Reducing heavy metals content in sugarcane molasses and its effect on ethanol fermentation efficiency

Abstract

The world energy scene is undergoing a period of transition. As the inevitability of exhaustion of fossil fuels is becoming increasingly intensive, efforts are exerted to find and use substitutes for energy. Bioethanol is one of the most substitute renewable fuels contributing to the reduction of the global warming effect and negative environmental impact. Bioethanol production generally utilizes derivatives from food crops such as corn grain and sugarcane. In Egypt, sugarcane molasses is mainly used as feedstock for bioethanol production. However, molasses contains a concentration of heavy metals. Heavy metals are presented in high concentrations in the fermentation medium causing a critical problem during fermentation. This study focuses on reducing heavy metals content in molasses to improve bioethanol fermentation using heating, centrifugation, sulfuric acid, and phosphoric acid. Heating and centrifugation were sufficient to decrease Ca with less effect on other metals. Sulfuric acid reduced heavy metals content and the reduction addition of phosphoric acid had less effect on lowering the levels of heavy metals in molasses. Pretreatment of molasses with 0.3% H2SO4 decreased the contents of various inhibitory metals: Ca, Cd, Cu, Fe, Ni, Pb, and Zn making molasses healthier for fermentation by yeast strains and increasing subsequent ethanol yield as well as high fermentation efficiency.