Effects of Ultrasonic Disintegration, Hot-Compressed Liquid Water Pre-Treatment, and Steam Explosion on Solvolysis and Digestibility Of Grain Sorghum Stover

One of the most promising renewable energy crops and biomass feedstock for biogas production in Europe is the C4 plant grain sorghum due to its high photosynthetic efficiency. The release of lignocellulosic material and therefore the acceleration of degradation processes of sorghum stalks and leaves can be achieved using mechanical and thermal pretreatments, which assist to hydrolyse the cell walls and speed the solvolysis of biopolymers. This study is focused on hotcompressed liquid water, steam explosion and ultrasonic pre-treatments of grain sorghum stover. The effectiveness of pre-treatments was evaluated by means of soluble chemical oxygen demand, biochemical oxygen demand, and by the biogas and methane productivities. The results show that the pre-treatments disintegrated the lignocellulosic structure, increased and accelerated the biogas and methane production, and increased the mesophilic anaerobic digestion potential of grain sorghum stover. Our laboratory tests demonstrated that the steam exploded grain sorghum stover possess the highest biogas productivity.