Waste water tanks at Daveyhulme wastewater treatment plant in Manchester, UK. United Utilities Daveyhulme plant process's all of Manchester's sewage and deals with 714 million litres a day. The sewage sludge from the plant is put in huge biodigesters which produce biogas from the human waste. This biogas is 70% methane a potent greenhouse gas. The biogas is burnt on site in a heat and power plant, preventing its release into the atmosphere. The plant generates around 7 megawatts of electricity per day from the renewable biogas.