The influence of C/N ratios and OLRs on pH values, alkalinity (Alk) production, volatile fatty acids
(VFAs) production, VFA/Alk, and methane yield were evaluated and present as following;
3.1. pH of co-digestion of Pennisetum pururem cv. Pakchong 1 grass and layer chicken manure.
pH is an important parameter influencing the performance of anaerobic digestion processes. In this
work, both reactors were operated without any adjustment for pH inside the reactor. The pH profiles of
co-digestion of Pennisetum pururem cv. Pakchong 1 grass and layer chicken manure are shown in Fig. 1.
The average pH of effluent from R1 and R2 were 7.08 ± 0.05 and 6.93 ± 0.03, respectively. This value
showed that the reactors worked within the optimum interval (pH