Water Quality Management


Biological methanation in fermenters of municipal WWTP

2018 - 2021

Bundesministerium für Nachhaltigkeit und Tourismus

Contact Person:
Karl Svardal Emailsvardal(at)

Project Staff:
J. Taubner, L. Jahn


Brief Description

Electricity production from renewable energy sources is sometimes subject to considerable seasonal and daily fluctuations. One way to stabilize the power grid and to transfer excess energy into a storable gas is the so called "Power to Gas" technology.

The principle of this method is to split water with an excess of energy by an electrolysis to hydrogen (H2) and oxygen (O2). The part of the generated hydrogen can be injected (up to 4%-Mol) and stored in the gas grid. One way to use the produced hydrogen is the biological methanation in municipal digesters. Municipal WWTP often have an anaerobic sludge treatment, where the biological process of the anaerobic organisms can be used for the conversion of H2 to methane. Through this process, the methane content in the biogas can be increased significantly. The advantage of using municipal digesters in combination with the "Power to Gas" technology is that digesters already exist and are equipped with gas storage tanks. Moreover, educated and experienced operational staff is available on-site. CO2 is produced during the anaerobic degradation of the biomass and has not to be provided additionally. Moreover, oxygen from the electrolysis can be used in the biological tank for the aeration.

As part of the "BioMAra" project, laboratory tests are carried out to investigate the efficiency of the biological methanation process for WWTP. Hereby, the methane production rate and the gas quality can be used as evaluation criteria.

An advantage is that digesters can be found much more frequently than waste fermentation plants and thus a comprehensive establishment of the "Power to Gas" technology could be sought on municipal digesters. The focus of the project is to investigate the extent to which both technologies can be economically linked without affecting the operation of municipal wastewater treatment and the objectives of sludge stabilization.