Closing the phosphorus loop

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Like a fickle god, phosphorus gives life and takes it away. If too much leaches into lakes and streams, algal blooms suck oxygen from the water and choke off life.

But if too little exists, we are all in trouble: Phosphorus is a dwindling, and non-renewable, component of agricultural fertilizers, essential to growing food for Earth's burgeoning population, says the International Institute for Sustainable Development, a Winnipeg-based environmental think tank, which recently released a report on phosphorus spills in Manitoba's waterways.

(The problem in Lake Winnipeg is so severe that the green-blue algae can be seen from space.)

In a race against time (some experts cite 30 years, some 100, until the resource runs out), scientists are scrambling to recapture phosphorus. "So, we convert a problem into a product," says Fred Koch, a researcher at the University of British Columbia.

Mr. Koch is a research associate of Don Mavinic, a UBC civil engineer who has designed a system that removes phosphorus from liquid sewage at wastewater-treatment plants and turns it into slow-release fertilizer pellets.

Their system capitalizes on the fact that humans expel about three million tonnes of valuable phosphorus a year, which, along with fertilizer runoff, often ends up in local waterways. "We prevent the pollution and we ship fertilizer into a marketplace that will literally be starving for phosphorus," Mr. Koch says.

"Clean phosphorus reserves are rapidly being depleted and there are no new reserves being found by the mining sector," Mr. Mavinic says.

While there is scientific debate over when we will see a shortage, researchers at the University of Technology in Australia and Linköping University in Sweden say we may have mined all the easily accessible, high-quality phosphate rock in as few as 30 years. By then, the United Nations estimates, there will be two billion more of us, clamouring to be fed. The implications are daunting. While there are alternatives to other finite resources such as oil in the form of renewable energy, there are no current substitutes for phosphorus.

Mr. Koch's and Mr. Mavinic's system of two-storey metal cone reactors was designed to deal with struvite, a byproduct of biological wastewater treatment that clogs pipes and valves and must be regularly removed at great cost. Struvite is a concrete-like substance made up of phosphate, magnesium and ammonium.

The invention takes struvite from the wastewater in its soluble state, before it can harden on pipe walls. The soluble struvite is then forced into giant metal cones, where it mixes until it hardens and forms phosphorus-based fertilizer pellets.

Ostara Nutrient Recovery Technologies, the Vancouver-based company created to commercialize the invention, built cone reactors at an Edmonton wastewater-treatment plant in 2007 - the first large-scale demonstration of the technology. Last summer, the first commercial system came online in Portland, Ore.

Oregon farmers are buying the pellets, and say they are happy to find high-quality fertilizer at a time when supplies are becoming uncertain and prices volatile.

Ostara estimates there are 200 plants across North America, and several hundred in Europe and the rest of the world, that are candidates for the technology. Two new struvite reactors are coming online early this year - one in Chesapeake Bay, Va., the other in York, Pa.

While there are a limited number of struvite-recovery operations in other countries - Japan leads the way - most have so far yielded pellets of uneven quality, Mr. Koch says.

Meanwhile, Ostara says its technology has passed performance tests in industrial wastewater-treatments plants, including corn-ethanol production plants. And Mr. Mavinic is now working with colleagues at UBC's Dairy Education and Research Centre on retrieving phosphorus from cow manure, which is an even richer source of this essential element.

"Globally, we have no choice but to implement phosphorus removal and recovery from wastewater-treatment plants. Otherwise, we cannot grow enough food to feed all those people, or raise cows and hogs," Mr. Mavinic says.