Sustainable Management of Sewage Sludge for the Production of Organo-Mineral Fertilizers

Circular Economy (CE) package accepted by the European Union (EU) in December 2015 promotes close-loop flows of materials. The main targets provided in the documents refer to the prevention of waste landfilling, efficient use of resources and energy, as well as re-use waste and by-products. Sewage sludge—residue from Waste Water Treatment Plant (WWTP)—has a great fertilizer potential and should be recycled in line with the CE strategy. Sewage sludge usage for agricultural purposes seems to be the best sustainable option of its disposal. New EU regulations related to fertilizers derived from bio-waste and by-products assume the uniformity of legislation in Member States and simplification of procedures for introducing innovative fertilizers into the internal market. The characteristic of organo-mineral fertilizers obtained from dried sewage sludge is presented in the paper. In order to obtain balanced NPK fertilizers straight mineral fertilizers, poultry litter ash and phosphoric/nitric acids or a mixture of these were added. As a result organo-mineral fertilizers with N + P2O5 + K2O > 20% were produced. It was found that the largest contribution of contaminants in products comes from Wet Process Phosphoric Acid.