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Feature Troublesome nutrients become life-giving fertilizer. Further Out: Electrochemical Nutrient Recovery Although the above technologies are state of the art, science is already working on new and potentially better ways to recover phosphorus and nitrogen to make fertilizer. Current practices require the addition of magnesium — magnesium chloride (MgCl2), magnesium hydroxide (Mg(OH)2), or magnesium oxide (MgO) — as the limiting reagent to successfully recover struvite. Another requirement for struvite is a pH in the range of 8.5 to 9.5, which is typically achieved by adding sodium hydroxide (NaOH). In Stuttgart, Germany, however, at the Fraunhofer Institute for Interfacial Engineering and Biotechnology, a new process has been patented that makes struvite without adding magnesium or sodium hydroxide. Not only does the process save money by not using chemical salts, but also energy consumption is extremely low at just 70Wh/m3 of wastewater. An electrolytic cell consisting of an inert cathode and sacrificial magnesium anode is the catalyst for operation. Water cleavage splits the water at the cathode and forms hydrogen and hydroxide ions, causing an increase of pH in the wastewater that remains constant at a value of nine — in the sweet spot for struvite recovery. Oxidation takes place on PREDICTING PEAK PHOSPHORUS — AND POTENTIAL CATASTROPHE Maintaining an adequate phosphorus supply is a are likely to increase," creating an "inherently matter of life and death, and some parties, many unstable" environment.2 academics among them, are calling for swift action Because phosphate rock is nonrenewable, to avoid global turmoil. The Sustainable Phosphorus formed only through the course of millions of years, Initiative, for example, was founded by scientists the point of "peak phosphorus" — when demand at Arizona State University's Global Institute of surpasses production, whether by sheer use or Sustainability precisely to create awareness and helped along by political factors — could trigger develop solutions for phosphorus scarcity. starvation and wars. Some studies speculate that The problem for those eyeing a shortage is that peak phosphorus will hit before midcentury, due to the world is completely dependent on phosphorus the demand of developing countries and "richer" for its food supply — it being a diets of meat and dairy products limiting factor for crop growth that require up to three times the (i.e. without it, crops won't grow). phosphorus of vegetarian diets. Unfortunately, the vast majority of With European countries lacking the world's phosphate rock is found significant phosphate rock reserves, in just a few countries. Morocco and The Hague is at least monitoring the the Western Sahara region of Africa, situation. according to a 2012 report from The On the other hand, the International Hague Centre for Strategic Studies Fertilizer Development Center (IFDC) (HCSS), are the sites of nearly issued a report in 2010 stating that Phosphate rock two-thirds of all known reserves, peak phosphorus will be stalled for followed by (in order, and in much several centuries.3 The International Fertilizer Industry Association (IFA) smaller percentages) Iraq, China, Algeria, Syria, Jordan, South Africa, the U.S., and supports the IFDC's conclusion and points out Russia. The report notes that 80 percent of global that, unlike phosphate rock, phosphorus itself is a exports come from Middle Eastern and North renewable resource that can — and therefore should African countries and that "political turmoil and — be reused within economic and technical limits.4 social unrest in phosphate rock producer countries On this particular point, all parties agree. 10 wateronline.com ■ Water Online The Magazine