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Anaerobic digestion of hydrothermally-pretreated lignocellulosic biomass: Influence of pretreatment temperatures, inhibitors and soluble organics on methane yield

Phuttaro, Chettaphong, Sawatdeenarunat, Chayanon, Surendra, K.C., Boonsawang, Piyarat, Chaiprapat, Sumate, Khanal, Samir Kumar
Bioresource technology 2019 v.284 pp. 128-138
Cenchrus purpureus, anaerobic digestion, bioenergy, biomass, feedstocks, furfural, hydrolysis, hydroxymethylfurfural, lignocellulose, methane production, models, slurries, temperature
Anaerobic digestion (AD) of lignocellulosic biomass has received significant attention for bioenergy production in recent years. However, hydrolysis is a rate-limiting in AD of such feedstock. In this study, effects of hydrothermal pretreatment of Napier grass, a model lignocellulosic biomass, on methane yield were examined through series of batch and semi-continuous studies. In batch studies, the highest methane yield of 248.2 ± 5.5 NmL CH4/g volatile solids (VS)added was obtained from the biomass pretreated at 175 °C, which was 35% higher than that from the unpretreated biomass. The biomass pretreated at 200 °C resulted in formation of 5-hydroxymethylfurfural and furfural, which significantly inhibited methanogenesis. In semi-continuous studies, digester fed with the biomass pretreated at 200 °C at organic loading rate (OLR) of 4 g VS/L.d resulted in digester failure. Thus, OLRsoluble/OLRtotal ratio <200 is proposed as an operating criterion for effective operation of digester fed with pretreated biomass slurry.