Many cities have pledged to achieve carbon neutrality. The urban water industry can also contribute its share to a carbon-neutral future. Using a multi-city time-series analysis approach, this study aims to assess the progress and lessons learned from the greenhouse gas (GHG) emissions management of urban water systems in four global cities:Amsterdam, Melbourne, New York City, and Tokyo. These cities are advanced in setting GHG emissions reduction targets and reporting GHG emissions in their water indus-tries. All four cities have reduced the GHG emissions in their water industries, compared with those from more than a decade ago (i.e., the latest three-year moving averages are 13％–32％ lower), although the emissions have 'rebounded"multiple times over the years. The emissions reductions were mainly due to various engineering opportunities such as solar and mini-hydro power generation, biogas valorization, sludge digestion and incineration optimization, and aeration system optimization. These cities have rec-ognized the many challenges in reaching carbon-neutrality goals, which include fluctuating water demand and rainfall, more carbon-intensive flood-prevention and water-supply strategies, meeting new air and water quality standards, and revising GHG emissions accounting methods. This study has also shown that it is difficult for the water industry to achieve carbon neutrality on its own. A collabora-tive approach with other sectors is needed when aiming toward the city's carbon-neutrality goal. Such an approach involves expanding the usual system boundary of the water industry to externally tap into both engineering and non-engineering opportunities.

Ka Leung Lam;Gang Liu;Anne Marieke Motelica-Wagenaar;Jan Peter van der Hoek

Division of Natural and Applied Sciences,Duke Kunshan University,Kunshan 215316,China;Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,Beijing 100085,China;Waternet,Amsterdam 1096 AC,Netherlands;Department of Water Management,Delft University of Technology,Delft 2628 CN,Netherlands

工程（英文）

[1]Ka Leung Lam;Gang Liu;Anne Marieke Motelica-Wagenaar;Jan Peter van der Hoek-.Toward Carbon-Neutral Water Systems:Insights from Global Cities)[J].工程（英文）,2022(07):77-85

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