Abstract
Swine manure mixed with sawdust was composted in 205 L pilotscale vessels. Four runs with a total of 22 vesselstudies were made during 1998 and 1999. Composting was conducted, with either continuous or intermittent aerationsupplied to each vessel, for 17 to 29 days. Temperatures, airflow, carbon dioxide production, oxygen uptake, and ammoniaproduction were monitored. Material masses, moisture contents, pH, and various chemical concentrations were determinedfor initial and final samples. Further, in the final two runs, condensate from the exhaust air stream from each vessel wascollected using watercooled condensers (40 cm, 15 C) and weighed every 12 hours. Condensates and extracts from initialand final material samples were analyzed by gas chromatograph with flame ionization detector for volatile fatty acids (VFAs).The results indicated that airflow had a strong effect on emissions. Ammonia release showed a linear trend vs. total airflow,with about 50% reduction in ammonia occurring for a 75% reduction in airflow. Acetic, propionic, and butyric acid emissionswere reduced by 68%, 68%, and 33%, respectively, and isobutyric, isovaleric, and valeric acid emissions were increased by151%, 8%, and 18% for a similar airflow reduction. Thus, there is potential for reduced odors with reduced airflow. Resultsalso indicated that initial pH influenced onset of composting and the potential for odor release. For vessels with initial pHbelow 5.95, compost heating was slow, and temperature and CO2 production patterns indicated gradual development of, andshifts between, mesophilic and thermophilic bacterial activity. For vessels that started at higher pH values, development wasmuch more rapid. These effects, combined with the fact that a significant majority of the VFAs initially present were not emittedbut were not present at the end of the runs (particularly in the higher pH vessels), indicated that high bacterial activity wasimportant for reduction of odor potential.
Published Version
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