Abstract
It is very difficult to ferment waste oil, and necessary to pretreat it somehow for decomposing into the matters such as short-chain fatty acids. Generally, oil is decomposed into carbon dioxide and water by microorganism under aerobic condition. However short-chain fatty acids will be formed invariably in the middle of aerobic decomposition process. In this study, we investigated suitable operation of the pretreatment of waste oil for mesophilic methane fermentation.