Analysing the co-benefits: case of municipal sewage management at Surat, India

Rapid growth of urban population in India has led to equally fast increase in the consumption of water and consequently to generation of wastewater. Presently, about 30% of the wastewater generated from major cities of India is being treated. Untreated wastewater leads to various environmental problems including pollution of air, water and land resources. This paper especially addresses the issue of methane emission from wastewater, which is a major contributor to climate change. The main aim of the paper is to document and analyse a climate change mitigation action so as to identify and disseminate innovative urban practices that can be replicated at other places. The paper presents a case study of methane recovery and power generation from Sewage Treatment Plants (STPs) in Surat city of Gujarat in India. Direct benefits of projects namely, methane extraction and electricity generation are quantified based on the data on total methane production and electricity generation from the STPs. Before implementation of the project, annual baseline Carbon Dioxide equivalent (CO2e) emissions from each STP were between 19,000 and 27,000 tonnes. After implementation of the project, the annual emissions are in the range of 3000–5000 tonnes from each plant. Thus, a total of 80,000 tonnes of CO2e emission reduction per year is estimated from the four STPs in Surat. These plants are also generating 1.5 to 2.5 million kWh electricity for captive use every year. Taking a co-benefit approach, in addition to the reduction of greenhouse gas emission, associated multiple benefits of the project are also quantified. Co-benefits such as production of useful bi-products and water pollution reduction were found to be significant. Many other social benefits have also been documented; however, these could not be quantified due to non-availability of suitable data.