Abstract
Biofuels have been identified as suitable in combating climate change as a result of green gas emissions from fossil fuels. Bioethanol is a biofuel from lignocellulosic biomass is considered a viable renewable energy alternative to fossil fuels. However, the recalcitrance of biomass feedstocks due to the presence of lignin, creates a barrier to glucose fermentation. This study compares enzymatic and dilute acid hydrolyses of cellulose substrates obtained from pretreated maize stalk. The cellulose substrates were hydrolysed into glucose using dilute H<sub>2</sub>SO<sub>4</sub>, dilute HCl and Cellulase enzyme. The glucose obtained was fermented using an active yeast strain (<i>Saccaromyces cerevisae</i>) and then distilled in accordance with ASTM D1078 to obtain bio-ethanol. High Performance Liquid Chromatography (HPLC) was used in quantitative analyses of the bio-ethanol produced while qualitative tests were done based on ASTM D7795-12 for physical tests (density, boiling point, miscibility, non-volatile residues, colour, flammability and distillation range) and chemical tests (Acidity, Alkalinity, Fusel oil, Readily carbonizable substances and readily oxidizable substances). Enzymatic hydrolysis gave a higher glucose yield, while there was no significant difference between hydrolysis using dilute acids. There was significant difference in extraction efficiencies between acid and enzymatic hydrolysis methods. The bio-ethanol produced has similar purity levels with qualitative properties to that of an industrial grade ethanol.
Highlights
Bioethanol is a biofuels that has been introduced as a partial replacement for fossil fuels in countries such as Brazil, India and the USA [1, 2]
The cellulose substrate for hydrolysis was obtained from alkaline-pretreated maize stalks
The recalcitrance of lignocellulosic biomass to hydrolysis is caused by the presence of lignin
Summary
Bioethanol is a biofuels that has been introduced as a partial replacement for fossil fuels in countries such as Brazil, India and the USA [1, 2] This biofuel has been produced from hydrolysis of starch which has created a competition between energy and food economies [3]. The production process in converting these biomass involves a pretreatment to remove lignin, followed by the conversion of complex sugars which are cellulose and hemicellulose into simple sugars such as, glucose and xylose, via hydrolysis. These are processed into ethanol, xylitol, organic acids, and other substances [7]. Corn stalk is one of the biomass with high potential for profitable use as a raw material for biofuel production, especially in bio-ethanol synthesis
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