Extracting struvite-K from fly ash to make fertilizer

struvite-K

Phosphorus is an essential compound for agriculture fertilizers and thereby most of the food we consume. But the phosphorus mines are running low and becoming increasingly polluted by cadmium, which can lead to kidney failures when consumed by humans.

A new study from DTU Chemical Engineering has shown how struvite-K, a phosphate mineral, can be extracted from otherwise polluted fly ash and thereby paving the way for reusing the mineral as a fertilizer.

Phosphorus production has been predicted to reach its high in 2069 and according to the main architect behind the study and Associate Professor at KT, Kaj Thomsen, we need to start the recycling of phosphorus if we want to keep on producing food.

“The phosphorus we import from Morocco, China and the US is getting more and more cadmium infected, but with this approach we can produce our own clean product,” he says.

Struvite, a mineral similar to struvite-K, is already being produced at three different plants around Denmark. They account for a production of 350 tons of struvite. Denmark annually imports around 14.000 tons of phosphorus, but according to the study we could reduce the import with 3000 tons per year by setting up more struvite plants.

Countries like Germany and the Netherlands are already far ahead of Denmark in terms of struvite production. In the Netherlands lots of plants are now producing struvite, the biggest of them producing 1000 tons per year.

According to Kaj Thomsen though, we don’t even need to look further than Sweden for inspiration.

Sweden has put a tax on cadmium. That makes it a lot easier to produce clean phosphorus rather than importing polluted phosphorus,” he says.

Even though the results of the study are promising more research still needs to be done on the area before integrating struvite-K as an agricultural fertilizer.

The study was done by Kaj Thomsen, Anders Lodberg, Mujeeb Ur Rehman and Umar Fayyaz – all from DTU Chemical Engineering.