Life Cycle Environmental Impacts and Decarbonisation Pathways of China’s Urban Water Systems

Urban water systems (UWSs) in China form an energy-intensive and intricate socio-technical network that links multiple components from water abstraction to sewage sludge disposal. As the country moves toward carbon neutrality, improving the environmental performance of the UWS has become essential. However, current studies leave two gaps: (1) the lack of systematic analysis of environmental impact across multiple categories from a whole UWS perspective; (2) the absence of understanding on climate change mitigation potential and other broader environmental impacts of decarbonisation measures (individually or combined) from a whole UWS level. These gaps underscore the necessity of this research and are filled through a set of objectives of this thesis. First, I develop a comprehensive life cycle assessment (LCA) framework to quantify the environmental impact of China’s UWSs across multiple categories, covering all key stages of UWS including water abstraction and treatment, waterwork sludge treatment, water distribution, sewage collection, stormwater drainage network, wastewater treatment, reclaimed water utilisation, and sewage sludge disposal. The environmental impacts of the UWSs in each province are analysed and the regional inequality across provinces is revealed. The environmental hotspots within the UWS and the major sources of each impact are identified. Second, I conduct a future-oriented and provincial-level LCA on China’s UWSs up to 2050, incorporating the power grid transitions and a series of decarbonisation measures. Water supply and wastewater volumes are projected to 2050 via a machine learning model, and two power system transition pathways (National Determined Contributions pathway and Peak-30 pathway) are applied to capture the changing background environmental impacts of electricity. 12 decarbonisation scenarios are designed and assessed, including individual measures (operational optimisation, reclaimed water use, on-site PV deployment, sludge harmless disposal, wastewater thermal energy recovery) and their combinations under each power system pathway. The future climate change mitigation trajectories of the UWSs under various measures are developed, the corresponding changes in other impact categories are analysed. The key findings include: (1) National total climate change impact from China’s UWSs was 87.4 Mt CO2-Eq in 2017, with the provincial totals ranging from 0.09 to 8.83 Mt and averaging 2.8 Mt. (2) Overall impacts are geographically higher in the east and south, lower in the west and north. However, at the functional unit level, northern and northeastern provinces show higher impact than other regions. (3) The wastewater treatment stage is the primary contributor to climate change, freshwater ecotoxicity, freshwater eutrophication, human non-carcinogenic toxicity, terrestrial acidification, terrestrial ecotoxicity impacts among all UWS stages. Purchased electricity is the main driver of climate change, terrestrial acidification, fossil resource scarcity, human non-carcinogenic toxicity. (4) Climate change impact of China’s UWSs would rise to 92.6 Mt by 2050 without internal actions, two decarbonisation pathways formed by combined measures under two grid backgrounds mitigate the CC impact to 37.1 and 31.1 Mt by 2050, along with co-mitigations of other environmental impacts. (5) Decarbonisation of the grid power significantly influence the performance of the energy-centred measures. The findings illustrate the necessity of recognising the life cycle environmental impacts of the UWSs across multiple categories, as the quantification of multiple environmental impacts and identification of major sources help pinpoint the critical levers for improving their environmental performance. Applying LCA to various decarbonisation measures under future UWS conditions allows a holistic evaluation of their mitigation effects across impact categories, prevents unintended shifts of burdens between UWS stages, and facilitate co-mitigation of multiple impacts. Overall, this study provides a holistic understanding of the environmental performance of China’s UWSs, and offers actionable guidance for national and provincial authorities, utility managers, and technology providers in prioritising effective solutions that align with China’s long-term climate and sustainability ambitions.<p></p>

Author dc:creator

• Hao Xu (21042089)

• Urban water systems
• Decarbonisation

Statement dc:rights

• All rights reserved
• Open Access after 2027-12-22

Identifier

10779/exe.32732964.v1

OAI identifier oai:identifier

oai:figshare.com:article/32732964