Journal of Energy Bioscience 2025, Vol.16, No.3, 151-162 http://bioscipublisher.com/index.php/jeb 152 maize ethanol is produced in large quantities and makes up most of the biofuel market (Ranum et al., 2014; Skoufogianni et al., 2019). Second-generation biofuels, on the other hand, are made from non-food materials, like crop residues and forestry waste. In the U.S., maize stover (maize stalks and leaves) is a major source of second-generation biofuels because it is an important agricultural waste product (Dhugga, 2007; Jones et al., 2017; Choudhary et al., 2020). A key advantage of second-generation fuels is that they do not use food, so they make better use of waste materials and reduce dependence on food crops (Dhugga, 2007; van der Weijde et al., 2013; Choudhary et al., 2020). The technology for first-generation fuels is already well-developed, with the main process being starch hydrolysis followed by fermentation, which is quite efficient. However, because the raw material is food, it competes with food supplies. Second-generation fuels are made from lignocellulose, such as maize stover, switchgrass, and miscanthus. The production process is more complicated and requires pretreatment and enzymatic hydrolysis, which demands more advanced technology (van der Weijde et al., 2013; Zhuang et al., 2013). 2.2 Maize grain and stover in ethanol and other biofuel production Maize kernels contain a lot of starch, which is a good material for making fuel ethanol. In countries such as the United States where maize is grown a lot, about 40% of maize is used to make ethanol (Ranum et al., 2014; Skoufogianni et al., 2019). Maize ethanol not only provides energy, but also drives many related industries, such as biorefining, feed production and by-product utilization. Maize stalks contain a lot of cellulose and hemicellulose. After pretreatment and enzymatic decomposition, these substances can be turned into sugars, which can then be fermented to produce ethanol or other biofuels (Dhugga, 2007; Choudhary et al., 2020; Pratikshya et al., 2025). The cellulose, hemicellulose and lignin content in the stalks will affect the fuel conversion efficiency (Dhugga, 2007; Pratikshya et al., 2025). Different parts of maize, such as leaves, stems and kernels, have different gas and alcohol production capabilities during fermentation. Choosing the right raw materials and fermentation methods can increase yields (Ibrahim et al., 2025). Collecting maize stalks can also reduce farmland waste, but if too much stalks are collected, the soil may deteriorate, such as reducing fertility or destroying the structure, so it must be handled scientifically. 2.3 Advantages and limitations of maize and other bioenergy crops Compared with bioenergy crops such as sweet sorghum, sugarcane, switchgrass, and Miscanthus, maize has high yield, strong adaptability, and the agricultural planting and processing system is already mature. In addition to being a staple food crop, maize also has considerable biomass yield and good conversion efficiency, especially in temperate regions such as North America and Europe (van der Weijde et al., 2013; Skoufogianni et al., 2019). Maize can also be used as food and energy at the same time, and it is easy to integrate into the existing agricultural system (Chen et al., 2013; Skoufogianni et al., 2019). Using maize grain to produce ethanol competes directly with food supply (Ranum et al., 2014; Choudhary et al., 2020). If too much maize stover is removed, it can negatively impact the soil, possibly causing degradation and affecting the ecosystem (Jones et al., 2017; Skoufogianni et al., 2019). Maize stover has a lot of lignin, which makes the biomass more difficult to process and convert (Dhugga, 2007; Choudhary et al., 2020). Maize can produce about 3.0 to 5.4 thousand liters of ethanol per hectare, but miscanthus can produce more than double that amount, using less land and water (Zhuang et al., 2013). 3 Genetic Traits Related to Biofuel Production 3.1 High starch content and fermentability The starch content in maize kernels is key to whether it can be used to produce first-generation bioethanol. This is because starch is easy to convert into sugar, which can then be fermented. Quality Protein Maize (QPM) inbred lines not only have high yields but also high starch and cellulose content, making them ideal for biofuel production (Pratikshya et al., 2025).
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