Standard research and revision suggestions on carbon emission accounting methods for sewage treatment plants.

The standard of accurate accounting method for carbon emissions of sewage treatment plants is studied. Based on the existing carbon accounting methods of wastewater treatment plants(WWTP) in China, combined with the research of carbon accounting standards and guidelines at home and abroad, we put forward some suggestions for revising carbon emission accounting methods of WWTP from the aspects of accounting boundary, greenhouse gas type, emission source and emission process. It is suggested to extend the accounting boundary both WWTP and its upstream/downstream, including upstream and downstream sewage pipe networks and downstream discharge water bodies on the basis of not causing double counting. It is also suggested that the fossil CO₂ originated from both sewage and the applied chemicals should be included in the accounting. Additionally, supplementary identification of fuel combustion, transportation equipment and fugitive emission sources within the plant boundary, and additional consideration of discharge sources such as outsourced transportation and sludge disposal are proposed. It is recommended to conclude the carbon emissions of energy(electricity and other forms of energy) and substances(chemicals, etc.) from the manufacturing and transportation links. And the fluctuation effect of wastewater treatment operating conditions on carbon emissions is considered. It is suggested that the optimal operation and management of WWTP and multiple forms of resource and energy recovery should be included in carbon offset. On this basis, the carbon emission process and carbon emission source of WWTP are summarized. In addition, how to optimize the carbon emission calculation of WWTP is prospected from the aspects of carbon accounting boundary, emission factor, model application and fossil CO₂. [ABSTRACT FROM AUTHOR]