Production of Clean Phosphorus Products from Sewage Sludge Ash using the Ash2phos Process

A growing population with an increased standard of living means an increasing need for the usage of natural resources. Phosphorus, a crucial element for all life forms, is especially important since its resources are limited and the majority of global reserves are concentrated in a few countries. The EU is highly dependent on phosphorus imports. Rock phosphate is also associated with several other problems such as contamination with cadmium and uranium. Loss of phosphorus fertilisers from farmed land may also lead to eutrophication of surface waters. Phosphorus needs to be removed from domestic wastewater for the same reason. Thus, phosphorus from virgin natural resources is ending up in a by-product from wastewater treatment in the form of sewage sludge.

In Europe less than half of sewage sludge is recycled back to agricultural land, with the remainder being either incinerated or sent to landfill, in equal proportions. The trend is towards increased incineration of sewage sludge, for several reasons. The sustainable use of phosphorus requires the maximisation of recycling opportunities. A viable solution needs to reduce consumption of virgin sources, contain a detoxification step to remove unwanted harmful content from recycled materials, and the products recovered from wastes should be commercial and effective in their applications.

This paper describes a new process named Ash2Phos which enables the production of clean commercial phosphorus products from ash of incinerated sewage sludge. The Ash2Phos process can fulfil the four above mentioned principles for a circular flow of phosphorus in society. The process is based on wet chemical processing of the ash of mono-incinerated sewage sludge. The extracted phosphorus is then concentrated to enable distribution to all agricultural land by allowing long-distance transportation, with non-contamination to ensure safe food production. The recycled fertiliser should have the same fertilising efficiency as mineral fertiliser. Extraction of phosphorus fertiliser from ash has the potential to partly replace rock phosphate-based fertilisers. The Ash2Phos process has been validated in a pilot plant and is now in the process of being scaled up.

Yariv Cohen, EasyMining Sweden AB, Travvägen 8, Uppsala, Sweden.

Patrik Enfält, EasyMining Sweden AB, Travvägen 8, Uppsala, Sweden.

Christian Kabbe, EasyMining Germany, Rudower Chaussee 25, Berlin, Germany.

19 pages, 5 figures, 1 table, 24 references