Heat can bring old biogas plants out of retirement

12.06.2025

Source: E & M powernews

What to do when you reach retirement age? What applies to more and more people also applies to biogas plants: keep working. After the EEG subsidy, they could still earn money in the heating network.

On June 12th, the "Energie Expo Münsterland" highlighted a perspective for operators of biogas plants that are no longer eligible for funding under the Renewable Energy Sources Act (EEG). At the industry meeting of the local regional association of the Renewable Energies Association (LEE NRW), the company 2G Energy explained its own idea of the "Green Cube".

The combined heat and power plant manufacturer from Heek builds its cubes, which are designed as energy containers, as part of a local heating supply. Jörg Lösing, Sales Manager for combined heat and power (CHP) in Germany, describes the Cube concept as an "intelligent combination" of combined heat and power (CHP) units and heat pumps. They are a way for cities to fulfill their task within municipal heat planning (KWP).

Municipalities would nevertheless have to provide a certain amount of space for the interaction of several components. Ideally, a heat storage tank with a capacity of 500 to 5,000 cubic meters should also be considered. 2G Energy therefore often builds its modular "energy centers" on the outskirts of towns.

400,000 euros in revenue possible for older CHP systems

In the heating network, the various components each have their own tasks. Renewable generation plants supply electricity directly to the buildings, to a heat pump or to the grid. The heat pump uses this electricity for its heating output. According to Jörg Lösing, combined heat and power generation is important as soon as renewables are unable to supply the required electricity during dark doldrums, for example.

And at this point, there would also be opportunities for biogas plants, which would fall out of the EEG subsidy after 20 years, i.e. retire, so to speak. On the contrary: with biogas, for example, the CHP plants could then reconvert to electricity and supply the necessary energy for heat in the absence of wind and sun.

Jörg Lösing calculated the economic viability of the biogas dinosaurs, of which there are many in Münsterland. If a CHP unit drives a heat pump, the latter could, for example, generate a thermal output of 750 kW if dimensioned accordingly. With an additional 250 kW from the CHP unit itself, operators could therefore sell a total of 1,000 kW of thermal output.

In a new heating network, around 10 cents per kWh could be achieved. If this assumption is correct, this could lead to an annual income of 400,000 euros for 4,000 operating hours. Converted to electricity, the kilowatt hour would reach a value of 40 cents. For Jörg Lösing, this form of extending the working life of biogas plants is an option that should definitely be considered for the industry.

Franziska Probst also sees biogas plants as a building block for the future heat supply. The project engineer at the Steinfurt-based community energy developer Enwelo, which stands for Energiewende lokal (local energy transition), sees one advantage of the plants in their controllability. This makes the plants base load-capable. Operators can run their CHP units more economically and flexibly. According to Franziska Probst, this allows the plants to "contribute to the heating market". In principle, it is important to bring electricity generation and demand together as the electrification of heat increases.

Author: Volker Stephan