Scientists Discover Hidden Methane Source Beneath Every Major City

An international team led by City University of Hong Kong estimated that sewer networks worldwide emit 1.18 to 1.95 million tons of methane a year.

The researchers also developed SeweX, a global model for calculating methane emissions from sewer systems.

The findings suggest urban sewers are a bigger warming source than previously recognized, with implications for climate accounting and wastewater policy.