Scientists testing sustainable P reclaimed from waste
Phosphorous recycled from human and animal waste for plant fertilizer could ease demand for the dwindling, increasingly expensive rock-mined element.
Scientists at Washington State University have found plants flourish with struvite, a material in waste composed of magnesium, nitrogen and phosphorous. Teamed with Multiform Harvest, a Seattle phosphorous recovery company, the researchers are fine-tuning the application and amounts of fertilizer in hopes of marketing a product and benefiting the world’s food supply.
"You can’t continue mining a finite resource forever,” said Rita Hummel, a scientist at the WSU Puyallup Research and Extension Center. "But as long as we … can reclaim struvite from animal manure and sewage, then this is something that’s sustainable.
We’re figuring out how to use it effectively and safely.”
Benefits to local economy, water quality
Hummel is using Multiform Harvest struvite from wastewater treatment plants at Yakima, Wash., and Boise, Idaho. In addition, struvite from manure at dairy farms could result in development of regional nutrient recycling.
"When you feed a cow, about 20 to 25 percent of the phosphorous the cow eats ends up in the milk carton,” said Joe Harrison, Hummel’s scientist colleague at WSU. "That means about 70 to 85 percent doesn’t end up in the milk carton and ends up in the manure.”
Not only could reclaiming struvite from waste localize production and distribution, but it could also help mitigate water pollution problems such as overloading phosphorous in agricultural soils.
"The research being performed at WSU is central to us generating the hard data we must have to get this recycled phosphorus into the agricultural market, from large fields to specialized greenhouses and nurseries,” said Kevin Fullerton, product developer for Multiform Harvest.
In previous greenhouse crop studies, Hummel discovered she could grow plants with struvite just as well as with the commercial phosphorous source, triple superphosphate. Crops like basil, cucumber, marigold and tomatoes barely sprouted without phosphorous, but flourished with struvite from King County municipal wastewater.
With support from a U.S. Department of Agriculture small business innovation research grant, she will experiment with different rates and ways of applying the struvite—adding it to the potting mix, sprinkling it on the surface or placing it beneath the plant—and looking at how quickly it is released.
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