The final stage in supplying any fuel is distribution to users. Gasoline and diesel fuels benefit from a well-established distribution system that cost-effectively makes them available for customers to purchase individually at service stations and for vehicle fleets at refueling stations. In 2008, about 160,000 refueling stations in the United States supplied several grades of gasoline and sometimes diesel. The distribution system meets the demand for gasoline with varied octane (antiknock) ratings, whose composition varies seasonally to compensate for changes in ambient temperature and because of fuel requirements related to air-quality control. Diesel fuel also varies seasonally in composition because of cold-weather requirements.

The biofuel that is most available and most used today is ethanol, which accounts for nearly 6 percent of U.S. gasoline use by volume and 4 percent by energy content. The supply of ethanol is expected to increase steadily over the next decade and beyond as a result of the Renewable Fuel Standard as amended in the 2007 U.S. Energy Independence and Security Act (EISA). One of the important challenges to widespread use of ethanol as a transportation fuel is that it cannot be transported and delivered in existing petroleum-delivery systems (for example, pipelines) because of the incompatibility of materials and water absorption by ethanol in the pipelines. Therefore, this chapter focuses on the transportation and distribution of ethanol. Synthetic gasoline and diesel fuels produced from biomass and coal and future synthetic biofuels, such as biobutanol, are expected to be compatible with the existing infrastructure for petroleum products; distribution costs for these synthetic fuels are expected to be similar to those for petroleum-based fuels. Although their volume is expected to grow over the next decade or

two, the increasing volume could be accommodated incrementally in the existing infrastructure, so it is not explicitly discussed here.

In considering ethanol as a transportation fuel, one needs to be aware that ethanol is not a one-to-one replacement for its petroleum-based counterparts. Ethanol contains only two-thirds of the energy of the same volume of gasoline. The corn grain used and the cellulosic biomass to be used to produce ethanol also vary in density and other physical characteristics that affect their costs of transportation from field to conversion plants, as discussed in Chapter 2. Most of the biomass will be produced in the interior of the United States (or from wood in the Northwest). The economics of transporting biomass feedstock versus finished transportation fuel favor biorefineries in the Midwest, but 80 percent of the U.S. population—representing the largest current and future transportation-fuel markets—lives along the coasts. Figure 5.1 maps existing biorefineries and those

FIGURE 5.1 U.S. ethanol and biodiesel plant locations compared with state population density as of July 1, 2007.

Source: Adapted from NBB (2007), U.S. Census Bureau (2007), and RFA (2008).

under construction that produce ethanol and biodiesel relative to U.S. state population densities. As discussed later in this chapter, there is an ethanol-compatible infrastructure for transporting ethanol to markets today for the relatively small volumes produced. However, if the ethanol markets increase rapidly over the next decade, the lack of delivery capacity and the complexity of constructing it will challenge the industry.

As of 2008, most of the ethanol produced is blended in gasoline at up to 10 percent by volume; such ethanol-containing gasoline is designated E10. There are few outlets for higher ethanol blends, such as E85; close to 15 percent gasoline (by volume) is blended with pure ethanol for several reasons, for example, to improve vehicle cold-starting. If E10 fuels were sold at every refueling station in the United States, about 15 billion gallons of ethanol would be consumed each year. If the United States plans to produce about 40 billion gallons of cellulosic ethanol each year to improve energy security and to reduce carbon emissions, the number of E85 refueling stations will have to be increased to more than the 1900 stations that exist in 2008.

More than two-thirds of the quantity of U.S. petroleum products is shipped via pipeline, and the rest via barge (27 percent), truck (3 percent), or rail (2 percent) (Booz Allen Hamilton, 2007). Ethanol is not compatible with existing petroleum pipelines; it can damage pipeline seals and other equipment and even induce cracking in pipeline steel (Farrell et al., 2007). The pipeline industry, however, is considering dedicated pipeline for ethanol as an option (as discussed later in this chapter).

A typical ethanol-distribution system is shown in Figure 5.2. Typical ethanol transportation fuels are E10 and E85. As shown in the figure, truck transportation is the critical last step in the system (transportation from blender to fueling station). It is unlikely that any other mode of transportation will replace trucks at this stage in the distribution system, because trucks are the most economical mode of short-range transportation.

If larger volumes are to be carried between biorefineries and blending stations, however, there could be several competing modes. A next-generation ethanol plant taking in 4 million tons of biomass per year would produce 30,000 bbl of ethanol per day. One inland barge would transport about 30,000 bbl (1.3 million gallons) of denatured ethanol, one railroad car about 750 bbl (33,000 gal),

and one truck about 200 bbl (8,000 gal) (USDA-AMS, 2007). For comparison, a 12-inch pipeline could move up to 100,000 bbl (4.2 million gallons) per day.

The cost of transportation and distribution is a substantial component of the total cost of ethanol. In the United States, ethanol is carried from biorefineries to staging¹ and blending² terminals and then to fueling stations by trains, trucks, and barges. Table 5.1 lists estimated costs associated with shipping ethanol via truck, rail, or barge (Jenkins et al., 2008). The cost of transporting petroleum fuels from refineries to fueling stations is about $0.03-0.05/gal, whereas the combined cost of transporting ethanol from production plants to fueling stations is estimated to be $0.13–0.18/gal (Morrow et al., 2006; GAO, 2007). However, as discussed later, the costs of ethanol transportation could be considerably higher if the delivery system is not optimized.

Trucking of fuel ethanol is the most efficient and cost-effective transportation mode for distances up to about 300 miles (Reynolds, 2002). Transportation costs for longer distances are much higher, $0.20/gal. A typical transport truck can carry about 8,000 gal/load (Reynolds, 2002).

Increasing the amount of E10 or E85 fuel distributed would require increases in the number of transport trucks. Today, for every 10 trucks transporting E10 fuel from a blending terminal to a fueling station, there is one truck carrying dena-

tured ethanol to a blending terminal. Expanded E85 distribution would require 8.5 truckloads of fuel ethanol for every 10 trucks leaving the blending terminal (API, 2008). The most pressing constraint on increasing ethanol transportation is the industry-wide shortage of drivers of long-haul, heavy-duty trucks, especially drivers with HAZMAT certification. The truck-transportation industry is already experiencing a shortage of drivers, and the imbalance between driver demand and working truck drivers is predicted to grow to more than 100,000 by 2014 (American Trucking Associations, 2005).

Ethanol transportation via barge or ship is limited to locations near large waterways, so only about 10 percent of the ethanol produced in the United States is transported by barges (USDA-AMS, 2007). Barges can, however, transport a large volume of ethanol in a single shipment. Inland tank barges, for example, can transport 1 million gallons of ethanol (USDA-AMS, 2007). Larger, ocean-faring ships and barges can transport about 1–12 million gallons of ethanol, depending on the size of the vessel and the final destination. Inland barges transport ethanol down the upper Mississippi River to staging terminals below the river’s navigation locks. Larger barges or ships that transport ethanol between staging facilities on the lower Mississippi and blending terminals on the West Coast require passage through the Panama Canal and take about 34 days to make the trip. Transportation times to East Coast locations take about 24 days (Reynolds, 2002). Shipments to the densely populated Northeast coast add $0.10–0.12/gal³ to the price of ethanol (Reynolds, 2002).

Funding to increase the size of the 1930s-built upper Mississippi navigation-lock system was approved in November 2007. The expansion from 600-ft locks to 1200-ft locks will open the upper Mississippi to larger modern barges. Increased barge and ship transportation will also require more and larger multipurpose staging facilities along waterways. Such intermodal facilities will be able to accept and quickly unload ethanol arriving by barge, rail, and truck from the Midwest and then distribute it by the most economical mode of transportation (truck, train, or barge or ship).

Trains currently transport most fuel ethanol from biorefineries to blending terminals throughout the United States. Unit trains⁴ are the most economical and efficient mode of transportation (see Table 5.2). Typical unit-train turnaround time for delivery from the Midwest to coastal blending terminals is about 6 wk. However, if a biorefinery has insufficient capacity to fill a unit train, a single-commodity train can gather ethanol from several biorefineries, or it can be shipped in a single car as part of a multicargo train. In those cases, assembly and disassembly increase the delivery time and cost. Because the costs and time for transporting ethanol via rail and barge are similar (Table 5.1), the main benefit of marine cargo transport is the ease of unloading at the destination because of its high volume (Reynolds, 2002).

As of January 1, 2007, 41,000 rail tank cars capable of shipping ethanol were in use (USDA-AMS, 2007). Existing rail capacity can accommodate current ethanol transportation demand, but increases in ethanol production will lead to a possible railcar shortage. Railcar manufacturers have a 1.5-yr backlog of tank-car orders, and shortages are expected to continue for the next few years because of the steep rise in ethanol production (Crooks, 2006).

Pipelines are the most economical method for transporting large quantities of liquids over long distances. Shipping fuel through pipelines costs $0.025/gal or less per 1,000 miles (Curley, 2008). Gasoline-transportation costs by the various modes were estimated as follows (Curley, 2008):

• Pipeline: $0.015–0.025/gal per 1000 miles.

• Barge: $0.04–0.05/gal per 1000 miles.

• Train: $0.075–0.125/gal per 1000 miles.

• Truck: $0.30–0.40/gal per 1000 miles.

Pipelines are not available for commercial biofuel transportation in the United States, although they might have much lower costs. The combination of increased ethanol production and demand with the time, volume, and cost benefits associated with pipeline transportation is spurring interest in overcoming the operational, technical, and economic issues associated with biofuel pipeline transportation. The primary issues associated with such pipeline transportation are these:

• Ethanol has a greater affinity for water than does gasoline.

• Ethanol is a much better solvent than gasoline.

• Ethanol is more corrosive than petroleum products.

• Existing pipelines are not near biorefineries.

• The practical bounds on the “transmix” (a term that the industry uses for a mixture of immiscible or otherwise incompatible fluids that need to be separated) have yet to be established.

Because of its affinity for water, ethanol is hydrated by ambient water from other transported fuels, terminals, and tank roofs as it flows through a multiuse, multipipeline network. Pipelines for transporting traditional petroleum fuels are not airtight, so moisture can get into the pipeline; the small amount of water that enters, however, does not mix with the gasoline and can be easily drained off. Ethanol, in contrast, has a higher affinity for water than does gasoline. Water contamination picked up during ethanol transportation will increase the fraction of water above allowable fuel-ethanol specifications, and the fuel will not be able to be sold to consumers. In a blended ethanol-gasoline fuel, once the ethanol absorbs enough water in a pipeline system, the fuel does not stay blended and separates

into an aqueous phase that contains ethanol and water and a gasoline-rich phase. In both cases, ethanol can be recovered from the aqueous phase only by distillation. Fuel ethanol is routinely shipped via pipeline in Brazil, where phase separation is mitigated by first shipping hydrous ethanol and then anhydrous ethanol (Hammel-Smith et al., 2002). Nonetheless, pipeline shipment of ethanol in the United States will require capital investment and involve additional maintenance costs.

Because ethanol is a better solvent than petroleum products, transporting ethanol through existing multiuse pipelines dissolves many common polymers in the pipelines and thus contaminates the fuel ethanol. According to ethanol-pipeline testing conducted by Buckeye and Williams Energy Services, frequent dewatering of pipelines,⁵ closed floater storage tanks, dry storage tanks, inline corrosion monitoring, and filtration systems would be required to transport ethanol through multiuse pipelines on a regular basis. Ethanol-only pipelines constructed of ethanol-compatible materials would avoid many contamination issues. However, construction of new pipelines would cost $1–2 million per mile, depending on, for example, right-of-way issues and material and labor costs (GAO, 2007). Costs could be even higher in a tight construction market as existed in the middle of 2008.

Another issue associated with the solvent properties of ethanol is an increase in stress-corrosion cracking (SCC) in pipelines in high-stress locations. Cases of SCC have been reported in pipelines, storage tanks, and associated handling equipment at distribution and blending terminals. No cases of SCC have been reported at biorefineries or after blending or in trucks, railcars, or barges (Kane and Maldonado, 2003). Thus, it might be possible to design new pipelines that minimize stress to reduce the possibility of SCC.

The pipeline industry throughout the world is seeking solutions to those issues. As Curley (2008) observed in his review of the problem,

Kinder Morgan Energy Partners started up a converted 106-mile-long ethanol-pipeline test in late 2008. The conversion and cleaning of the petroleum-fuel pipeline included replacing gaskets and rotating element pumps with ones that are compatible with ethanol. Extra pipe scrubbers were sent to remove excess buildup to prevent ethanol from picking up contaminants along the way. The pipeline was used to send pure ethanol that was batched side by side with gasoline going through the pipe. Corrosion inhibitor was to be injected into the entire batch (Gunter, 2008a). In October 2008, Kinder Morgan said that the pipeline test was a success and that clients could start shipping ethanol in the middle of November 2008 (Gunter, 2008b).

Retrofitting all existing multipurpose pipelines is likely not practical; however, new multipurpose pipelines could be designed with ethanol-compatible polymers in valves, gaskets, and seals and designed to minimize SCC. Laying ethanol-only pipelines next to existing multipurpose pipelines would be more cost-effective than purchasing rights-of-way for new routes.

Integration of ethanol into the commercial fuel-shipment schedule with other fuels and fuel grades requires that economical trailback tests⁶ and transmix-handling procedures be developed. Transporting a biofuel, such as ethanol, directly before or after a conventional petroleum fuel will result in a mixture of ethanol and hydrocarbons that is beyond the acceptable specification for either fuel. The points where the transmix starts and ends are related to the acceptability of trace amounts of fuel contamination (Curley, 2008). The trailback threshold depends on whether low levels of biofuels affect the performance of other fuels, such as aviation fuel, and whether the biofuels meet acceptable specification after shipment.

As of 2008, delivery of ethanol from plant to refueling station takes place in an existing system of trucks, barges, rail, and central blending plants. The system has expanded incrementally as ethanol production has increased. However, if the large production volumes envisioned by the EISA occur and the majority of ethanol is produced in the Midwest and consumed on the coasts, the delivery infrastructure will have to be expanded considerably. The alternative would be to use ethanol close to where it is produced.

Although the cost of delivery is a small portion of the overall ethanol-fuel cost, the logistics and capital requirements for widespread expansion could be substantial hurdles if they are not planned well. Morrow et al. (2006) provided a thorough analysis of the complexities and costs of widespread fuel ethanol expansion in the United States. If planning is suitable and fuel ethanol’s cost is competitive in the fuel market, the panel believes that the ethanol-delivery infrastructure would be expanded to meet demand. Brazil, where almost all new vehicles sold are capable of using fuel from E20 to E95, provides a good example of how a distribution system for ethanol, the retailing of fuel, and the production of flexible-fuel vehicles could work smoothly without being expensive.

The panel cautions that biofuel technologies will probably evolve from ethanol to biofuels that are more compatible with the existing petroleum infrastructure. Thus, planning for biofuel expansion should consider when biofuels other than ethanol might come onto the market and ensure that the ethanol-delivery infrastructure is not overbuilt and underused.

Consumer acceptance of biofuels will be determined by a combination of favorable prices relative to those of conventional petroleum products; subsidies and mandates for biofuel; the prevalence of E85 and biodiesel fueling stations (Figure 5.3); and the availability and affordability of flexible-fuel vehicles.

Refueling availability is fundamental to the widespread adoption of alternative fuels. Biofuel-refueling stations must grow beyond niche markets to a density sufficient for supporting alternative-fuel vehicles. The number of fueling stations

FIGURE 5.3 U.S. biodiesel and E85 fueling-station locations.

required to service a community adequately is unknown. However, a recent assessment based on urban population density relative to existing petroleum fueling-station density estimated that about 50,000 stations would provide sufficient coverage for the general public while providing retail competition between stations. That translates to about 0.5 station per square mile in a city with a population of 500,000 and a population density of 2,000 per square mile. The estimated upper and lower bounds on sufficient urban station coverage are shown in Figure 5.4 (Melaina and Bremson, 2008).

Retrofitting existing fueling stations with storage and dispensing equipment compatible with the chemical properties of E85 fuels is often expensive, and some station owners are averse to carrying these biofuels. To retrofit existing fueling stations, underground storage-tank systems, pumps, and dispensers must be converted to be compatible with the higher-ethanol blends. Several issues associated with retrofitting existing fueling stations are similar to those associated with pipeline transportation of ethanol and ethanol blends: phase separation as a result

FIGURE 5.4 Estimated sufficient alternative fueling-station coverage relative to urban population density. Upper and lower boundaries are shown.

Note: ppsm = persons per square mile; spsm = stations per square mile.

Source: Reprinted from Melaina and Bremson, 2008. Copyright 2008, with permission from Elsevier.

of hydration, SCC, and contamination as a result of incompatible materials commonly found throughout conventional fueling stations.

Another hurdle in adding E85 capability to fueling stations is the restrictions placed on branded stations and the ability to obtain insurance (Johnson and Melendez, 2007). Many refining companies that own major gasoline brands do not allow E85 dispensers to be placed under the same canopy as their branded gasoline dispensers. If a branded fueling station wishes to add E85 capacity, a separate canopy must be added. That requirement increases the total cost of an E85 retrofitting project (Johnson and Melendez, 2007).

The National Renewable Energy Laboratory conducted a survey and literature search on the cost of adding E85-fueling capacity to existing gasoline stations (NREL, 2008). The survey included the costs incurred for 120 E85 stations, 84 of which would have new tanks installed and the remainder would convert existing tanks. Replacing one gasoline dispenser and retrofitting existing storage tanks to carry E85 at an older existing fueling station would cost $1,736–68,000. The installation cost for a new E85-compatible fueling station would be $7,559–247,000. The generalized costs for retrofitting or building a new E85-compatible fueling station collected from the literature are listed in Table 5.3 (NREL, 2008). The installation or retrofitting costs might not be considered high for some, but they might not be feasible for some individual station owners.

As of 2007, there were about 5 million flexible-fuel cars and light trucks in the United States—about 2 percent of the total U.S. fleet. Since their introduction, the number of flex-fuel vehicles⁷ available has steadily increased. The increase, however, is largely a result of U.S. corporate average fuel economy (CAFE) mile-

age rating requirements as opposed to the availability of E85 fuel or consumer demand for alternative-fuel vehicles.

Building a vehicle capable of running on E85 fuel adds about $100 to its production cost. Flexible-fuel vehicles have upgraded fuel systems with large fuel pumps and injectors that enable them to accommodate the greater fuel volume required for the same energy content as gasoline (Hammel-Smith et al., 2002). The fuel tanks and lines are composed of ethanol-compatible materials. Operating on E85 involves an increase of a few percent in horsepower as a result of extra cooling of the in-cylinder air and the higher fuel octane rating, and maximum vehicle acceleration is higher. Because of the lower energy of ethanol relative to gasoline, fuel consumption (in gallons per 100 miles) with ethanol is about 25 percent higher, although overall vehicle efficiency can be up to 5 percent better (West et al., 2007). The attractive antiknock characteristics of ethanol could be used to improve the efficiency with which engines use gasoline in a dual-fuel engine setup (Edmunds, 2008).

Encouraging the use of flexible-fuel vehicles and the use of gasoline with a high proportion of ethanol is a complex issue. As discussed earlier in this chapter, getting large quantities of those fuels to where the vehicles are can be challenging. In the past, the U.S. Congress mandated that federal agencies gradually increase the number of flexible-fuel vehicles in their fleets, but most purchased vehicles are used in places where flexible fuel is not readily available (Kindy and Keating, 2008). To complicate the issue, many of those flexible-fuel vehicles are large sedans and sport utility vehicles. Because of their large flexible-fuel engines and low fuel efficiency, those vehicles used more gasoline than smaller and more fuel-efficient vehicles (Kindy and Keating, 2008). The simultaneous implementation and market penetration of E85 fuel and flexible-fuel vehicles is an important practical consideration.

Finding 5.1

The need to expand the delivery infrastructure to meet a high volume of ethanol deployment could delay and limit the penetration of ethanol into the U.S. transportation-fuels market. Replacing a substantial proportion of transportation gasoline with ethanol will require a new infrastructure for its transport and distri-

bution. Although the cost of delivery is a small fraction of the overall fuel-ethanol cost, the logistics and capital requirements for widespread expansion could present many hurdles if they are not planned for well.

Recommendation 5.1

The U.S. Department of Energy and the biofuels industry should conduct a comprehensive joint study to identify the infrastructure system requirements of, research and development needs in, and challenges facing the expanding biofuels industry. Consideration should be given to the long-term potential of truck or barge delivery versus the potential of pipeline delivery that is needed to accommodate increasing volumes of ethanol. The timing and role of advanced biofuels that are compatible with the existing gasoline infrastructure should be factored into the analysis.

Finding 5.2

Expansion of the flexible-fuel vehicle fleet needs to be complemented by the presence of ethanol stations close to where the vehicles are used. Past policy that mandated the increased use of alternative-fuel vehicles did not result in reduced gasoline consumption, because ethanol pumps were not readily available in many areas where flexible-fuel vehicles were used. The close coupling of alternative fuels and alternative-fuel vehicles is an important practical consideration. Future policy measures need to take into account implementation of alternative-fuel vehicles, availability of alternative fuels, and proximity of vehicles to fueling stations to ensure an effective vehicle and fuel transition.

American Trucking Associations. 2005. The U.S. truck driver shortage: Analysis and forecasts. Available at http://www.truckline.com/StateIndustry/Pages/DriverShortageReport.aspx. Accessed October 19, 2008.

API (American Petroleum Institute). 2008. Shipping Ethanol Through Pipelines. Available at http://www.api.org/aboutoilgas/sectors/pipeline/upload/pipelineethanolshipmentfinal-3.doc. Accessed October 19, 2008.

BNSF Railway Company. 2007. Pricing Update: October 2007 Ethanol Rate Adjustment. Available at http://www.bnsf.com/markets/agricultural/ag_news/year2007/pricing07/p08-23-07a.html. Accessed October 13, 2008.

Booz Allen Hamilton. 2007. Rationalizing the Regulatory Environment for Renewable Energy: Overcoming Constraints for Rapid Growth in the Biofuels Industry. McLean, Va.: Booz Allen Hamilton.

Crooks, A. 2006. From grass to gas: On the road to energy independence, how soon will cellulosic ethanol be a factor? Rural Cooperatives (Ethanol Issue, September/October):16-18.

Curley, M. 2008. Can ethanol be transported in a multi-product pipelines? Pipeline and Gas Journal 235:34.

Edmunds, Inc. 2008. Edmunds.com. Available at http://www.edmunds.com. Accessed October 19, 2008.

Farrell, A., D. Sperling, S.M. Arons, A.R. Brandt, M.A. Delucchi, A. Eggert, B.K. Haya, J. Hughes, B.M. Jenkins, A.D. Jones, D.M. Kammen, S.R. Kaffka, C.R. Knittel, D.M. Lemoine, E.W. Martin, M.W. Melaina, J. Ogden, R.J. Plevin, B.T. Turner, R.B. Williams, and C. Yang. 2007. A Low-Carbon Fuel Standard for California. Part 1: Technical Analysis. Davis: University of California, Davis.

Hammel-Smith, C., J. Fang, M. Powders, and J. Aabakken. 2002. Issues Associated with the Use of Higher Ethanol Blends (E17-E24). Golden, Colo.: National Renewable Energy Laboratory.

GAO (U.S. Government Accountability Office). 2007. Biofuels: DOE Lacks a Strategic Approach to Coordinate Increasing Production with Infrastructure Development and Vehicle Needs. Washington, D.C.: GAO.

Gunter, F. 2008a. Kinder Morgan makes waves with Florida ethanol line. Houston Business Journal, March 28. Available at http://houston.bizjournals.com/houston/stories/2008/03/31/story4.html. Accessed November 11, 2008.

Gunter, F. 2008b. Ethanol pipeline test a success, says Kinder Morgan. Houston Business Journal, October 16. Available at http://houston.bizjournals.com/houston/stories/2008/10/13/daily42.html. Accessed February 11, 2009.

Jenkins, B., N. Parker, P. Tittman, Q. Hart, J. Cunningham, and M. Lay. 2008. Strategic Development of Bioenergy in the Western States. Available at http://www.westgov.org/wga/initiatives/transfuels/reports/Biomass%20.ppt#256,1. Accessed October 13, 2008.

Johnson, C., and M. Melendez. 2007. E85 Retail Business Case: When and Why to Sell E85. Golden, Colo.: National Renewable Energy Laboratory.

Kane, R.D., and J.G. Maldonado. 2003. Stress Corrosion Cracking of Carbon Steel in Fuel Grade Ethanol: Review and Survey. Washington, D.C.: American Petroleum Institute.

Kindy, K., and D. Keating. 2008. Problems plague U.S. flex-fuel fleet: Most government-bought vehicles still use standard gas. Washington Post, November 23. Available at http://www.washingtonpost.com/wpdyn/content/article/2008/11/22/AR2008112200886_pf.html. Accessed February 9, 2009.

Melaina, M., and J. Bremson. 2008. Refueling availability for alternative fuel vehicle markets: Sufficient urban station coverage. Energy Policy 36:3223-3231.

Morrow, W.R., W. Michael Griffin, and H. Scott Matthews. 2006. Modeling switchgrass derived cellulosic ethanol distribution in the United States. Environmental Science Technology 40:2877-2886.

NBB (National Biodiesel Board). 2007. National Biodiesel Board Annual Report 2007. Jefferson City, Mo.: NBB.

NREL (National Renewable Energy Laboratory). 2008. Cost of Adding E85 Fueling Capacity to Existing Gasoline Stations: NREL Survey and Literature Search. Golden, Colo.: NREL.

Reynolds, R.E. 2002. Infrastructure Requirements for an Expanded Fuel Ethanol Industry. South Bend, Ind.: Downstream Alternatives.

RFA (Renewable Fuels Association). 2008. Changing the Climate: 2008 Ethanol Industry Outlook. Washington, D.C.: RFA.

U.S. Census Bureau. 2007. Population Profile of the United States. Available at http://www.census.gov/population/www/popprofile/profiledynamic.html. Accessed October 10, 2008.

USDA-AMS (U.S. Department of Agriculture, Agricultural Marketing Service). 2007. USDA Ethanol Transportation Backgrounder. Available at http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5063605&acct=atpub. Accessed October 13, 2008.

West, B.H., A. Lopez, T. Theiss, R. Graves, J. Storey, and S.A. Lewis, Sr. 2007. Fuel economy and emissions of the ethanol optimized Saab 9-5 biopower. In Society of Automotive Engineers Powertrain and Fluids Meeting, Chicago, Ill.