Mesophilic anaerobic characteristics of honeysuckle and midday tea herbs residues

A self-prepared anaerobic reactor was utilized to treat the residues of honeysuckle and midday tea in semi-solid phase media. The anaerobic sludge was inoculated into the residues for anaerobic digestion at the temperature of (37±1)℃ and under the inoculum to substrate ratios (ISRs) of 1∶2, 1∶1, 2∶1 and 3∶0, respectively. The results showed that the ultimate maximum yield of methane was under ISRs of 1∶1, and the cumulative methane production volume of honeysuckle and midday tea dregs was 78.2 and 109.0 mL/g, respectively. Under the optimal inoculation ratio of 1∶1, another mesophilic anaerobic experiment was carried out by mixing the residues of honeysuckle and midday tea as substrate at different ratios of 0∶3, 1∶2, 1∶1, 2∶1 and 3∶0, respectively, at (37±1)℃. The result indicated that the ultimate maximum yield of methane was under mixed ratio of 1∶2, and the cumulative methane production volume of the mixed Chinese herbs residues was 138.2 mL/g. Furthermore, the zero-order kinetic model was found to be suitable to characterize the removal ratio of substrate during 0-96 h digestion while the biogas was generated fast, and the kinetic constant k was 1.11 mL/(h·g). To obtain the ultimate maximum rate of methane production, the anaerobic reaction should be controlled under the stage of zero-order reaction.