The potential. of biogas generation from dairy cow manure (DCM) was determined using Graphical. Statistics Analysis Method, which was developed by Ho Kang. The aim of this study was to evaluate the performance of biogas production by semi-dry anaerobic digestion (AD) with DCM.
Total. solids (TS) and Volatile solids/Total solids (VS/TS) of DCM were 13-17% and 88%, respectively. During the process of AD, DCM mixed with liquid phase inoculum ratio 1:1 in AD produced the most biogas, while the treatment without the inoculum showed the lowest biogas production. The organic matter (OM) in the substrate was rapidly degraded for 41 days with the kinetic constant k1 and then, OM was remained with the slow degradation rate of k2 until the process termination of AD.
Total. chemical. oxygen demand (TCOD) of fresh dairy cow manure (F-DCM) and mixture of dairy cow manure and sawdust amendments (DCM+S) from cow farm house was recorded 266,000∼304,000 mg L-1 and 240,000∼264,000 mg L-1, respectively. At the same time, biodegradability of fresh dairy cow manure and mixed dairy cow manure with sawdust from cow farm house was observed as 37~46% and 30~40%, respectively. The kinetic constant k1 and k2 of fresh dairy cow manure were recorded as 0.069~0.078/day and 0.002~0.005/day, respectively. According to the organic matter degradation, the 88~95% of degradation with kinetic constant k1 and 5∼12% of that kinetic constant k2 were observed through AD process. In case of AD, the kinetic constants k1 and k2 from DCM-S were lower than F-DCM alone as 0.048∼0.072 (k1) and 0.001∼0.003 (k2). During the AD with DCM-S using the Semi-Continuously Fed and Mixed Reactor (SCFMR), the inlet TS of substrate were adjusted to 13, 15, and 17%, optimum hydraulic retention times (HRTs) of SCFMR were 25~30 days (13% of TS) and 30~35 days (15 and 17% of TS), respectively. The optimum organic loading rates (OLRs) were as 3.7∼4.5 kgVS/m3-day(13% of TS), 3.5∼4.3 kgVS/m3-day (15% of TS) and 4.1∼4.8 kgVS/m3-day (17% of TS). The biogas production using SCFMR showed
the highest performance from optimum HRTs at the level of 17% TS in DCM-S, which were followed by the level of 15% TS and 13% TS. Biogas production in reactor with TS levels of 15% and 17% was increased when HRTs were changed from 40 to 30 days, while biogas production of the reactors was decreased when HRTs were shorten to less than 30 days. Biogas production in reactor with TS level of 13%was increased when HRTs were change from 40to 35 days, while biogas production in reactors was drastically decreased in less than 25 days HRTs. By adding micro elements [Ni (10 mg), Co (10 mg), Mo (0.2 mg), Fe (2 g)] to each reactor with the TS　level　of 13%, 15%, 17%, total. biogas production and methane content in the biogas were increased. The optimum HRTs each TS level of 13%, 15%, and 17% were 25~30 days and 30-35 days, respectively. The optimum OLR each TS level of 13%, 15%, and 17% were 3.7∼4.5 kgVS/m3-day, 4.3 kgVS/m3-day and 4.1∼4.8 kgVS/m3-day, respectively.
The compression process of AD of DCM and livestock manure led to removal of moisture level and the increase of VS/TS content. The low calorific values of DCM and korean native cattle manure were increased by the compression process. On the other hand, the low calorific value of swine manure was not significantly changed. The compression process decreased the chloride concentration in the korean native cattle manure and the swine manure. The optimum moisture content of livestock manure to of pelletize by wheel type press and screw type press was around 25% and 40%, respectively. However, in this study, the cylindrical. rotary pelletizer was developed and it required for livestock manure moisture content around 70%. Drying time of livestock manure using convection dry oven was inversely proportion to the particle size. When the infrared ray was used for drying process of livestock manure solid fuel, the results were similar to the case of using the convection dry oven process.