Fossil Carbon Transformation in Municipal Wastewater Treatment and Its Implications for Greenhouse Gas Accounting

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🔬研究者:Provides a novel methodology combining 14C analysis and continuous GHG monitoring to trace fossil carbon in wastewater systems, with implications for carbon cycle science and inventory methods.

🏢実務担当者:Demonstrates that fossil carbon in influent significantly affects direct CO2 emissions, urging wastewater operators to monitor carbon sources and adjust emission factors for accurate reporting.

🏛政策担当者:Supports revision of GHG accounting guidelines to differentiate fossil-derived and biogenic CO2 from wastewater, improving the accuracy of national emission estimates and mitigation targets.

Abstract While growing evidence indicates that petrochemical compounds from detergents, pharmaceuticals, and industrial discharges introduce fossil carbon into municipal wastewater, it remains poorly understood to what extent this fossil carbon is transformed into atmospheric CO 2 during wastewater treatment. Here, we integrate online greenhouse gas (GHG) monitoring with radiocarbon ( 14 C) analysis of liquid, solid, and gaseous carbon pools to trace fossil carbon transfer and transformation within municipal wastewater treatment plants and to provide a first-order national estimate of fossil-derived CO 2 emissions from China’s municipal wastewater sector. Fossil carbon accounted for 3.86–23.04% of influent carbon and 2.66–19.05% of off-gas CO 2 from biological treatment units, indicating that fossil-derived CO 2 emissions are measurable across different treatment systems. The relationship between influent fossil carbon and emitted fossil CO 2 varied substantially among plants, suggesting that wastewater source structure, carbon biodegradability, external carbon addition, and operating conditions regulate the fate of fossil carbon during treatment. At the plant level, fossil-derived CO 2 contributed up to 52% of total direct GHG emissions, highlighting its potential importance in wastewater-sector GHG accounting. By integrating field measurements with literature data and national wastewater treatment statistics, we estimate that China’s municipal wastewater sector emitted 1135.7 Gg of fossil-derived CO 2 in 2020, representing ~ 10% of its direct GHG emissions. Although this estimate remains uncertain due to the limited number of radiocarbon-constrained plants, the results indicate that fossil-derived CO 2 from MWWTPs is not negligible and may be overlooked when direct CO 2 is assumed to be entirely biogenic. Incorporating carbon origin into wastewater GHG inventories can improve urban carbon accounting and support more targeted decarbonization strategies for wastewater infrastructure.

• crossref https://doi.org/10.21203/rs.3.rs-10415373/v1first seen 2026-07-28 06:22:58