For some years now, the application of farm manure in Germany has been facing a radical change, which will force livestock farms to adopt new approaches in the long term. A major problem is nutrients leaching into groundwater. In addition to the increased costs of supplying drinking water, high nitrate levels pose long-term risks to the environment. Last year, this led to Germany being condemned by the European Court of Justice for failing to comply with the EU Nitrates Directive, Directive 91/676/EEC. As a result of the verdict, which was foreseeable at the time, the Fertilizer Ordinance was tightened in 2017.
Groundwater pollution and the waste of valuable resources is caused by excessive application of farm manure locally. On behalf of the Mobile Schlammentwässerungs GmbH – MSE, the Institute of Engineering at RWTH, ISA, is preparing a study in the RANGER project to provide clarity regarding the amount of farm manure produced and its composition. This includes the site-specific calculation of the manure quantities generated and an investigation into the composition of liquid manure. It also involves processing farm manure in order to increase its transportability and to identify the location of suitable recycling sites. A key objective here is to uncover the regional potential of farm manure accumulation.
With the help of animal numbers from the "Herkunftssicherungs- und Informationssystem für Tiere", abbreviated as HIT, and average excretion quantities, scientists can conclude the nutrient accumulation per animal and year. The slurry and solid manure formation, as well as digestate from agricultural biogas plants, are recorded in a relational database created by ISA at a resolution down to the local county level, so that local regional phosphorus and nitrogen levels can be calculated.
Farm manure can be processed in order to recover these nutrients and make distribution within Germany more effective. The separation of slurry and digestate into a solid and a liquid phase is already common practice on some farms. The high water content renders transportation over long distances uneconomical, which is why further processing, especially of the liquid, nitrogen-rich phase, is becoming more important as the legal conditions in some regions are tightening. The task for the future is to be able to operate the technologies economically while producing marketable fertilizer products that can easily be transported.