How wastewater management can reduce greenhouse gas emissions

A new study commissioned by the German Environment Agency (UBA) examines how wastewater management can contribute to Germany’s climate protection goals. Wastewater treatment is usually the largest single energy consumer for municipalities, yet at the same time, treatment plants generate usable energy in the form of gas, electricity and heat. The UBA research analyses the climate protection and energy efficiency potential in wastewater management. “The project focuses on the evaluation of technical options in wastewater management to reduce greenhouse gas emissions by substituting fossil fuels in the areas of electricity, heat, and mobility,” the report states. The study presents a benchmark scenario, illustrating the already possible but often not realised optimisation potentials in the current system, and an innovative scenario, in which wastewater treatment plants contribute to balancing energy in the region.

According to the study, the total electricity consumption of all German municipal sewage treatment plants fell from approximately 3.7 terawatt-hours (TWh) a year in 2011 to around 3.4 TWh a year in 2017, a decrease of 8 percent overall and an annual reduction of 1.3 percent. The decline was largely due to an increase in energy efficiency. In the past 20 years, meanwhile, the amount of sewage gas generated in municipal sewage treatment plants has increased steadily by 2.1 percent a year. The development is attributable to such factors as the construction of digestion plants, improved management of digester reactors and an increased use of co-substrates. A biogas plant that went into operation last year in Hamburg is supplying some 5,700 households with energy by producing methane from the city’s largest sewage treatment facility.