Feasibility assessment of inter-industry solid residue utilization for soil amendment - Trace element availability and legislative issues

Inter-industry utilization of solid residues for soil amendment was investigated by combining desulphurization slag, fly ash, paper mill sludge and lime waste arising within the steel, pulp and paper industries. Manufactured sample analysis included relevant physicochemical properties, easily available plant nutrient concentrations and trace element availability (CH ₃COOH, NH ₂OH·HCl, H ₂O ₂ + CH ₃COONH ₄, HCl + HNO ₃) with respective pseudo-total concentrations according to USEPA 3051A (HCl + HNO ₃). Additionally, the relevant regulatory framework is discussed with respect to inter-industry residue utilization as opposed to disposal. Based on the acquired data, the attained soil amendment shows promise in the replacement of commercial liming materials (neutralizing value 38.3% Ca equivalents, d.w.). Additionally, as attested by the sequential extraction procedure and respective pseudo-total concentration determination, the pseudo-total concentrations of regulated trace elements were lower than the Finnish statutory limit values for fertilizers (Decree on Fertilizer Products 24/11) and the European limit values for awarding the Community eco-label for soil improvers (Commission Decision, 2006/799/EC). Only Ba and V showed potential availability (Ba, 85.4 mg kg ^-1, d.w., by CH ₃COOH; and V, 54.4 mg kg ^-1, d.w., by NH ₂OH·HCl) under natural conditions. However, the industrial residues used in the proposed soil amendment are defined as waste in accordance with the Waste Framework Directive (2008/98/EC). The feasibility of utilizing the material is also influenced by the prerequisites for losing this waste status and for applying product based legislation to the potential product instead. European Union's waste policy is built on the waste hierarchy which strongly supports recycling and re-use of waste materials, but innovative material and product solutions, such as the proposed soil amendment, may face a challenge under the waste-stream based regulatory regime. Enabling such residue utilization would, from a life-cycle perspective, improve the material efficiency of industrial processes and contribute to the sustainable use of natural resources.