Compositional Assessment of Selected Plant-based Substrates for Biogas Production

Abstract

Enormous quantities of plant biomass are generated annually, as agricultural wastes. Lignocellulose is the main structural constituent of plants and represents the primary source of renewable organic matter on earth. This study was carried out to evaluate the lignocellulose composition, proximate and selected physicochemical characteristics of some selected plant-based substrates for biogas production. The substrates were: Corn cobs, Rice straw and Water hyacinth (Eichhorniacrassipes). They were collected, cut, dried for 72 hours at 320C, milled and subjected to hemicellulose, lignin and cellulose compositional analyses, using the standard Sox let extraction method. Standard methods were employed for proximate and physicochemical analyses. Results of the compositional evaluation showed that corn cob has the highest percentages of cellulose (42.0%), while extractives content was least (2.18%) in Rice straw. For the proximate analysis, the percentage carbohydrates (24.22) and ash (24.40) were highest in rice straw, while fat content  had the least values of 0.65%  recorded in corn cobs. The results of the physicochemical analysis showed that Rice straw had the highest values of TS (94.55%) and phosphorus (928.57mg/kg), Corn cob had the highest TVS (85.53%) and organic carbon (50.46%) while Water hyacinth recorded the highest Nitrogen content (2.33%). They are good substrates for energy generation, and lignocellulosic biomass holds a huge potential to meet the current energy demand of the modern world. The knowledge of the lignocellulosic composition of the biomass would help in choosing appropriate pretreatment measures to achieve better hydrolysis which would translate to higher biogas yield.