Ash2Phos

From sewage sludge ash to clean phosphorous products

EasyMining is focused on creating circular material flows from waste. Phosphorus is an essential element for life as a key nutrient for agriculture. Via the food cycle, phosphorus ends up in sewage sludge. This sludge can be spread on agricultural land, used for soil production, or be incinerated. Incineration is today mainly used as a method to reduce the amount of waste to land fill, or destruction if the sludge quality is too low for other uses.

The phosphorus content of ash from incinerated sewage sludge is high, and through this unique patented process, we are able to extract clean commercial phosphorus products from the ash. In addition to the phosphorus, the Ash2Phos process can recover precipitation chemicals and at the same time remove heavy metals. Due to the continuous creation of the raw-material, the process allows for profitable plants along with a low risk of investment.

Easymining is currently working together with COWI as an engineering partner in the development of the first Ash2Phos factory. Upscaling of the process is ongoing and the a full-scaled plant in southern Sweden is being planned. Parallel to that are several additional plants in Europe currently being considered together with different partners.

Background

Phosphate rock is the primary raw material source for phosphate production, but unfortunately mineable phosphate rock is a limited non-renewable resource that may only last an additional 100 years. 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. 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. Currently 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.

Ash from mono-incinerated sewage sludge contain a high concentration of phosphorus (7-10%), iron (10-15%), and aluminium (5-10%), but also contains unwanted heavy metals such as cadmium. The high content of metal has up until now created an obstacle for possible applications for the phosphate rich ash.

As long as society exists, sewage sludge will be created. Combined with the end of phosphate rock reserves in sight and the need for phosphorus in our society, phosphorous recycling will be an inevitable part of the future society.

Solution

The Ash2Phos process can transform the sludge ash into raw material for phosphorus extraction and thereby be a part of a circular solution for phosphorus management. The process consists of 3 sequencial steps: a first acidic step, a second alkaline step (where intermediate products are produced), and finally a conversion step where the intermediates are processed into final products.

The main inputs of the process are

  • Ash from incinerated sewage sludge
  • Acid (hydrochloric acid, HCl)
  • Lime

The process consists of several successive chemical reactions undertaken at room temperature (though one process step may benefit from a temperature of 40°C). There is no need for pressurized vessels or for exceptional materials to be used for the equipment. The mass balance of the process is favourable, since all input chemicals become part of the products.