Especially in atmospheric gasification, larger hydrocarbons are formed, generally categorized as “tars.” When condensing, they foul downstream equipment, coat surfaces, and enter pores in filters and sorbents. To avoid this, their concentration throughout the process must be below the condensation point. On the other hand, they contain a lot of potential CO and H2. They should thus preferably be cracked into smaller hydrocarbons. Fluidized beds produce tar at about 10 g/mNTP3 or 1-5 wt% of the biomass feed (Boerrigter et al. 2003; Milne et al. 1998; Tijmensen 2000). BTX, accounting for 0.5 volume % of the synthesis gas, have to be removed prior to the active carbon filters, which otherwise sorb the BTX com­pletely and quickly get filled up (Boerrigter et al. 2003).

Three methods may be considered for tar removal/cracking: thermal cracking, catalytic cracking, and scrubbing. At temperatures above 1000-1200°C, tars are destroyed without a catalyst, usually by the addition of steam and oxygen, which acts as a selective oxidant (Milne et al. 1998). Drawbacks are the need for expensive materials, the soot production, and the low thermal efficiency. Catalytic cracking (dolomite or Ni based) is best applied in a secondary bed and avoids the mentioned problems of thermal cracking. However, the technology is not yet fully proven (Milne et al. 1998). It is not clear to what extent tars are removed (Tijmensen 2000) and the catalyst consumption and costs are matters of concern.

TABLE 2.2 Estimated Contaminant Specifications for Methanol Synthesis1 and Cleaning Effectiveness of Wet and Dry Gas Cleaning Treatment Method and Remarks
	Dry Gas Cleaning3
Sorbents under development. All tar and BTX: Catalytic tar cracker, other catalytic operations. Under development. In-bed sorbents or in-stream sorbents. <1 ppm. Guardbeds necessary.
All nitrogen: catalytic decomposition, combined removal of NH3/H2S. Selective oxidation under development. All sulfur: In-bed calcium sorbents. Metal oxide sorbents <20 ppm.

TABLE 2.2 (CONTINUED)

Estimated Contaminant Specifications for Methanol Synthesis1 and Cleaning Effectiveness of Wet and Dry Gas Cleaning

1 Most numbers are quoted from Fischer-Tropsch synthesis over a cobalt catalyst (Bechtel 1996; Boerrigter et al. 2003; Tijmensen 2000). Gas turbine specifications are met when FT specifications are.

2 Cleaning requirements for MeOH synthesis are 0.1 (van Dijk et al. 1995) to 0.25 ppm H2S (Katofsky 1993). Total sulfur <1 ppmV (Boerrigter et al. 2003). For Fischer-Tropsch synthesis requirements are even more severe: 10 ppb (Tijmensen 2000).

3 Hot gas cleaning was practiced in the Varnamo Demonstration plant, Sweden (Kwant 2001). All data on dry gas cleaning here is based on the extensive research into high-temperature gas cleaning by Mitchell (Mitchell 1997; Mitchell 1998).

4 Bergman et al. (Bergman et al. 2003).

Per kg dry wood (15% moisture), 0.0268 kg dolomite. Part of the H2S and HCl present adsorb on dolomite (van Ree et al. 1995). The tar crackers can be integrated with the gasifier.

Tars can also be removed at low temperature by advanced scrubbing with an oil-based medium (Bergman et al. 2003; Boerrigter et al. 2003). The tar is subsequently stripped from the oil and reburned in the gasifier. At atmospheric pressures BTX are only partially removed, about 6 bar BTX are fully removed. The gas enters the scrubber at about 400°C, which allows high-temperature heat exchange before the scrubber.

After steeping, the germ (which contains most of the corn oil) is dislodged from the kernel by gentle disruption using a germ mill. The germ fraction is separated in hydroclones based upon its low density (high oil content) and then washed to remove loose starch and gluten. The germ is pressed and dried, and the oil is either extracted on-site or sold to a corn oil refiner. If the oil is extracted on-site, the residual material is blended into corn gluten feed. The slurry exiting the hydroclones is screened to separate fiber from protein (gluten) and starch. Fiber is repeatedly washed and the destarched fiber is incorporated with steepwater solids and the bottoms of the distillation column into corn gluten feed. Gluten is separated from starch by centrifugation and dried to produce corn gluten meal. Corn steep liquor, the liquid remaining after removal of kernel components, can also be sold separately as either a feed or fermentation ingredient.

Novel Downstream Processing

Gas Stripping

Gas stripping is a simple technique that can be applied for recovering butanol (ABE) from the fermentation broth (Maddox, 1989; Qureshi and Blaschek, 2001b). Oxygen-free nitrogen or fermentation gases (CO2 and H2) are bubbled through the fermentation broth followed by cooling the gas (or gases) in a condenser. As the gas is bubbled through the fermentor, it captures ABE, which is condensed in the condenser followed by collection in a receiver. Once the solvents are condensed, the gas is recycled back to the fermentor to capture more ABE. This process continues until all the sugar in the fermentor is utilized by the culture. In some cases, a separate stripper can be used to strip off solvents followed by recycling the stripper effluent that is low in ABE. Figure 6.3 shows a typical schematic diagram of solvent removal by gas stripping. Gas stripping has been successfully applied to remove solvents from batch (Ennis et al., 1986b; Maddox et al., 1995; Ezeji et al., 2003), fed-batch (Qureshi et al., 1992, Ezeji et al., 2004), fluidized bed (Qureshi and Maddox, 1991a) and continuous reactors (Groot et al., 1989; Ezeji et al., 2002). In addition to removal of solvents, a concentrated sugar solution was fed to the reactors to reduce the volume of process streams and economize the butanol production process. The reader is referred to the Batch process with concentrated sugar solutions and fed-batch fermentation sections of this chapter where concentrated sugar solutions were successfully fermented in combination with product recovery by gas stripping. In these pro­cesses, the reactor productivities and product yield were also improved (Maddox

et al., 1995; Qureshi and Maddox, 1991a; Ezeji et al., 2002). Additional advan­tages of gas stripping included achieving a high product concentration in the condensed stream and the requirement for no membrane or chemicals for the recovery process.

Strategies for tailoring the properties of Nafion membranes include surface mod­ification of the membrane with a barrier less permeable to methanol that still allows facile proton conduction, addition of intercalants into the membrane to react with methanol to reduce crossover, and blending Nafion with other polymers to form hybrid membranes.

Palladium metal is of particular interest for researchers as it is impermeable to methanol but not proton [33,56]. A variety of methods to apply the Pd layer to Nafion have been assessed and the effectiveness of the modification in reducing methanol crossover evaluated.

Ma et al. looked at the effectiveness of reducing methanol crossover by sputtering a Pt/Pd-Ag/Pt layer onto Nafion [32]. It was found that while the layers were not crack-free, the Pd alloy-coated Nafion had increased performance over uncoated Nafion. A DMFC made with a Nafion membrane coated with a 1-pm thick Pd alloy layer generated a maximum current density roughly 35% (2.3 vs. 1.7 mW cm-2) higher than a control DMFC made with twice the electrocatalyst loading, though, the power densities are lower than one might expect.

Hejze et al. evaluated the performance of electrolessly deposited Pd-coated Nafion 117 to that of unmodified Nafion 117 membrane [56]. Here, Pd layers were coated onto fully hydrated Nafion substrates and the performance as a separator evaluated in a specialized cell for methanol concentrations <10%. Over the course of 10 hours, methanol crossover through the Pd-coated membrane was found to be much lower than for the unmodified Nafion control. The design of the fuel cell and large iR drop disallowed using realistic current densities. The authors think the technology can be applied to MEA type cells and acknowledge the increased cost of using another noble metal in a DMFC.

Methods to deposit Pd onto the surface of Nafion membranes by means of ion exchange and chemical reduction were studied by Hong et al. [33]. Palladi — nized Nafion PEMs were found to be less permeable to methanol and uptake more water then unmodified Nafion. A DMFC made with the palladinized Nafion PEM generated roughly 40% higher maximum current density than the Nafion control cell. Of the palladinized membranes tested, the best performers were found to have nanoparticles deposited near the surface of the membrane.

Choi et al. modified Nafion membranes in one of three ways: plasma etching the Nafion surface, sputtering Pd onto the Nafion surface, and combining both plasma etching and Pd sputtering [34]. Plasma etching changes the membrane morphology. Sputtering Pd “plugs” the pores of the water-rich domain of the membrane that allow proton conduction, but acts as a barrier to methanol cross­over. When tested against an untreated Nafion membrane, it was found that all three treated membranes had lower permeability to methanol with the plasma/Pd sputtered membrane having the lowest permeability. When the membranes were tested in single DMFCs, it was found all of the test cells had higher open circuit potentials than the control cell. The current-voltage performance of the Pd sput­tered and plasma-etched cells were superior to the control cell. The test cell with both treatments performed poorly relative to the control cell. The Pd sputtered cell had a power maximum of ~80 mW cm-2, which is slightly more than twice the control cell power maximum.

Kim et al. used supercritical carbon dioxide (sCO2) to graft polystyrene onto Nafion 115 as sCO2 produces low thermal stress and has a plasticizing effect when used as a swelling agent in polymers [35]. Following impregnation, the membrane was sulfonated and its properties compared to unmodified Nafion. Impregnated membranes have higher ion exchange capacity and lower perme­ability to methanol. DMFCs made with impregnated membranes generate more current at 350 mV (~140 mA cm-2) than a Nafion 115 control cell (—113 mA cm-2).

Kang et al. deposited thin (0.1 pm), clay-nanocomposite films onto Nafion 117 using layer-by-layer assembly [57]. The purpose was to reduce methanol crossover using exfoliated (leaf-like) clay nanosheets that are efficient compo­nents in barrier membranes for gas and water vapor. Permeability of methanol and ionic conductivity of the treated Nafion are measured and compared to a Nafion control. The control membrane has a methanol permeability of 1.91 x 10-6 cm2 s-1 and in-plane conductivity of 0.122 S cm-1. The Nafion modified with a 20-bilayer nanocomposite, has roughly half the methanol permeability as the control Nafion, 7.58 x 10-7 cm2 s-1 and nearly the same in-plane ionic conductivity, 0.124 S cm-1.

Chan et al. modified Nafion 115 membranes using in situ acid-catalyzed polymerization of furfuryl alcohol (PFA) to introduce highly cross-linked and methanol impermeable domains into the Nafion matrix. Modified and untreated Nafion PEMs were prepared and characterized [58]. It was found that methanol flux through the membranes, measured potentiostatically, changed as a function of the wt% of PFA in the membranes. A “sweet spot” of 8 wt% showed the lowest methanol flux, nearly 3x smaller than unmodified Nafion, while membranes with lower and higher PFA content had methanol flux intermediate to the 8 wt% and control. The PFA membranes were integrated into DMFCs and the output at room temperature and 60°C compared to that of a native Nafion control DMFC. Under all conditions, the DMFCs made with PFA PEMs generated significantly more power than the control DMFC. Peak power densities for DMFCs made with the PFA membranes were 2 to 3x larger than the unmodified Nafion DMFC.

One strategy to enhance water retention in PEFCs is to incorporate inorganic particulates into the PEMs of fuel cells [59,60,61]. Nafion membranes impreg­nated in this fashion act as a barrier to methanol crossover and can be used in high temperature (—150°C) direct alcohol fuel cells and H2/air fuel cells [44]. Arico et al. evaluated the surface properties of basic and neutral alumina, ZrO2, SiO2, and SiO2-phosphotungstic acid (SiO2-PWA) using X-ray photoelectron spectroscopy (XPS), Brunauer Emmett and Teller (BET) surface area, and acid — base characterizations. Composite membranes were prepared by recasting Nafion with the inorganic fillers. The resulting membranes were incorporated into DMFCs [44]. All of the membranes showed similar methanol crossover behavior of 4 ± 1 x 10-6 mol min-1 cm-2 at 145°C and 0.5 A cm-2. The electrochemical performance and conductivity of the composite membranes tracks the acidity of the intercalants and follow the series: SiO2-PWA > SiO2 > ZrO2 > n-Al2O3 > b — Al2O3. That is, the membranes with the best performance were the most acidic. Here “n” stands for neutral and “b” for basic. The DMFC made with the hybrid SiO2-PWA/Nafion membrane produced 400 mW cm-2 at 900 mV using pressur­ized O2 and a cell temperature of 145°C.

In another study Baglio et al. studied Nafion-TiO2 membranes for use in high temperature DMFCs [45]. The electrochemical performance of the membrane is significantly influenced by the properties of the intercalants such as surface area and pH. Here, the TiO2 intercalated into the membranes had been calcined at temperatures ranging between 500 and 800°C. The pH of the resulting particles trends with the temperature; a lower calcination temperature gives a particle with lower pH. As seen in [44], the membrane with the highest acidity generated the most power. Under similar operating conditions of 145°C cell temperature, 2.0 M methanol solution, and pressurized O2, a DMFC using TiO2 calcined at 500°C generated 350 mW cm-2. This DMFC, subjected to longevity tests, operated for a month with daily cycles of start-up and shut-down under the conditions men­tioned above. The cell potential was potentiostatically held at 400 mV. At start­up, the cell generated ~800 mA cm-2 (320 mW cm-2) and decreased to roughly 760 mA cm-2 (304 mW cm-2) after 4 hours of operation. This occurred daily. Upon feeding water to the anode, start-up performance was restored the following day.

Bauer and Willert-Porada characterized Zr-phosphate-Nafion membranes as candidate materials for use in DMFCs [62]. The inorganic filler reduced methanol permeability and the phosphate layer had preferred permeability to water over methanol. The preliminary results suggest Zr-phosphate can be used to tailor such Nafion properties.

The type of fish the project will use are tilapia. They are a very forgiving fish, adaptable to a wide range of environments. They are fecund (have lots of babies) and grow from birth to marketable size in 6 months. They are efficient users of feed (5 pounds of feed = 1 pound of fish). By contrast, beef requires 19 pounds of feed to produce 1 pound of gain. Tilapia are the answer to a hungry world. The flesh is mild and flavorful. They are mouth breeders (the mother carries the eggs in her mouth until they hatch) and a tropical fish that require warm water, so there is no danger of their “escape” from cultivation and contamination of local waterways.

Auto-Feeders

The fish finish tank will be equipped with auto-feeders, which hold a reserve of feed and are activated by hungry fish bumping a rod that projects down into the water. When activated, it releases a small amount of pellets to the fish below. The fish always have a supply of feed before them that is released on their demand. As a result, the feed is always fresh and overfeeding is reduced thereby enhancing
the quality of tank water. Water quality drops when uneaten feed is present on the bottom of the tank. This eliminates the need for 5-6 hand feedings throughout the day. Labor then is only required to assure that the auto-feeders are kept full. The fish are trained in the hatchery to receive food in this manner.

A broad range of hydrocarbons, ranging from methane to waxes of high molecular weight can be produced from synthesis gas using an iron or cobalt catalyst. These are called Fischer-Tropsch (FT) liquids or Gas-to-Liquids (GTL). By cracking the longer hydrocarbons and refining, a diesel is produced that can be blended into standard diesel. FT diesel has very low levels of sulfur and aromatic com­pounds compared to ordinary diesel and, when processed in an internal combus­tion engine, emit less NOx and particulates than diesel fuels.

The FT process was first developed at commercial scale for the production of synthetic oil in Germany during the Second World War and was further developed by Sasol in South Africa. Sasol remains today the only producer of FT products from low grade coals. The rising oil price, availability of large amounts of “stranded gas,” and decreasing investment costs have increased the interest in FT liquids. Qatar seems to be the driver of FT development, with planned projects totaling to 800,000 bbl/day or about 114 ktonne/day (Bensaid 2004).

In 1999 when the world had a considerable surplus of methanol production capacity, several companies proposed to retrofit methanol plants to produce alter­native products, e. g., Fischer-Tropsch liquids or hydrogen (Brown 1999; Yakob — son 1999). The demonstration unit of Choren in Freiberg Germany, has produced both FT liquids and methanol.

Zein is a biodegradable resin that has value for food and cosmetic uses, however, currently available methods for recovering and purifying zein protein from corn are too expensive to compete with petroleum-based films and plastics. The COPE (corn oil and protein extraction) process is being developed to inexpensively extract zein protein from either milled corn or DDGS, for use in the plastic and film-packaging industries [45]. Achieving cost-effective methods for extraction of zein and synthesis of zein-based biodegradable polymers could add value to DDGS and the nonstarch fraction of corn.

The Corn Ethanol Industry Hybrid and Strain Development

“Self-processing” hybrid corn kernels are being developed. This type of hybrid accumulates starch-hydrolyzing enzymes in the endosperm of transgenic corn kernels [46]. Work has also been carried out to construct fermenting yeast strains with built-in amylolytic activity [47]. Using these strategies, genes for enzymes with known properties and specificities could be used to engineer customized grains and/or yeast. Self-processing grains or starch-degrading and fermenting yeast would thus have built-in enzymatic activities designed to meet specific processing requirements. Other genetically modified corn hybrids are being devel­oped to generate alternate starches and complex carbohydrates. Starch from these hybrids would have improved gelling properties, viscosity, flavor, stability, adhe­sion, film formation, or properties that enhance the efficiency of starch processing.

conclusions

Use of ethanol, a renewable transportation fuel, is expected to expand significantly because of concerns regarding the environment and energy security. The U. S. ethanol industry will continue to utilize corn as its primary source of fermentable sugar. New feedstocks, technologies, and products moving from the laboratory to the marketplace will increase the productivity and viability of the fuel ethanol industry.

Gregory W. Davis, Ph. D., P. E.

Director, Advanced Engine Research Laboratory and Professor of Mechanical Engineering, Kettering University, Flint, Michigan

CONTENTS

History…………………………………………………………………………………………………………… 138

Types of Vehicles Using E85…………………………………………………………………………. 139

Flexible Fuel Vehicles……………………………………………………………………….. 139

Off-Road Vehicles……………………………………………………………………………. 140

Material Compatibility………………………………………………………………………………….. 140

Metallic Substances………………………………………………………………………….. 141

Nonmetallic Substances……………………………………………………………………. 142

Vehicle Fuel Pumps…………………………………………………………………………… 142

Property Comparison with Gasoline……………………………………………………………… 143

Effect of E85 on Vehicle Fuel Economy, Performance, and Safety…………….. 145

Fuel Economy…………………………………………………………………………………… 145

Vehicle Power……………………………………………………………………………………. 147

Cold Startability……………………………………………………………………………….. 147

Safety……………………………………………………………………………………………….. 147

Effect of E85 on the Environment………………………………………………………………… 148

Vehicle Tailpipe Emissions……………………………………………………………….. 148

Other Environmental Emissions……………………………………………………….. 149

Sustainability……………………………………………………………………………………. 149

Future Trends in E85……………………………………………………………………………………… 150

References…………………………………………………………………………………………………….. 151

Abstract The use of E85 as a fuel for vehicles is discussed in this chapter. E85, a blend of 85% ethanol and 15% gasoline is a liquid fuel that can be utilized in a wide variety of vehicles. The use of E85 has been encouraged because it dramatically reduces exhaust and greenhouse gas emissions. Additionally, the ethanol used can be derived from renewable sources. In order to use E85, the vehicle must have a spark-ignited engine. Furthermore, this engine must be adapted to accept E85.

E85 is a high-blend alcohol-based fuel containing 85% ethanol and 15% gasoline by volume. Because pure ethanol has a lower vapor pressure than gasoline, it is blended with 15% gasoline to produce E85 in order to minimize difficulties in starting engines and with drivability during cold weather.

E85 is used to operate spark-ignited engines that have been modified to accept this fuel. Spark-ignited engines cannot directly use E85 without modification due to higher mixture requirements and some material compatibility issues. E85 is used in vehicles to reduce vehicle tailpipe emissions. Further, E85, in which the ethanol has been derived from biomass, also reduces the net production of carbon dioxide, a greenhouse gas. Additionally, E85 is becoming cost competitive with gasoline, with wholesale prices lower than gasoline in early 2005 in the United States. Because of this, and the fact that ethanol can be produced from renewable resources instead of petroleum has led to its development and use in a variety of vehicles. The use of E85 is growing rapidly in the United States; however, the total number of vehicles currently using E85 is still small when compared with the total number of vehicles on the road.1

Batteries

Batteries are usually categorized as primary batteries, secondary batteries, or fuel cells [4]. Primary batteries cannot be recharged, because they have irreversible electrochemistry. They are single use and disposable. Examples of a primary battery include alkaline batteries (such as silver oxide/zinc, mercury oxide/zinc, and manganese oxide/zinc) [5]. Secondary batteries experience reversible elec­trochemistry, so they are reusable and can be recharged by an external power supply after the operating voltage has dropped to zero. Examples of a secondary battery include nickel-cadmium, nickel-metal-hydride, and lithium-ion batteries. Problems associated with secondary batteries are that they undergo hysteresis, which prohibits them from being recharged to their original state once used [4]. Unlike secondary batteries, fuel cells do not undergo hysteresis. A fuel cell is an electrochemical device that generates power upon fuel addition; therefore, it is not of single use nor does it need to be recharged by an external power source, but only by the addition of more fuel.

A battery is a portable, self-contained electrochemical power source that consists of one or more voltaic cells [5]. Single voltaic cells consist of two electrodes (an anode and a cathode) and at least one electrolyte. In all electro­chemical power sources, electrodes are used to donate and accept electrons in order to generate power. Oxidation of fuel occurs at the anode electrode, while reduction occurs at the cathode electrode. Traditional electrode materials utilized in batteries are metal-based, such as platinum, nickel, lead, and lithium. Employ­ment of these catalysts is limited due to the fact that they are nonrenewable resources and highly expensive. In addition, precious metal catalysts when employed at electrodes will oxidize a variety of fuels (hydrogen gas, methane, and alcohols: methanol, ethanol, propanol, butanol, other alkyl alcohols) and therefore they are nonselective catalysts.

Due to the nonspecificity of the catalysts, a salt bridge must be employed to separate the anode and cathode compartments in order to increase the operating voltage of the electrochemical cell by separating anodic fuel from cross-reacting at the cathodic electrode. Theoretically, if selective catalysts were utilized at both electrodes, the polymer electrolyte membrane that acts as a salt bridge in a typical cell can be eliminated from the system. This can result in simplifying the elec­trochemical power system as well as the manufacturing procedure, which will result in lower production costs. Elimination of resistance that is associated with the polymer electrolyte membrane results in an increase in ion conductivity that results in higher power density outputs.

Whereas the first phase of the project is primarily passive, i. e., simply recapturing waste biomass, the second phase will actively demonstrate the culture, growth, harvest, and use of renewable biomass fuels — biomass here being defined as plants specifically grown for their fuel value. The project will also be conducting research into the production of oilseed crops specific to this geographic region — these crops can be directly converted into biodiesel, and used for either electric generation or transportation. Crops specifically grown for gasification include hybrid poplar, salix (willow), and alfalfa. Crop by-products that can be gasified include corn cobs, corn stover, sawdust, wood chips, and chipped brush. Non­crop items include rubber tires, plastic, and construction debris. Oilseed crops include canola (rapeseed), soybeans, and corn. All energy crops will be irrigated with fish effluent with controls in place to determine the beneficial effect this waste product has on field-grown plants.