Microsoft has signed a carbon removal deal with Arca, an industrial mineralization company, for almost 300,000 tons of carbon removal credits over a ten-year period.

The agreement will support the scaling of Arca’s carbon removal technology, which repurposes the byproducts of mining (mine tailings and waste rock) to accelerate a natural geochemical process called carbon mineralization – the transformation of gaseous CO2 into a solid mineral form.

Through this, Arca said it can deliver measurable, independently verified, and highly durable carbon removals.

Commenting on the deal, Phil Goodman, director of Microsoft’s Carbon Dioxide Removal Program, said: “This offtake agreement diversifies Microsoft’s carbon removal portfolio into a pathway that combines scalability and permanence."

"Arca brings notable scientific expertise and has proven they can sequester carbon through their demonstration project, giving us confidence to enter into a multi-year agreement. We are pleased to support Arca in advancing industrial mineralization.”

The company completed its first full-scale mineralization demonstration project in 2025. The project, completed at an active mine in Western Australia, lasted 18 months and resulted in a 10x to 20x increase in mineralization rate above baseline.

According to the company, it is currently expanding its pipeline of mineralization projects to support its growth from pilots to million-ton operations.

“We have a unique opportunity to utilize one form of waste (mine tailings) to neutralize another (excess atmospheric CO2). The result is less waste and a healthier environment”, said Paul Needham, Arca CEO. “This agreement with Microsoft validates Industrial Mineralization as a viable pathway for durable carbon removal with the potential to scale and meaningfully contribute to global climate goals.”

The company is based in Vancouver, Canada, and was founded in 2021. Arca said it has identified 21 gigatonnes of carbon removal capacity in suitable historical mine waste material, plus gigatons more in other streams of alkaline industrial waste. It claims that its solution is low-cost and easily integrated within existing industrial footprints.

Microsoft has signed numerous carbon removal deals in 2025 so far. Earlier this month, it inked a deal with enhanced rock weathering firm Undo for 28,900 tons of carbon removal credits. It has also signed deals to purchase 2.95 million tons of removal credits from a CCS project in Denmark, a 2.6 million credit deal with sustainable farming group Agoro Carbon Alliance, and a 44,000 credit deal with biochar firm Carba.