CHENNAI: After earning more than Rs 550 crore since 2020 by selling treated sewage water to industries, the Chennai Metropolitan Water Supply and Sewerage Board (Metro Water) is now looking to generate revenue by commercialising biogas produced during the sewage treatment process.
As per official documents, sewage treatment plants (STPs) generate large volumes of sludge, which in turn produce biogas through anaerobic digestion. At present, a significant portion of this gas is either flared or used internally to run internal STP power generation. To tap its commercial potential, the board plans to study ways to purify and compress the gas for sale. “CMWSSB aims to undertake a study on how the biogas generated during the anaerobic digestion of sewage sludge can be purified and compressed for commercial use such as bottling for sale or supplying to city gas distribution entities,” the document stated.
Currently, Metro Water operates 20 STPs across the city with a combined treatment capacity of 957.80 million litres per day (MLD). On average, about 650 MLD of sewage is being treated daily. Of the 20 plants, 11 are equipped with facilities to generate biogas. These plants together generate biogas of around 24,500 cubic metres per day.On average, about 50 kg of biogas is produced per million litres of sewage treated. At present, around 55% to 65% of the gas is utilised to run the STPs, while the rest goes unused. Metro Water plans to appoint a consultant to prepare a detailed feasibility report on the proposed initiative. The consultant will study the technical and commercial aspects of purifying and compressing the biogas.