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The effects of pre-aeration and inoculation on solid-state anaerobic digestion of rice straw

Zhou, Ying, Li, Chao, Nges, Ivo Achu, Liu, Jing
Bioresource technology 2017 v.224 pp. 78-86
aeration, anaerobic digestion, biodegradation, biomass, buffering capacity, inoculum, lignocellulose, mass transfer, methane, methane production, rice straw, temperature, volatile fatty acids
Pre-aeration was investigated for enhancing biodegradation of recalcitrant lignocellulosic structure of rice straw under various low temperatures regimes (25, 35 and 45°C) and aeration durations (0, 2, 4, 6 and 8days). It was demonstrated aerated rice straw for 2days at 35°C resulted in highest hydrolytic efficiency and biochemical methane potential (BMP) (355.3±18.7mlCH4/gVS). Furthermore, both methane yields and initiation speeds of the solid-state anaerobic digestion (SS-AD) were inversely proportional to substrate-to-inoculum ratios due to the accumulation of volatile fatty acids (VFAs) and poor mass transfer. The highest methane yield achieved under SS-AD was 234mlCH4/gVS at TS of 16% which 72% of the BMP. Inoculum dilution with recycled water improved buffering capacity and mitigated accumulation of VFAs, resulting in an improved SS-AD performance. The combined pre-aeration and SS-AD was therefore established as a viable option to accelerate methane production for lignocellulosic biomass.