If the caloric value of the unconverted synthesis gas is too low for (direct) combustion in a gas turbine, this could be compensated for by cofiring natural gas. Besides raising the heating value of the gas, the application of natural gas can also increase the scale, thermal efficiency, and economics of the gas turbines.

Natural gas can also be applied as cofeeding in the entire process. Or, vice versa, the large scale of existing methanol production units could be utilized by plugging in a biomass gasifier and gas make-up section. The product can be considered partially of biomass origin.

Black Liquor Gasification

Pulp and paper mills produce huge amounts of black liquor as a residue. They are the most important source of biomass energy in countries such as Sweden and Finland, representing a potential energy source of 250-500 MW per mill. As modern kraft pulp mills have a surplus of energy, they could become key suppliers of renewable fuels in the future energy system, if the primary energy in the black liquor could be converted to an energy carrier of high value.

Ekbom et al. (2003) have evaluated the production of methanol and DME (see below) from black liquor gasification (BLGMF process). This scheme could be realized against reasonable costs, if heat recovery boilers, which economic life has ended, are replaced by BLGMF. Using black liquor as a raw material for methanol/DME production would have the following advantages:

1. Biomass logistics are extremely simplified as the raw material for fuel making is handled within the ordinary operations of the pulp and paper plant.

2. The process is easily pressurized, which enhances fuel production efficiency.

3. The produced syngas has a low methane content, which optimizes fuel yield.

4. Pulp mill economics becomes less sensitive to pulp prices as the eco­nomics are diversified with another product.

5. Gasification capital cost is shared between recovery of inorganic chem­icals, steam production, and synthesis gas production.

Other Biofuels via Gasification

Gasification, gas cleaning, and make-up are important parts of the process to make methanol from biomass. These parts are also key to the production of hydrogen and Fischer-Tropsch liquids from biomass. Development of methanol from biomass thus offers synergy with development of hydrogen and Fischer — Tropsch liquids. Methanol can also be an intermediate in the production of other renewable fuels such as synthetic diesel, gasoline, and dimethyl ether.

Hydrogen

The production of hydrogen from synthesis gas is somewhat simpler and cheaper than the production of methanol. The gasification step should aim at maximizing the hydrogen yield, which can be further increased by reforming any methane left and a water-gas-shift reaction. Hydrogen separation takes place by pressure swing adsorption or (in future) membranes.

Hydrogen is already produced at large scale in the chemical and oil industry. It is often seen as the future fuel for the transportation sector and households.

With regard to feed coproducts, there is a need to diversify the markets for DDGS. Research aimed at modifying the amino acid composition, protein composition, and phosphorous content of DDGS should result in higher quality, consistent composition of feed ingredients and encourage expanded use of DDGS in poultry and swine rations. Nonfeed uses for DDGS have also been developed, prompted by the increased availability of DDGS resulting from increased ethanol produc­tion. Deicers, cat litter, and lightweight “ag-fiber” shipping containers can be produced from DDGS. DDGS could also be used to produce biogas, which could be recovered and used on-site to fuel the plant [26]. A plant fueled in this way would be less dependent on feed selling prices and power and natural gas purchase prices.

Since the 1980s, there has been increased interest in low concentration blending of ethanol with diesel fuel. Ethanol/diesel blends are commonly referred to as E — diesel. They generally contain from 10% to 15% ethanol and are used for many of the same reasons that ethanol/gasoline blends are used (decreased petroleum need and decreased emissions). Ethanol and diesel blending is more complicated than ethanol/gasoline blending, because of the low solubility of ethanol in diesel at low temperatures and the high flammability. At temperatures below 10°C, ethanol and diesel will separate [39]. The solution is either to add an emulsifier or a cosolvent. Boruff et al. has shown that approximately 2% surfactant (emul­sifier) is needed for every 5% of ethanol added to diesel fuel (40). The addition of the surfactant to the ethanol/diesel blend led to transparent solutions with no visible separation down to -15.5°C (40). Ethyl acetate has been studied as a co­solvent. Researchers have shown that adding 2.5% ethyl acetate for every 5% ethanol will ensure no separation down to 0°C (41). Cosolvents have been more popular than surfactants. The second issue with e-diesel is the increased risk of fire and explosions compared to plain diesel fuel. The National Renewable Energy Laboratory recommends solving this problem by equipping all fuel tanks with vents, better electrical grounding, and employing safer fuel tank level detectors (42). The physical properties of E-diesel compared to ethanol and diesel are shown in Table 7.5.

Blending ethanol with diesel fuel decreases emissions in a similar way to ethanol/gasoline blends. E-diesel has achieved reported 20% to 30% decreases

in carbon monoxide emissions and 20% to 40% decreases in particulate matter emissions (43). Miyamoto et al. showed that these improvements in emissions depend directly on the oxygen content (44). However, minimal decreases in NOx emissions have been reported (43) and an increase in hydrocarbon emissions have been reported (45-46). Table 7.6 shows the vehicle emissions from the use of 10% and 15% ethanol in diesel.

As far as engine use is concerned, the decrease in fuel viscosity and lubricity have been investigated for ethanol blends with diesel, but they do meet diesel specifications (42). Materials compatibility has also been investigated. E-diesel was found to have similar corrosive properties to typical diesel (42).

It is important to note that E-diesel fleet demonstrations have shown no fire or explosions incidents and no mechanical failures associated with the fuel system 43). Many studies of engine wear have been conducted and have shown no abnormal wear or deterioration due to the blending of ethanol with diesel at low concentrations (10-15%). E-diesel does shows a reduction in engine power, but this reduction is small and equivalent to the reduction in energy content of the ethanol versus diesel (39). The main engine performance issue with E-diesel is the leakage of fuel from the fuel injection pump due to slight decrease in viscosity of the blended fuel. Studies of engine power loss have shown decreases in power from 4% to 10% for ethanol/diesel blends ranging from 10% to 15% ethanol (46-48). Therefore, ethanol is a good choice as an oxygenate for diesel. It has minimal effect on engine power while dramatically decreasing particulate matter and carbon monoxide emissions.

TABLE 7.6

Vehicle Emissions from the Use of 10% to 15% Ethanol in Diesel

Emissions Range
(% ratio of blend/diesel)

73-80 59-70 96-100 95-100 80-160 73-140 171-200 175-210

Source: Data compiled from Hansen, A. C., Lye, P. W. and Zhang, Q., ASAE Paper No. 01-6048, Aug. 2001; Waterland, L. R., Venkatesh, S. and Unnasch, S., NREL/SR-540-34817, Sept. 2003; Spreen, K., Final Report for Pure Energy Corporation prepared at SRI, San Antonio, TX, 1999; Kass, M. D., Thomas, J. F., Sto­rey, J. M., et al., SAE Technical Paper 2001-01-2018, 2001.

CONCLUSIONS

Ethanol can be blended with gasoline to produce an oxygenated fuel with lower hydrocarbon emissions. Ethanol can also be blended with diesel to decrease carbon monoxide emissions and particulate matter emissions. Although green­house gas emissions are decreased with ethanol-blended fuels, emissions of certain aldehydes are increased, which could cause health issues. Automobiles can be operated on ethanol/gasoline blends from 5% to 25% and ethanol/diesel blends from 10% to 15% without need for any alterations in engine equipment or settings and with no effect on engine lifetime.

Sabina Topcagic, Becky L. Treu, and Shelley D. Minteer

Department of Chemistry, Saint Louis University, Missouri

CONTENTS

Introduction…………………………………………………………………………………………………… 216

Portable Electrical Energy Sources………………………………………………………………… 216

Batteries……………………………………………………………………………………………. 216

Fuel Cells…………………………………………………………………………………………… 217

Biofuel Cells……………………………………………………………………………………… 218

Enzyme Immobilization Techniques…………………………………………………………….. 220

Wired Technique………………………………………………………………………………. 221

Sandwich Technique………………………………………………………………………… 222

Entrapment Technique…………………………………………………………………….. 222

Nafion® Modification……………………………………………………………………… 223

NAD+-Dependent Alcohol Dehydrogenase Biofuel Cells…………………. 225

PQQ-Dependent Alcohol Dehydrogenase Biofuel Cells……………………. 226

Membraneless Biofuel Cells……………………………………………………………… 227

Conclusions…………………………………………………………………………………………………… 229

References…………………………………………………………………………………………………….. 230

Abstract There are three types of batteries: primary, secondary, and fuel cells. A fuel cell is an electrochemical device that converts chemical energy into electrical energy via catalysts. Fuel cells have many advantages over the two other types of batteries due to the fact they can be regenerated with the addition of fuel specific to the system. Traditional fuel cells employ heavy metal or precious metal catalysts, whereas biofuel cells employ biological catalysts (enzymes). Enzymes are highly specific catalysts, so they allow for the simplifi­cation of the fuel cell by eliminating the need for a polymer electrolyte membrane, which is one of the mostly costly parts of a fuel cell. Dehydrogenase enzymes have been employed at the anode of biofuel cells to oxidize alcohols. Methanol, ethanol, propanol, and butanol are examples of alcohols that can be used in biofuel cells. Long-term goals include investigating a variety of power applications for this technology ranging from portable electronics to sensors.

INTRODUCTION

Previous chapters of this book detail methods for producing ethanol from agri­cultural products and biomass. Although many of these methods are efficient, it is crucial to be able to efficiently convert energy to electrical power. As detailed in an earlier chapter, researchers have been attempting to develop direct ethanol fuel cells (DEFCs), but there have been problems because traditional precious metal catalysts (Pt-based catalysts) are unable to efficiently catalyze the oxidation ethanol and maintain an electrode with minimal fouling at low temperatures. However, living organisms are capable of efficiently catalyzing the oxidation of ethanol at 20-40°C. Living organisms, such as Pseudomonas aeruginosa [1], acetobacter [2], and gluconobacter [3], contain enzymes that can oxidize a variety of alcohols, including ethanol. Over the last 40 years, researchers have been working on employing living organisms and/or their enzymes in a fuel cell to convert chemical energy to electrical energy. This type of battery or fuel cell is referred to as a biofuel cell. The early research was plagued with enzyme stability problems and low power densities, but those issues are being overcome with current research. In this chapter, we will discuss the brief history, techniques, and applications of alcohol-based biofuel cells.

The Food Pantry has established a Web presence. During construction it will be possible to tape record and follow along step by step and document just how the greenhouses were sited, erected, equipped, and operated. As such, this will be a soup-to-nuts type of educational experience, giving students an in-depth picture of the entire project. The Website will be upgraded to an interactive site with periodic live teaching segments — broadcast directly from inside any of the outbuildings live over the Internet through streaming video — which will enable viewers to ask questions in real time. The segments will be archived for down­loading as a reference and offered for sale in CD format for a modest fee. In this way, the project can offer 1/2-hour teaching segments on every aspect of the system and from every location within the system through the use of a Web cam. Land lines will connect all the external buildings to project offices and computers. Everything then can be broadcast live over the Internet. A certain amount of upgrading will be required to make the offices suitable for this purpose.

The project will be promoting the use of this system worldwide, and modified to meet almost any climatic conditions. Phase 2 of this project will address the adaptation of this system to differing worldwide climatic needs, and other sources of renewable and sustainable fuels to power the project according to those needs. Through the Web page and e-mail, the project would be able to act as a resource to anyone anywhere in the world. Upon completion, it will be a powerful learning tool.

• Methanol fuel cells: transportation, stationary, and portable power.

• Production of biodiesel.

• Sewerage treatment denitrification.

• Fuel for standby turbine electric generators.

• Pulp and paper bleaching replacing chlorine.

• Stock-car racing fuel.

• Replacement for diesel fuel for stationary diesel engines.

• Converting methanol to hydrogen. Eliminating storage and trans­portation.

• Fuel additives for diesel fuel. Preventing gelling and fuel line freeze.

• Intermediate for production of dimethyl ether, acetic acid, and form­aldehyde.

• Environmental cleanup of perchlorate at military installations.

All referenced data in this chapter comes from the U. S. Environmental Pro­tection Agency (http://www. epa. gov).

An additional characteristic of alfalfa that makes it attractive for biorefinement is that it is amenable to genetic transformation. Rapid and efficient methods for transformation using Agrobacterium tumefaciens have been developed and gene

promoters identified for high constitutive expression and for tissue-specific expression (reviewed by Samac and Temple, 2004; Somers et al., 2003). Trans­formation has been used to alter alfalfa for production of valuable coproducts (Table 5.2) and for improving digestion of alfalfa fiber. Transgenic alfalfa has been shown to be capable of producing high levels of phytase (Austin-Phillips and Ziegelhoffer, 2001; Ullah et al., 2002), a feed enzyme that degrades phytic acid and makes phosphorus in vegetable feeds available to monogastric animals such as swine. Adding phytase to feeds reduces the need to add supplemental phosphorus to feed and reduces the amount of phosphorus excreted by animals. In field studies, juice from wet-fractionated alfalfa plants contained 1-1.5% phytase. Phytase activity in juice was stable over two weeks at a temperature of 37°C. Activity is also stable in dried leaf meal. Both juice and dried leaf meal added to feed were as effective in feeding trials as phytase from microbial sources. The value of the enzyme and xanthophyll in the juice was estimated at $1900/acre (Austin-Phillips and Ziegelhoffer, 2001). A wide range of feed enzymes is used to enhance digestion of feed and improve animal performance. Use of feed enzymes in monogastric and ruminant animals in expected to increase worldwide (Sheppy, 2001). Production of feed enzymes in transgenic plants, particularly in plants used as animal feed, would be an opportunity to increase feed utilization as well as value of the feed.

Transgenic alfalfa has also been used to produce several industrial enzymes. A manganese-dependent lignin peroxidase, which can be used for lignin degra­dation and biopulping in the manufacture of paper, was expressed in alfalfa. However, high levels of production of this enzyme appeared to be detrimental to plants (Austin et al., 1995). In the same study, a-amylase was produced at a level of approximately 0.01% of soluble protein without having a negative effect on plant development. Two cellulases, an endogluconase and a cellobiohydrolase, have been expressed at low levels in alfalfa (Ziegelhoffer et al., 1999). These enzymes were stable in dried leaf meal. Expression of cellulose degrading enzymes in biomass plants is one strategy to decrease the costs of saccharification that precedes ethanol fermentation. Alfalfa plants have also been shown to be an excellent “factory” for the production of chitinase (Samac et al., 2004). Chitin, found in shells of crustaceans, is the second most abundant carbohydrate after cellulose, and a potential feedstock in a biorefinery.

In addition to production of proteins, the use of transgenic alfalfa to produce other industrial feed stocks has been explored. Polyhydroxyalkanoates (PHAs) are produced by many species of bacteria and some PHA polymers are commer­cially valuable as biodegradable plastics. PHA synthesis in plants is seen as a more economically viable means of producing large quantities of these polymers (Poirier, 1999; Slater et al., 1999). Alfalfa was engineered to constitutively express three bacterial genes for the production of poly-p-hydroxybutyrate (PHB) (Saruul et al., 2002). Granules of PHB were shown to accumulate in chloroplasts without any negative impact on plant growth. Yield of PHB by chemical extrac­tion was relatively low (1.8 g kg-1 DM), but may be improved by optimizing extraction methods or by utilizing stronger gene promoters.

A major limitation to use of biomass in the production of ethanol is the recalcitrance of the material to saccharification. Cross-linking of lignin with cell — wall polysaccharides interferes with enzymatic degradation of cellulose and can severely limit the conversion of herbaceous plant material into ethanol. Lignin in alfalfa stems also limits digestion of feed by ruminant animals. In experiments aimed at increasing feed digestion by ruminants, transgenic alfalfa was produced that had decreased expression of caffeoyl coenzyme A 3-O-methyltransferase, an enzyme involved in synthesis of lignin precursors. These plants were shown to have approximately 20% less lignin and 10% additional cellulose than the controls (Marita et al., 2003). The rate of digestion of the transgenic material was deter­mined by in vitro rumen digestibility assays. In the transgenic material, a 2.8-6.0% increase in the rate of digestion was observed (Guo et al., 2001). This material could have a very significant impact on both animal nutrition and alfalfa biorefining. Casler and Vogel (1999) determined that a 1% increase in forage digestibility would lead to a 3.2% increase in average daily live-weight gain by beef steers. Although this material has not yet been tested with different pretreat­ment methods or used in saccharification or fermentation studies, based on chem­ical analyses, it may also have improved qualities as a feedstock for bioethanol production.

During the past several years, barrel medic (Medicago truncatula) has been the object of a broad range of research efforts worldwide. This annual plant, which is closely related to alfalfa, is a model plant for study of plant-microbe interactions and plant development (Cook, 1999). Chromosome mapping has shown that there is a high degree of gene synteny between the two species as well as a high degree of DNA sequence homology (Choi et al., 2004). Numerous genomic tools have been developed for M. truncatula including isolation of over 189,000 expressed sequence tags (ESTs), identification and sequencing of more than 36,000 unique genes (http://www. tigr. org/tigr-scripts/tgi/T_index. cgi? spe- cies=medicago), extensive genetic and physical mapping (Choi et al. 2004), development of microarrays for transcript profiling, and a genome sequencing project is currently underway (http://www. medicago. org). In particular, micro­arrays are valuable tools for identifying genes involved in important agricultural processes as they enable researchers to measure expression of thousands of genes simultaneously. More than 100 genes are involved in cell-wall biosynthesis in plants and little is known about regulation of their expression. EST resources may be useful both as markers for selecting plants with favorable characteristics in bioconversion and in modifying gene expression in transgenic plants for enhancing the efficiency of ethanol production or enhancing yields of valuable coproducts.

One of the main motivations for using E85 is its ability to help reduce the impact of vehicle emissions on the environment. E85 provides major reductions in some tailpipe emissions compared to gasoline. E85 is also less toxic than gasoline. Furthermore, the ethanol used in E85 can be derived from renewable resources, thus reducing net greenhouse gas emissions.

Vehicle Tailpipe Emissions

Determining the effect of E85 on vehicle emissions is complex, since many factors influence the emissions of vehicles. Further, E85 use is a politically charged issue, effecting the environment, domestic employment, and petroleum imports. Finding reliable emissions data is, therefore, challenging. Actual emissions will vary with engine design and calibration. One of the more recent sources, the U. S. Environ­mental Protection Agency (EPA), reports potential substantial tailpipe emissions benefits when using E85 relative to conventional gasoline.18 These benefits are shown in Figure 8.1. This source suggests these benefits for an engine optimized to operate on E85. The EPA also reports that fewer total toxics are produced, and that the hydrocarbon emissions have a lower reactivity. The use of E85 does produce higher ethanol and acetaldehyde emissions than gasoline.

Other sources provide different values, but most sources tend to show sub­stantial reductions in carbon monoxide. For example, the Renewable Fuels Asso­ciation reports a reduction of 25%.19 E85 typically results in slightly reduced levels of unburned hydrocarbons. Emissions of nitrous oxides (NOx) are slightly

Emissions Species

FIGURE 8.1 Estimated emissions reductions for an engine optimized to use E85 com­pared to those when operating on gasoline. Source: Data compiled from U. S. Environ­mental Agency, EPA420-F-00-035, Mar. 2002.

reduced with some sources showing slight increases and others showing decreases. Again, much of the data is subject to the test schedule used, and the vehicle and its optimization for E85.

Data from a snowmobile powered by a four-stroke, spark-ignited engine modified to operate using blends up to E85 is shown in Figure 8.2.20

If the ethanol used in E85 comes from renewable resources such as corn, E85 can show substantial reductions in greenhouse gas emissions. In 1998, the U. S. DoE Argonne National Laboratory estimated that 1 gallon of E85 reduces greenhouse gas emissions by 16-28% compared to gasoline.21 Other references suggest higher reductions exceeding 50%.22

Pilar Ramirez de la Piscina and Narcfs Homs

Inorganic Chemistry Department,

Universitat de Barcelona, Spain

CONTENTS

Background…………………………………………………………………………………………………… 233

Energetically Integrated Ethanol Reforming Processes………………………………… 236

Catalytic Systems…………………………………………………………………………………………. 238

Mechanistic Aspects…………………………………………………………………………. 240

Nickel — and Cobalt-Based Catalysts………………………………………………… 241

Noble Metal-Based Catalysts…………………………………………………………… 243

Catalysts for Autothermal Steam Reforming………………………………….. 244

Perspectives…………………………………………………………………………………………………… 244

References…………………………………………………………………………………………………….. 245

BACKGROUND

Energy is one of the main factors that must be taken into account when sustainable development of our society is envisioned because there is an intimate connection between energy, the environment and development. In response to the need for cleaner and more efficient energy technology, a number of alternatives to the current energy network have emerged. In this context, the general use of fuel cells for automotive purposes or stationary power generation is envisioned in the medium term. This is a promising advance in the production of electrical energy from chemical energy, since the efficiency of a fuel cell is much higher than that of a combustion engine.

The fuel most widely studied for use in a fuel cell is hydrogen. Although the ideal situation would be the production of hydrogen from water, using renewable energy sources (e. g., solar energy), this is unlikely to become extensively oper­ative in the short to medium term. At present, hydrogen is mainly produced by steam reforming of fossil fuel-derived feedstock, mostly natural gas and naphtha.

The main objective of the steam reforming process is to extract the hydrogen from the substrate. From hydrocarbons, hydrogen is obtained via the general equation:

CnH2n+2 + nH2O о nCO + (2n + 1)H2 AH0 > 0

Then, the production of hydrogen is completed by the successive water gas shift reaction (WGSR):

CO + H2O о CO2 + H2 AH° = -41.1 kJ mol1

Both reactions can only be carried out in a practical way by catalytic means. The steam reforming reaction is endothermic and the real amount of energy required depends on both the stability of the substrate to be reformed and the ability of the catalyst to activate and transform the substrate into the products. The WGSR is slightly exothermic, and the forward reaction is not favored at the temperature used for steam reforming, which is higher than 1000 K for CH4. Therefore, the overall process requires the use of different catalysts, which operate under different reaction conditions in separate reactors. In the case of natural gas and naphtha, many years of industrial practice have led the total process to become technologically mature. However, if a strong increase in the demand for hydrogen is contemplated, some advanced research and development in catalysis and tech­nology would still be needed in the next few years [1,2].

On the other hand, society has become environmentally conscious and sen­sitive to its oil dependency because petroleum is likely to become scarce and expensive and the reserves are concentrated in a few countries. If a long-term global solution is envisioned, other, nonfossil-derived fuels, which are renewable and environmentally friendly must be contemplated for the supply of hydrogen. In this context, ethanol is a very promising alternative. As has been stated in previous chapters, ethanol, which can be considered a renewable and ecofriendly hydrogen carrier, can be produced from a large variety of biomass-based sources.

The catalytic steam reforming of ethanol may provide up to 6 moles of hydrogen per mol of ethanol reacted:

CH3CH2OH + 3H2O о 2CO2 + 6H2 AH° = 173.4 kJ mol-1

If the primary production of CO is considered in the steam reforming of ethanol, the WGS reaction must be taken into account. The overall process, then, will be the combination of both reactions:

CH3CH2OH + H2O о 2CO + 4H2
CO + H2O о CO2 + H2

Although globally the reaction releases 2 moles of carbon dioxide, the total process is almost neutral from the point of view of CO2 generation, since it may be assumed that the CO2 produced is consumed in biomass growth. Consequently, the use of the steam reforming of ethanol as a source of hydrogen can contribute to the global reduction of CO2 emissions. Moreover, other emissions of green­house or polluting gases such as hydrocarbons and NOx could also be mitigated.

As we have just said, the reaction of ethanol steam reforming is highly endothermic. However, theoretical and experimental studies have shown that ethanol steam reforming can take place at temperatures above 500 K [3]. Table 13.1 shows that relatively high values of equilibrium constant (Kp) can be achieved for temperatures of over 600 K. On the other hand, it is worth mentioning that, in this case, the energy required per mol of hydrogen generated (Table 13.1) is lower than half of that required to obtain hydrogen from the steam reforming of hydrocarbons. As an example, values of H (kJ per mol of hydrogen generated) at 600 K can be considered; 32.33 kJ must be supplied when H2 is obtained from ethanol, and 72.82 kJ if methane is used [4].

An issue of major importance in ethanol steam reforming is the development of catalysts that operate with high levels of activity, selectivity, and stability. Several products that can be formed under reaction conditions could need other experimental conditions to be reformed. Consequently, the total process leading to an effluent that mainly contains H2 and CO2 and is free of undesirable products may be complex. Depending on the reaction conditions and catalyst used, the following reactions could contribute to a low selectivity of the process, among others:

CH3CH2OH ^ CH3CHO + H2
CH3CH2OH ^ CH2CH2 + H2O
CH3CH2OH ^ CH4 + CO + H2
CH3CHO ^ CH4 + CO

COx + (2 + x)H2 ^ CH4 + xH2O

Thus, after the steam reforming, an additional purification of the effluent could be necessary, but this will depend on the fuel cell to be fed. For hydrogen operating in a polymer membrane fuel cell (PEMFC) or phosphoric acid fuel cell (PAFC) the limit of CO concentration in the fuel is 50 ppm and 0.05%, respec­tively [5]. These low CO concentrations may be achieved by subsequent catalytic selective oxidation or methanation processes or by the use of H2 selective mem­branes. An additional purification of the reformed effluent might be unnecessary when a molten carbonate fuel cell (MCFC) or a solid-oxide fuel cell (SOFC) is used. Both fuel cells, which operate at high temperatures, may convert impurities of CH4 and CO in the anode chamber [5,6].

Moreover, to make the steam reforming of ethanol operative in practice it must be energetically integrated with other exothermic processes, e. g., combus­tion or partial oxidation, which may supply the energy required for the steam reforming.

In the following sections, some propositions for globally energetically inte­grated processes and the main catalytic systems used to date for the different reactions will be analyzed. Finally, relevant perspectives of the development of the ethanol reformation to hydrogen in the near future will be presented.

Today’s military has become increasingly reliant on portable power to main­tain a devastating advantage over less sophisticated enemies. Vital communica­tions equipment, night-vision goggles, and weapon systems are being developed and deployed that require immense amounts of portable power available to the individual soldier. Lieutenant Marc Lewis was quoted in Iraq in June 2003 stating, “If we run out of batteries, this war is screwed.” Soldiers are typically employing disposable batteries and some rechargeables for their equipment. Batteries can account for up to 50 pounds of a soldier’s rucksack due to inability to recharge batteries in the field. To reinforce the reliance on batteries, a 12-person Special Forces team on a 30-day deployment can go through 3000 batteries at a cost of $350,000 [3]. Many of these batteries are only used for 10-20% of their capacity before being discarded. This may immediately seem wasteful but imagine staking your combative edge on being able to see at night or communicate with other troops; one would much rather pop open a new battery than use one that was not fully charged.

Portable fuel cells could provide incredible advantages to the military. Rather than carrying a number of disposable or rechargeable batteries, a solider could carry a couple fuel cells and the fuel needed to refuel them as needed in the field. Additionally, because fuel cells can provide more energy for longer periods of time than batteries, they could enable the next generation of electronic devices for the military to further enhance its combative advantage.