M. C. Wiles*2, J. C. Amburgey§, D. C. Borger*, L. B. Willett*, H. M. Keener2,
and D. L. Elwell21
*The Ohio State University Department of Animal Sciences
§The College of Wooster Department of Chemistry
2The Ohio State University Department of Food, Agricultural, and Biological
Engineering
Offensive odors evolved during the decomposition of swine waste have resulted in complaints from neighbors in agricultural areas. This study showed that the chronological monitoring of the formation of volatile fatty acids (VFAs) could be used in conjunction with the composting process to optimize conditions that minimize the release of malodorous compounds. Mixtures of swine waste and sawdust (3.5:1) were placed in 91 kg reactor vessels and constantly aerated over a 21-day period to chronologically monitor fermentation and formation of acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids. Composting conditions were shown to be adequate based on carbon to nitrogen ratios and moisture contents.
The 21-day aerobic treatment decreased all VFAs retained in the biomass by 50 to 100%, with an average of 87%. Chronological monitoring of volatile emissions from the vessels showed that prior to peak gas volatilization, when the vessels attained peak composting temperatures, acetic acid was emitted in the greatest amounts, followed by butyric, propionic, valeric, isovaleric, and isobutyric acids. Following peak gas volatilization, butyric acid accumulated in the greatest amounts followed by acetic and propionic acids, valeric, isovaleric, and isobutyric acids.
Peak VFA emissions occurred simultaneously with the greatest headspace temperatures, peak rates of O2 uptake, and peak production of condensate, ammonia, and CO2. Therefore, stringent control of these factors may decrease VFA emissions. Fewer VFAs were emitted from those vessels that quickly heated and were active for short periods of time, whereas much greater amounts of VFAs were emitted over longer periods of time from those vessels that possessed adequate conditions for composting for longer periods of time.
1 For more information, contact at: The Ohio State University, Ohio Agricultural Research and Development Center, 121B Agricultural Engineering Building, 1680 Madison Avenue, Wooster, OH 44691, 330-263-3862, e-mail: elwell.1@osu.edu