Performance Quantification of Manure Management Systems at 11 Northeastern U.S. Dairy Farms

Abstract

Abstract. The performance of manure management systems, on a component-by-component basis, at 11 Northeastern U.S. dairy farm concentrated animal feeding operations (CAFO) was quantified by semi-continuous monitoring for 15 months. Each collaborating farm (CF) had one or more of the following: solid-liquid separation (SLS), separated solids(SS) treatment by lime, rotary drum processing and windrow composting, anaerobic treatment by anaerobic digestion (AD), lagoons, and long-term storage(s). Operational and performance metrics included: temperature, pH, total solids (TS), volatile solids (VS), loading rates, and biogas production. Generally, most CFs had functional and well-operating systems based on expected and optimal operating conditions and sample constituent changes, although, sampling and monitoring limitations restricted complete performance assessments. Despite the limitations, differences in treatment effectiveness were noted, which were often related to influent conditions. Higher SLS solids capture efficiencies (typ. > 40%), and biogas production rates (= 3.8 m3 d-1 lactating cow equivalents (LCE)-1), were associated with more concentrated manure slurry influents [TS > 0.050 g g-1 wet basis (w.b.)]. Anaerobic digester configuration and the use of co-substrates also influenced anaerobic treatments. Generally, intensively managed ADs outperformed passively managed lagoons, and co-digestion enhanced biogas production (= 4.3 m3 d-1 LCE-1) and VS reductions (up to 48% w.b.), though co-digestion sometimes hampered process stability. The effectiveness of SS processing was also treatment dependent, with well-managed windrows yielding the greatest increases in TS concentrations (up to 0.600 g g-1 w.b.). Long-term storage of manure slurry had modest, non-significant, impacts on TS and VS concentrations, and pH. This work illustrated a range of manure management systems used on NE dairy farm CAFOs, parameterized their treatment of manure slurries and SS, and established a baseline for additional studies aimed at the capacity of these systems to mitigate emerging contaminant like antibiotic residues. Keywords: Anaerobic digestion, Antimicrobial resistance, Biogas, Compost, Lime treatment, Long-term storage, Solid-liquid separation.