Waste nutrients from U.S. animal feeding operations: Regulations are inconsistent across states and inadequately assess nutrient export risk.

Livestock production in the United States has been transformed over the past several decades, largely as a result of widespread development of industrial-scale mass production facilities, termed Animal Feeding Operations (AFOs). These facilities generate massive amounts of animal waste that can concentrate in small areas. Animal wastes from AFOs have led to high levels of nutrients and other pollutants in nearby surface waters, as well as groundwater. The environmental problems associated with these disposal practices have led to federal and state modifications to the rules and regulations governing waste practices. We summarize the federal guidelines for AFO nutrient management, focusing on swine, and compare the regulations of four AFO-rich states in different regions of the USA. Furthermore, we discuss inconsistencies among regulations and regulatory gaps, and identify issues with waste nutrient management practices that lead to environmental degradation in watersheds hosting AFOs. Finally, we address these shortcomings and the need to implement policy updates that would alleviate some of these environmental and human concerns.