Using straw as a bio-ethanol source to promote anaerobic digestion of waste activated sludge

Commercial ethanol production from straw is a series of complex processes that are energy-intensive and uneconomical. Corn straw was used as a bioethanol source to mix with waste activated sludge for improving anaerobic co-digestion (AcoD) in this study. Ethanol production from the straw after yeast fermentation was 1400-2200 mg COD/L, accounting for about 0.1% of the fermentative effluent, but methane production of the yeast-group increased by 36% compared to that of control-group with no ethanol production in advance. Volatile suspended solid removal achieved 60%, obviously higher than common anaerobic digestion (AD). Multiple lines of evidence including sludge conductance, effects of activated carbon on methanogenesis and microbial community demonstrated that ethanol from the straw fermentation stimulated direct interspecies electron transfer to be established in the digesters. The results suggested that using ethanol produced from straw was a cost-effective novel way for energy recovery from disposal of agricultural and municipal wastes.