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Purpose: Methane production potential in aerobic digestion was assessed according to feed to inoculum (F/I) ratio for food waste only, and mixing ratio of two materials for food waste and swine manure to give a basic data for the design of anaerobic digestion system. Methods: Anaerbic digestion test was performed using a lab scale batch reactor at for six different feed to inoculum (F/I) ratios (0.50, 0.72, 1.14, 1.50, 2.14 and 3.41), three food waste to swine manure ratios (100:0, 60:40 and 40:60) with two different loading concentrations (10g VS/L and 30g VS/L). Results: For food waste only, the highest biogas yield of 1008 mL/gVS was obtained at 0.50 of F/I. For the co-digestion of food waste and swine manure mixture, the highest biogas yield of 1148 mL/gVS was obtained at a mixing ratio of 40:60 with loading concentration of 10g VS/L. Conclusions: F/I ratio for the food waste only, mixing ratio of food waste and swine manure, and co-substrate loading rate affected the biogas production rate. For the low loading rate, there was not so much difference according to the mixing ratio of food waste and swine manure, but for the high loading rate higher biogas yield was acquired for the co-digestion of food waste and swine manure than for the food waste alone (mixing ratio, 100:0).

A 30-day bench-scale aeration experiment was carried out with three different aeration levels, i.e., +35 mV ORP, 1.0 mg O2 L-1, and 3.0 mg O2 L-1, to treat swine manure with solids levels from 0.5% to 4.0% for solids decomposition and odour control. Solids changes during the aeration process were characterized by total solids (TS), total volatile solids (TVS), total suspended solids (TSS), and total volatile suspended solids (TVSS). Volatile fatty acids (VFAs) was used to evaluate the odour generation potential in the aerated manure. The overall TS removal efficiencies from 6.0% to 44.9%, 18.6% to 50.3%, and 42.3% to 56.4% were observed for the three different aeration levels, respectively, with reductions from 6.6% to 48.9%, 26.0% to 61.1%, and 57.3% to 69.9% for manure TVS. The ratios of TVS/TS, TSS/TS and TVSS/TS in manure were found to increase with solids levels in the 30-day aeration process under the three aeration intensities. Reductions of BOD5 reached 78.5% to 92.0%, 79.4% to 96.0%, and 91.2% to 97.0%, while reduction of VFAs reached 12.7% to 99.0%, 71.7% to 99.0%, and 87.8% to 99.3%. The biodegradation of solids, BOD5, and VFAs was effectively enhanced when aeration length and level were increased. Low solids levels in manure offered a more advantageous condition for aerobic decompositions of solids, BOD5, and VFAs. Linear correlation analysis proved that the odour generation potential in manure being treated by aeration process could be distinctly characterized by the change of solids in different forms and/or by the BOD5 levels.

The influences of aeration rates (0.5, 1.2 and 1.9 L/M) for different temperatures (5, 15, and 25 oC) on the ammonia emission and the breakdown of organic material were studied for 21 days of biodegradation using 15.3 L of batch reactors. From 9.7 to 37.7 % of total Kjeldahl nitrogen was removed during the experiment with higher values for the higher manure temperatures and the higher aeration rates. From 0.7 to 25.8 % of initial TKN was volatilized as ammonia gas showing higher value according to manure temperature and aeration rate. The ratio of volatilized ammonia gas to the reduced TKN was from 6.5 to 68.5 showing also higher value according to manure temperature and aeration rate. BOD5 removal was also higher with the higher temperature and the higher aeration rates with the exception between 0.5 and 1.2 L/M for the manure of 5 and 15 oC. Higher aeration (1.9 L/M) for the lower temperature (5 oC), and lower aeration (0.5 L/M) for the higher temperature (15 – 25 oC) were desirable to reduce ammonia emission while satisfying BOD5 removal to a certain extent.

A bench-scale study on swine manure stabilization for odour control was conducted using batch aeration reactors. In trial 1, two aeration lengths, i.e., 0.5 and 4.0 day, were used under uncontrolled ambient temperature that increased gradually over the experimental period. While in trial 2, a 16.0-day aeration scheme was employed under constant 17 °C. An airflow rate of 1.2 L/s/m 3 was used for both trials to aerate batch reactors containing finishing pig manure with initial total solids (TS) levels ranging from 0.5 to 4.0%. Manure stabilization during the 90-day post-treatment storage was evaluated by the changes in organic materials, nitrogen and volatile fatty acids (VFA). The odour generation potential in the treated manure was determined by the changes in VFA. Up to 827 mL of liquid was lost due to aeration related foaming. The reductions in total volatile solids (TVS), 5-day biochemical oxygen demand (BOD 5 ), total Kjeldahl nitrogen (TKN) and VFA during storage were improved when aeration length increased. Low solids levels offered a more advantageous circumstance for manure stabilization and odour control. Biodegradation of organic matter, removal of nitrogen, and breakdown of VFA would increase with increasing ambient temperature. VFA removals in manure under 16.0-day aeration were higher than those under 0.5- and 4.0-day aeration; however, VFA regeneration started to exceed its consumption on day 20 (4 days after the aeration treatment). BOD 5 was the best estimate of VFA concentration in the aerated manure during storage. The 4.0-day aeration scheme was sufficient to stabilize manure to effectively assuage odour generation potential during the 90-day storage under increasing ambient temperature conditions.