Ethanol biomass-derived

Hydrogen Production from Biomass-Derived Ethanol.213... 

Scheme 1 Carbon cycle energy diagram for the production of H2 from biomass-derived ethanol.18...

Fatsikostas, A.N., Kondarides, D.I., and Verykios, X.E. Production of hydrogen for fuel cells by reformation of biomass-derived ethanol. Catalysis Today, 2002, 75 (1—4), 145. 

The carbonate fuel cell utilizes both H2 and CO at the anode. The conunonly available fuels being considered for carbonate fuel cells include natural gas, gaseous fuels derived from biomass and coal, landfill gas, biomass-derived ethanol, propane, diesel, and bio-diesel. Important properties of these fuels from fuel cells viewpoint are listed in Table 1. Sulfur and halogens present in some of these fuels are eonsidered harmful to fuel processing catalysts and the fuel cell. Therefore, these undesired components need to be removed from the fuel stream. Other potential contaminants such as siloxane in the renewable fuels (biomass digester gas and landfill gas) also should be removed from the fuel prior to fuel processing for fuel cells. 

Large-scale biomass production will come at a considerable cost to the society. We have already given an order of magnitude estimate for wood plantations. When biomass raw material is processed that competes with the food chain, as vegetable oils and sugars, the situation is even worse. For instance Smil [4] mentions that if the US vehicles were to run solely on corn derived ethanol the country would have to plant corn on an area 20% larger than is currently cropland . 

The potential of combining a lower need for deoxygenation and a higher product value is illustrated in Fig. 2.15. It shows that the selective incorporation of oxygen into a hydrocarbon, as done in the petrochemical industry, is very expensive. In contrast, the bio-based alternative enjoys two advantages. Firstly, the feedstock is cheaper than crude oil, even on an energy and carbon base, as discussed above. Secondly, its selective deoxygenation has been proven to cheaper than the petrochemical route in a few cases, e.g., for ethanol and furfural. The same can be expected for other biomass derivates in the future. 

The compactness and complexity of (ligno)cellulose makes it much more difficult to attack by enzymes with respect to starch. Therefore, the cost of bioethanol production is higher [23], To be cost competitive with grain-derived ethanol, the enzymes used for biomass hydrolysis must become more efficient and far less expensive. In addition, the presence of non-glucose sugars in the feedstock complicates the fermentation process, because conversion of pentose sugars into ethanol is less efficient than conversion of the hexose sugars. 

Bioethanol is one of the first and the largest markets to profit from cheap biomass feedstock. Ethanol is usually produced from dextrose, which in the USA tends to derive from corn. The first ethanol biorefmery based on waste biomass is already online. It is a Canadian venture operated by Iogen and receiving investment from Shell, Petro Canada, and the Canadian government. With an annual capacity of 700,000 liters it is semi-commercial in scale and not cost-competitive with conventional ethanol refineries. However, the technology is expected to improve quickly. 

We are capable of producing hydrogen from different sources, for example, coal, natural gas, liquefied petroleum gas, propane, methane, gasoline, light diesel, dry biomass, biomass-derived liquid fuels, such as methanol, biodiesel, and from water. Among the liquid sources to produce hydrogen, ethanol is an excellent aspirant. 

Figure 2.1.2 Selected biomass-derived platform chemicals that have been demonstrated to be feedstocks for the production of potential biofuels (EtOH, ethanol BuOH, butanol).

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