Beyond waste: Transforming manure into a resource through integrated systems

Intensification of US livestock production, generating an estimated 1.27 billion metric tons of manure per year from nearly 10 billion animals, presents both a nutrient resource and an environmental challenge. This technical review synthesizes current knowledge on manure's agronomic and soil health benefits versus its environmental risks. The study compares different management approaches, land application, stockpiling, lagoons, and critically assesses advanced treatment and valorization technologies, including anaerobic digestion, solid-liquid separation, nutrient recovery (struvite precipitation, ammonia stripping), biochar co-composting, and precision application tools (injection, variable-rate spreading, and real-time nutrient sensors). Adoption drivers such as regulatory frameworks (Clean Water Act, concentrated animal feeding operation permits, and California SB 1383), economic incentives (Environmental Quality Incentives Program [EQIP] cost-share and carbon and nutrient credit markets), and digital innovations are also evaluated alongside persistent barriers of high capital costs, logistical constraints in nutrient transport, knowledge gaps in emission quantification (CH₄, N₂O, and NH₃), pathogen fate, and site-specific trade-offs among air, water, and soil quality. The review also outlines potential future scenarios, from incremental technology mainstreaming to integrated circular biorefineries, and highlights research priorities to optimize manure as a circular resource while safeguarding ecosystem and human health. By contextualizing manure management within a climate-resilient, circular agricultural economy, this review identifies the research gaps and informs researchers, extension agents, and policymakers on strategies to advance sustainable livestock systems in the United States and beyond.