by Enrico Villamaino

Phosphorus fertilizer is an essential element needed for agriculture. Unfortunately, it is also a considerably limited resource; there are finite amounts of phosphorus found in ore deposits located in a few locations scattered across the globe. Countless nations import phosphorus fertilizer for their agricultural producers.

The increasing scarcity of this element has led researchers to investigate a way to better conserve the phosphorus available to the farming industry. A recent study headed by Dr. Stephen Powers, a professor at Washington State University, undertook an extensive mapping of phosphorus deposits worldwide as well as areas where potential phosphorus recycling is highest.

Addressing the challenges his research attempts to address, Powers said, “Compared to other vital ingredients such as water, carbon and nitrogen that sustain life, phosphorus is not abundant in the atmosphere, and not renewably cycled between the atmosphere and soils. An important part of the equation is that animal and human wastes contain recoverable phosphorus, much of which ultimately originated from distant phosphate rock mines. If we can recycle more of this locally-available waste phosphorus back into agriculture, we might be able to keep it away from leak points while reducing our dependence on future fertilizer imports and mining. Livestock production is on the rise globally – and with that, comes more phosphorus-rich manure. We’re still figuring out what to do with all that phosphorus, and often there’s a disposal mentality that runs counter to the idea of a circular economy.”

According to Dr. David Vaccari, director of the department of civil, environmental and ocean engineering at the Stevens Institute of Technology in Hoboken, NJ, recycling phosphorus is the “low hanging fruit” of the mineral’s conservation efforts. Vaccari’s work in mapping out “hot spots” where demand for fertilizer is high and potential for recycling phosphorus from animal and human waste is strong is regarded as a breakthrough, as work on this matter conducted on a global scale had never before been attempted.

Vaccari said, “Three-quarters of the phosphorus deposits on earth are located in phosphate rock mines found in just three countries – China, the United States and Morocco, which has just passed the U.S. and is now second only to China in worldwide phosphate mining.”

The data collected show there are considerable untapped opportunities for recycling phosphorus. “If we want to seriously address phosphorus recycling, these places we’ve identified are where we’re going to get the most bang for our buck,” said Vaccari.

Explaining the importance of finding a way to reduce dependency on importing phosphorus, Vaccari added that “if economic and logistical obstacles were overcome, and 100% of the phosphorus used could be recycled, worldwide demand for importing the element could be reduced by 46%… Even if a more reasonable rate of recycling half of the phosphorus used resulted in a 23% reduction on the phosphorus imports needed, it would be a substantial improvement.”

As 72% of croplands with significant manure production nearby and 68% of croplands with significant human populations nearby are in regions that are heavily dependent on imported phosphorus, finding and implementing effective recycling strategies could prove to be exceedingly helpful to these farms.

Asked what types of agricultural operation would benefit markedly by recycling the phosphorus used, Vaccari responded, “CAFOs, or concentrated animal feeding operations, is where we’ve observed the most waste. Recycling in these operations would be a great start.” Vaccari, who hails from central New York, is quick to add that “many of the smaller farms in that region are already doing their fair share and attempting to utilize phosphorus recycling technologies.”

Powers argued that the abundance of phosphorus recycling opportunities in nations that have relied on fertilizer imports or have experienced rising fertilizer demand could prove very useful in development of local, recyclable phosphorus sources and, more broadly, agricultural independence. As an essential element in food production, phosphorus plays a role in the food security of nations, making the political implications of this issue all too clear. Powers’ work maps potential phosphorus recycling sites across the world’s croplands – in particular, cultivated areas with lots of phosphorus rich manure and lots of people. These areas have combinations of high cropland extent, manure-phosphate production and population density, making them potential “hot spots” for local recycling. Such local recycling methods include reuse of manure, biosolids or other recovered substances that contain phosphorus, such as food waste or compost.

Powers further laid out that phosphorus recycling from wastewater, manure and food waste are not the only options for alleviating phosphorus import dependency and satisfying agricultural demand for the element. Other options include “a closer matching of fertilizer phosphorus application with crop needs, biotechnological reductions in phosphorus requirements of plants and animals, reduction of phosphate-containing wastes such as wastewater, food waste and agricultural runoff, and facilitated crop uptake of residual phosphorus stores already in soils.”

“When I have conversations with people about the current global system of phosphorus fertilizer trade,” Powers explained, “often the reaction I get is ‘How did I not know this? Why aren’t more people talking about this?’ My response is some of us are working hard on that!”