November 30, 2010

Human Excrement Could Help With Global Food Security

A new report released Monday by Britain's largest organic certification body finds that the world's supply of phosphate rock is running out faster than previously believed, posing a threat to global food security.

"Intensive agriculture is totally dependent on phosphate for the fertility needed to grow crops and grass," said the Soil Association.

The global supply of phosphorus from mined phosphate rock could peak as early as 2033, after which it will become increasingly costly and scarce, the report said.

However, human excreta could play a vital role in helping to prevent a plunge in crop yields due to a shortage of phosphorus inputs, the report's authors wrote.

"It is estimated that only 10 percent of the three million metric tons of phosphorus excreted by the global human population each year are returned to agricultural soils," the Soil Association said.

An adequate supply of phosphorous is critical for seed formation, root development and the maturing of crops.

"Worldwide, 158 million tons of phosphate rock is mined every year, but the supply is finite," the organic body said.

"This critical issue is missing from the global policy agenda. Without fertilization from phosphorus it has been estimated that wheat yields could more than halve in coming decades, falling from nine tons a hectare to four tons."

"We are completely unprepared to deal with the shortage of phosphorus inputs, the drop in production and the hike in food prices that will follow."

Phosphorus has historically been returned to agricultural land in Europe through the application of animal manure and human excreta.  However, that practice changed during the mid nineteenth century, and was replaced by phosphate mined in distant places.

The report urged European Union regulators to make changes to allow the use of treated sewage sludge, known as biosolids, on organic certified land. 

EU regulations currently prohibit the use of biosolids on organic land out of concern about the toxic effects of heavy metals caused by combining human excreta with other waste products, such as industrial effluent. 

However, appropriate restrictions on concentrations of heavy metals could be incorporated into any new regulations, the Soil Association said.

"Heavy metal levels have declined in recent years and are now low enough for the organic movement to re-consider allowing treated sewage sludge to be used where it meets strict standards," the report read.

The report's authors also called for a reduction in human consumption of meat to lessen demand for mined phosphorus.

"This is because the efficiency with which phosphorus inputs are converted into dietary phosphorus is much higher in vegetable-based products than livestock products."


On the Net:

  • The full report, entitled "A rock and a hard place: Peak phosphorus and the threat to our food security",  can be downloaded here. (PDF)