“Life can multiply until all the phosphorus is gone, and then there is an inexorable halt which nothing can prevent. We may be able to substitute nuclear power for coal, plastics for wood, yeast for meat, and friendliness for isolation—but for phosphorus there is neither substitute nor replacement.”
The Greeks called phosphorus “the bearer of light,” a chalky white mineral that ignites spontaneously and gives pizazz to matchsticks and fireworks. Theories suggest it even arrived on Earth in a fiery meteorite crash billions of years ago.
The fifteenth element could also be called the bearer of life. Wound into DNA and RNA, phosphorus forms the backbone of our genetic material and provides cellular energy as adenosine triphosphate or ATP. It also makes up the fertilizer that provides global food security.
But phosphorus supplies are shrinking.
Eighty-five percent of the world’s readily available reserves are located in Morocco where, with conflict and political strife, it is mined from phosphate rock and auctioned to an ever more competitive market.
Although phosphorus can’t be manufactured or synthesized, it can be recovered and recycled. New technologies have emerged to help salvage the precious mineral—including a portable “struvite machine” at the Washington State University Puyallup Research and Extension Center.
The nutrient recovery system, as it’s formally known, transforms cow manure into a dry, sand-like fertilizer called struvite, composed of magnesium, ammonium, and phosphate. It was developed by WSU professor of animal science Joe Harrison together with research associate Liz Whitefield ’07 MS and Keith Bowers of Multiform Harvest.
The idea hinges on the fact that animals and humans excrete nearly all of the phosphorus they take in as food. Traditionally, phosphate-rich manure and human waste were returned to the soil as fertilizer. Not so much today.
“Seventy percent of the phosphorus dairy cows consume stays on the farm as phosphate in feces and urine,” says Harrison. “Only about 27 percent leaves the farm in milk cartons.”
Washington dairies often spread that manure in fields where the phosphate accumulates over time. Harrison says they want to lower the buildup and bring the farms back into “phosphorus balance.” With the mobile recovery unit, excess phosphorus can be extracted from manure on any of the 400 dairy farms across the state. The resulting struvite can then be used as fertilizer or sold to other farms.
Harrison first learned of the concept from a poster at a national manure conference. Bowers, an engineer, had invented the method as a way to recover phosphate from swine feces.
When Bowers later moved to Seattle, he and Harrison formed a partnership that eventually led to the debut of the portable struvite machine. Bowers also went on to found Multiform Harvest, a company that recovers phosphorus from municipal wastewater plants.
Harrison says the struvite they create is dry and coarse like sand, and very user-friendly compared to the wet slurry products produced by earlier techniques.
In essence, manure from a dairy lagoon is pumped into their cone-shaped machine and mixed with chemicals that precipitate struvite at the bottom. Excess liquid runs out the top and back into the lagoon.
“The material we capture is a good source of fertilizer,” he says. “It’s easily transported and it gets the buildup off the farms.
“It’s also environmentally friendly. You can actually put seeds right into the soil with struvite with no burning effect.”
Hoping to balance the phosphorus cycle on an even wider scale, Harrison is now working with forage growers in eastern Washington.
He says while phosphate accumulates on dairy farms west of the Cascades, it is simultaneously being depleted in hayfields east of the mountains. Nutrient-rich alfalfa and timothy hay grown in the Columbia Basin, for example, is regularly shipped to western Washington to feed dairy cows.
“Seventy percent of the phosphorus that was in the hay stays on dairy farms,” Harrison says. “So, let’s capture it as struvite, put it in super sacks, and let the empty hay trucks carry it back to eastern Washington.”