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Spinning sewage sludge into fertilizer gold

Technology developed at University of British Columbia turns the effluent from water treatment plants into a high-value phosphorus-based nutrient.

by Tim Lougheed

spinning_sewage
Agricultural crops rely on phosphorus in the soil to flourish.

It’s one of those win-win-win situations that seem almost too good to be true. A University 
of British Columbia spin-off company, Ostara Nutrient Recovery Technologies Inc., has developed a system that recovers phosphorus from municipal wastewater, solving several problems at once.

The wastewater treatment plants no longer have to deal with the steady buildup of phosphorus inside drainage pipes. Nor will nearby waterways be choked with algae fed by high concentrations of this essential nutrient. And the treatment plants are left with a new high-value commodity: a slow-release fertilizer to help farmers treat phosphorus-poor soils.

“This is a very important milestone for Canadian environmental technology,” said UBC civil engineering professor Don Mavinic, whose research team developed the process. “We are probably eight to 10 years ahead of the world with our technology.”

Dr. Mavinic still marvels at the implications of a process he began exploring more than a decade ago. At the time he was simply helping BC Hydro come up with a way of extracting the phosphorus that was building up behind dams. He subsequently discovered that the people who run city water plants were even more interested in this work. Phosphorus in human urine forms a cement-hard mineral called struvite, which builds up inside pipes, necessitating replacement of the pipes on a regular basis.

To Dr. Mavinic, getting rid of struvite meant capturing it before the trouble starts. By 2005, he and his colleagues had developed a process that did just that and licensed it to Ostara for commercialization. The company’s tall, cone-shaped processors precipitate the struvite from wastewater in the form of tiny pellets. The resulting product, dubbed Crystal Green, is sold as fertilizer. Just as importantly, the struvite never sees the inside of a drainage pipe, nor will this phosphorus compound make its way into the wider environment.

Ostara has installed six pilot plants in cities around the world, including a major operation set up in Edmonton in 2007. The Edmonton reactor produces about 500 kg of the Crystal Green product a day, which is bagged on site and ready for commercial sale. The City of Edmonton is planning to build several more of the reactors.

Although Ostara employs only a couple of dozen employees, last fall the firm made the Guardian newspaper’s Global Cleantech 100 list of most promising enterprises. Around the same time, the journal Nature cited the Ostara recovery process in an article highlighting the growing economic and environmental significance of phosphorus.

Dr. Mavinic said inquiries about the Ostara technology are coming in from around the world, especially from places like China, where phosphate pollution is ruining the health of lakes and rivers. The company has opened a U.S. office and added prominent environmental lawyer Robert Kennedy Jr. to its board of directors (the first Ostara reactor in the U.S. was installed at the Durham Treatment Facility in Oregon and others are planned in Pennsylvania and Virginia).

Mr. Kennedy was front-and-centre in Vancouver last May at an international conference that focused on nutrient recovery from wastewater. Dr. Mavinic said foreign engineers and government officials who attended assured him that Ostara’s technology was superior to anything else available. They also stressed the importance of finding new sources of phosphorus.

Along with nitrogen and potassium, phosphorus is essential to plant growth and is an agricultural cornerstone. However, while nitrogen and potassium remain relatively abundant, good sources of phosphorus are getting harder to find. “In the last year or so, I’ve realized just how scarce a resource this is in the global market,” said Dr. Mavinic.

Fertilizer manufacturers typically obtain phosphorus from strip mining. North America has only a handful of viable sites, with the result that a growing proportion of the phosphorus we use comes from elsewhere. China, which has substantial reserves, recently raised the export tax on this material by more than 100 percent.

In Europe, meanwhile, governments are increasingly eager to recycle what they already use. By 2015, for example, Sweden’s Environmental Protection Agency expects to recover 60 percent of the phosphorus found in that country’s sewage sludge. Such goals make Ostara’s technology highly attractive, said Dr. Mavinic.

Paul Voroney, a soil researcher with the University of Guelph’s department of land resource science, is unsure whether the world is heading toward drastic changes in the price and availability of phosphorus. Regardless, he noted that soils in many parts of Canada are actually suffering from a surplus of phosphorus, and he therefore applauds any effort to reduce the amount of this material that makes its way into the local environment.

In a further twist, some streams in B.C. are lacking phosphorus due to the decline in salmon stocks. When the salmon die, they add phosphorus and other nutrients to the water. The B.C. Conservation Foundation is now using Crystal Green pellets to replace the nutrient value of the missing salmon carcasses.

This brings Dr. Mavinic’s work full circle, since the reason BC Hydro first approached him all those years ago was because the company was concerned that their dams were causing the rivers downstream to become nutrient-poor and were looking at ways to extract the phosphorus in a convenient form from behind the dams to reseed these waterways.

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