Start-up Vaulted Deep, which just signed a deal with Microsoft, says storing human waste deep underground can keep carbon dioxide out of the atmosphere and pollutants like forever chemicals out of surface ecosystems
By James Dinneen
24 July 2025
Processing tanks at a site in Kansas where waste is pumped into an underground salt cavern
Vaulted Deep
A start-up called Vaulted Deep has signed a deal with Microsoft to pump millions of tonnes of treated human excrement, manure and other organic waste deep underground as a way to remove carbon dioxide from the atmosphere. This approach could also avoid above ground contamination from PFAS “forever chemicals” and other chemical pollutants leaching out of the waste.
“We solve these two problems at once,” says Omar Abou-Sayed at Vaulted Deep. “We solve waste issues that impact local water, local air, local land, but we also do it in a way that addresses climate.”
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Over the past few years, the Texas-based company has injected nearly 70,000 tonnes of carbon-rich waste deep underground, amounting to over 18,000 tonnes of carbon dioxide removed. The company’s approach is enabled by technology developed for the oil and gas industry that can inject a slurry of liquids, solids and gases underground all at once. This type of waste is normally put in landfills or spread on fields.
Injecting the waste far underground prevents it from decomposing and releasing the carbon it contains back into the atmosphere for thousands – and potentially millions – of years, says Abou-Sayed. The company then sells each tonne of CO2 removed from circulation to companies or governments to count against their own emissions.
The agreement with Microsoft to remove 4.9 million tonnes of CO2 over the next 12 years comes as the carbon dioxide removal industry has faced challenges attracting customers. Microsoft has purchased more carbon removal credits than any other corporation in its bid to be carbon negative by 2030.