Mixture 2 yielded the optimum percentage of methane gas on the 22nd day with 49%. However, fluctuations were observed on the 31st, 34th and 37th days. For Mixture 3, the optimum methane was produced on the 25th day with 46%. In general, the graph for Mixture 3 is stable because food waste content and sludge are balanced (1.5 kg: 1.5 kg). On the basis of the results, the highest percentages and production of methane gas were generated with Mixture 2, followed by Mixtures 3 and 1. This finding may be attributed to the amount of food waste and sludge. Even though more CH4 was produced in the thermophilic digester, there are several signifi cant microbiology characteristics associated with thermophilic anaerobes and digestion process that will affect the digester performance. These include the low bacterial growth or yield, high endogenous death rates of these bacteria and lack of diversity of anaerobes (Gerardi, 2003).