Biofuel production, application

Scragg, Alan. Biofuels Production, Application, and Development. Cambridge, Mass. CAB International, 2009. Looks at biofuel production, concentrating on technological issues, benefits and problems, and existing and future forms of biofuels. 

Increased consumption of agricultural lipids as fuels, either for boilers or diesel engines, could increase their prices and curtail their availability, impacting their use in traditional applications. All these changes are dependent on the future course of petroleum fuel prices, on research advances to reduce biofuel production costs, and/or on the establishment and continuation of government programs providing financial incentives that foster the use of renewable fuels. 

As crop residues are by-products of food production they are termed as so-called second-generation feedstock, especially for biofuels production (see e.g., [35]). So far, no world market for straw aimed at industrial applications exists. However, prices can be approximated by calculating production and logistics costs [36]. 

Biofuels including ethanol and biodiesel have always been controversial regarding food vs fuel and fuel vs arable land. PHA-based biofuel production from wastewater or from activated sludge enjoys the advantages of wastewater treatment accompanied by energy generation. These results unlock a new area for PHA application in the energy sector. 

Enzymes can convert lignocellulosic biomass into a suitable fermentation feed-stock for biofuel production. Different yeast strains are used for ethanol production, such as S. diastaticus, Candida sp., S. cerevisiae and K. marxianus, as well as different bacteria such as Zymomonas mobilis. The employment of distillation is desirable for food grade purity of applications other than that of biofuel. In fact, batch fermentation was coupled with a membrane distillation process developed with the application of a membrane distillation bioreactor for ethanol production. Meanwhile,... 

Using immobilized mediators for NADH regeneration to circumvent drawbacks of dissolved mediators is also described in literature. The electropolymerization of neutral red (NR) led to formation of a redox active film on the electrode surface [21]. At negative potentials a current of NAD" reduction was observed at modified electrodes. It was shown that the main product of NAD" electroreductimi was the enzymatically active NADH. Immobilized mediators can also be used in biofuel ceU applications. Arechederra et al. have developed a biobattery on the basis of poly (neutral red) [22]. Poly(neu-tral red) was used for both oxidation of NAD(P)H and reduction of NAD(P), which is necessary in a rechargeable biobattery environment. 

In conclusion, lipases are enzymes with an ability to carry out a wide variety of chemo-, regio-, and enantioselective transformations in both aqueous and nonaqueous media. Such enzymes show several applications in areas of industrial microbiology and biotechnology. Today, environmental issues are taken into account when it comes to industrial processes. Thus, enzyme technology contributes significantly to a reduction of these negative effects such as toxicity and emission of particulate matter. Environmental concerns and the depletion of oil reserves have resulted in research into the use of lipases for environmentally friendly and sustainable biofuel production. 

The above outline highlights the need for liquid transportation fuels, particularly for the aviation and maritime transport applications. Already well established is the use of ethanol typically as blend-in fuel (E5 or ElO). A whole range of other biofuels is on the horizon, produced via chemical, physicochemical, or biological means. This review focuses on the role of prokaryotes in the production of biofuels. Prokaryotes are highly versatile catalysts for the production of both specialty and bulk biochemicals, and the present need for liquid biofuels gives major impetus to research on prokaryotic biofuel production. We will discuss the known feedstocks for biofuel production, production via pure cultures and microbial populations, and light-driven biodiesel generation. Finally, perspectives for prokaryote research and development in this field will be provided. 

With the growing industrial interest in the production of biofuels, the most important areas that need attention and research seem to be (i) scale-up, (ii) cost efficiency, (iii) better fuel properties, (iv) norms and standards for producers and end-users, (v) environment health and safety issues in biomass io el handling, transportation and usage, (vi) encouragement to implement thermo-chemical processes and applications, (vii) efficient utilization of byproducts for value-added chemical or material production, and (viii) information dissemination. The biomass conversion process can be economically viable if used in an integrated manner for generation of other marketable co-products in addition to the primary biofuel product, thus contributing to sustainable development. 

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