Influence of straw types and nitrogen sources on mushroom composting emissions and compost productivity

The effects of different straw types and organic and inorganic nitrogen (N) sources on the chemical composition and odor concentration (OC) of mushroom composting emissions, compost parameters, and mushroom yield were examined using bench-scale and large-scale (windrows and aerated tunnels) composting systems. There were close correlations between the butanol or combined H2S+dimethyl sulfide (DMS) concentration and OC of air samples taken from different composting ingredients (r=0.83 and 0.76-0.87, P<0.01, for log(e)-transformed data). Differences in N availability, in terms of NH3 and N losses during composting, were found between different N sources. Materials in which the N was less available (chipboard and digester wastes, cocoa shells, ammonium sulfate) produced lower mushroom yields than materials in which the N was more readily available (poultry manure, urea, brewers' grains, hop and molasses wastes, cocoa meal). Replacement of poultry manure with the other N sources at 50-100% or wheat straw with rape, bean, or linseed straw in aerated tunnel or windrow composts reduced the OC and emissions of odorous sulfur-containing compounds, but also reduced yield. Urea and cocoa meal may be suitable for "low odor" prewetting of straw, with addition of poultry manure immediately before aerated tunnel composting. Rape straw in compost reduces the formation of anaerobic zones and resulting odorous emissions, since it maintains its structure and porosity better than wheat straw.