Membranes for nutrient recovery from waste and production of organo-mineral fertilizer in the context of circular economy

There is a notable necessity to discover novel alternative fertilizers since the nutrients are non-renewable sources and are limited to strict regions of the globe. Under a circular economy perspective, different wastes can now be considered as potential sources of nutrients. This review explores the potential of reusing different wastes as fertilizers or as raw materials for fertilizer production. The composition of vinasse, sewage sludge, wastewater from livestock, and olive mills were summarized, followed by a discussion in terms of nutrient availability, the necessity for supplementation to attain the nutrient demand of different crops, and the risks associated with the presence of toxic compounds in these residues. To extend the practice of fertigation, and for it to be comparable with commercial fertilizers, it is necessary to reduce the transportation costs and increase the nutrient content of these residues. For that, one alternative explored was the use of membrane separation processes. Their potential use was critically discussed, emphasizing their potential to concentrate on nutrients and their valorization. Soon, it is expected that these technologies will offer the promise of concentrating on nutrients and enhancing their value, furthering the circular economy's objectives towards better resource management.