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Valorization of agro-industrial waste into bioethanol: a case of brewers spent grain

Mintesinot Dessalegn Dabaro, Hundessa Dessalegn Demsash

Abstract


Abstract

The global impetus to produce alternatives to petroleum-based fuels and value-added chemicals to reduce greenhouse gases are putting pressure on the industries to diversify and valorize byproducts. By-products valorization of the brewery industry such as spent grain has given critical attention for long-term socio-economic and environmental benefits. Brewer`s spent grain is the major by-product of the brewing industry, represses around 85% of the total by-product generated. In the current work, hydrolysis is employed for the production of bioethanol from the spent grain.  Due to it’s low cost and high fermentable sugar yield, dilute phosphoric acid hydrolysis was conducted. The hydrolysis parameters were reaction temperature, retention time and dilute phosphoric acid concentration with operating range of (140-150, (20-30) min and (2-3) % respectively. The optimum operating process parameters were found to be a reaction temperature of 1500C, retention time of 20min, the phosphoric acid concentration of 3% yielding 57.8% total reduced sugar. After the hydrolysis stage, fermentation was carried out for 72 hours with the substrate to yeast strain ratio of 10:1. The fermentation process was conducted at a temperature and pH range of (30-38,  and (4.5-5.5) respectively. It was found that temperature and pH of 320C and 5 is optimum for fermentation with coefficient of determination 0.99. The kinetic analysis was also conducted for the fermentation process and found that the order, rate constant, frequency factor and activation energy were 1.0043, 0.01225hr-1, 2.4   and 16.133 KJ, respectively.

 Key Words:  spent grain, hydrolysis, fermentation, bioethanol, Kinetics


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References


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