Manure processing as a pathway to enhanced nutrient cycling

Manure and its potential – and the need to develop more sustainable manure management systems – has been the theme of numerous projects in the Baltic Sea Region. One of SuMaNu’s tasks was to gather and synthesize knowledge produced by previous projects, and now the team for work package 2 has completed the task.

In their report Manure processing as a pathway to enhanced nutrient recycling, the team discusses the need, state-of-the-art, and potential for manure processing. Currently available technologies are also described.

The report presents the nutrient availability and needs in four countries, namely Finland, Sweden, Germany, and Poland. However, the challenge is universal: the regional supply of manure doesn’t meet the demand. Livestock production and crop production have become more and more segregated and thus, manure and its nutrients accumulate in certain areas or regions. There is a need to find methods to process manure into products that are easier to use and transport.

Manure can be processed into recycled fertilizer products using different technologies. Depending on the technology used, renewable energy can be produced simultaneously. The aim can be to enhance farm-level nutrient use or to reallocate nutrients regionally from surplus regions to those in deficit. This also determines the level of processing: simpler technologies are used on farm-scale, while in large processing plants the processing chains may include several technology steps and produce a number of different products.

In this report, the following manure processing methods are presented:

  • Mechanical separation
  • Slurry acidification
  • Composting
  • Anaerobic Digestion
  • Thermal drying
  • Pelletizing/granulation
  • Pyrolysis
  • Hydrothermal carbonization
  • Combustion/incineration
  • Gasification

Manure is a valuable source of nutrients, organic matter, and energy. The main benefit comes from more efficient manure usage in crop production, and the usage should be optimized to reduce nutrient loss to air and water. Increased manure nutrient use efficiency will decrease the need for mineral fertilizers and enhance carbon sequestration into soil. In this report, environmental aspects are also discussed.