ODOROUS EMISSIONS AND ODOR CONTROL IN COMPOSTING SWINE MANURE/SAWDUST MIXES USING CONTINUOUS AND INTERMITTENT AERATION
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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.Keywords:
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Hog manure amended with sawdust (moisture 56~60% wet basis, C/N 19-21) was composted in pilot-scale vessels using continuous aeration(CA) and intermittent aeration(IA) for 3 and 4 weeks. In two subsequent runs of the same duration, composts resulting from each of the first runs were used as a biofilter on the exhaust gas from newly composting material. Conditions between each of these paired sets appeared to be similar. Ammonia was released from the biofilter material during the first week of stabilization while the compost produced ammonia after the first week of composting. In both cases substantial absorption, 61~96 %, of ammonia production from the composting raw material was achieved in the stabilizing material during the final weeks of operation and indicates the use of the stabilizing hog manure/sawdust compost as a biofilter can reduce ammonia emissions. Total emissions during run 2 in IA was less than 2/3 of those in CA. Dry solids loss for the stabilized compost (6~8 weeks) was 19~46%.
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The effects of using intermittent aeration during composting on ammonia emissions and dry matter loss were determined during composting of hog manure amended with sawdust. Composting trials lasted three weeks and used pilot-scale 200 liter vessels (four). The experimental design used replication of two treatments, continuous aeration (CA) and intermittent aeration (IA), in two series of experiments (total of eight tests). In the CA sequence, compost temperatures were controlled at 60°C using feedback control on high and low air flow fans while the IA sequence consisted of five minutes of air flow followed by 55 minutes of rest. Mixing ratios of hog manure to sawdust were 1:1.1 and 1:1.7 dry weight basis with resulting C:N ratios of 18.2 ± 1.2 and 23.7 ± 2.2 for the two series of tests. Airflow reduction was 63 percent for IA compared to CA. Percent nitrogen loss between treatments were moderately statistically different (α = 0.14) with average percent nitrogen loss at 29.7 percent for CA and 23.0 percent for IA. Nitrogen loss as ammonia-N was higher for CA than IA (25.9 versus 14.3) but was not statistically different. No significant differences existed in dry solids loss between treatments and the physical and chemical properties of the compost produced from IA were similar to that from CA for each series. Results showed that IA compared to CA may be a practical way to reduce nitrogen loss and ammonia emissions during composting of swine manure with sawdust.
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This study investigates the influence of the different types of biofilters and media depths on ammonia emissions during biofiltration for reducing odor from manure composting. We examine the effects of ammonia gas from dairy manure composting using the following biofilter media: wood chips, sawdust, manure compost and manure compost mixed with wood chips.
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This study was conducted to determine the effects of pig manure composting on emission of dinitrogen oxide () that is greenhouse gas. Fresh pig manure was mixed with sawdust as bulking agent and moisture content of mixed compost was adjusted by 61.9%. After mixing bulking agent with pig manure that was left to compost with aeration in composting chamber for an initial period of 30 days. At the end of this period, that was decomposed and a second period of composting was conducted without aeration for 60 days. Temperature during the initial composting period was above for 7 days. Moisture reduction rate by composting pig manure was 36.7%. Produced during composting was 0.043g/T-Ng.
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Compost stability represents the state of microbiological activity and measurements of respiration either through evolution or uptake should provide the best indication of this state. Hog manure amended with sawdust was composted in a pilot-scale reactor vessels using continuous and intermittent aeration for 3 weeks. In this study we evaluated the respiration rate effect of aeration method on the reduction of evolution, and investigated the stability of fresh and finished compost for plant growth. The intermittently aerated composting is a practical proposition for a very stable compost making. The respiration rate in the fresh and finished compost during intermittently aerated composting was maintained from 0.3 to 1.4 and was good for use in horticulture, while the continuously aerated composting was 7 to 23 and needed more time for compost curing.
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This study was conducted to find out the optimal aeration rates for minimizing odor emission and for increasing biological activities during composting of livestock manure in the enclosed bench-scale reactor system. It was treated with the mixture of poultry manure and sawdust controlled the initial water content of 60%, then aerated continuously at four different aeration rates (0.1, 0.2, 0.4 and 0.6 L/min/kg dry-solids). The average emitted concentration of ammonia in 0.6 L/min/kg dry-solids during composting reached the level of 40% in comparison with that of 0.2 L/min/kg dry-solids. In cases of sulfur compounds such as hydrogen sulfide, methylmercaptan and ethylmercaptan, their concentrations decreased with increasing aeration rates and the emission time was shortened. But they didn't detect in the treatment of 0.6 L/min/kg dry-solids. The biological activity for composting showed a trend of increasing as aeration rates increased. The treatment of 0.6 L/min/kg dry-solids gave the highest biological activity and the best compost quality.
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