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2024 11 28 LuftaufnahmeThe Gemeinschaftskraftwerk (GKS) is planning a major transformation by 2028: replacing coal with sewage sludge as the primary fuel for district heating production. This initiative aims to reduce environmental impact, lower costs, and significantly decrease emissions.Currently, GKS burns both waste and coal to produce district heating. (Photo: Anand Anders)

The material from which district heating in Schweinfurt is made is to become better from 2028: better for the climate, better for the wallets of district heating recipients. How to do it.

Just waste, coal is still burned in the Gemeinschaftskraftwerk (GKS) in Schweinfurt. Coal. This is bad for the environment, expensive and a discontinued model. For a maximum of ten years, the joint power plant could burn coal in addition to the waste from all over Lower Franconia, calculates Managing Director Ragnar Warnecke. Then it would be over according to the legal requirements.

The clock is ticking, even in the case of sewage sludge disposal. In 2032, sewage sludge may no longer be spread on fields. What used to be considered fertilizer is now a waste product that no one wants anymore; contaminated with heavy metals and drug residues. Municipalities will therefore have to dispose of the sludge from their sewage treatment plants differently in the future. For example, in the GKS.

In Bavaria, says Managing Director Warnecke, GKS plant will probably be one of the few plants that incinerate sewage sludge. He only knows of one case: Schwandorf. There, too, sewage sludge incineration is being considered. Otherwise, most of them are concerned with drying the sewage sludge from their own plant in order to have it disposed of elsewhere. There are already drying plants in Hofheim and Aschaffenburg. Würzburg, Bamberg, Coburg are also playing with the idea, says Warnecke.

He and his team have made contacts in all directions to offer themselves as waste disposal companies. The GKS entered the topic of sewage sludge incineration at an early stage. It has been running since 2020, but still in manageable quantities and on the previous lines. In 2023, it was around 4000 tonnes, similar to the previous year.

Investment in New Infrastructure

GKS is investing €84 million in building a dedicated sewage sludge incineration plant and upgrading its technology. The new facility will process 60,000 tons of dried sewage sludge annually, replacing 30,000 tons of coal. Operations are expected to commence by late 2028.

And yet the district heating that the GKS gives to its shareholders will become cheaper. Even cheaper than today, says Warnecke. Because with the switch, the GKS saves money. On the one hand, it does not have to buy coal, but earns money by purchasing municipal sewage sludge; on the other hand, there are almost no more CO2 taxes, says Warnecke. Another plus point: emissions will also be lower and district heating will then be "largely CO2-neutral". The State Office for Environmental Protection, says Warnecke, sees the Schweinfurt plans as a lighthouse project.

In 2025, the GKS will submit the first application for a building permit. The plant is then scheduled to go into operation at the end of 2028 and burn municipal sewage sludge on a large scale, mainly from Franconia, according to Warnecke. 60,000 tons of dried sewage sludge will replace the 30,000 tons of coal that the GKS burns per year to generate the necessary district heating. In order to be able to absorb peaks, wood pellets will also be used in the future.

With sewage sludge instead of coal, the GKS relies on a safe energy source, explains the GKS managing director. Sewage sludge is always available, and in relatively constant quantities. 1.6 million tons of dry matter are produced in Germany every year, a lot of sludge that has to be disposed of. It will be incinerated in the planned plant (as well as garbage) at 435 degrees Celsius. The requirements for the emissions are strict, explains Warnecke.

Photo: Katja Beringer | Worth millions and a real investment in the future, this is how GKS Managing Director Ragnar Warnecke (left) and Organization Manager Marcel Strätz describe the planned new plant for sewage sludge incineration at the GKS in Schweinfurt. In Bavaria, the GKS will then be one of the few plants that can dispose of dried sewage sludge

Between 300 and 370 gigawatt hours of district heating per year

The GKS produces up to 370 gigawatt hours of district heating per year; in this there will be around 300, Warnecke estimates. The reason: the mild temperatures. The demand is there. If necessary, the GKS could supply far more, theoretically supplying all of Schweinfurt, Warnecke had explained in 2023. The source is not the problem, but the distribution. 70 percent of district heating goes to industry, 30 percent to the municipal utilities, which supply private consumers and commercial enterprises.

Photo: Anand Anders | The delivery of dry sewage sludge.

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