Information

Background

Phosphate rock is the primary raw material source for phosphate production, but unfortunately is mineable phosphate rock a limited non-renewable resource. Large amounts of phosphorus end up in manures and in urban waste, mainly in sewage sludge and slaughterhouse waste. Today are EU countries re-circulating phosphorus by distributing 48% of the sludge back to farmland, as can be seen in figure 1. The positive aspect is that phosphorus is re-circulated, but it’s not problem free. Sewage sludge can still contain viruses, heavy metals, and other substances that could be harmful to human health. Today 27% of the phosphorus is being transported to land fills or „other“, which are routes that rarely recover any phosphorus. 25% of the sludge is incinerated and the ash is mainly transported to land fills. The Ash2Phos process can in a near future transform the sludge ash to a raw material for phosphorus extraction and thereby be a part of a circular solution for phosphorus management.

Problem

Ash from mono-incinerated sewage sludge has a high concentration of phosphorus (7-10%), iron, and aluminium (5-10%), but also contains unwanted heavy metals such as cadmium. The high content of metal creates an obstacle for possible applications for the phosphate rich ash.

Solution

In the Ash2Phos process, sludge ash is treated in a wet chemical process for the recovery of phosphorus, aluminium, and iron as clean commercial products, and at the same time are the unwanted heavy metals separated for disposal.

The Ash2Phos process comes in two designs, the MAP or DCP. The commercial products from the MAP process are:

• Mono-ammonium phosphate (MAP)
• Calcium chloride
• Iron Chloride
• Aluminium Sulphate

The commercial products from the DCP process are:

• Di-calcium phosphate (DCP)
• Iron Chloride
• Aluminium Sulphate

Economical benefits

• Low energy consumption – 30 kton ash plant requires energy equivalent to approx 80 households
• Favorable mass balance – Operative income/cost ratio estimation 1,55
• Relatively low capital cost investment

Technological benefits

• Produce valuable high-grade commercial products independent of ash quality: MAP/DCP and Iron chloride & Aluminium sulfate.
• Removes cadmium and heavy metals from the phosphorus (< 1 mg Cd/Kg P, < 0.5 mg Cd / Kg P2O5))
• More than 90% recovery rate of phosphorus from the ash
• Can use waste acid from incineration plants
• Low labor intensity

Environmental benefits

• Recovery of clean phosphorus products
• Production of precipitation chemicals that can be recycled to waste water treatment plants
• Detoxify the waste
• Reduce the need for virgin rock phosphate
• Reduce the amount of waste for disposal
• Create a circular flow of resources

A new factory is planned based on the patented Ash2phos technology.

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Further Information

Project website