Manure processing as a pathway to enhanced nutrient recycling : Report of SuMaNu platform

Abstract

Circular economy is increasingly demanded across the world to minimize the need for non-renewable sources of materials and energy. The need to introduce new nutrients into the current demand from mineral resources could be reduced significantly via nutrient recycling. This means recovery of nutrients from different nutrient-rich side-streams and their reuse in different measures, the most significant being food production. Nutrients, especially phosphorus (P) and nitrogen (N), are vital for crops to grow. The amounts required as fertilizer products are large. Still, at the time of writing nutrients are not effectively recycled, but a significant share is lost as final disposal and emissions. Recyclable nutrients are available in different side-streams from agriculture, municipalities and industry. The most significant recyclable material is animal manure which is traditionally used as a fertilizer. However, due to segregation of crop and animal production, manure is often regionally concentrated so that its nutrients may be available in excess to the region’s need. This may result in excessive use of manure in the regions of concentrated animal production, while the crop producing regions need to rely on mineral fertilizers. Both have negative environmental consequences. Thus, solutions for regional manure reallocation via improving the transportability of manure are needed to reallocate the nutrients to areas in nutrient deficit. To enable such transportation over long distances and to separate P and N from each other and thus enhance their reuse, manure processing could be used. Manure can be processed with different technologies providing various end-products. The aim of processing is usually to reduce the mass of manure and to concentrate nutrients to improve their transportability. An important aim is also to produce such fertilizer products that replace mineral fertilizers and provide reduced emissions into the environment. Several processing technologies are available and more are being developed. At the time of writing, manure processing is still limited mainly due to challenges with profitability. The investment into large-scale manure processing as required by regional nutrient reallocation is significant and the market for the novel manure-based fertilizer products is only starting to develop. Development of practices for the storage and spreading of the products is also still required. In this report, examples of regions in need of nutrient reallocation via manure processing are described for the Baltic Sea Region and the potential and challenges of manure processing as one solution to reduced nutrient emissions discussed. Summaries of available processing technologies and their end-products as fertilizer products are also presented.