The maximum residual sugar in continuous ethanol fermen- tation was 3.9 g/L, which contributed to TOC of 1560 mg/L in the stillage. The TOC concentration in the stillage was determined to be approximately 10,000 mg/L. A low heat value of 100 kcal could be gained from 1 L of stillage, by assuming that biogas of 1870 mL/g- TOC was produced and that the methane content in the biogas was 60%.