Laboratory and field production of bioethanol from cassava peel-waste using dilute acid low temperature hydrolysis and fermentation processes

By: Davies E. Mweta, Joseph Kumphanda, Joseph Issa,

Abstract

In tropical countries, agricultural wastes such as cassava peel are potential raw materials for production of bioethanol because they are renewable, cheap and widely available. This study investigated the potential of cassava peels as raw materials for ethanol production following dilute acid hydrolysis and fermentation using Saccharomyces cerevisiae (baker’s yeast). The experiments were conducted both under laboratory and field conditions. In the laboratory experiments, dry cassava peel flour samples (1.0g) were hydrolysed with sulphuric acid (50mL; 0.1M) at different temperatures ranging from 25°C to 70°C and hydrolysates were analysed for reduced sugars. The optimum result of the acid of hydrolysis was fermented by baker’s yeast for a period of six days at room temperature, distilled and the alcohol yield was determined using an alcoholimeter. In the field experiment, 6 kg of dry cassava peel flour were hydrolysed with 30L of 0.1M battery acid in a Solar Still for hydrolysis for three days, after which it was neutralised and anaerobically fermented with 150g of baker’s yeast at room temperature for four days. The fermented mixture was filtered using mutton cloth, distilled using the local distillation apparatus and the alcohol content of the filtrate determined. In the laboratory experiment, maximum reducing sugars yields of 45% were obtained at 70°C over a period of two days and the maximum obtainable yield of bioethanol was 12%. In the field experiment, the highest ethanol yield was 7.5% ethanol. The results suggest that it is possible to hydrolyse cassava peels using dilute acid. However, there is need to maintain higher temperatures under field conditions throughout the year and more specifically during the period of cassava harvest.