Journal of Energy Bioscience 2025, Vol.16, No.4, 172-181 http://bioscipublisher.com/index.php/jeb 179 9 Comparative Insights and Challenges 9.1 Comparison with other energy crops and sites Sweet potato is a good biomass energy crop that performs well in producing biogas and methane. Compared with common energy crops such as cassava and corn, the effect of sweet potato is basically the same. Studies have found that when sweet potato and cassava are fermented together, the unit gas production is similar, 0.449 cubic meters/kg for sweet potato and 0.457 cubic meters/kg for cassava. The methane content of both is about 61%, with little difference (Montoro et al., 2025). The reducing sugar and moisture content of sweet potato are higher than that of corn, which is beneficial for anaerobic fermentation (De Paula Batista et al., 2019). However, there are still great differences between different sweet potato varieties. For example, the Laranjeiras variety has a particularly high gas production (De Paula Batista et al., 2019). Moreover, sweet potatoes can provide nutrition and energy at the same time, and have good adaptability in different regions, which also makes it more advantageous in rural energy systems (Tedesco et al., 2023). 9.2 Technical limitations Although sweet potatoes are used to produce biogas, they also have some technical difficulties. First, it contains a lot of water and sugar, which helps to produce gas, but its starch structure is complex, especially amylopectin, which is not easy to decompose, and the fermentation time will be longer (Catherine and Twizerimana, 2022). Sweet potatoes are seasonal crops, with concentrated harvest time, and storage is not easy. They are easy to rot, affecting the continuous supply of raw materials (De Paula Batista et al., 2019; Catherine and Twizerimana, 2022). To improve efficiency and shorten the fermentation cycle, pretreatment, such as heating or adding alkali, is also needed to optimize substrate stability and equipment operation time (Catherine and Twizerimana, 2022). 9.3 Institutional and financial barriers Sweet potato biogas projects have also encountered many difficulties in terms of policies and funds. Currently, policy support is not enough, and the investment payback time is long. Although joint fermentation can improve economic benefits and make money in many cases, the project requires a lot of investment in the early stage and maintenance is not cheap. Farmers and enterprises do not have so much money and lack technical support (Montoro et al., 2025). Some local policies are not perfect and lack specific incentive mechanisms. These problems limit the promotion and long-term development of sweet potato biogas projects (Tedesco et al., 2023; Montoro et al., 2025). 9.4 Adoption constraints Many farmers are not familiar with the technology of sweet potato biogas production and are not very receptive. The main reason is that people do not understand this new technology and lack training and follow-up service support. In addition, sweet potatoes are important food and cash crops. Some farmers think that they are more suitable for eating or selling rather than fermenting. This contradiction between "eating and using" will also affect promotion (Tedesco et al., 2023). The current technical service system is not perfect enough, and there is no efficient promotion mechanism. These have become the main obstacles to the popularization of sweet potato biogas technology in rural areas (Tedesco et al., 2023; Montoro et al., 2025). 10 Conclusion and Recommendations Different varieties of sweet potatoes vary greatly in yield and composition. Some varieties, such as Laranjeiras and BRS Cuia, produce more biogas, which has a lot to do with the amount of reducing sugars and water they contain. This shows that sweet potatoes are promising as energy crops. From a technical point of view, if sweet potato waste is treated with thermochemical methods, such as sodium hydroxide (NaOH), and then fermented, not only can the production of biogas and methane be increased, but the methane content can also be increased from 42% to 64%, and the fermentation time will be shortened, and the efficiency of energy conversion will also be improved. In rural areas, sweet potatoes are abundant and easy to obtain. Using them to develop biogas can not only reduce the waste of agricultural waste, but also bring clean energy to farmers, which is suitable for large-scale promotion.
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