Managing and optimizing biogas yield need to survey quantitatively the effects of parameters on anaerobic digestion. In this research, changes of pH and oxidation reduction potential (ORP) along with temperature in biogas yield from cattle manure were investigated. The study was carried out by using batch manure mixed 1150-ml anaerobic digester for a duration of 130 days in the mesophilic range (37oC). Temperature change was also stimulated on the day 45 by decrement from 37 to 25 oC for one day and then restored to previous condition. Results of biogas yield in different phases showed that the hydrolysis and acetogenic phases occur within 13 days. Biogas production (76.7 %) occurred within 32 days at pH=7.4 and ORP=-358 mV. The temperature change stopped biogas yield for 29 days without affecting pH and ORP values and subsequently after that gas production was restored. Results showed that changes in pH and ORP were compatible to each other and biogas production. Also temperature change had no significant effect on pH and ORP but causes delay in the gas production. The results could serve as preliminary criteria for different kinetic analyses and operational guidelines and restoration of the reactors of anaerobic digestion of cattle manure.
