A Preliminary Comparative Study of Three Manure Composting Systems and their Influence on Process Parameters and Methane Emissions

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Abstract
Three cattle manure composting systems — windrowing, forced aeration with temperature feedback control and simple minimal intervention (manure stacks — “passive composting”) were compared with respect to specifically selected and operationally important process parameters including dry matter, moisture and volatile solids losses, volume reduction and bulk density changes. The windrowing method proved to be the most effective with respect to the above parameters. Preliminary investigations of methane from the three systems during processing showed that the minimal intervention method produced high levels of methane (> 4 percent) in the waste matrix. The intervention methods, of windrowing or forced aeration, drastically reduced methane output. The importance of animal manures in global agriculture, with reference to methane emissions and global warming, is briefly reviewed. The widespread reliance of manure disposal by the use of simple stacks, sometimes erroneously elevated to a processing status by use of the term “passive composting”, is questioned on ecological and environmental grounds. The data from this preliminary study shows the enormous impact that simple windrowing techniques can achieve in terms of organic waste conversion and product quality, concomittant with ecologically acceptable treatment routes.