Exploration of the Bioethanol Yield of Single and Multi-Substrate Biomass from Cassava Processing Wastes

Abstract

Cassava processing generates large quantities of wastes which contribute significantly to environmental pollution. These wastes are abundant and inexpensive feedstock for bioethanol production that are available all year round in every region in Nigeria. Despite their wide availability, optimal generation of bioethanol from these wastes has not been achieved. This study explored the bioethanol yielding potential of single and multi-substrates biomass from cassava processing wastes. Physicochemical characterization of the cassava processing wastes viz: cassava peels (Cp), cassava pulp (Cpu) and cassava wastewater (Cw) revealed the followings: low pH, cyanide, high total organic carbon and organic matter; low total nitrogen and phosphorus content. Among the single substrates, cassava peels (Cp) gave the highest glucose yield (GY), (48.04 mg/g) and total reducing sugars (TRS), (103.44 mg/g) respectively; while the combination of cassava peel, pulp (Cpu) and wastewater (Cw) (CpCpuCw) gave the highest GY (61.67±0.03mg/g) and TRS (111.36±0.04mg/g) among the multi-substrates. The ethanol yield obtained from the substrates at 24 hours, 48 hours and 72 hours of fermentation were: Cp (337.5m3/kg, 354.0m3/kg and 348.6m3/kg), Cpu (249.4m3/kg, 270.6m3/kg and 264.6m3/kg), Cw (86.2m3/kg, 109.2m3/kg and 109.0m3/kg), CpCpu (352.3m3/kg, 386.9m3/kg and 381.5m3/kg), CpCw(339.0m3/kg, 370.6m3/kg and 359.4m3/kg), CpuCw (267.9m3/kg, 279.5m3/kg and 271.2m3/kg), and CpCpuCw (408.7m3/kg, 427.5m3/kg and 410.6m3/kg) respectively. The study revealed that the combination of the three wastes (CpCpuCw) produced the highest GY/TRS and yield of bioethanol among the substrates, while the maximum ethanol yield was obtained at 48 hours of fermentation. Hence bioethanol production from multi-substrates biomass of cassava processing wastes should be fully explored.