Slaughterhouse by-products composting: can microorganisms inoculum addition mitigate final compost odor emission?

Small slaughterhouses generate biowaste, which for economic reasons, is generally destined for composting. Inoculating appropriate microorganisms can improve biodegradation efficiency and mitigate odor generation during the composting process and can give rise to composts with neutral or pleasant odors. Therefore, the aim of this study was to compare the odor intensity reduction of compost generated with and without a formulated inoculum (Saccharomyces cerevisiae, Bacillus subtilis, and Rhodopseudomonas palustris). A set of experimental data was collected and analyzed according to the German "Verein Deutscher Ingenieure" odor protocol. The results showed that adding microorganisms was effective in reducing unpleasant odors in all three composts generated from swine, cattle, and poultry slaughterhouse by-products during both summer and winter seasons. Additionally, soil odor was predominant in composts that were inoculated in the two tested seasons (i.e., summer and winter). On the other hand, composts without inoculation had odors similar to peat for swine compost, ammonia for cattle compost, and manure for poultry compost, regardless of the season tested. Overall, composting process with appropriate inoculum can help in the correct disposal of slaughterhouse wastes by transforming organic matter into composts, which can have economic and environmental value as a soil conditioner and/or fertilizer.

Development of a low-cost inoculum to improve composting of cattle slaughterhouse by-products.

The composting process is an option for acceptable environmental management of cattle slaughterhouse by-products. The goals of this article were (i) to make a low-cost inoculum using popular supermarket ingredients and microorganisms that are already present in the composting environment, and (ii) to compare the efficiency of the composting process with and without the application of formulated inoculum. Initially, a consortium of microorganisms already present in the composting environment (Saccharomyces cerevisiae, Bacillus subtilis, and Rhodopseudomonas palustris) was prepared in a low-cost culture medium for use as an inoculum for the composting process. The composting process with the addition of the inoculum was more efficient than the composting process without the inoculum, in terms of both the chemical composition and the process efficiency, but mainly in relation to the time required for composting, with the mean times for decay of 50% of the windrows' temperature (taking in to account the difference between internal and external windrow temperatures) being 96 days without inoculum and 65 days with inoculum. Thus, inoculum made with low-cost supermarket products reduced the composting time and yielded compost of better quality.