Evaluation and Modeling of Bioethanol Yield Efficiency from Sweet Sorghum Juice
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Evaluation and Modeling of Bioethanol Yield Efficiency from Sweet Sorghum Juice Elham Ebrahimiaqda 1
&
Kimberly L. Ogden 1
# Springer Science+Business Media, LLC, part of Springer Nature 2018
Abstract One of the challenges with using sweet sorghum as an energy crop is that although fermentation of the juice to ethanol does not require enzymes, the juice can easily spoil. One strategy to avoid spoilage is to harvest the juice in the field, place it into a tanker for transport, and add the yeast immediately to initiate the fermentation process to begin during transport. Hence, it is also important to understand how the fermentation process is influenced by pH, temperature, and dissolved oxygen, since these parameters would not be Bcontrolled^ during transport. A full factorial design was applied to examine and optimize yield efficiency of ethanol production for the fermentation of sweet sorghum juice. Bioethanol yield efficiency was modeled using a linear equation. Under optimal pH (5.5), temperature (28 °C), and dissolved oxygen (0%) conditions, a maximum theoretical yield efficiency of 0.75 was achieved for bioethanol produced from M81E variety of sweet sorghum. Keywords Bioethanol . Sweet Sorghum . Fermentation . Factorial design . Yield efficiency
Introduction The U.S. Energy Information Administration predicts that the total US energy consumption would increase to 114.5 quadrillion BTU by 2035 [1]. Fossil fuel alone cannot be the resolution for the fast growth rate of energy demand in modern society; additional sustainable sources of liquid fuels are needed. According to the Renewable Fuel Standard (RFS2), bioethanol is categorized as a renewable fuel [2]. Bioethanol is a liquid biofuel that can be produced from renewable feedstocks rich in sugar, starch, or lignocellulosic biomass. Bioethanol as biofuel may contribute to reduction of greenhouse gas emissions and global warming [3]. Sweet sorghum, a C4 crop is considered as one of the most promising feedstocks in bioenergy production especially to produce bioethanol [4]. Since sweet sorghum has a short growth period and can be planted in rotation with other crops, [5] its use does not require changes in land management and contributes to nitrogen fixation and uptake of nutrient residuals [6, 7].
* Elham Ebrahimiaqda [email protected] 1
Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ 85721, USA
Furthermore, it has a high tolerance to severe environmental conditions such as hot and dry weather and alkalinity and acidity toxicity, as well as the ability to grow using brackish or saline waters for irrigation [8]. Sweet sorghum juice is fermented directly, which reduces the cost of the bioethanol production processes [9]. Juice is extracted from the raw sorghum stalk and a sugar-rich juice can be used for bioethanol fermentation. The biggest drawback of sweet sorghum juice is its short shelf life, which leads to an increase of storage and transportation costs for this product. In-field fermentation can redu
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