Assessment of Different Agricultural Waste Feedstock Options in Makurdi for Bioethanol Production

Abstract

The growing demand for sustainable and environmentally friendly energy sources has intensified interest in bioethanol production from renewable biomass, particularly lignocellulosic agricultural residues. This study evaluated the bioethanol production potential of selected agro-wastes including corn cob, rice straw, cassava peels, sawdust, and groundnut shells, sourced from Makurdi, Benue State, Nigeria, with the aim of identifying a feasible and sustainable feedstock for renewable fuel generation. The substrates were subjected to alkaline pre-treatment using sodium hydroxide to enhance saccharification, followed by fermentation using Saccharomyces cerevisiae (PWA) under controlled laboratory conditions. Variations in pH, reducing sugar concentration, ethanol yield, and yeast growth dynamics were monitored over a four-day fermentation period. The results revealed substrate-dependent fermentation behavior. pH values remained predominantly within a slightly alkaline range across all substrates, with cassava peels exhibiting a progressive decline from pH 8.0 to 6.0, while groundnut shells showed an increase to pH 9.1 by day four. Reducing sugar concentrations decreased over time in all substrates, indicating active microbial utilization, with rice straw recording the highest initial reducing sugar concentration (0.076 ± 0.001 g/g). Ethanol production peaked between days one and two, depending on the substrate, with cassava peels yielding the highest ethanol concentration (0.045 ± 0.001 g/g). Yeast growth trends correlated positively with fermentable sugar availability, as cassava peels consistently supported the highest Saccharomyces cerevisiae (PWA) population, reaching 4.82 × 10 6 CFU/mL by day four. Overall, cassava peels demonstrated superior fermentability, ethanol productivity, and microbial support compared to the other agricultural residues evaluated. The findings highlight the significant potential of locally available lignocellulosic wastes for sustainable bioethanol production and underscore their role in waste valorization, greenhouse gas mitigation, and renewable energy development. This study provides valuable insights for advancing biofuel technologies in Nigeria and contributes to efforts toward achieving the United Nations Sustainable Development Goal 7 on affordable and clean energy.