Ethanol production from tropical sugar beet juice

Abstract

Starch and sugar resources have been extensively researched to find a suitable renewable source of energy to supplement the world’s ever increasing demand for energy while also abating global warming by stemming the addition of earthbound carbon dioxide into the atmosphere. Sugar beet has been used as a source for sugar production for some time, but its development as a large scale agricultural crop in South Africa has been limited by the large production of sugarcane in tropical areas. Recent trials in the Eastern Cape region have shown some promise for cultivating sugar beets on a large scale. In this study, the influence of process variables such as initial sugar concentration (dilution), pH, yeast concentration and nitrogen source addition were investigated to assess the influence of these variables on the bioethanol production potential of tropical sugar beet. High ethanol yields were obtained without dilution (approximately 0.47 g.g sugar^-1) while a pH of 4 and a concentration of 5 g.L^-1 yeast (Saccharomyces cerevisiae) produced the largest amount of ethanol in the shortest fermentation time. The addition of a nitrogen source such as ammonium sulphate significantly  increased the ethanol yield. It was concluded from the results of this research that bioethanol can be produced economically from tropical sugar beet cultivars grown in South Africa.

Key words: Tropical sugar beet, fermentation, dilution, pH, bioethanol yield.