Effect of Mechanical Solids Separators on Potential Reduction of Methane Emissions From Dairy Manure Storage

Abstract

Highlights Four mechanical manure separators were evaluated in on-farm studies. Mass balances and biochemical methane potential tests were conducted to measure on-farm separation efficiencies. Separator performance depended on environmental, material, and design factors. Over 70% solids separation and methane emission reduction potentials were achieved. Abstract. The separation efficiencies of four mechanical solid-liquid separation technologies and their effect on the reduction of methane production potential from dairy lagoons were studied using on-farm separator measurements and laboratory biomethane potential tests. The studied technologies included 1-stage sloped dual-screen, 2-stage sloped dual-screen, 1-stage horizontal scraped screen, and 1-stage sloped single-screen separators. The technologies were evaluated across various seasons on four dairies in California. On-farm sampling and measurements of the influent of flushed manure and the mass of the solids separated, as well as in-laboratory measurements of methane (CH4) production potential, were carried out. A mass balance approach was employed to determine the removal efficiencies of total and volatile solids (TS and VS) and nutrients, as well as methane emission reduction potential. The performance of the separators depended on manure characteristics, system design (e.g., screen size and orientation), separator operation and management (e.g., manure flow rate), and manure processing pit type and configuration. Among the four studied separator systems, the 2-stage sloped dual-screen separator showed the highest average TS and VS removal efficiencies, and methane emission potential reduction of 52.5%, 59.7%, and 55.8%, respectively. The 1-stage horizontal scraped screen separator had the lowest TS and VS removal efficiencies, and methane emission reduction potential of 6.3%, 9.3%, and 4.9%, respectively. The results have potential implications for nutrient and greenhouse gas management strategies and/or policies in agriculture. Keywords: Greenhouse gas, Lagoon, Manure management, Separation efficiency, Settling basin, Solid-liquid separation, Sustainable agriculture.