Recycled quota crucial for critical raw materials like phosphorous
Phosphorous (P) is a key nutrient in the global food value chain yet arguably one of the most underappreciated essential elements on the periodical table. While the European Commission added phosphate rock to its Critical Raw Materials list in 2014, more needs to be done, now, to simultaneously stimulate recovery technologies and encourage market uptake of recycled phosphorous.
In short, phosphorous is an indispensable element for all forms of life, and amongst other things, plays an important role in the metabolic transfer of energy in plants and animals, in genetic material (DNA), in nerve cells and in bones.
– That’s why phosphorous is a key component in agricultural fertilisers, used to promote plant growth, vitality and yield, and in feed phosphate, to ensure the vitality and health of livestock, says Anna Lundbom, Marketing and Product Sales Manager at EasyMining.
However, phosphorous is a finite resource, extracted primarily from phosphate rock (apatite) that is found in a few deposits around the world. Herein lies the challenge. Globally, approximately 85 percent of the extracted phosphate is used in fertilisers and around 7 percent is used in livestock feeds. In Europe, there is a small deposit in Finland meaning that over 90 percent of phosphorus used in the EU-27 (The 27 member countries of the EU) is imported from outside the EU. In numbers, figures (2017) from Eurostat and Fertilizers Europe suggest that the EU-27 uses about 1.1 million tonnes of elemental phosphorous in European fertilisers.
Growth of sewage sludge incineration
This implies that the entire EU agriculture- and food value chain is almost completely reliant on imported phosphorus, with all the associated geo-socio-political risks that such dependency entails. Thus, from a circular “grow, eat, defecate and flush” perspective, it stands to reason that sewage sludge, a residual of municipal wastewater treatment plants (WWTPs), would be the natural go-to source of “post-consumer” phosphorous for recycling. Using sanitised sewage sludge as a fertiliser is though strictly regulated on account of it containing other undesirable components, such as heavy metals, pharmaceutical residues, consumer chemicals, and microplastics.
As a result, agricultural valorisation of sewage sludge is decreasing. Instead, sewage sludge incineration is fast becoming the sludge treatment method of choice. Especially for high population density countries like the Netherlands, and Germany. In doing so, the volume of sludge material is radically reduced, sanitary safety is ensured, and organic contaminants such as pharmaceutical residues, microplastics or PFAS (Per- and Polyfluoroalkyl Substances) are eliminated.
Leveraging sewage sludge ash
According to figures compiled by EasyMining, an estimated 990 000 (dry) tonnes of sewage sludge was incinerated in the EU-27 in 2017. By 2030, this is expected to over double to around 2.26 million tonnes. Left from incineration is the sewage sludge ash (SSA) that contains both the desirable phosphorous (but in a form which is no longer plant-available) along with unwanted heavy-metal contaminants. This means that as ash, the phosphorous cannot be recycled to agriculture and goes to landfill, something that EasyMining has addressed.
EasyMining has developed Ash2Phos, a proprietary chemical process to recover phosphorus without contaminants from the ash.
– The ash from mono-incinerated sewage sludge typically contains seven to ten percent phosphorus making it a rich source to recover phosphorous from, says Anna Lundbom.
The three-step chemical process is energy efficient using room temperatures and atmospheric pressure.
– With our Ash2Phos extraction process we can recover at least 90 percent of the phosphorous from the sewage sludge ash, Lundbom says.