Published by the Natural Resources Defense Council (NRDC) Support Us

Sign Up for Our Newsletter


A Hidden Cost of Farming

VIEW FROM 800 FEET Waste fills an impoundment at a Lakeland, Florida, phosphate mine.

When Don Mavinic looks at cow manure he sees a puzzle in need of a solution. There's phosphorus locked in there, and the world is desperate for it.

Mavinic is a professor of civil engineering at the University of British Columbia in Vancouver, and he knows that there are three essential nutrients on which all plant life is based: nitrogen, potassium, and phosphorus. The problem is that phosphate rock, the ore from which the mineral is extracted, is in finite supply. Over the past several years, scientists, government officials, and corporations have begun to worry about what will happen when the rock runs out. Though the immediacy of the problem is subject to debate, the need for long-term solutions is indisputable. Mavinic believes that cow pies are the future.

"You talk about peak oil, but I don't have any sympathy for that. Oil is just another form of energy that can be substituted," Mavinic says. "You can't live without phosphorus. Anything that grows needs it."

In the 1960s and 1970s, the use of chemical fertilizers skyrocketed. New, specialized breeds of grain responded well to extra fertilizer and helped to usher in an age of abundance known as the green revolution. Today more than 99 percent of America's farmland is treated with chemical fertilizers, most of which contain phosphorus. The United Nations projects that to feed at least another two billion humans -- the number by which the world's population is expected to increase by 2050 -- global food production must increase by 70 percent, and that will require the extraction of as much as twice the amount of phosphate mined today, an amount that already tops 160 million metric tons a year.

In 2009, Dana Cordell, a researcher at the University of Technology in Sydney, Australia, published a paper in the journal Global Environmental Change arguing that the world's phosphate reserves would run out within 100 years. Later that year, the prestigious British journal Nature published a report entitled "The Disappearing Nutrient," and the United Nations convened a working group to begin to address phosphate depletion. Others argue that the world has 300 years left, but few question that most of the United States' phosphate mines will be much shorter lived.

"Basically, you're looking at about 25 to 30 years of good mining left," says Stephen Jasinski, a mineral commodity specialist at the United States Geological Survey.

The majority of the phosphate deposits in the United States are found in Florida, North Carolina, and Idaho. In Florida, the state with the largest reserves, uranium and radium occur naturally alongside phosphorus, and for every pound of phosphate extracted, five pounds of a radioactive byproduct called phosphogypsum are left behind. In the Bone Valley, enormous white hills made of more than a billion tons of phosphogypsum tower over central Florida's flatlands. Similar mounds of waste are heaped near processing sites around the world, and they grow at a rate of 110 million metric tons a year.

As supplies dwindle and demand increases, it becomes more economically viable to import higher-quality rock from overseas. China and Morocco control more than half of the world's phosphate reserves, and the United States has signed a free-trade agreement with Morocco to secure phosphate supplies for the future.

"The common phrase is that Morocco is the 'Saudi Arabia of phosphorus,' " says David Vaccari, director of the Department of Civil, Environmental and Ocean Engineering at Stevens Institute of Technology in Hoboken, New Jersey. "Our whole addiction to Middle Eastern oil is going to be replicated in this situation. We shouldn't be exploiting phosphorus with abandon; we should be thinking about and planning to make its use sustainable."

Eighty percent of the phosphorus mined is lost to erosion and runoff before it can be absorbed by plants and, ultimately, humans by way of our dinner plates. Farmers are beginning to rein in the overuse of fertilizer, and Mavinic, among others, is looking for ways to intercept the nutrient before it runs into the world's rivers and oceans -- by capturing it from human and animal waste.

Plants need phosphorus to grow; people and animals eat plants. As a result, their waste is filled with the nutrient. Mavinic has already developed a technology that recycles 85 percent of the phosphorus from liquid sewage and turns it into seed-size crystals that can be used as a fertilizer. Ostara, a Canadian company formed to market the technology, has already installed its third phosphorus recycling system in a Suffolk, Virginia, sewage plant that feeds into the James River, a tributary of the Chesapeake Bay.

One cow expels as many nutrients as 15 to 20 people, which is why Mavinic is taking his technology to livestock farms. All the wastewater treatment plants in the United States might supply one million metric tons of recycled phosphorus in a given year, but farms could supply five million tons. Consider that we currently use 22 million tons of phosphorus a year, and recycling programs start to look pretty appealing.

At his high-tech cow farm near the northern edge of the Cascade Mountains, Mavinic and his students have built a pilot plant that uses microwaves to break down waste from the feedlot in order to retrieve its valuable elements. Mavinic calls it his "sludge buster" and envisions a future in which farms around the world process their animal manure in plants like this one and use the crystal end-product as fertilizer.

"Phosphorus is sustainable forever as long as we have humans and pigs and cows running around, eating and producing waste," says Mavinic. "If you compare that to the phosphate rock reserves of the world that are disappearing, you say 'Jeez, this is not a bad alternative.' "

image of Daniel Grushkin
Daniel Grushkin is a freelance writer who covers science and the environment. His articles have appeared in The New York Times, Businessweek, National Geographic Adventure, Popular Science, and Scientific American. He is also a co-founder of Genspace... READ MORE >
I'm all for recycling bovine phosphorous (and human for that matter). But I wouldn't dismiss Peak Oil too lightly. There's an awful lot of oil in a pound of beef by the time it gets to your plate. All energy substitutes for oil are more expensive (coal, gas) or too diffuse to run intensive rearing operations with microwave poo ovens attached. Ergo, peak oil means less beef, means less recycled bovine phosphorous in the long run. Good luck all the same.
"Oil is just another form of energy that can be substituted," Mavinic says. I'm sad to say this fellow civil engineer fails to connect the dots in this grossly simplified statement. He dismisses rates of extraction and diminishing rates of return over time that outpace our technological ability to replace shortages in pace with accelerating shortages. He should have been an economist. Mining phosphorus from cow manure?! Sounds like we're finding the most profitable way to work our way back to the age of composting. Or shall we say new age?
"Once plants and animals were raised together on the same farm — which therefore neither produced unmanageable surpluses of manure, to be wasted and to pollute the water supply, nor depended on such quantities of commercial fertilizer. The genius of America farm experts is very well demonstrated here: they can take a solution and divide it neatly into two problems." Wendell Berry, The Unsettling of America : Culture & Agriculture (1996), p. 62 Yes the feed lot manure is a potential resource, but this is an expensive way to solve the problem. The real solution lies in integrating animals and their feed - creating smaller nutrient cycles. Larger cycles take more (potentially scarce) energy to close, a problem Mavinic chooses to ignore. A system is sustainable only if it captures more energy than it takes to maintain and replace it. The feed lots that he depends on will eventually fold since they are an unsustainable arrangement: modern agriculture takes 10 units of energy to produce 1 unit of food energy. In the medium term, using biodigestors to extract the energy in the manure and then shipping the concentrated waste may be a more economic way of recovering the lost nutrients. Another possibility is running the waste through marshes of Typha, fermenting the starch into alcohol fuel and using the leftover mash as fertiliser. Other improvements include preventing erosion with water harvesting earth works and dynamic accumulator plants, catching wild sources of minerals (wind blown, bird droppings, bedrock), and improving soil quality. Everyone should source their own vegetables and greens locally, compost their waste and return it to the soil. Superphosphate needs to be eradicated - it acidifies soil and necessitates the use of herbicides, pesticides and fungicides which damage the soil life, the wider ecosystem and pollute water catchments. Use Permaculture for the design of appropriate solutions. Be cautious of high technology solutions.
Would like to know more about marshes of Typha. Haven't come across it before. How/ when is it harvested? What climate suits it?
Typha Latifolia (known as cattails in the US) is a universal species - it grows almost everywhere, including arid climates. It thrives in shallow water or boggy areas and is commonly used in reedbed treatment of sewage and waste water. Its lightly anchored starchy roots are probably best harvested (not sure exactly how - I'm sure a mechanical solution could be developed) at the end of the growing season, but the leaves could be cut a few times per year. The plant spreads by rhizomes, as well as by its prolific seed. "Matching up a cattail system located alongside an animal feeding operation or dairy, with alcohol production - where both the stillage and manure are cycled through the marsh - might make for a very dynamic, productive system." Alcohol expert David Blume (