The area of “Stadtwerke Marsberg” was declared as a protection zone for the drinking water production in 2006. A new regulation was instaured saying that the use of non treated manure (liquid and solid) in the drinking water protection zone was forbidden without any treatment in order to reduce the sanitary risks of the manure in the drinking water.

At this time the nitrate load in the drinking-water was 55 mg/l. The biogas technology was implemented to produce renewable energies and to produce the needed heat for the thermal treatment of the whole output of the biogas plant at 70°C for 1 hour before spreading out the fertilizer.

The biogas plant in Marsberg was initiated by the “Stadtwerke Marsberg” as a collective project together with 90 farmers from the region. These farmers are responsible to deliver and produce all necessary biomass for the biogas plant.

Due to the thermal treatment at 70°C for 1 hour in a batch system, the whole output of the biogas plant (ecofertiliser in liquid form) represents no more sanitary risks and is used as fertilizer on the farmland situated in the drinking water protection zone.

Thanks to the improvement of the quality of the organic fertilizers and the additional improvement of the material flow management (ideal distribution of the organic fertilizer between the different farms) and the use of the best available technology for the spreading on farmland, the nitrate load in the drinking water has been decreased from 55 mg/l (2006) to 46 mg/l (2010).