Does environmental protection engineering necessarily save energy and reduce carbon emissions? ——Carbon Emission Accounting of Shouchang Wastewater Treatment Plant in Jiande City, Hangzhou

Abstract: This study takes Shouchang Wastewater Treatment Plant in Jiande City, Hangzhou as an empirical case to explore the energy-saving and carbon reduction effects of county-level environmental protection projects. The paper starts with theory and methods, introduces the direct and indirect carbon emission accounting methods in the sewage treatment process, and uses the accounting of Beijing Gaobeidian Sewage Treatment Plant as a reference to calculate the carbon emissions of Shouchang Sewage Treatment Plant in detail. Research has found that the Shouchang Wastewater Treatment Plant will treat approximately 15 tons of total nitrogen and 2 tons of total phosphorus annually in 2023. The total carbon emissions generated are 1105.51 tons of CO ₂ equivalent, and the carbon intensity per unit of water treatment is 0.397 kgCO ₂ equivalent/ton of water. Electricity consumption is the main source of emissions, and sludge drying and incineration technology effectively reduces carbon emissions. To manage the environment, it is necessary to construct and operate sewage treatment plants, but these plants themselves also generate carbon emissions. This study proposes to convert the nitrogen and phosphorus reduction effects of water environment protection projects into the number of sewage treatment plants, which can be used for carbon emission calculation and comparison benchmarks of water ecological projects, providing scientific support for carbon emission reduction assessment of water environment purification ecological environmental protection projects.