<b>Performance Evaluation of the Effect of pH and Temperature on the Biogas Yield of Co Digestion of Pig Manure and Water Hyacinth</b> In this research work, the effect of pH and temperature on the biogas yield of co digestion of Pig manure and water hyacinth were investigated experimentally in laboratory scale anaerobic bioreactors. The co digestion was run for a Hydraulic Retention Time thirty six days. The volumetric yield of biogas was noted once there is biogas build up at regular intervals using water displacement method. A total of ten evacuations were made and the data obtained was used to evaluate the effect of the aforementioned anaerobic digestion parameters. The experimental results revealed that a neutral pH value of 7 yielded optimum biogas yields compared to a pH value above and below 7. Moreover, from all the experimental mesophilic temperature used in this research work, an optimum mesophilic temperature of 37 oC favoured the optimum biogas yield. pH, Biogas yield, Hydraulic retention time, Pig manure, Water Hyacinth, Optimum biogas yield 455-457 Issue-2 Volume-3 Nse Peter Essang