Journal of Energy Bioscience 2024, Vol.15, No.2, 108-117 http://bioscipublisher.com/index.php/jeb 110 There is a growing interest in second-generation biofuels, supported by research and development efforts and government incentives. Countries like the United States, Canada, and members of the European Union are investing in advanced biofuel technologies to overcome the limitations of first-generation biofuels. Additionally, there is a significant focus on developing third-generation biofuels, with numerous pilot projects and research initiatives aimed at scaling up algae-based biofuel production (Gendy and El-Temtamy, 2013). Despite these advancements, biofuels still represent a small fraction of the global energy mix. The future growth of biofuel production will depend on technological innovations, economic viability, and the development of sustainable agricultural practices. Policies that promote research, provide financial incentives, and ensure sustainability standards will be crucial in shaping the biofuel industry and maximizing its benefits. 3 Selection Criteria for Energy Crops 3.1 Agronomic factors The selection of energy crops for biofuel production involves a comprehensive evaluation of various factors to ensure sustainability, economic viability, and minimal environmental impact. This section outlines the key criteria for selecting energy crops, categorized into agronomic, environmental, economic, and socio-economic factors. Agronomic factors are critical in determining the suitability of a crop for biofuel production. High yield, appropriate growth cycle, and adaptability to different environmental conditions are essential characteristics. High biomass yield is a primary criterion. For instance, Miscanthus × giganteus has shown promising results with an average annual yield of 30 t/ha and a maximum of 61 t/ha in trials conducted in Illinois (Heaton et al., 2008). Similarly, maize classes 600 and 700 have demonstrated high biomass yields in Northern Italy (González-García et al., 2013). The growth cycle of the crop should align with the local agricultural calendar to optimize land use. Perennial crops like switchgrass and Miscanthus are advantageous due to their long growth cycles and minimal replanting requirements (Heaton et al., 2008; Zegada-Lizarazu et al., 2013). Crops must be adaptable to local soil and climatic conditions. For example, switchgrass and Miscanthus have been successfully cultivated in both the USA and Europe, indicating their adaptability to diverse environments (Zegada-Lizarazu et al., 2013). 3.2 Environmental factors Environmental sustainability is a crucial consideration in the selection of energy crops. Factors such as water usage, soil requirements, and climate resilience play significant roles. Efficient water use is vital, especially in regions with limited water resources. Microalgae, for instance, require relatively small amounts of water compared to conventional land crops (Peng et al., 2019). The ability to grow in marginal soils without significant soil degradation is important. Warm-season grasses (WSGs) and short-rotation woody crops (SRWCs) can improve soil properties and sequester soil organic carbon (SOC), making them suitable for marginal lands (Blanco-Canqui, 2010). Crops must be resilient to climatic variations. C4 crops like Miscanthus and switchgrass are known for their high photosynthetic efficiency and resilience to arid conditions, making them suitable for energy farming. 3.3 Economic factors Economic viability is essential for the large-scale adoption of energy crops. Factors such as the cost of cultivation, market value, and availability of subsidies influence the economic feasibility. The cost of growing, harvesting, and processing energy crops should be competitive. For example, the cost of growing willow, including transportation and shredding, is about $510 per hectare, with a payback period of 3.8 to 11 years depending on the use of biomass (Nosko et al., 2019). The market value of the biofuel produced from the crops should justify the investment. Crops like sugarcane, which is highly efficient in bioethanol production, have a significant market value. Government subsidies and incentives can enhance the economic attractiveness of energy crops. Policies such as the Renewable Energy Development Plan for Europe have historically supported the growth of energy crops (Nosko et al., 2019).
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