Professor Zhiguo Yuan AM Leads Pioneering Nature Water Research Offering Tool for Carbon Neutral Wastewater Management

Prof. Zhiguo Yuan AM, together with co-authors of the Nature Water study on global sewer methane emissions and a new tool for carbon-neutral wastewater management, namely Dr. Keshab Sharma, Dr. Jiuling Li, Dr. Tao Liu, Dr. John Willis, Dr. Yiwen Liu, Mr. Zhiyu Zhang, and Prof. Zhiguo Yuan.

The School of Energy and Environment (SEE) at City University of Hong Kong (CityUHK) proudly announces that Chair Professor Zhiguo Yuan AM has published his latest landmark study, “Estimating methane emissions from global sewer networks”, in the prestigious journal Nature Water, a leading international journal dedicated to advancing research on water science, technology, and sustainability.

Led by Prof. Yuan, together with his co‑authors, the study provides conclusive evidence of substantial sewer methane (CH₄) emissions, overturning the long‑standing “zero emission” assumption made by the Intergovernmental Panel on Climate Change. Until now, the global magnitude of sewer CH₄ emissions had remained unknown. By ingeniously integrating mechanistic and knowledge‑supported data‑driven modelling, the team derived, from relatively small datasets, a simple set of robust and interpretable equations to estimate CH₄ emissions from sewer networks based on readily available information such as sewer geometry, the design and actual dry weather flows, and wastewater temperature.

With this tool, the team estimates that globally sewers emit 1.18–1.95 million tons (teragrams) of CH₄ annually (95% confidence interval), adding 15.7–37.6% to the currently estimated carbon footprint of wastewater management and 1.7–3.3% to the currently estimated global methane emissions by the waste sector. The developed tool can reliably and efficiently estimate sewer methane emissions, supporting water authorities worldwide to establish emissions inventories and to pursue carbon‑neutral wastewater management.

Given methane’s high global warming potential and shorter atmospheric lifetime compared to carbon dioxide, the study underscores the urgency of mitigation. It also aligns with international efforts such as the Global Methane Pledge, under which more than 150 countries have committed to reducing methane emissions by 30% by 2030.

The full paper can be accessed at: https://www.nature.com/articles/s44221-025-00574-w