COMPARISON OF BIOETHANOL YIELD FROM FOUR COCOYAM SPECIES IN NIGERIA

Abstract

This work was undertaken to compare the yield of bioethanol from four species of Cocoyam: Edeofe (Colocasia esculenta Nce 003), Edeanambe (Colocasia esculenta Nce 001) and Edeuhie (Xanthosoma sagittofolium Nxs 002), Edeocha (Xanthosoma sagittofolium Nxs 001). Two hydrolysis steps was carried out in the work (acid hydrolysis was carried out using two acid types, sulphuric and hydrochloric acids while enzymatic hydrolysis was carried out using alpha-amylase and glucoamylase). Fermentation of the hydrolysates was done using commercial baker’s yeast (Saccharomyces cerevisiae) at pH 5.0 for four days. The result shows that the highest ethanol yield of 4.89ml/20g (0.00024Lg-1) with 19.32% yield was obtained from enzymatic hydrolysis as compared to 3.86ml/20g (0.00019Lg-1) with 15.26% yield from acid hydrolysis with H2SO4. “Edeofe†produced the highest yield of ethanol when compared with other species: from enzymatic hydrolysis, Edeofe produced 0.00024Lg-1 when compared to 0.00021Lg-1, 0.00020Lg-1 and 0.00022Lg-1 for Edeanambe, Edeuhie and Edeocha respectively. The same trend occurred in acid hydrolysis. Though enzymatic hydrolysis produced higher ethanol yield than acid hydrolysis, hydrolysis using H2SO4 was a better option than that of HCl: Edeofe produced 0.00019Lg-1 with 15.26% yield with H2SO4 hydrolysis when compared to 0.00015Lg-1 with 12.0% yield from HCl hydrolysis. Thus cocoyam, especially Edeofe specie, has shown to be a promising source of biomass for bioethanol production. Thus farmers should be encouraged to cultivate more of the specie in order to boost the bioethanol industry in Nigeria. Key words: Cocoyam, Bioethanol, Biofuel Production, Colocasia esculenta, Xanthosoma sagittofolium