Human Waste Could Be Phosphate Source

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Human excreta could have a key role in securing future food security, helping prevent a sharp drop in yields of crops such as wheat due to a shortage of phosphorus inputs, a UK organic body said Nov. 29.

“It is estimated that only 10 per cent of the three million tonnes of phosphorus excreted by the global human population each year are returned to agricultural soils,” Britain’s largest organic certification body, the Soil Association, said.

An adequate supply of phosphorus is essential for seed formation, root development and maturing of crops.

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

“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,” the Soil Association said.

Historically in Europe, phosphorus was returned to agricultural land through the application of animal manure and human excreta but from the mid nineteenth century it was replaced by phosphate mined in distant places.

Fewer heavy metals

The report called for a change in European Union regulations to permit the use of treated sewage sludge, known as biosolids, on organic certified land, subject to appropriate restrictions on issues such as concentrations of heavy metals.

EU regulations prohibit the use of biosolids on organic land due to concerns about the toxic effects of heavy metals cause by combining human excreta with other waste products such as industrial effluent.

“Heavy metal levels have declined in recent years and are now low enough for the organic movement to reconsider allowing treated sewage sludge to be used where it meets strict standards,” the report said.

The report also called for a reduction of the amount of meat in human diets to reduce 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,” it said.

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