Harnessing Carbon Removal Opportunities in Wastewater Treatment

This report by RMI examines the potential for integrating carbon dioxide removal (CDR) technologies into municipal and industrial wastewater treatment and biosolids management. It identifies two primary intervention categories: alkalinity management to store carbon as bicarbonates in water, and the processing of biosolids through methods like biochar production, biomass burial, and incineration with carbon capture. The report highlights synergies such as the safe disposal of hazardous contaminants like PFAS and the use of existing pumping infrastructure to reduce capital and energy costs.

• Wastewater treatment plants can achieve carbon removal through alkalinity management, which converts dissolved carbon dioxide into stable bicarbonates. This can be done via Wastewater Alkalinity Enhancement (WAE), where alkaline feedstocks are added in closed environments, or Ocean Alkalinity Enhancement (OAE), which raises the pH of seawater outflows to increase the ocean's capacity to absorb atmospheric CO2.
• Carbon removal can be integrated into biosolids management to prevent the release of carbon from sewage sludge. Methods include biomass burial in anoxic environments, pyrolysis to create biochar for soil application, supercritical water oxidation to break down complex molecules and PFAS, and incineration equipped with carbon capture and storage (CCS).
• Integrating CDR into wastewater treatment offers significant synergies, including the ability to destroy hazardous contaminants like PFAS, pharmaceutical compounds, and microplastics that are difficult to remove with conventional methods. Additionally, it leverages existing infrastructure for pumping and transporting waste, which can save the majority of capital equipment and a significant portion of total energy costs compared to standalone CDR projects.
• The theoretical global carbon removal potential from municipal wastewater is between 120 and 460 million tons of CO2 per year, with WAE potentially capturing 100–400 MtCO2 and biosolids management capturing 20–70 MtCO2. However, because only 56% of municipal wastewater is currently treated, the actual achievable capacity through existing systems is estimated at 70–260 MtCO2 per year.
• Scaling alkalinity-based carbon removal to 300 MtCO2 per year would require 0.5 to 1 billion tons of limestone or other alkaline minerals annually. This represents approximately one-tenth of the global limestone market, which exceeds 5 billion tons per year, suggesting that dedicated quarrying for CDR is feasible.
• Several barriers hinder large-scale deployment, including the need for standardized carbon accounting protocols to verify additionality, a lack of industry visibility, high feedstock costs for small-scale pilots, and the need for infrastructure to transport and store concentrated CO2 streams from incineration or supercritical water oxidation.

APA

Clark-Sutton, K. (2026). Harnessing Carbon Removal Opportunities in Wastewater Treatment. RMI. https://rmi.org/resources/harnessing-carbon-removal-opportunities-in-wastewater-treatment/

Chicago

Clark-Sutton, Kyle. Harnessing Carbon Removal Opportunities in Wastewater Treatment. RMI, 2026. https://rmi.org/resources/harnessing-carbon-removal-opportunities-in-wastewater-treatment/.

Wikipedia

{{cite report |last1=Clark-Sutton |first1=Kyle |title=Harnessing Carbon Removal Opportunities in Wastewater Treatment |publisher=RMI |date=29 May 2026 |url=https://rmi.org/resources/harnessing-carbon-removal-opportunities-in-wastewater-treatment/ |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{clarksutton2026harnessing, author = {Clark-Sutton, Kyle}, title = {{Harnessing Carbon Removal Opportunities in Wastewater Treatment}}, institution = {RMI}, year = {2026}, month = may, url = {https://rmi.org/resources/harnessing-carbon-removal-opportunities-in-wastewater-treatment/}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }