Effect of Fungal, Bacterial and Alkaline Augmentations on the Biogas Composition of Selected Plant-based Substrates

Abstract

Lignocellulosic residues are interesting sources of renewable energy, if only their biomass recalcitrance could be reduced through appropriate pretreatment technologies and augmentations, to enhance anaerobic digestion. This study aimed at assessing the effects of bacterial, fungal and alkaline augmentations, on the biogas composition of selected plant-based substrates, namely: maize cob , rice straw and water hyacinth. Standard methods were adopted; the substrates were mechanically pretreated, loaded in single, dual and composite combinations, into five 54 L capacity metallic batch anaerobic digesters. Codigestion was encouraged with the addition of cow rumen waste. The set ups were allowed to run for 42 days under mesophilic conditions, while stirring daily. The biogas composition namely: methane, carbon IV oxide and hydrogen sulfide concentrations were measured on the 42nd day. The results showed that the composite with the combined treatments showed the highest concentration of methane (87%), followed by the composites with fungal augmentation (80%), bacterial (77%) and then alkaline (75%) augmentations. The least percentage of methane (9%) was recorded in the composite without treatment and no cow rumen waste added, which also had the highest percentages of hydrogen sulphide and carbon IV oxide. To improve the yield and quality of biogas generated from a lignocellulosic biomass, appropriate pretreatment strategies and augmentations are required.