Farm fertilizer as silo maize substitute for biogas plants

Research project with the Münster University of Applied Sciences

Farm fertilizer as silo maize substitute for biogas plants

In this research project, the solid/liquid separation in the field of slurry and fermentation residue treatment was investigated in order to develop a solution that on the one hand increases the energetic use of manure and on the other hand separates valuable nutrient resources such as phosphorus, potassium and magnesium under economic conditions and makes them available for other regions with nutrient deficiencies as mineral fertilizer substitutes. Using the Klass spiral filter and organic precipitation and flocculation aids, an optimal and economic separation of manure and fermentation residues was investigated. Two research objectives were in focus: Firstly, the increased use of separated liquid manure in biogas plants, the determination of biogas yields and the increase in energy production from manure as a silage maize substitute and secondly, maximum mineral separation (phosphorus, magnesium, potassium). The aim of these research series was to develop a technical and economic assessment of when and under what conditions farmyard fertilizers are an interesting substrate option for biogas plants and which separation potentials can be achieved with regard to minerals. The separation tactics in connection with precipitation and flocculation aids were investigated and optimized for these applications, so that a technical further development in this subject area is achieved and thus contributes to sustainable development in rural areas.


  • The animal excreta must be processed as continuously as possible, as otherwise high losses are caused by the storage of the raw manure. This can be avoided by processing and storing the produced solids.
  • The storage of raw manure records losses of up to 50 % already after one week of storage and losses of 90 % after 8 weeks.
  • In contrast, the separation and storage of the produced solids preserves the achievable biogas potential. Losses of only around 10 % can be found here over a total storage period of 8 weeks.
  • Potential for substituting silage maize with processed manure. Thus, at the same cost and yield, around 14 % of the silage maize to be used can be substituted by processed manure. The additional transport costs are offset by the higher efficiency.
  • The filtrates from the separation can be used directly on the farm and are characterized by higher fertilizer quality and simpler handling.

Products used