Integrated Catalytic Upgrading of Biomass-Derived Alcohols for Advanced Biofuel Production

Abstract

Sustainable biofuel production is necessary to meet the daunting challenge of “fueling” growing economies with a significantly reduced carbon footprint. Although its higher oxygen content often hinders the direct conversion of lignocellulosic biomass (LCB) into energy-dense biofuels, microbial biofuel production from LCB still has potential. The production of primary alcohols by acetone–butanol–ethanol (ABE) fermentation has been practiced for more than a century to attain near-theoretical maximum. However, ABE produced conventionally by native microorganisms is not equivalent to fossil fuel-based aviation fuels in terms of energy density, volatility, and cost-efficiency. Various strategies have been adapted for the microbial synthesis of advanced fuels from renewable feedstock with the advancements in genetic engineering. Yet, the presence of inhibitors and the inefficiency of microbes to utilize or transport the sugar mixtures from LCB often impede titer and yield. However, ABE mixtures can act as platform chemicals to synthesize high-value biofuels by biocatalytic or chemo-catalytic applications. Chemical catalysts, in particular, are used to produce higher alcohols ranging from 3-carbon to 20-carbon fuels from the ABE fermentation mixture. This article reviews the recent trends in the production of higher biofuels from ABE mixtures using biological and chemical catalysts. Focus is placed on genomic and metabolic engineering strategies implemented to upgrade microbes for higher biofuel production via the fermentation of renewable feedstocks. This paper also summarizes the advancements in the chemical conversion route of an ABE fermentation mixture into higher biofuels. Finally, the review provides insights into future research toward commercializing renewable and sustainable higher biofuels and chemicals.

Biofuel production from agricultural residues: A promising pathway for renewable energy

“…However, the absence of comprehensive kinetic models that adequately capture the complicated conversion processes involved limits the efficient use of these wastes for biomass energy generation. Process optimization, reactor design, and the development of credible economic feasibility studies are all hampered by the lack of strong kinetic models [8]. While the biochemical and thermochemical events that occur during biomass conversion are complex, existing kinetic models tend to oversimplify them.…”