Phosphorus is a vital element not only for plants but also for all living organisms. In recent times, however, farmers have been faced with a growing shortage of this essential mineral, and the price of phosphate-based fertilizers has been steadily increasing. It is therefore high time to start looking for alternatives. This is not an easy task, because phosphorus cannot be replaced by any other substance. But researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have found a solution that makes use of locally available resources which, as unlikely as it might seem, are to be found in plentiful supply in the wastewater from sewage treatment plants and in the fermentation residues from biogas plants: a perfect example of the old saying "from muck to riches". The new process was developed by a team of scientists led by Jennifer Bilbao, who manages the nutrient management research group at the IGB. "Our process precipitates out the nutrients in a form that enables them to be directly applied as fertilizer," she explains.
Mobile pilot plant for field tests
The main feature of the patented process, which is currently being tested in a mobile pilot plant, is an electrochemical process that precipitates magnesium-ammonium phosphate also known as struvite by means of electrolysis from a solution containing nitrogen and phosphorus. Struvite is precipitated from the process water in the form of tiny crystals that can be used directly as fertilizer, without any further processing. The innovative aspect of this method is that, unlike conventional processes, it does not require the addition of synthetic salts or bases. Bilbao: "It is an entirely chemical-free process."
The 2-meter-high electrolytic cell that forms the centerpiece of the test installation and through which the wastewater is directed contains a sacrificial magnesium anode and a metallic cathode. The electrolytic process s
|Contact: Jennifer Bilbao |