DETERMINATION OF BIO-ETHANOL YIELD FROM SELECTED LIGNOCELLULOSIC BIOMASS

Abstract

This research work examined the viability of producing bioethanol from seven lignocellulosic biomass feedstock samples of grass, maize grain, maize husk, maize cob, cassava, sawdust and paper through bio-chemical and biological processes. A sample size of 200 grammes was adopted for each of the feedstock in three replicates using Separate Hydrolysis and Fermentation (SHF) method. All of the biomass were grounded wet using manual grinder (Coroner brand) except sawdust that was used as received and further processed with the addition of 500 ml of water and 25 ml of concentrated acid (H2SO4). Each grounded samples were then raised to boiling in a pressure pot at 121 ℃ for 2 hours. Anhydrous Sodium Carbonate was added to the hot mixture to raise the pH from 3 to 8 in the pre-treatment stage. The alkaline mixture was cooled to a temperature of 37.5 ± 2.5 ℃. Ethanol resistant strain of yeast,saccharomyces cerevisiae (baker’s yeast) was added to the mixture, stirred and allowed to stay in a limited supply of air under controlled temperature of 40 ℃ to 45 ℃ for four days. The mixture was left to ferment for four days. It was sieved with 0.2 mm size, distilled and collected in sample bottles. The resulting (distillate) bioethanol from the distillation, was weighed on Pascal digital chemical scale model KD-CN. This procedure was repeated in three replicates per biomass. The replicates were analyzed using refractometer to check effective pre-fermentation process as well as the bioethanol volume per volume ratio in percentages. Further analysis was carried out using Fourier Transform Infra-Red (FTIR) spectrometry to identify the organic materials (radicals) present in each sample. Each of the seven Bioethanol samples were characterized namely, pour point, flash point, density, viscosity, boiling point and Octane rating. Gas Chromatography-Flame Ionization Detector (GC-FID) alcohol profile was carried out on the bioethanol to ascertain the presence of ethanol and the percentages by mass in the sample. The yield of the three replicates were analyzed statistically and the result was used to determine the mean yield per feedstock sample as follows: paper was 7.295g, maize grain was 17.125g, maize husk was 6.420g, maize cob was 8.203g, grass was 7.159g, saw dust was 8.066g and cassava was 16.686g, with the maize grain having the highest yield ratio of 17.125g. The high yield of ethanol from maize grain is influenced by the nature of biomass which consist mainly simple sugar (glucose) as against higher complex sugar (cellulose, lignin and hemicellulose). Hydrolysis is more effective to break the simple sugar, more than the complex sugar (lignocellulosic) that has strong bond between its sugar compositions namely, lignin, and cellulose and hemicellulose components in the biomass samples. The result showed that ethanol could be economically produced from all the samples and help to solve energy crisis by cultivating both energy and food crops as job creation.