Journal of Energy Bioscience 2024, Vol.15, No.6, 358-367 http://bioscipublisher.com/index.php/jeb 362 “bio-refinery”, which is to convert plant materials such as sorghum into various biofuels and chemical products, making the uses of sorghum more diverse and valuable. Because sorghum can produce a large amount of biomass and has multiple uses, it has become an important crop in the production of biofuels and biochemicals. However, more research is needed to identify which processing methods are the most effective and cost-effective (Stamenković et al., 2020). Using sorghum to produce bioplastics and chemicals can also reduce reliance on fossil fuels such as oil and alleviate environmental pressure. 6 Environmental Benefits and Challenges 6.1 Contribution to carbon sequestration and reduction of greenhouse gases Sorghum, especially energy sorghum, has great potential in absorbing carbon dioxide and reducing greenhouse gas emissions. The roots of this kind of sorghum grow very deep and can help the soil store more organic carbon, which is very important for achieving carbon sinks (Figure 2). Its root system can penetrate deeper than 2 meters, not only accumulating a large amount of biomass, but also increasing the level of organic carbon in the soil, which helps to reduce greenhouse gas emissions (Lamb et al., 2021). Using sludge and digestion liquid instead of chemical fertilizers to grow sorghum can also reduce carbon emissions. Studies have found that doing so can reduce carbon dioxide equivalent by 14% and 11% respectively, and it is a promising low-carbon agricultural method (Głąb and Sowiński, 2019). The nationwide simulation results also show that growing sorghum in large areas such as the southern and Midwestern United States can achieve net carbon sinks and further illustrate its role in emission reduction (Gautam et al., 2020). Figure 2 Bioenergy sorghum root anatomy (Adopted from Lamb et al., 2021) Image caption: Roots were collected by probe truck to a soil depth of 120 cm from field-grown plants ~100 days after planting in 2020. (a–c) Bioenergy sorghum nodal root cross-sections showing cortical cells (C), metaxylem (Mx), phloem (Ph), and parenchyma (Pr) cells (scale bars = 50 µm). (b) Formation of aerenchyma (Aer) in cortical cell layers. (c) Nodal roots showing degradation of cell layers external to the endodermis (En). (d) Representative assortment of lateral roots at the same magnification as nodal roots (scale bar, 250 µm). (e) Lateral root with partial conversion of cortical cells to aerenchyma (scale bar = 50 µm). (f) Lateral roots with a central metaxylem (Mx) and protoxylem (Px) lacking cell layers outside of the endodermis (Adopted from Lamb et al., 2021) 6.2 Role in soil health improvement and erosion control The root system of sorghum not only helps absorb and store carbon, but also plays a significant role in improving soil health and preventing soil erosion. The roots of sorghum used for bioenergy are deep and strong, which can improve the soil structure, increase the organic carbon in the soil, and enhance the soil fertility and yield (Lamb et al., 2021). Studies have found that when growing sorghum, using the sludge after sewage treatment can improve the physical and chemical properties of the soil, such as loosening the soil, increasing nutrients and organic carbon, which is very important for soil health (Zuo et al., 2019). Planting sorghum together with cover crops can further increase the storage of carbon and nitrogen in the soil, reduce nitrogen loss and greenhouse gas emissions. All these are helpful for protecting the soil and preventing erosion (Sainju et al., 2018).
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