Category Archives: Biofuels from Agricultural Wastes and Byproducts

Renewable Sources of Glycerol

Glycerol is present in animal fats and oils in the form of triglycerides. These triglycerides consist of three fatty acids linked to three hydroxyl groups of glycerol through an ester bond. In most industrial applications, glycerol is recovered from the triglyceride molecules by breaking the ester bonds through various chemical or biological processes. Fatty acids present in triglycerides are directly […]

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Handling of Baled Feedstock

Lignocellulosic plant biomass like corn stover and switchgrass is harvested and packaged in bales that are delivered in flatbed trucks. Unlike granular feedstocks that have a high density and are free flowing, bales have low density, typically 160-200kg/m3 . They come in bulky packages of biomass that are either round, square, or rectangular, and require man-operated handling equipment like forklifts […]

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Pretreatment of Lignocellulosic Biomass and Generation of Microbial Inhibitors

One of the key steps in the conversion of lignocellulosic biomass to fermentable sugars is pretreatment. The goal of pretreatment is to alter the biomass macroscopic and micro­scopic size and structure as well as its submicroscopic chemical composition so that enzymatic hydrolysis of the carbohydrate fraction to monomeric sugars can be achieved with greater yield (Figure 3.1; Mosier et a

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Outlook

Anaerobic digestion of agricultural wastes is a mature technology with numerous full-scale digesters located all over the world. Noteworthy is the recent interest in digesting or co­digesting of bioenergy crops in the EU because of the relative high-energy efficiency of methanogenic food webs (no side product formation and product inhibition). Even though the level of maturity is high, research on […]

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Enhancement of Yield and Productivity of Ethanol

Identification of pathways and environmental conditions affecting the metabolism of glycerol under anaerobic conditions by wild-type E. coli provide opportunities to manipulate the microorganism for enhancement of ethanol yield and productivity. Fermentation of glycerol to either ethanol and H2 or ethanol and formate is one of the most effective ways of exploiting the reduced property of glycerol for bioproducts production.

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Adding Reducing Substances

Unfavorable oxidation-reduction potential (ORP) has also been cited as a cause of poor fer­mentability (Leonard and Hajny 1945). Collingsworth and Reid (1935) found that the addition of reducing agents to media improved their fermentability. Three methods have been pro­posed for overcoming unfavorable ORP in fermentation media: phytochemical reduction by large amounts of yeast; use of reducing agents; and production of […]

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Cell-Surface Enzyme Systems

In contrast to the free enzyme systems, some enzymes are attached directly to the cell wall. This is frequently accomplished in Gram-positive bacteria via a specialized type of module, the S-layer homology (SLH) module, previously shown to be associated with the cell surface of Gram-positive bacteria (Lupas et al. 1994). Attachment of enzymes to the cell wall may have evolved […]

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