Environmental impact and economic performance analysis of two faecal sludge treatment plants in Beijing: A life cycle perspective.

As demand for non-sewered sanitation continues to increase globally, faecal sludge management (FSM) continues to have critical implications for public health and sustainable development. However, understanding of the life-cycle performance of alternative FSM technologies is lacking. Here, we address this gap and present a framework for combined life cycle assessment and cost analysis to systematically quantify the carbon footprint and economic viability of faecal sludge treatment plants (FSTP). We apply the framework to two case study FSTPs in Beijing (FSTP1 and FSTP2), which serve as representative examples of FSM in mega-cities in China and the world. These plants use different FSM technology and process different waste mixtures, with FSTP1 using traditional physicochemical processes to treat single-source faecal sludge and FSTP2 co-processing faecal sludge, food waste, and municipal sludge through anaerobic digestion, combined with biogas and crude oil recovery. Carbon emissions analysis shows that FSTP1 emits 54.7 ± 2.08 kg CO₂-eq/t organic waste (OW), which is considerably lower than FSTP2's net emission of 70.5 ± 8.45 kg CO₂-eq/t OW. This accounts for FSTP2's 43.6 % emission reduction from resource recovery, which partially offsets the plant's otherwise much higher carbon emissions. Transportation distance and grid GHG emission intensity are key factors that affect each plant's carbon footprint. Thus, emissions could be reduced through development of low-carbon faecal sludge treatment technologies and optimization of regional logistics and energy structures. Economic analysis shows that the life cycle costs for FSTP1 and FSTP2 are 79.7 million CNY (≈11.2 million USD)¹ and 282 million CNY (≈39.7 million USD), respectively. Although FSTP2 requires a higher initial investment, its diversified revenue structure and stable treatment fees result in a higher operating income, shortening the investment payback period to just over 10 years, compared to the 14 years required by FSTP1. This indicates the greater economic feasibility of the synergistic treatment and resource utilization approach in the medium to long term. The research findings can inform optimized urban faecal sludge management strategies and selection or promotion of lower-carbon treatment technologies and circular economy models.

Duke Scholars

Author Marc A. Jeuland Sanford School of Public Policy