Wastewater treatment plants could become infrastructure for removing CO₂ from the atmosphere. Microsoft has signed a long-term agreement with CREW Carbon to purchase carbon removals using exactly this approach.
The technology is integrated into existing water-treatment systems: alkaline minerals are added to the treatment process, causing dissolved carbon dioxide to convert into stable bicarbonates that leave with the treated water—effectively resulting in long-term storage in the ocean. No new plants or carbon-removal fields need to be built; the approach makes use of infrastructure that municipalities have already built.
For Microsoft, this is a bet on low-cost, verifiable carbon dioxide removal (CDR). The company is purchasing carbon-removal contracts by the tonne—from biochar to direct air capture—to address the growing carbon footprint of its AI data centers. Wastewater treatment is particularly attractive because the process can be measured relatively easily: wastewater volumes, water chemistry, and bicarbonate concentrations are already monitored by operators.
The question is whether it can scale.
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