Swine manure-sawdust mixes were composted in 205 L pilot scale vessels. Four runs, comprising a total of 22 vessels, were made which extend previous work. In each case, composting was conducted with either continuous or intermittent aeration for 17 to 29 days. Airflow, various temperatures,
carbon dioxide production, oxygen uptake, and ammonia production were monitored throughout all runs. Material masses, moisture contents, pH, and various chemical concentrations were determined for initial and final samples from all runs. Additionally, in the final two runs, the exhaust air
stream from each vessel was passed through water-cooled condensers, and total condensate was collected and weighed every 12 hours. Both condensate samples and extracts from initial and final material samples were analyzed by gas chromatograph with flame ionization detector for volatile fatty
acids (VFAs). 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 emissions were reduced by 68,
68 and 33%, and isobutyric, isovaleric and valeric acid emissions were increased by 151, 8 and 17% for a similar airflow reduction. Thus, there is potential for reduced odors with reduced airflow. Results also indicated that initial pH influenced onset of composting and the potential
for odor release. For vessels with initial pH below 6.0, compost heating was slow, and temperature and CO2 production patterns indicated gradual development of, and shifts between mesophilic and thermophilic bacterial activity. For vessels that started at higher pH values, development
was much more rapid. These effects, combined with the fact that most VFAs initially present were not emitted but still were not present at the end of the runs (particularly in the higher pH vessels), indicated that high bacterial activity was important for reduction of odor potential.
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