Study finds wastewater emissions significantly underreported globally

A new study published in Nature Climate Change finds that greenhouse gas emissions from wastewater systems are being substantially underestimated in national inventories, with implications for climate policy and utility operations.

The research, led by Princeton University scientists, analyzed wastewater emissions reporting across 38 countries and found that emissions of methane and nitrous oxide are underestimated by approximately 19% to 27%. These gaps are largely attributed to outdated accounting methods and incomplete inclusion of sources such as untreated sewage, decentralized systems and latrines.

In total, the study estimates that between 94 million and 150 million metric tons of carbon dioxide equivalent emissions may be missing from annual global inventories due to these omissions. Researchers note that wastewater systems are a significant but often overlooked source of greenhouse gases, with emissions comparable in scale to sectors such as aviation or shipping.

The study also highlights data gaps in areas such as sewer leakage, where limited monitoring has made it difficult to fully account for emissions and nutrient losses. In some cases, a substantial portion of wastewater-related pollutants may bypass treatment systems entirely.

Researchers say improving emissions accounting—by updating methodologies, expanding system coverage and incorporating more real-world measurements—could help utilities and policymakers better target mitigation strategies.

The findings underscore the growing importance of wastewater systems in climate discussions, particularly as utilities invest in technologies such as nutrient removal, resource recovery and energy optimization that can influence greenhouse gas emissions.