Organic compounds such as proteins and starch contained in sweet sorghum juice cannot be utilized during ethanol fermenta- tion. However, little attention has been paid on the surplus organic compounds, although performed anaerobic digestion of the remaining biomass after hydrogen fermentation of sweet sorghum juice. Thus, it is important to add an additional process, such as methane fer- mentation, following ethanol fermentation to recover the most energy from sweet sorghum juice and reduce the content of organic compounds released into the environment.