Many areas in the world produce more manure nutrients than available cropland can assimilate due to the agglomeration of livestock production. The development of technologies for nutrient reuse was identified as one of the five main challenges in waste management within a circular economy. More sustainable techniques using nitrogen (N) and phosphorus (P) recovery for both solid and liquid waste are important to close nutrient cycle loops in both livestock agriculture and municipal sewage systems. A circular economy in agriculture is a way of agricultural production that benefits with inputs from recycling or renewable sources. Animal manures contain many valuable materials such as ammonia, phosphorus, proteins/amino acids, compost materials, and clean water for reuse that could be extracted, recovered, and reused in a circular agriculture. The recycling and reuse of agricultural residues and concentrated products could make the most efficient use of natural sources, close the loop in nutrient cycling, and bring new income to farmers.
Keywords: Nutrient Recovery, Nutrient Re-Use, Upcycling, Waste, Manure, Organic Fertilizers, Sustainability, Concentration of Nutrients, Value-Added Products, Circular Economy