A PRELIMINARY COMPARATIVE-STUDY OF 3 MANURE COMPOSTING SYSTEMS AND THEIR INFLUENCE ON PROCESS PARAMETERS AND METHANE EMISSIONS

Three cattle manure composting systems - windrowing, forced aeration w ith temperature feedback control and simple minimal intervention (manu re stacks - ''passive composting'') were compared with respect to spec ifically selected and operationally important process parameters inclu ding 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 investiga tions of methane from the three systems during processing showed that the minimal intervention method produced high levels of methane (> 4 p ercent) in the waste matrix. The intervention methods, of windrowing o r forced aeration, drastically reduced methane output. The importance of animal manures in global agriculture, with reference to methane emi ssions and global warming, is briefly reviewed. The widespread relianc e of manure disposal by the use of simple stacks,sometimes erroneously elevated to a processing status by use of the term ''passive composti ng'', is questioned on ecological and environmental grounds. The data from this preliminary study shows the enormous impact that simple wind rowing techniques can achieve in terms of organic waste conversion and product quality, concomittant with ecologically acceptable treatment routes.