As production of biofuels increase to counter dependence on foreign oil and high fuel prices, some scientists worry that the world's phosphorus supply will slowly diminish, limiting our ability to grow crops and forcing fertilizer prices through the roof.
Phosphorous is essential to plant growth. Mined out of phosphate rocks, it is one of the three critical elements found in fertilizer along with potassium and nitrogen.
"From our country's deposits, we could run out in 50 to 100 years, which isn't very long," said Jessica Davis, professor of soil and crop sciences at Colorado State University. "I think that people aren't really aware of it."
Land resources in the U.S. are capable of producing a sustainable supply of 1.3 billion tons per year of biomass, or energy from natural sources such as wood, according to the Renewable Fuels Association, using a significant amount of phosphorous.
Dan Bush, professor and chair in the biology department at CSU, agrees we could eventually deplete our supply of phosphorous but biofuels will not be the only cause, he said. Farming will also contribute to the decline, Bush wrote in an e-mail to the Coloradoan.
"In all farming, for food or fuel, some nutrients are removed with the harvested material," Bush wrote. "Over time, any given required nutrient can become limiting as it moves out of the field with the harvested tissue."
Phosphorous is mined throughout the world including in the United States in Florida, North Carolina, Idaho, Montana and Utah, according to the U.S. Geological Survey.
In 2007, the United States produced 29 million tons of phosphates, down from 30 million tons in 2006 and 36 million tons in 2005, according to the USGS.
While phosphorus goes through a natural cycle back into the earth through plants and cattle excretions, phosphorus is declining in the United States. The country will then have to obtain its supply from North Africa, according to the USGS.
Some say farmers are already seeing an increase in fertilizer prices.
"Fertilizer prices are astronomically high," said Ernie Marx, extension agent for agriculture and natural resources at the Larimer County and CSU extension office.
Marx, however, said that could be contributing to several things including high oil prices and natural gas prices which are needed, in part, to produce fertilizer.
"What we hear is that there is a shortage of sulfuric and phosphoric acid," said Ed Race, operations manager at Poudre Valley Coop Association Inc., which provides fertilizer in bulk.
Bob Kraft, owner of Kraft Livestock LLC, a farm and ranch north of Fort Collins, said he has seen phosphorous prices jump in the last several years as well, paying approximately $1,100 a ton for phosphorus this year.
"Prices keep going up but we aren't getting that much more for our product," he said.
Michael Massey, a graduate student at CSU, extracted phosphorous from dairy cattle wastewater and then used it to fertilize greenhouse plants. Cattle release phosphorous in their waste from consumption of food.
Methods, like Massey's, of obtaining used phosphorous may be important as raw phosphorous depletes.
"I think recovery is going to play an increasingly important role," Massey said.
Bush also said that as scientists switch to cellulosic biofuels - which use the woody tissue of a plant rather than the seed - instead of just corn ethanol, biofuel crops tend to replenish phosphorous in the earth.
"For cellulosic crops like perennial grasses, fewer nutrients are removed because many are recycled into the below ground tissue at the end of the season before harvest," Bush said. "The bottom line: Many factors will have to be addressed as new energy crops take on a major presence in agriculture."