Journal of Energy Bioscience 2024, Vol.15, No.3, 208-220 http://bioscipublisher.com/index.php/jeb 212 Moreover, the development of very high gravity (VHG) fermentation technology has emerged as a versatile method to save process water and energy. This technology allows for the fermentation of higher concentrations of sugar substrates, resulting in increased final ethanol concentrations and improved fermentation efficiency without major alterations to existing facilities (Puligundla et al., 2011). The use of hybrid membrane fermentation and heat integration through Pinch Analysis has also been evaluated, showing potential in reducing overall energy consumption and increasing surplus electricity generation (Lopez-Castrillon et al., 2013). 4.2 Integration of biotechnology in corn ethanol production The integration of biotechnology in corn ethanol production has led to more sustainable and efficient processes. For example, the blending of commercial xylose-fermenting and wild-type Saccharomyces yeast strains has been shown to improve ethanol yields from deacetylated corn stover and sugarcane bagasse. This approach not only increased ethanol production by 6.5% but also reduced the residual xylose content and the amount of yeast required for inoculation (Wang et al., 2019). Additionally, the incorporation of energy cane juice into the corn ethanol production process has demonstrated several benefits. Energy cane juice provides sugars that reduce the amount of corn and enzymes needed, decreases water usage, and significantly increases fermentation efficiency by providing minerals that support yeast growth (Sica et al., 2021). This integration makes the fermentation process more efficient and the production systems more sustainable. 4.3 Improvements in process efficiency and energy consumption Improvements in process efficiency and energy consumption are critical for the economic viability of ethanol production. The integration of different technologies, such as the traditional dry-grind process with the gasification of corn stover followed by syngas fermentation or catalytic mixed alcohols synthesis, has shown to optimize energy use and reduce production costs. This integrated process requires only 17 MW of energy and 1.56 gallons of freshwater per gallon of ethanol produced, resulting in a production cost of $1.22 per gallon (Čuček et al., 2021). Furthermore, the application of in situ ethanol removal during high solid fermentation has led to significant improvements in the fermentation process. This method allows for the complete fermentation of high solids slurries and faster fermentation rates, reducing the fermentation time by more than 50% and increasing ethanol yield by 88% compared to conventional processes (Kumar et al., 2018). The use of repeated fermentation with cell reuse has also been effective in improving fermentation efficiency and achieving high ethanol productivity from corncob residues (Fan et al., 2013). 5 Economic Analysis 5.1 Cost of corn production and processing The cost of corn production and processing is a critical factor in the economic viability of corn ethanol fuel. The production costs are influenced by several factors, including the scale of the facility and the type of feedstock used. For instance, a study evaluating the economic feasibility of producing ethanol from various feedstocks found that the minimum ethanol selling prices (MESP) for a 50 million gallon per year facility ranged from $2.24 to $2.96 per gallon, which is comparable to gasoline prices. However, smaller facilities with a capacity of 1-2 million gallons per year had significantly higher MESPs, ranging from $5.61 to $7.39 per gallon, indicating that economies of scale play a crucial role in reducing production costs (Ro et al., 2019). Additionally, the integration of first- and second-generation ethanol production can potentially reduce downstream processing costs and improve overall economic feasibility (Joelsson et al., 2016). 5.2 Market trends and price volatility The ethanol market is subject to significant price volatility, which is influenced by various factors including corn market uncertainty and oil price fluctuations. A study examining the impact of corn market uncertainty on US ethanol prices found that ethanol prices react positively to corn market volatility shocks, particularly when these
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