Green infrastructure (GI) is identified as the critical technology to sustainable urban development in the United Nations New Urban Agenda. GI not only has the function of ecological services but also has the function of reducing carbon emissions, which is very important for building low-carbon cities. The carbon emission reduction effect of GI in Sponge City was analyzed by comparing the traditional drainage system (TDS) and the green drainage system (GDS). TDS also indicated combined sewer system (CSS), which undertakes a large amount of urban runoff and transfers it to wastewater treatment plant (WWTP). GDS mainly depends on rain gardens, grass planting ditches, etc., to purify and transfer rain-runoff, so the rain-runoff no longer enters into WWTP. TDS consumes much energy for pumping and wastewater treatment, which produces carbon emissions. GDS reduces the amount of water through the pumping station and sewage treatment plants resulting in a significant reduction in carbon emissions. In order to assess the carbon reduction effect of GDS, a new set of calculation has been proposed. Taking Dongying (Shandong province, China) as an example, the carbon-reduction benefit of the drainage system in Sponge City is calculated based on hydrological datasets and the carbon emission coefficients. The results show that the carbon emission is reduced by 54.3%, 43.3%, and 38.9%, for wet, normal and drought year, respectively.
Keywords Low carbon city, Green Infrastructure, Carbon Reduction Effect, Sponge City, Drainage System