A compost facility processing up to 1,200 tons of organic material annually has become the testbed for a patent-pending carbon capture system that pulls CO2 straight off the pile — the first demonstration of integrated carbon capture at a university composting operation.

Graduate student Pablo Ortiz Paciello, working in NC State University's Biocarbon Utilization and Sequestration (BUS) Lab, is running the system at the Compost Facility and Research Cooperative off Lake Wheeler Road in Raleigh, North Carolina. The U.S. Department of Agriculture and Cotton Incorporated fund the work. The technology aims to collect carbon dioxide before it reaches the atmosphere and lock it into mineral carbonate compounds sold as a value-added product for wastewater treatment.

"If we can take biogenic carbon, convert it to a stable form, including a carbonate mineral, we can prevent carbon from returning to the atmosphere," said Joe Sagues, an associate professor of biological and agricultural engineering who leads the BUS Lab and supervises the project.

Why capture CO2 at a compost facility?

Composting already diverts food waste and other organics from landfill, where anaerobic decomposition releases methane. But the aerobic process is not carbon-neutral. As organic matter breaks down inside windrows and piles, CO2 still escapes into the atmosphere.

Biomass carbon removal addresses that residual stream by capturing the carbon and fixing it into durable products such as mineral carbonates, or routing it to permanent storage. The NC State project targets exactly that gap between landfill diversion and true carbon closure.

What separates built capacity from lab precedent?

The process was first demonstrated at bench scale by Ethan Woods, a BUS Lab alumnus who recently completed a Ph.D. in biological engineering and now researches carbon removal at ETH Zürich. Ortiz's project is the scale-up step.

"My project is to take what Ethan did and prove that we can replicate it at a larger scale," Ortiz said.

The engineered system uses negative aeration — pulling air down through the compost pile rather than blowing it out — and sensors monitor CO2 concentration in the captured gas stream.

"Once the system's sensors detect the right amount of carbon is being produced, we can use that concentration to test it for treatment of alkaline wastewater," Ortiz said.

The feedstock slate includes both food waste and cotton textile materials, the latter reflecting Cotton Incorporated's involvement in the funding consortium.

Where does the captured stream go?

A local mining company has expressed interest in two outputs:

• captured biogenic CO2 for neutralizing alkaline wastewater;
• finished compost as a component of a topsoil product.

No commercial contract is signed yet; the offtake interest follows successful system testing at the Raleigh facility.

What happens next?

Sagues frames the work as closing a gap in industrial bioprocessing rather than opening a new one. "Many other industrial bioprocess systems have conducted commercial trials of carbon capture, but not industrial composting," he said. "I think it was just a matter of time, and I'm glad NC State was the one to be able to showcase that."

The near-term milestone is straightforward: proving reliable CO2 capture at the 1,200-ton-per-year facility's operating scale. If the demonstration holds, it creates an economic case — carbonate byproduct sales plus offtake agreements — for attaching capture systems to industrial compost operations beyond Raleigh. The metric that decides the outcome is capture reliability at pile scale, and that data is what USDA- and Cotton Incorporated-funded trials must now deliver.