Second-generation bioenergy from oilseed crop residues: Recent technologies, techno-economic assessments and policies
2022
Yong, Khai Jie | Wu, Ta Yeong
Global issues such as the depletion of fossil fuels, global warming, and increasing energy demand have called for alternative sustainable energy sources. Oilseed crops such as soybean, cottonseed, sunflower, rapeseed, peanut, and oil palm have been largely cultivated owing to the wide applications of their seeds. A large volume of residues is generated from the harvesting and processing of oilseed crops, which, therefore, is presented as a sustainable lignocellulosic source for biofuel production. The oilseed crop residues could be transformed into biofuels such as ethanol, methane (biogas), bio-oil, butanol, and hydrogen via either thermochemical or biological methods. Pretreatment methods such as acid, alkali, hydrothermal, deep eutectic solvent, and steam explosion pretreatment could disrupt the recalcitrant structure of oilseed crop residues and thereby enhancing biofuel production. Pre-hydrolysis simultaneous saccharification and fermentation, utilization of thermotolerant yeasts, and co-fermentation using xylose and pentose-fermenting yeasts have been proposed to improve ethanol production from oilseed crop residues. Co-digestion of oilseed crop residues and animal manure has been regarded as the key strategy to enhance methane yield by maintaining an optimal carbon-to-nitrogen ratio during anaerobic digestion. Catalysts could improve the quality of bio-oil produced from the pyrolysis of oilseed crop residues by reducing the oxygen content in the bio-oil via deoxygenation reactions. Several techno-economic assessments indicated that raw material is one of the highest cost-contributing factors. Oilseed crop residues with high holocellulose content that are low cost are preferred to improve the economic viability of biofuel production. Lastly, various countries have implemented policies to promote the production and use of second-generation biofuel by introducing volume mandates or providing subsidies.
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