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Biogenic methane generation from lignite is investigated using biochemical methane potential (BMP) tests. It is found that 8.4% w/v of lignite as a sole substrate does not produce a significant amount of methane. It is considered that the bioavailability of lignite is low and the inhibition of methane generation occurs when there is a high concentration of lignite. In order to initiate and stimulate biogenic methane generation in high concentrations of lignite, an external substrate such as rice straw, which is easily obtainable and a cheap material in East and Southeast Asia, is added to the lignite. For a low rice straw addition to lignite (6.25% w/w), the inhibition of methane generation is found, but as the amount of rice straw increases, methane is produced from the lignite. At the end of the incubation period, the calorific value of the incubated lignite decreases as the amount of rice straw increases, which agrees with the trend of increasing methane generation as the amount of rice straw increases. [ABSTRACT FROM AUTHOR]