Manure Composting as a Strategy to Mitigate Antibiotic Resistance Dissemination in Agricultural Systems

ABSTRACT

Livestock manure is a valuable agricultural resource but may introduce antibiotic residues and antibiotic resistance genes (ARGs) into the environment. This review critically evaluates the fate of antibiotics and ARGs during manure composting and identifies the principal factors controlling their attenuation. It integrates composting‐system configuration and phase‐specific operating conditions with antibiotic properties, microbial‐host succession, extracellular DNA, mobile genetic elements (MGEs), post‐application risks, and alternative manure‐treatment technologies. Composting can reduce many antibiotic residues by 80%–90% or more, although apparent removal may reflect degradation, transformation, sorption, or reduced extractability and remains strongly compound‐ and process‐dependent. ARG responses are more variable and often non‐linear. Sustained thermophilic conditions can reduce ARG‐carrying microorganisms and MGEs, but selected genes may persist or rebound during maturation because of microbial recolonization, residual selection pressure, extracellular DNA persistence, and horizontal gene transfer (HGT). Temperature and exposure duration, aeration, moisture, C:N ratio, bulking materials, biochar, and microbial inoculants are therefore key determinants of treatment performance. Composting substantially mitigates antimicrobial‐resistance risks but does not guarantee complete elimination of transmissible ARGs. Standardized monitoring, full‐scale validation, and long‐term assessment of soil and crop compartments are required to support safe agricultural use of composted manure.