Towards circular nutrient economies: An integrated manureshed framework for agricultural and municipal resource management

Authors: AKANBI, OLATUNDE - Case Western Reserve University (CWRU); GUPTA, ATHARVA - Case Western Reserve University (CWRU); MANDAYAM, VIBHA - Case Western Reserve University (CWRU); Flynn, Kyle; SABO, ROBERT - Environmental Protection Agency (EPA); YARUS, JEFFREY - Case Western Reserve University (CWRU); BARCELOS, ERIKA - Case Western Reserve University (CWRU); FRENCH, ROGER - Case Western Reserve University (CWRU)

Submitted to: Resources Conservation and Recycling
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2025
Publication Date: 11/20/2025
Citation: Akanbi, O.D., Gupta, A., Mandayam, V., Flynn, K.C., Sabo, R.D., Yarus, J.M., Barcelos, E.I., French, R.H. 2025. Towards circular nutrient economies: An integrated manureshed framework for agricultural and municipal resource management. Resources Conservation and Recycling. https://doi.org/10.1016/j.resconrec.2025.108697.
DOI: https://doi.org/10.1016/j.resconrec.2025.108697

Interpretive Summary: The manureshed framework explores how nutrients from livestock operations are moved and reused to grow crops. Traditionally focused on farms within county borders, this study reimagines that system by incorporating nutrient discharges from municipal wastewater treatment plants. By shifting to a watershed perspective and analyzing national datasets from 2016, the study reveals how the addition of municipal sources reshapes nutrient flow patterns. Key changes include large increases in areas identified as sources of nitrogen and phosphorus when city waste is considered, particularly in regions such as the Southeastern U.S., Eastern Texas, and the Pacific Northwest. Urban areas near the Great Lakes experience the most dramatic shifts in nutrient dynamics due to this integration. The results show that many of these nutrient-rich areas are closely connected to places lacking nutrients, creating pathways for more efficient redistribution. Transition networks suggest a strong potential for local nutrient recycling, made even more feasible with municipal contributions. Ultimately, this research presents a more unified vision of nutrient management, encouraging collaboration between urban and agricultural systems to recover and reuse vital resources across landscapes.

Technical Abstract: The manureshed concept provides a framework for understanding nutrient flows from confined animal feeding operations to agricultural lands, traditional focusing on agricultural sources at county-level scale. This study extends the manureshed framework by integrating agricultural and municipal wastewater treatment plant (WWTP) sources at the watershed scale to analyze nutrient redistribution potential. Using 2016 Nutrient Use Geographic Information System (NuGIS) and Environmental Protection Agency (EPA) datasets, we quantified how WWTP integration transforms manureshed source-sink dynamics across U.S. watersheds. Agricultural data were combined with EPA WWTP discharge data within a unified watershed-based classification system. WWTP integration significantly altered classifications, with nitrogen Source areas increasing by 167.9% and phosphorus by 24.4%. Agricultural sources demonstrated strong regional concentration: the Southeastern United States and Eastern Texas as major nitrogen and phosphorus source regions, and the Pacific Northwest as the most extensive phosphorus source region nationally. The Great Lakes region showed substantial transformation through municipal integration, with new urban source areas around metropolitan centers. Transition probability networks revealed substantial local redistribution potential, with Source areas showing over 70% adjacency to Sink Deficit areas for both nutrients, indicating strong opportunities for direct transfers. WWTP integration enhanced redistribution pathways, with Source-to-Sink Deficit transitions increasing from 73.2% to 79.6% for nitrogen, demonstrating how municipal sources create new localized opportunities within the manureshed system. This study provides the first comprehensive framework integrating agricultural and municipal sources within the manureshed concept, creating new opportunities for nutrient recovery and redistribution coordinating agricultural and municipal sectors.