Cornell study: recycled animal and human waste could meet U.S. crop nitrogen needs

Nutrients recovered from animal and human waste could, in theory, meet 102% of U.S. agriculture’s nitrogen needs and 50% of its phosphorus — a resource worth more than $5.7 billion a year — according to a Cornell University study published in Nature Sustainability.

The bigger obstacle is geography, not supply. Researchers mapped waste sources and crop nutrient demand across 15 major crops at roughly 10-kilometer resolution and found a persistent mismatch. Surpluses cluster in population-dense and livestock-heavy regions such as the Northeast and parts of the West, while deficits run through the Midwest and southern Great Plains.

Even with those constraints, the team found that 37% of recoverable nitrogen and 46% of phosphorus could be used locally, and more than half of the surplus could be shipped to nearby regions at low economic and environmental cost. “This is a coordination problem, not a resource problem,” said corresponding author Chuan Liao, an assistant professor at Cornell.

The authors frame recovered nutrients as a way to cut reliance on synthetic fertilizers, which are energy-intensive to produce, frequently imported and a source of water pollution. They also found that areas of very high or very low nutrient supply often overlap with poorer counties, suggesting nutrient flows track social inequality.

Liao’s team argues for decentralized, local processing that pairs livestock operations with neighboring cropland, noting the technology already exists and the missing pieces are governance and infrastructure. The study was funded by the National Science Foundation and the USDA, with seed funding from the Cornell Atkinson Center for Sustainability.

Source: Cornell University