Winnipeg-University of Manitoba researchers are working on a process to extract a granular form of phosphorous fertilizer from livestock manure. “We haven’t invented anything new, but are trying to put existing technologies together so this process will be so cheap everyone will do it because it saves them money on fertilizer,” lead investigator Joe Ackerman told Green Markets. Ackerman said that dissolved phosphorous will precipitate out of solution when magnesium is added to liquid manure. Struvite crystals are formed when the alkalinity is raised from pH 7 to pH 8.5 and allowed to settle overnight. Ackerman said that so far the effort is a pilot-scale project, with two 100 gallon plastic tanks installed at a hog farm. “Our system has been successful in removing 70 percent of total phosphate from the lagoon liquid and produces a settled sludge that can be dried.” He said analysis of the dried sludge reveals it is approximately 30 percent struvite, 20 percent calcium phosphate, and 50 percent organic solids. There will be agronomic studies of nutrient availability undertaken this summer. Struvite is a slow-release fertilizer because it is less soluble than ammonium phosphate, and a market is developing from golf courses and horticulture. Wastewater treatment struvite systems produce nearly pure struvite, but those systems are prohibitively expensive for farm application. They cost several million dollars and require influent with low suspended solids.
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