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The production of biogas from lignocellulose by anaerobic digestion (AD) has attracted much attention recently. However, the over-acidification phenomenon and low biogas yield often occur during the AD of lignocellulose. In this work, the liquid-state fermentation mode using pretreatment liquor from dilute acid treated rice straw without detoxification for continuous biogas production in a 100 L internal circulation reactor was studied. The highest biogas yield reached 0.66 m3/kg CODconsumption while the methane yield was 0.38 m3/kg CODconsumption. The pH values of outlet were maintained at 6.9–7.4, and even the inlet pH values were lower than 6.0. Furthermore, from the second day to the end of fermentation, the COD removal rates were more than 90%, even though the inlet COD was close to 20000 mg/L. The organic substances from acid pretreated rice straw were efficiently degraded by AD, which was confirmed by substrate metabolism analysis. These results indicated that the whole fermentation process of AD was very stable and showed great potential for industrial application. [Display omitted] • AD of pretreatment liquor from dilute acid treated rice straw without detoxification. • The COD removal rate during the AD process was more than 85%. • The sugars and organic acids could be utilized efficiently. • Continuous biogas production in a 100 L IC reactor was investigated. [ABSTRACT FROM AUTHOR]