[show abstract][hide abstract] ABSTRACT: The substitution potential of sewage sludge for German primary phosphate imports has been estimated as 40%. Yet, a marketable option for the full scale recovery has been lacking. This study focuses on a full-scale process for the manufacture of a P-fertilizer from sewage sludge ash (SSA) adapted from the production of Triple Superphosphate. Given (i) conformity of the input with phosphate ores mined from sedimentary deposits, (ii) comparability of the product with a commercially available P-fertilizer regarding contaminant levels, P-fractionation and yield effects, and (iii) compliance of the output with the German Fertilizer Ordinance the RecoPhos P 38 fertilizer was discharged from the waste legislation regime. The fertilizer is currently being produced at a rate of 1000tonnes per month and sold at a competitive price.
[show abstract][hide abstract] ABSTRACT: Ashes from the mono-incineration of municipal sewage sludge (SSA) have a high potential for phosphorus recovery and are suitable for the substitution of primary phosphate. In an approved full-scale test the RecoPhos process turned out to be a robust technology for the production of a P‑fertilizer from SSA. It was shown that input qualities correspond to sedimentary phosphate rock and that the product matches a conventional fertilizer (Triple Superphosphate) regarding P‑contents and P‑fractionation as well as yield effects
in pot and field experiments. The contents of metals, metalloids and perfluorinated compounds of the product conform to the German fertilizer ordinance. Thereby, the end-of-waste criteria were met and RecoPhos P 38 is being industrially produced and sold at a competitive price. Nevertheless, the extension of production capacities stagnates. A more coherent position of the regulating bodies with the German resource efficiency programme would be desirable. Obstacles include the re-coding of certain SSA as a hazardous waste in spite of unchanged elemental composition and an over-literal application of the German fertilizer ordinance. Since the latter excludes dusts of the last filtering unit from fertilizer production ashes coded as 19 01 14 (German identifier “filter dust”) have been rejected irrespective of whether or not they included the air Pollution control residues of the last unit. The above shows the urgent need of a harmonized view on the use of SSA for P‑recovery. Otherwise a readily available P‑recovery process developed by an SME may fail instead of boosting resource efficiency.