Phosphorus, an element essential to every harvest and every meal, is quietly becoming one of the world’s most consequential supply risks. The United States could exhaust its domestic phosphate resources within roughly 40 years, while Europe, Latin America and Southeast Asia already rely heavily on imports from China and Morocco. A new analysis from University of Arkansas researchers and colleagues argues that the answer may not lie in discovering another mine, but in redesigning the way phosphorus moves through farms, livestock operations, cities and soils. By recovering the nutrient from waste and accumulated soil reserves, the United States could build a more resilient and circular fertilizer system before shortages begin to threaten food production.
Phosphorus is one of the three nutrients represented in the familiar agricultural acronym NPK, alongside nitrogen and potassium. It is indispensable for plant energy transfer, root development, cell formation and reproduction. Plants absorb phosphorus primarily in the form of phosphate, but the element is chemically reactive and readily binds to minerals in soil. That tendency makes phosphorus difficult for crops to access after it is applied. According to Becca Muenich, an associate professor of biological and agricultural engineering at the University of Arkansas, farmers may apply large quantities of fertilizer because only a fraction becomes available to plants. The remainder can remain locked in soil, move into waterways or accumulate in agricultural landscapes.
Most modern phosphorus fertilizer begins as phosphate rock, a finite geological resource that must be mined, crushed and chemically processed, commonly with sulfuric acid. The resulting products are transported through long international supply chains before reaching farms. This system is both energy-intensive and vulnerable to geopolitical disruption. The United States classified phosphate as a critical mineral in 2025 because interruptions in access could affect agriculture, food prices and national security. Although phosphorus itself does not disappear when used, it often becomes dispersed or chemically immobilized, making recovery difficult and expensive. The challenge is therefore not simply a lack of phosphorus on Earth, but a growing mismatch between where the nutrient exists and where crops need it.
In a paper published in Proceedings of the National Academy of Sciences, Muenich and collaborators at North Carolina State University’s Science and Technologies for Phosphorus Sustainability Center assembled one of the most comprehensive pictures yet of phosphorus use and recovery potential across the United States. Their analysis covers 3,142 counties and combines historical records dating to 1866 with projections extending to 2050. The researchers tracked phosphorus entering agricultural systems, remaining in soils and appearing in recoverable materials such as manure, crop residues, livestock bones, eggshells and sewage sludge. Their results reveal that American farms have accumulated a vast reserve of phosphorus over more than a century of fertilizer use.
Since 1866, approximately 145 teragrams of phosphorus have been applied to U.S. agricultural land. One teragram equals 1 million metric tons. By 2023, about 52 teragrams remained in cropland soils, while another 47 teragrams were stored in pasturelands. Taken together, these reservoirs represent phosphorus that has already been transported into the agricultural system but has not yet been removed by crops or carried away by erosion and runoff. The study also found that potentially recyclable phosphorus from soils, animal manure, food and agricultural residues and sewage sludge amounted to nearly 125% of the phosphorus applied to fields during the period examined. That figure does not mean all of the material can be immediately recovered or substituted for mined fertilizer, but it demonstrates the scale of the resource embedded in existing waste streams.
The accumulation comes with an environmental cost. When phosphorus escapes fields and enters rivers, lakes and coastal waters, it can stimulate excessive growth of algae and aquatic plants. As this biological material decomposes, microorganisms consume dissolved oxygen, creating conditions that can suffocate fish and disrupt entire aquatic ecosystems. At the same time, phosphorus trapped in soil may remain unavailable to crops, forcing farmers to apply more fertilizer to maintain yields. The result is a circular contradiction: farms import phosphorus, lose much of its immediate agricultural value, retain some of it in the soil and risk exporting the rest into waterways. Recovering that nutrient could improve fertilizer efficiency while reducing pollution, but the technology must be matched to the chemical and physical characteristics of each source.
“There’s not one technology that would solve the phosphorus problem,” Muenich said, because phosphorus appears in many forms across the environment. In sewage, it may be dissolved or attached to organic matter and mineral particles. In manure, it is mixed with water, fibers and other nutrients. In crop residues, it is distributed through large volumes of low-density plant material. Soil phosphorus may be spread across millions of acres and bound to iron, aluminum or calcium compounds. Recovery systems therefore range from biological treatment and chemical precipitation to thermal processing, composting and the production of concentrated mineral fertilizers. Each approach has different energy requirements, costs and implications for contaminants such as heavy metals or pathogens.
The economics of recovery remain a central obstacle. Mined phosphate rock is relatively inexpensive wherever supplies are stable, creating little financial pressure to adopt more complicated recycling systems. Transport is another major barrier. Dairy and livestock manure can contain substantial amounts of phosphorus, but it is mostly water and is expensive to move over long distances. Recycling is most practical when farms producing waste are located near cropland that needs nutrients, or when processing facilities can remove water and concentrate phosphorus before transport. The researchers’ county-level analysis is designed to reveal these geographic relationships, showing where phosphorus surpluses overlap with areas of fertilizer demand and where regional circular systems could be developed.
Arkansas stands out as a particularly promising test case. The state’s northwest is home to major poultry and cattle operations that generate manure containing recoverable phosphorus, while agricultural regions farther east produce rice, corn and soybeans that can require substantial fertilizer inputs. Because these production systems are located within the same state, Arkansas may be able to connect phosphorus sources with nearby agricultural demand more efficiently than regions dependent on long-distance shipping. Such a network could include manure processing, nutrient recovery from wastewater, improved soil testing and precision fertilizer application. Instead of treating animal waste as a disposal problem and fertilizer as a mined commodity, the state could begin managing both as parts of a single nutrient economy.
The pressure to make that transition is likely to increase. A growing global population could require as much as 60% more food in the coming decades, increasing demand for phosphorus even as easily accessible reserves become more constrained. The new study does not present recycling as an instant replacement for mining, nor does it suggest that every accumulated gram of soil phosphorus can be economically extracted. Instead, it identifies a portfolio of opportunities: use existing soil reserves more intelligently, recover phosphorus from concentrated waste streams, locate processing near farms and reduce losses from fields into waterways. The researchers argue that acting before supply disruptions occur would give communities time to develop infrastructure, refine technologies and create markets for recycled fertilizer. The future of phosphorus may depend less on finding a new source than on recognizing how much of the old one is already surrounding us.
Subject of Research: Not applicable
Article Title: Opportunities to strengthen US phosphorus supply resilience through circular pathways
News Publication Date: 10-Jun-2026
Web References: https://www.pnas.org/doi/10.1073/pnas.2530690123
References: Proceedings of the National Academy of Sciences; DOI: 10.1073/pnas.2530690123
Image Credits: Whit Pruitt
Keywords: Phosphorus, phosphate fertilizer, soil science, soil fertility, agricultural chemistry, sustainable agriculture, farming, nutrient recycling, circular economy, wastewater recovery, manure, food security, critical minerals, environmental pollution, University of Arkansas
