Mixture 2 yielded the optimum percentage of methane gas on the 22nd day with 49%.
However, fl uctuations 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 fi nding 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