Journal of Energy Bioscience 2024, Vol.15, No.3, 208-220 http://bioscipublisher.com/index.php/jeb 210 2.3.3 Fertilization strategies Fertilization strategies play a critical role in corn cultivation. The application of both organic and inorganic fertilizers can provide the necessary nutrients for corn growth. Studies have demonstrated that combining fertilizers with soil amendments like biochar can further enhance nutrient availability and uptake, leading to increased crop productivity (Wijitkosum and Sriburi, 2021). 2.3.4 Pest and disease management Effective pest and disease management is vital for maintaining healthy corn crops. Integrated pest management (IPM) strategies, which include the use of resistant corn varieties, biological control agents, and appropriate chemical treatments, can help mitigate the impact of pests and diseases on corn yield. The development of disease-resistant corn varieties has also been highlighted as a key factor in ensuring sustainable corn production (Okudoh et al., 2014). 2.4 Harvesting and post-harvest handling Timely and efficient harvesting is crucial to prevent losses and maintain the quality of corn for ethanol production. Mechanized harvesting techniques can improve efficiency and reduce labor costs. Post-harvest handling, including proper drying and storage, is essential to prevent spoilage and maintain the starch content of the corn. Ensuring that harvested corn is stored in optimal conditions can significantly impact the overall yield and quality of the ethanol produced (Nguyen et al., 2007). 3 Processing Steps of Corn Ethanol Production 3.1 Overview of corn processing steps Corn ethanol production involves several key steps, from the initial processing of corn to the final production of ethanol. The primary stages include milling, pretreatment, enzymatic hydrolysis, fermentation, and distillation. Each step is crucial for converting the starch in corn into fermentable sugars and ultimately into ethanol. Studies have shown that while cassava starch yields a slightly lower final ethanol concentration compared to dent corn starch, corn still holds significant advantages in bioethanol production (Figure 1). By optimizing process conditions and enzyme usage, the utilization of corn starch and ethanol yield can be significantly improved. Additionally, corn, with its high starch content and lower gelatinization temperature, offers greater economic viability and operability in industrial production. Figure 1 illustrates the efficiency comparison of corn and cassava as raw materials for bioethanol production and details the processes of traditional and GSH methods. In the traditional process, corn starch is liquefied at 60 ℃ using α-amylase, followed by saccharification at 30 ℃to produce ethanol via solid-state fermentation. In the GSH process, cassava starch is incubated at 48°C using GSH enzymes, followed by the same solid-state fermentation to produce ethanol. The bar chart in the figure shows that the final ethanol concentration from cassava starch is comparable to that from high-amylose corn starch, slightly higher than waxy corn starch, but lower than dent corn starch. This indicates that while corn has a slight edge in ethanol yield, cassava also holds considerable potential as a feedstock. By presenting the details of different processes and raw materials, the figure provides valuable insights for optimizing bioethanol production processes. 3.2 Dry milling vs. wet milling processes Corn can be processed using either dry milling or wet milling methods. In the dry milling process, the entire corn kernel is ground into flour, which is then mixed with water to form a mash. This mash undergoes enzymatic hydrolysis to convert starches into sugars, which are then fermented to produce ethanol. The wet milling process, on the other hand, involves soaking the corn kernels in water and sulfur dioxide to separate the kernel into its component parts: starch, fiber, germ, and protein. The starch is then processed into ethanol. Wet milling is generally more complex and capital-intensive but allows for the production of multiple co-products, such as corn oil and animal feed (Han et al., 2011; Kang et al., 2014; García-Velásquez et al., 2020).
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