Journal of Energy Bioscience 2024, Vol.15, No.3, 208-220 http://bioscipublisher.com/index.php/jeb 215 biomass can lower production costs and increase the commercial viability of cellulosic ethanol (Rosales-Calderon and Arantes, 2019). As the industry evolves, continued research and policy support will be crucial in addressing the environmental and economic challenges associated with corn ethanol production and maximizing its potential as a renewable energy source. 8 Case Studies 8.1 Successful implementations of corn ethanol production Corn ethanol production has seen significant advancements and successful implementations, particularly in the United States. From 2005 to 2019, the U.S. corn ethanol industry experienced a substantial increase in production, from 1.6 to 15 billion gallons. This growth was driven by supportive biofuel policies and resulted in a notable reduction in greenhouse gas (GHG) emissions. The carbon intensity (CI) of corn ethanol decreased by 23%, from 58 to 45 gCO2e/MJ, due to improvements in corn grain yield, ethanol yield, and energy efficiency in ethanol plants. These advancements led to a total GHG emission reduction benefit of 544 million metric tons of CO2e during this period (Lee et al., 2021). In Brazil, the integration of energy cane juice into corn ethanol production has shown promising results. Energy cane juice can significantly enhance fermentation efficiency and reduce the amount of corn and water needed for ethanol production. This integration not only improves the sustainability of the production process but also supports the growth of the corn ethanol industry in regions like the Center-West of Brazil (Sica et al., 2021). 8.2 Comparative analysis of regional production systems Comparative analyses of regional corn ethanol production systems reveal significant differences in energy efficiency and environmental impact. In the United States, the carbon intensity of corn ethanol has been actively researched and quantified, with recent life cycle analyses (LCAs) showing a central best estimate of 51.4 gCO2e/MJ, which is 46% lower than the average CI for neat gasoline (Fiture n1). The largest contributors to the total CI are ethanol production and farming practices, while land use change (LUC) is a minorcontributor (Scully et al., 2021). In Brazil, the integration of sugarcane, corn, and grain sorghum in multipurpose plants has been evaluated. The environmental and energy performance of these integrated systems is greatly influenced by agricultural activities, with sugarcane cultivation playing a crucial role. However, the integration of starchy sources like corn and grain sorghum can increase the environmental impact, particularly in terms of climate change and human toxicity (Donke et al., 2016). Figure 2 from Lee et al. (2021) illustrates the system boundaries and key parameters for the life cycle assessment of corn ethanol production. This includes four main stages: corn cultivation, ethanol production, ethanol transportation and distribution, and ethanol combustion. The figure details the greenhouse gas emissions at each stage, especially focusing on farm production inputs, corn growth, and the energy usage of biorefineries. By clearly indicating the carbon emissions at each stage, Figure 1 helps us understand the primary sources and influencing factors of greenhouse gas emissions throughout the corn ethanol production process, aiding in the development of strategies and measures to reduce emissions. 8.3 Lessons learned and best practices Several lessons and best practices have emerged from the successful implementations and comparative analyses of corn ethanol production systems. Key lessons include: 1) Efficiency Improvements: Enhancing the efficiency of ethanol plants and agricultural practices can significantly reduce the carbon intensity of corn ethanol. For example, increasing corn grain yield and ethanol yield, along with reducing energy use in ethanol plants, has proven effective in the U.S. (Lee et al., 2021).
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