Biofuels challenges

Lee, R.A. and Lavoie, J.-M. (2013) From first-to third-generation biofuels challenges of producing a commodity from a biomass of increasing complexity. Anim. Front., 3, 6-11. 

Leite, G.B., Abdelaziz, A.E.M., Hallenbeck, P.C., 2013. Algal biofuels challenges and oppoituni-ties. Bioresour. Technol. 145, 134-141. 

Second, sensors are often intended for a single use, or for usage over periods of one week or less, and enzymes are capable of excellent performance over these time scales, provided that they are maintained in a nfild environment at moderate temperature and with minimal physical stress. Stabilization of enzymes on conducting surfaces over longer periods of time presents a considerable challenge, since enzymes may be subject to denaturation or inactivation. In addition, the need to feed reactants to the biofuel cell means that convection and therefore viscous shear are often present in working fuel cells. Application of shear to a soft material such as a protein-based film can lead to accelerated degradation due to shear stress [Binyamin and Heller, 1999]. However, enzymes on surfaces have been demonstrated to be stable for several months (see below). 

A major issue for biomass as a raw material for industrial product manufacture is variability. Questions of standardisation and specifications will therefore need to be addressed as new biofuels, biomaterials and bioproducts are introduced onto the market. Another major challenge associated with the use of biomass is yield. One approach to improve/modify the properties and/or yield of biomass is to use selective breeding and genetic engineering to develop plant strains that produce greater amounts of desirable feedstocks, chemicals or even compounds that the plant does not naturally produce (Fernando et al., 2006). This essentially transfers part of the biorefining to the plant (see Chapter 2 for some example of oils with modified fatty acid content). 

A unique plant on many levels, the distinctive properties of the Jerusalem artichoke (Helianthus tuberosus L.) present novel answers to some of today s most pressing problems. Jerusalem artichoke is potentially a major source of inulin, a fructose polymer that provides dietary health benefits as a prebiotic that promotes intestinal health and as a low-calorie carbohydrate to combat obesity and diabetes. Inulin also has myriad industrial applications, including ethanol production — making Jerusalem artichoke a potential source of biofuel. With its ready cultivation and minimal pest and disease problems, Jerusalem artichoke is an underutilized resource that possesses the potential to meet major health and energy challenges. 

Lignocellulose, which comprises the main construction material of plant biomass, accounts for up to 90% of all biomass and is formed in amounts of approximately 1.5 trillion tons per year [12]. Consequently, lignocellulose is much more abundant than available amounts of vegetable oils, starch, and sugar crops. In addition to the high abundance of lignocellulose, it is inedible, and its utilization as feedstock for production of biofuels and chemicals could drastically reduce challenges of food versus fuel production. 

The main potential of mediated ET lies in the increase of current densities, as the essential challenge of designing biofuel cells is to increase the biocatalytic power of these devices. Biofuel cells presently reach a power output in the range of about 10 to 10 Wcm . Practical conventional fuel cells operate in the range of about 1 to 10 Wcm [303]. Taking the calculations from Barton and coworkers into consideration [70], in which, as mentioned above, the theoretical current density of a monolayer was estimated to be about SOpAcm" one would require thousands of layers to obtain a current density above 10 mA cm f... 

The development of new technologies for the more efficient production of both food and biofuels is a challenge for all of us, and it should be emphasized that chemistry plays a very special role in the discovery of new alternatives in this field. 

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