Low greenhouse gas emissions during composting of solid swine manure

Methane and N2O fluxes during composting of solid swine manure were studied using three aeration systems being, forced aeration (FA), wire mesh (WM) and turnover (TO) and no aeration, for 85d to suggest strategies of mitigating GHG emissions during composting. Manure was collected from a swine research barn by a scraper system and mixed with sawdust as a bulking agent. The manure sawdust mixture was placed in linear low density polyethylene containers for each composting method. A steady state chamber covering each container was used to measure CH4 and N2O fluxes during composting in order to sample temporal and spatial heterogeneous fluxes. Air samples were continuously analyzed for CH4 and N2O by a high frequency trace gas analyzer. Mean CH4 fluxes from FA, WM, TO, and no aeration were 5.2, 3.8, 7.5, and 34.6μg/m2/s, respectively. Mean N2O fluxes from FA, WM, TO, and no aeration were 1.6, 3.1, 7.9, and 11.4μg/m2/s, respectively. Ratios of CO2-equiv. emitted from FA, WM, TO and no aeration were 0.14, 0.24, and 0.59, respectively. Nitrous oxide was the main contributor to CO2-equiv. fluxes. The FA system had the lowest emissions, but WM had the advantage of not requiring electricity for aeration. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.