A treasure hunt for nutrients – recovering potassium and phosphorus from bioindustry ashes

Sustainable fertiliser production is vital for society, as global food security remains a critical challenge. Potassium and phosphorus fertilisers are still largely produced from virgin mining - a resource-intensive process with significant economic and environmental drawbacks.

“Presently, Canada, China, Russia, and Belarus dominate the global potassium production and European Union countries are highly dependent on imports. It is high time, that we start developing processes to become self-reliant,” says Cristian Tunsu, Lab Manager and Senior R&D Engineer.

An important alternative lies in secondary sources, particularly byproducts and waste from bio-industries, which could supplement or replace conventional fertilisers. However, many of these streams are currently underused, often ending up as low-quality fertilisers or in landfills because of contamination with heavy metals, pathogens, and undesirable organic compounds. Their incineration can solve the biological and organic contamination, while concentrating the contained nutrients, but does not remove the heavy metals.

Swedish innovation company EasyMining is coordinating a research project, in which a process to recover important nutrients such as potassium and phosphorus from bioindustry waste is being developed. The process aims at turning these nutrients into high-quality, heavy-metal-free fertilisers with well-defined chemistry and application areas. Read more here

The project began with evaluating over twenty ash sources, identifying those with the highest promise for sustainable fertiliser production. One of the investigated materials is bioindustry ashes, particularly from poultry litter incineration, which offers a promising secondary source of critical nutrients.

“Poultry litter fly ash contains high concentrations of potassium, over 20 wt.% elemental potassium, as well as phosphorus. However, heavy metals such as copper, zinc and magnesium are also present, so direct application on arable land is harmful to the environment, which makes our process even more important,” says Ehsan Moslehi, advanced R&D engineer and lead scientist for the project.

Ehsan Moslehi, advanced R&D engineer and lead scientist for the project, and Cristian Tunsu, Lab Manager and Senior R&D Engineer.

The process can specifically extract potassium using water, separating it from phosphorus and heavy metals, which is further concentrated into a solid undissolved fraction. Heavy-metal-free potassium sulphate and chloride salts can then be recovered as directly applicable substances through crystallisation processes.

If phosphorus recovery is also desired, pure phosphate fertilisers can be recovered from the undissolved ash fraction using, for example, EasyMining’s patented Ash2Phos process. This allows for the recovery of high purity calcium phosphate for use as feed or fertiliser, while also obtaining the heavy metals as a separate fraction for safe disposal.
 
“We are currently working on growth tests with recycled fertilisers to validate their effectivity, industrial upscale scenarios, and a life-cycle-assessment of our process, which will be completed in early 2026. That assessment has a focus on the environmental impact of the developed process and comparisons with the virgin production of fertilisers,” concludes Cristian Tunsu.

The project is funded under the strategic innovation program BioInnovation, a joint venture of Vinnova, Formas and The Swedish Energy Agency.

Transitioning from a linear to a circular economy – an approach that applies not only to sustainable potassium, but to all areas of EasyMining’s work.

 

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