Tucked away in Oregon’s Willamette Valley, three massive metal cones could help address the world’s dwindling supply of phosphorus, the crucial ingredient of fertilizers that has made modern agriculture possible. The cones make consistently high-quality, slow-release fertilizer pellets from phosphorus recovered at the Durham Advance Wastewater Treatment Facility, less than 10 miles from downtown Portland. By generating about one ton of pellets every day, they are changing the view that such recycling could not be done efficiently. Ostara, the firm that makes the reactors and sells the pellets as Crystal Green, thinks that Durham is one of hundreds of facilities that could use the technology.

Humans excrete some 3.3 million tons of phosphorus annually. In fact, phosphorus from domestic sewage, in addition to fertilizer runoff, has traditionally been a nuisance, because it triggers blooms of algae that deplete local waters of oxygen. In some wastewater plants the element can also bind with ammonia and magnesium to form a mineral called struvite, which keeps phosphorus out of waterways but clogs pipes at the facilities. The growing recognition that cheap supplies of phosphorus will grow scarce in the coming decades has led some nations to consider conservation. Sweden has mandated that 60 percent of phosphate be recycled from wastewater by 2015. In 2008 China slapped a 135 percent export tariff on phosphate.

These pressures have made struvite a hot topic in sewage circles. Japan has been recycling struvite for a decade, but the cost-effectiveness and quality of the pellets varied, according to Don Mavinic, professor of civil engineering at the University of British Columbia (U.B.C.) and co-inventor of Ostara’s technology. “There’s always been a problem of struvite removal,” Mavinic says. “I wanted to build a better mousetrap.”

To take up phosphates and nitrogen, many sewage facilities use bacteria, which settle down after ingesting the nutrients and are ultimately removed with the sludge. But dying bacteria rupture and release a little of the phosphate back into the wastewater, potentially leading to struvites.

Mavinic got interested in the struvite problem because of the maintenance issue at the plants, but ultimately a grant to find local nutrient sources jump-started the work. U.B.C.’s “mousetrap” pumps treated effluent and magnesium chloride into a 24-foot-tall reactor, where the cone shape acts to create essentially a turbulent thundercloud, tossing around the particles until they form pellets. Mavinic is now fine-tuning the system so that reactors can be sized to make a specific pellet grade for local industries.

In Oregon interest comes primarily from nurseries, where farmers have traditionally bought polymer-coated slow-release fertilizer. Wilco, a farmer-owned co-op about 30 miles from the Durham plant, has been selling Crystal Green since the reactors went online in May. “Having a local source of high-quality slow-release sustainable fertilizer is a great thing,” says Jeff Freeman, a regional sales manager at Wilco. “It’s something our customers are looking for, and the product has performed outstandingly.”

Because of the demand for such fertilizer, the estimated payback of the investment is about five years. Mark Poling, wastewater treatment director at Durham, says it could be faster, because the reactors are functioning better than expected.

The company has sent prototype reactors to wastewater plants in Israel, the U.K. and various cities in the U.S. Shanghai was expected to get a delivery this fall. But Ostara says it is looking to corner the U.S. market first, where the Environmental Protection Agency has been pushing states to more heavily regulate nutrient pollution, including phosphate in sewage effluent.

Wastewater represents a ripe, but small, low-hanging fruit for phosphate recycling, according to experts. It holds only a small fraction of recoverable phosphate, and not all facilities create struvite. “Unfortunately, the phosphorus in human waste is only about 10 percent” of mined phosphate rock, explains David A. Vaccari, director of civil, environmental and ocean engineering at the Stevens Institute of Technology. “Even if you got 8 percent, it would be one piece of the puzzle. And it’s one part we should do, but it’s only a slim fraction of what we need.”

4 Comments

1. 1. RZ0001 10:10 AM 11/3/09

   It is understood that an in-depth analysis of sidebar issues is not practial in a short article like this; but, one major issue should at least be mentioned:
   
   With massive concern and proof that synthetic hormones and pharmaceuticals are not being filtered out by current wastewater treatment plants, is this fantastic solution for phosphorus recovery making this problem worse?
   
   Are we spreading MORE of these problem "contaminants" onto our food-growing fields in addition to dumping them in our streams and waterways? Will this strategy be dumping anitbiotics onto our soil and worsening the super bug problems?
   
   A brief follow-up woul dbe helpful.

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2. 2. eco-steve 07:33 PM 11/11/09

   RZ0001 : The solution is as simple was the treatment of the hole in the ozone layer : BAN hormones in agriculture! All they do anyway is to increase the ammount of water in meat, which is why they are illegal in Europe. Also ban the systematic use of antibiotics in farms. The Swiss banned the use of phosphorous in detergents years ago to preserve Lake Geneva which was becoming badly polluted.

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3. 3. jhboettcher 01:24 AM 11/24/09

   Phosphorus (P) is an important nutrient for the productivity of grass, crops and farm animals. It is brought onto the farm either through chemical fertiliser or feedstuffs.
   On a typical 100-dairy cow farm the amount brought on to the farm would equate to approximately 2 tonnes of P per year. However, only 40 percent of this P leaves the farm in produce such as milk, calves and cull cows. This difference between the output and input can be treated as a surplus. The highest surpluses are found on intensive and highly stocked farms with high P fertiliser usage and high levels of concentrates fed. So what happens to this surplus P?
   Accumulation in soil
   P is accumulating in soils. The build up of P in soils is evident from soil analysis results over the last 50 years. Soils have changed from being predominantly deficient to predominantly excessive in P.
   Leached to drainage water
   P is held tightly by the soil. However, as soil P levels increase an increasing amount of P is lost in drainage water. The level of leaching is small at approximately 1 KG P/ha/yr, but nevertheless highly significant in terms of nutrient enrichment of water.
   Direct run-off
   A significant amount of P can also be lost directly to watercourses from farms with poor waste management practices. The most common sources of problems are leaking and overflowing tanks, dairy and parlour washings, and run-off from dirty yards. Run-off from fields following applications of slurry can also lead to significant loss of nutrients including P. Research shows that the risk of contamination of drainage water occurs not just in the days immediately after slurry is applied but continues for a number of weeks afterwards, if water is flowing in the drains.
   Addressing the imbalance
   In Northern Ireland there is a surplus of approximately 10,000 tonnes of P brought on to farms every year. This surplus will be reduced by the voluntary step taken by the feed industry to reduce the level of P in ruminant concentrates, and the recently introduced Phosphorus Regulations. These Regulations require that farmers must not apply any chemical fertiliser containing P unless there is a requirement. This can only be established through a soil test. Applying fertilisers at the correct amount and at a time when conditions allow uptake of nutrients will lead to greater nutrient efficiency and greater financial benefit. If you find low P levels in some fields you need to ask yourself  where has this P gone?

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4. 4. jhboettcher 01:43 AM 11/24/09

   Agricultural use does not lessen the problem of eutrophication, as most of the excess Phosphorus (P) and Nitrogen (N) is from excessive agricultural application of fertilizers. Mostly for the production of animal feeds for factory farms, e.g. beef and pork feedlots, and chicken farms.
   At least the city sewage is being treated, unlike the agricultural runoff from badly managed farms and feedlots.
   
   "On a typical 100-dairy cow farm the amount of P brought on to the farm would equate to approximately 2 tons of P per year. However, only 40 percent of this P leaves the farm in produce such as milk, calves and cull cows. This difference between the output and input can be treated as a surplus. The highest surpluses are found on intensive and highly stocked farms with high P fertilizer usage and high levels of concentrates fed. So what happens to this surplus P?
   1.Accumulation in soil:
   The build up of P in soils is evident from soil analysis results over the last 50 years. Soils have changed from being predominantly deficient to predominantly excessive in P.
   2.Leached to drainage water:
   P is held tightly by the soil. However, as soil P levels increase an increasing amount of P is lost in drainage water. The level of leaching is small at approximately 1 KG P/ha/yr, but nevertheless highly significant in terms of nutrient enrichment of water.
   3.Direct run-off:
   A significant amount of P can also be lost directly to watercourses from farms with poor waste management practices. The most common sources of problems are leaking and overflowing tanks, dairy and parlour washings, and run-off from dirty yards. "
   

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