Nutrients recovered from animal and human waste could drastically reduce synthetic fertilizer use in the U.S., according to a new Cornell study that takes into account real-world implementation challenges like processing and transport.
In the study, published April 15 in Nature Sustainability, researchers found that animal and human waste in the U.S. could theoretically meet 102% of nitrogen and 50% of phosphorus needs for the nation's agriculture, a value of more than $5.7 billion annually. But they also identified a major hurdle: a frequent mismatch between the location of the waste - often in areas densely populated with people or livestock - and agricultural regions with the highest fertilizer needs.
Still, by mapping and analyzing the sources of waste and of agricultural need, the research team found that large percentages of recoverable nutrients - 37% of nitrogen and 46% of phosphorus - can be used locally, and more than half of the surplus nutrients can be redistributed to nearby regions with low economic and environmental costs.
"This is a coordination problem, not a resource problem," said corresponding author Chuan Liao, assistant professor in the Cornell CALS Ashley School in the College of Agriculture and Life Sciences. "Even considering the real-world constraints, there's still a substantial amount of nutrients that can be economically redistributed to meet crop needs."
The research provides a blueprint for harnessing the vast, untapped potential of animal and human waste to reduce the U.S.'s reliance on synthetic fertilizers, which are energy-intensive to produce, harmful to the environment and often made overseas.
"Excessive use of synthetic fertilizers leads to water pollution, and the production itself generates more emissions - it's a very intensive process," Liao said. "And you can see with the Iran War, there are supply-chain issues that can lead to great food insecurity as well."
