Abstract
The need for fossil fuel alternatives keeps increasing. Bioethanol and biohydrogen have emerged as significant renewable options. However, these bioprocess routes have presented various challenges, which constantly impede commercialization. Most of these bottlenecks are hinged on feedstock logistics, low biofuel yield and enormous process costs. Meanwhile, a large output of renewable energy can be generated from mixed starch-based agricultural wastes due to their intrinsic bioenergy characteristics. This study, therefore, focuses on the production of bioethanol and biohydrogen from mixed starch-based agricultural wastes. The content further highlights the current challenges of their individual processes and elucidates the prospects for improvement, through an integrated biofuel approach. The use of mixed starch-based agricultural wastes as substrates for integrated bioethanol and biohydrogen production was proposed. Furthermore, the use of mixture-based experimental design for the determination of optimal values of critical factors influencing biofuel production emerges as a viable prospect for profitable bioethanol production from the starch-based biomass. Additionally, biohydrogen production from effluents of the mixed starch-based waste bioethanol looked promising. Thus, the study proposed valuable insights towards achieving a cost-effective biofuel technology.
Highlights
The escalating demand for energy in recent years, food security concerns and increasing environmental pollution has positively driven the growth and focus on bioenergy and subsequently, biofuel production [1]
The simultaneous saccharification and fermentation (SSF) process allows for enzymatic hydrolysis/saccharification and fermentation to be executed in a single vessel under the same conditions [14,15]
Various renewable options have been investigated for important biofuels such as bioethanol and biohydrogen, the search for more viable solutions to the persistent challenges is inevitable
Summary
The escalating demand for energy in recent years, food security concerns and increasing environmental pollution has positively driven the growth and focus on bioenergy and subsequently, biofuel production [1]. The combustion of hydrogen does not result in environmental pollution, the route to production greatly does [8] This has led to the emergence of biohydrogen as a rather sustainable form of hydrogen due to its production from organic sources such as wastes by the biological process of dark fermentation. Lignocellulosic biomass and waste-based integrated biofuel production have been reported for bioethanol, biohydrogen, biodiesel and/or biogas production These fuels have been reportedly generated from the combination of pure lignocellulosic substrates and non-starch-based agricultural wastes [17,24,25,26], or a combination of food crops and agricultural wastes [27]. Agricultural waste-biofuel processes generate effluents, which constitutes a nuisance to environmental bodies and soil microorganisms These waste streams contain organic and inorganic compounds that can be utilized for additional biofuel products, thereby increasing the profitability of the biorefinery. A full pathway of integrated bioethanol and biohydrogen production from mixed starch-based agricultural waste was proposed as a panacea to the challenges of the individual processes
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