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Optimization of Maximum Biogas Production from Anaerobic Digestion of Dairy Cow Manure using Semi-Continuously Fed and Mixed Reactor (SCFMR)
Efforts were made to identify the optimum operational condition of Semi-continuously Fed and Mixed Reactor(SCFMR) to treat the dairy cow manure and saw dust mixture. Step-wise increase in organic loading rates (OLRs) and decrease in hydraulic retention times (HRTs) were utilized until the biogas volume became significantly decreased in SCFMR at mesophilic temperature (35℃).
The optimum operating condition of the SCFMR fed with TS 15% dairy cow manure and saw dust mixture was found to be at HRTs of 30 days and its corresponding OLRs of 4.27 kgVS/m³-day. The optimum ranges of biogas and methane production rates were 1.47 volume of biogas per volume of reactor per day(v/v-d) and 1.14 v/v-d, respectively. This result was due to the high alkalinity concentration of SCFMR fed with the original substrate, dairy cow manure and saw dust mixture whose alkalinity was more than 10,000 mg/L as CaCO3. The parameters for the reactor stability, the ratios of volatile acids and alkalinity concentrations (V/A) and the ratio of propionic acid and acetic acid concentrations (P/A) appeared to be 0.07-0.09 and 0.38-0.43, respectively, that were greatly stable in operation.
The Total Volatile Solids(TVS) removal efficiency based on the biogas production was 45.2% at the optimum HRTs. Free ammonia toxicity was not experienced at above 160 mg/L due to the acclimation of high concentration of ammonia by the high reactor TS content above 9.0%.
