnes of carbon removal credits, marking the technology company’s first enhanced rock weathering deal in Asia.
Under the agreement, 36,920 metric tonnes of carbon dioxide removal credits will be delivered by 2029 from Alt Carbon’s Darjeeling Revival Project in eastern India.
Microsoft also has the option to buy additional credits if the startup meets delivery and verification milestones.
Deal follows climate commitment questions
The agreement comes after reports suggested Microsoft had paused parts of its carbon-removal procurement programme.
The company denied those reports, saying it remained committed to its climate targets while refining its sustainability strategy.
Microsoft is the world’s largest buyer of carbon-removal credits.
Enhanced rock weathering project
Founded in 2023, Bengaluru-based Alt Carbon focuses on carbon removal technologies, including enhanced rock weathering.
The process involves spreading crushed basalt and other silicate rocks on farmland to accelerate natural reactions that capture carbon dioxide.
Alt Carbon sources basalt from the Rajmahal Traps in eastern India and deploys it across farms in West Bengal.
The rock reacts with rainwater and atmospheric carbon dioxide to form stable bicarbonates.
More monitoring required
According to Alt Carbon co-founder and president Sparsh Agarwal, discussions with Microsoft began in early 2025 and concluded more than a year later after scientific reviews, due diligence and contract negotiations.
Agarwal told TechCrunch that Microsoft required additional monitoring, reporting and verification measures beyond existing registry requirements.
These included:
- Expanded data-sharing
- Additional carbon quantification protocols
Supply remains limited
“The problem that exists right now is that there are a lot of suppliers, but there are very few verified deliveries out there,” Agarwal said.
“When companies are able to deliver, everyone wants to ensure that they get a part of the supply.”
According to Agarwal, Alt Carbon has issued nearly 10,000 carbon-removal credits through enhanced rock weathering, which he said represents the largest issuance globally for the technique.
The company expects to issue another 15,000 credits by the end of the year.
Expansion across North Bengal
Alt Carbon operates two projects in North Bengal.
One serves Japanese shipping company Mitsui OSK Lines, while the larger programme will supply credits under the Microsoft agreement.
The startup has expanded beyond tea estates into rice-growing regions and now works with more than:
- 35,000 farmers
- About 80,000 acres
Credits for the Microsoft deal will be issued through Isometric, a carbon-removal registry that has developed a methodology for enhanced rock weathering.
Growing role for emerging markets
Agarwal said developers from the Global South now account for around 26 per cent of carbon-removal credit issuances, up from about 2 per cent in 2022.
He said confidence in Indian carbon projects has improved as issuance volumes have increased and verification standards have become stricter.
Microsoft had earlier signed another carbon-removal agreement in India.
In January, the company agreed to purchase more than 100,000 tonnes of carbon dioxide removal credits over three years from Indian startup Varaha, whose projects are based on biochar.
Scaling plans
Alt Carbon plans to increase its deployment footprint by about five times over the next four to five years.
The company raised $12 million in seed funding last year in a round led by technology investor Lachy Groom.
It has also developed its own monitoring, reporting and verification infrastructure, including laboratories in Bengaluru and Darjeeling used to analyse soil and water samples.
Agarwal said lowering verification costs and improving measurement capabilities will be important for scaling enhanced rock weathering projects.
TL;DR:
Microsoft has signed a deal with Bengaluru-based Alt Carbon to buy nearly 37,000 carbon removal credits by 2029. The agreement marks Microsoft’s first enhanced rock weathering project in Asia and highlights India’s growing role in the carbon-removal market.
AI summary:
- Microsoft will buy 36,920 carbon removal credits from Alt Carbon.
- The deal is Microsoft’s first enhanced rock weathering project in Asia.
- Credits will come from the Darjeeling Revival Project in eastern India.
- Alt Carbon works with more than 35,000 farmers across 80,000 acres.
- The startup plans to expand its footprint fivefold over the next five years.
