A review of the production of bioethanol from rice husk biomass.

Abstract

Rice husk is the most abundant resources and attractive lignocellulosic materials for bioethanol production. This substrate includes cellulose and hemicellulose contents that are hydrolysed into fermentable sugars. Rice straw substrate contains a high quantity of lignin in their composition, and needs an appropriate pretreatment approach for bioethanol production. Bioethanol is got from alcoholic fermentation of sucrose or simple sugars, which are produced from biomass using hydrolysis process. Bioethanol can be obtained using enzymatic hydrolysis and acid hydrolysis. Filtrates after hydrolysis of the various husks were subjected to 7 days’ fermentation with yeasts from palm wine as well as bakers’ yeasts. Bioethanol yields got from palm wine yeast fermented husk as well as sugar from other treated husks were obtained. During the process of enzymatic hydrolysis of the pretreated RH, using the acid cellulose enzyme, it was found that the highest concentration of TRS in the samples was 7.788gTRS/L, obtained in a time of 24 hours of hydrolysis. After the alcoholic fermentation of the glucose syrups obtained, at a laboratory scale, a distillate with a concentration of 3.7% v/v was achieved by simple distillation. For the pilot-scale process, 450.00g of RH pretreated with NaOH solution 2.00%w/v (430.47g drybase) were treated, with the subsequent enzymatic hydrolysis with acid cellulase, the alcoholic fermentation of the sugars reducers obtained in the hydrolysis, and fractional distillation of the must, it was possible to obtain four samples of bioethanol with concentrations of 71.3,30.0,10.3, and5.3%v/v of alcohol, which when mixed produced a sample of 95mL of solution with a concentration of 27%v/v of alcohol (4.70g/100g of RH), therefore, taking as a reference the theoretical value of 30 gethanol/100g of RH, a yield of 15.67% was obtained. The production of bioethanol on a laboratory scale is preferred because it was found out that the highest bioethanol within 7 days after the alcoholic fermentation of the glucose syrup than that of the pilot scale as it will be discussed later.

Key words: - Bioethanol, Rice husks, Bio mass, Saccharification, Hydrolysis, Lignocellulosic biomass