Mechanical Pretreatment of Lignocellulosic Biomass for Methane Fermentation in Innovative Reactor with Cage Mixing System

Disintegration of lignocellulosic biomass for energy purposes has been extensively studied. The study aimed to investigate the influence of crushed and uncrushed lignocellulosic biomass on the biogas production in an innovative reactor. The substrate fed to the reactor was Sida hermaphrodita silage mixed with cow manure. The bioreactor had an innovative design of the mixing cage system. The mixing system of the bioreactor consisted of two cylindrical stirrers in the form of a cage. The cages simultaneously rotate around the axis of the bioreactor at against their own axes. The bioreactor is currently presented under the Record Biomap program (Horizon 2020). The bioreactor was operated at organic compounds loading of 2 kg/(m3∙d) and 3 kg/(m3∙d) and hydraulic retention time was 50 d and 33 d, respectively. The biogas production under the organic compounds loading of 2 kg VS/(m3∙d) was 680 L/kg VS from crushed lignocellulosic biomass and 570 L/kg VS from uncrushed lignocellulosic biomass. The biogas production under the organic compounds loading 3 kg VS/(m3∙d) was 730 L/kg VS from crushed lignocellulosic biomass and 630 L/kg VS from uncrushed lignocellulosic biomass. The crushing of substrate did not influence the methane content in the biogas. In all experiments, the biogas comprised about 54% of methane. The net energy efficiency was calculated as well.