From waste to fertilizer - phosphorus and carbon waste mining as nutrient recycling strategy for the future

Sustainable soil management is crucial to maintain our limited soil resources fertile for the food production for a rapidly growing global population. Phosphorus is one of the most important essential plant nutrients with typically low availability in soil. Natural P deposits are rapidly vanishing while large amounts of P are annually deposited with waste materials in landfills. The main objective of this project is the development of a production process resulting in a range of innovative fertilizers consisting of phosphorus recovered from waste materials and various proportions of stable organic carbon for impoverished agricultural soils. Waste materials are used instead of exhaustible, natural resources. The application of these products in agriculture will • close open nutrient cycles for phosphorus, thereby facilitating a more efficient use of this resource • support the conservation of rock phosphate resources • replenish soil deficient in organic carbon, thereby creating the basis for carbon farming Thermo-chemical conversion technologies will be the key processes to achieve the necessary stabilization of the carbon from waste materials alongside with the transfer of phosphorus from raw materials (green waste, residual wood, food processing residues, cellulosic fiber pulp, sewage sludge, landfill material etc.) to stabilized products. Detailed characterizations of pollutant concentrations and ecotoxicological behavior will ensure that the products fall within threshold concentrations for heavy metals and organic pollutants as prerequisite for legal admission as plant fertilizer. The research studio will further provide R&D services and consultancy to support industrial stakeholders and communities in process-technological, agronomical, and environmental/toxicological questions arising during the whole process chain. Detailed project objectives: • Comparison of different thermo-chemical conversion processes (combustion, gasification, pyrolysis, hydrothermal carbonization) and for individual raw materials to produce a stable organic carbon-phosphorus-fertilizer • Determination of the necessary mix of raw materials to achieve a balanced organic carbon-phosphorus ratio with good bioavailability • Optimisation of the process parameters as well as combinations for the applied processes in dependence of the raw materials to comply with the threshold values of the Compost Directive, European Biochar Certificate and mineral fertilizer admission rules • Production of a highly adsorptive carbon product for enrichment with phosphorus from waste water treatment plant effluents • Analysis of the product characteristics concerning phosphorus bioavailability for plants, carbon stability, potential contaminants and physic-chemical effects on soil • Screening tests in preparation for official national fertilizer admission by AGES • Assessment of energy balances, nutrient balances, and economic feasibility