Journal of Energy Bioscience 2025, Vol.16, No.5, 263-272 http://bioscipublisher.com/index.php/jeb 268 6. Challenges and Limitations 6.1 Technical bottlenecks The high moisture and high sugar content characteristics of sweet potatoes and their residues make them extremely prone to spoilage and deterioration, resulting in severe loss of raw materials during harvesting, transportation and storage, and affecting the subsequent processing efficiency and product quality (Costa et al., 2018; Tedesco et al., 2023). Especially in regions with hot climates or high humidity, the storage period of sweet potato tubers and waste is extremely limited. They have to rely on cold chain or rapid processing systems; otherwise, they are prone to mold and spoilage, increasing raw material management and logistics costs. The structure of sweet potato starch is complex, and it has a high dependence on enzyme preparations during hydrolysis and saccharification. Moreover, efficient enzyme preparations are expensive, which has become an economic obstacle restricting large-scale promotion (Lyu et al., 2021). At present, although the advancements in enzyme engineering and biotechnology have led to some cost reductions, further breakthroughs are still needed in the research and application of efficient and low-cost enzyme preparations (Okoro et al., 2022). The starch content, fiber structure and resistance characteristics of different varieties vary greatly, making it difficult to unify the process parameters of hydrolysis, fermentation and anaerobic digestion, which affects the utilization rate of raw materials and product consistency (Lyu et al., 2021; Tedesco et al., 2023). The presence of amylopectin and cellulose in sweet potato residue will reduce the enzymatic hydrolysis efficiency, prolong the reaction period, increase energy consumption and the difficulty of by-product treatment (Costa et al., 2018). In biogas production, the high moisture content and high organic load of the substrate can easily cause operational problems such as acidification, foaming and clogging of the reactor, which puts forward higher requirements for the stability of the anaerobic digestion system. 6.2 Infrastructure and market shortcomings The collection, transportation and preliminary processing of sweet potatoes and their residues lack an efficient and low-cost logistics and processing network, resulting in an unstable raw material supply chain and affecting the continuous production and economies of scale of the factory (Costa et al., 2018). In many major sweet potato production areas, raw materials are mostly grown in a scattered manner, lacking centralized purchasing and standardized pretreatment facilities, which increases raw material loss and transportation costs, and also limits the large-scale expansion of the industry (Tedesco et al., 2023). The downstream markets of bioethanol and biogas are not yet fully mature. There is a lack of a complete product distribution, storage and terminal utilization system, resulting in limited product sales channels, large fluctuations in market prices, and affecting the investment enthusiasm of enterprises and the stability of the industrial chain. The upstream and downstream of the sweet potato biofuel industry chain are not well connected, and there is a lack of efficient value chain integration and diversified product development capabilities. Processing enterprises in many regions are limited to the production of a single product (such as ethanol or biogas), and fail to achieve the high-value utilization of by-products (such as digestive juices, organic fertilizers, feed, etc.), resulting in resource waste and a decline in economic benefits (Okoro et al., 2022; Tedesco et al., 2023). The lack of professional technical services and industrial alliances has restricted the promotion of new technologies and industrial collaborative innovation. 6.3 Policy and institutional obstacles Although some countries and regions have introduced biofuel development plans and subsidy policies, the overall policy system is still imperfect and lacks specific support measures for non-grain biomass raw materials such as sweet potatoes (Tedesco et al., 2023). In practice, biofuel projects often encounter problems such as cumbersome approval processes, difficult land transfer, and inadequate implementation of tax incentives, which increase the institutional transaction costs of enterprises (Costa et al., 2018). There is considerable uncertainty in the market access, price mechanism and subsidy policy of biofuel products. The investment risk for enterprises is high, which affects the continuous investment of capital and technology (Tedesco et al., 2023).
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