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Applicability of the Optimized In-vessel Food Waste Composting for Windrow Systems

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  037016,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13927) @2003
Authors:   Deniz Cekmecelioglu, Ali Demirci, Robert E. Graves
Keywords:   Composting, pathogens, thermopiles, inactivation, in-vessel, windrow

Statistical Extreme Vertices Mixture Design Method was used to design, evaluate, and determine optimum mixture composition of in-vessel composting system (55 L) utilizing food waste (40-60%), cow manure (10-30%), and bulking agents (10-30%). The mixture design method yielded nine compost mixtures, and all was replicated 3 times. Temperature was monitored during 12-day composting period to indicate the efficiency of composting. Initial and final chemical characteristics (moisture content, C/N ratio, pH, and volatile solids) and microbial survival (fecal coliforms, fecal streptococcus, Salmonella spp. and E. coli O157:H7) of mixtures were also determined. Mixtures 4 and 6 reached thermophilic range (=45-50oC) in 3 days, and remained 2.5 days in this range. Also, mixture 6 demonstrated reduction of fecal coliforms from initial number of 459.5 MPN/g dry compost to 71.4 MPN/g dry compost. Similarly, Salmonella spp. and E. coli O157:H7 were reduced from initial values of 321.1 and 459.5 MPN/g dry compost to final values of <0.79 and 24.2 MPN/g dry compost, respectively. As a result of data obtained from nine compost mixtures, mixture surface analysis showed that the optimum level of food waste, manure, and bulking agents was 50, 40, and 10%, respectively. The optimum mixture was also attempted to validate by windrow composting. Conventional layering and mixing methods were used for windrow construction. Layering method resulted in higher and more stable temperature profiles remaining at 57-61oC for 20 days, while mixing method yielded 55-59oC for 4-5 days. Fecal coliforms and fecal streptococcus were reduced from 448.8 MPN/g dry compost to 0.4, and 65.9 MPN/g dry compost, respectively within 2 monthcomposting by layering method. Salmonella and E. coli O157:H7 were similarly reduced from 448.8 MPN/g dry compost to <0.4 MPN/g dry compost. However, all piles presented leaching problems for the first 15-20 days. Future work will be focused on minor revision of statistical approach for windrow composting to eliminate these environmental problems.

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