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Manure map raises recycling hopes

A study shows potential for farmers to reclaim phosphorus fertilizer

A map shows the distribution of manure-rich cultivated areas. The green spots demonstrate the areas with the most potential for phosphorus recycling.

A New Jersey university is mapping the world’s manure in an effort to jump-start a movement to recycle phosphorus.

In the April 2019 issue of Earth’s Future, a research team from Stevens Institute of Technology mapped the journey of phosphorus from soil to crops, to livestock and humans, and eventually into sewers and landfills.

This year, farmers will use over 45 million metric tons of phosphorus fertilizers worldwide.

The study identified regional “hot spots” where there’s significant demand for fertilizers and significant potential for recapturing phosphorus.

“If we want to get serious about phosphorus recycling, these are the places where we’re going to get the most bang for our buck,” said David Vaccari, director of the Stevens Institute’s department of civil, environmental and ocean engineering.

Of croplands that are heavily dependent on imported phosphorus, 72 per cent have significant manure production nearby, and 68 per cent have significant human populations nearby.

The study also identifies significant surpluses of phosphorus-rich waste in much of Asia, Europe, and the United States.

The results also show that at least five times as much phosphorus is contained in animal manure as human waste, suggesting that livestock operations are the starting point.

Almost half of the world’s farmlands are near livestock operations, suggesting that in many regions manure could be applied to fields directly, or processed using biodigesters to extract phosphorus.

Researchers are now working out exactly how much phosphorus can be recaptured from animal and human waste, and identify other opportunities.

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