Turn dirt into fertilizer: Every year, around 1.2 million tons of sewage sludge are produced in the two Munich sewage treatment plants Gut Großlappen and Gut Marienhof. It comes from the sewage of Munich and 22 surrounding communities. And this sludge contains a valuable raw material: phosphorus, which is processed into fertilizer, among other things. About 3.1 percent of this is contained in the dry matter of sewage sludge. From 2029 onwards, the Munich city drainage (MSE), a municipal company, must completely recover the phosphorus, which is stipulated by the sewage sludge ordinance passed by the federal government in 2017.
The city is therefore building a new incineration plant in Großlappen, in which only sewage sludge is “thermally recycled”, as experts call it. So that the phosphorus can be recycled from the ash, no other substances may be burned. At the moment, the incineration plant in Großlappen, which has been in operation since 1998, only manages 70 percent of the sludge, the rest ends up in the waste block of the North thermal power station. In the future, the new plant will be able to handle all of the sewage sludge. The recovery of the phosphorus is not part of the project, here the MSE is still examining the possibilities.
On Tuesday, the city council’s urban drainage committee decided on the new building, which will cost 404.5 million euros and should start at the end of 2024. Commissioning is planned for 2027/28, i.e. before the Sewage Sludge Ordinance comes into force. According to the administration, the Großlappen location has the advantage that a large part of Munich’s sewage sludge is already dewatered, dried and thermally treated there. In this way, necessary components of the existing infrastructure can continue to be used. The new system should have fewer emissions and be more efficient in terms of energy, for example through photovoltaics on the roof surfaces.