Characterization of Italian and Tunisian Paper Sludges to Employ It as Soil Amendment

Recycling paper generates large quantities of Deinking Paper Sludge (DPS), which contains high content of organic matter that can be valorized as a soil amendment. The production process can include mechanical action to detach the ink from the fiber or a combined mechanical and chemical process. For optimal DPS valorization, chemical and physical characterization are necessary. Italian and Tunisian DPS were analyzed and compared for chemical (pH, OM, total N, C/N ratio, mineral nutrients, and trace metals), surface chemistry (DRIFT, FTIR), and thermal stability (TGA). The elemental analysis revealed similar carbon (C) and nitrogen (N) contents. Both materials showed high mineral nutrients and trace elements below the limits for soil amendments with no risk for soil contamination. Surface chemical analysis evidenced similar materials rich in aromatic, phenolic, aliphatic, and polysaccharide structures and the presence of clay minerals and carbonates. No evidence was found in the analyzed DPS concerning the organic pollutants. The thermal analysis also evidenced similar decomposition temperatures of organic matter in both DPS. Practical implications of the results are discussed from the perspective of the opportunity to develop international standards for DPS management, considering the similarity in their characteristics.