October 28, 2011
This is the fifth blogpost in the series, “Corn-Fed Cars: On the Road with Ethanol.”
Discussions about the environmental impacts of corn ethanol often come around to the inputs and outputs associated with growing the corn and processing it into a fuel. In fact, in this series’ third post, “Does Ethanol Pollute the Environment… Or Does Corn?,” we tackled this topic.
Understanding the environmental impact of growing the corn and producing the ethanol fuel is obviously very important—but it is not the only critical piece of an exceedingly complex puzzle. Another important component of the ethanol supply chain is the so-called distribution infrastructure. In other words: What happens after the corn is grown, transported to the production facility and processed into ethanol? How does it get from the plant to your gas tank, and what are the possible environmental and health concerns along the way?
Let’s imagine the typical journey that U.S.-made corn ethanol might take. After the corn is grown and the ethanol is produced (most likely in the Midwest—see the Renewable Fuel Association’s map of biorefineries in the U.S.), it is transported by truck or rail car to a blending facility. Here it is mixed with fuel additives and gasoline to create ethanol blends such as E10 (10 percent ethanol—which is the standard gasoline you fill your tank with these days) or E85 (85 percent ethanol—more commonly used by flexfuel vehicles in the Midwest). About 75 percent of ethanol is transported by rail and about 25 percent by truck, according to a 2006 report from the Renewable Fuels Association.
Unlike gasoline, which is transported through extensive underground pipeline systems, there has been little development of commercial scale pipelines for ethanol, with the exception of a relatively small ethanol pipeline that began running between Tampa and Orlando in 2009. Thus far, the development of a larger scale ethanol pipeline has been cost-prohibitive given current usage levels.
Well, why can’t we just use the gasoline pipelines to transport ethanol? For one, while much gasoline in the U.S. is refined in the South and transported to the population hubs throughout the country, ethanol’s route to the end user is different. But the main complicating factor regarding ethanol transport is the fact that it has corrosive properties that require it to be stored and transported in compatible materials. If ethanol is transported or stored in inappropriate materials, leaks and contamination could occur.
Potential environmental releases of concern include air emissions from blending, storage and dispensing facilities, water contamination and environmental damage from spillage and leaks of the fuel and its co-products. Due to ethanol’s chemical characteristics, the risk of flammability and explosions are also specific concerns.
In recent years, there have been several highway incidents involving explosions with trucks carrying ethanol. Rail transport can also present public safety concerns, and some communities have voiced opposition to these trains traveling through densely populated areas.
The more we learn about ethanol’s corrosive properties, the more it becomes clear that if we continue to use higher ethanol blends, it will require a new or retrofitted infrastructure throughout the entire storage and distribution process—as existing pipelines storage tanks and gas pump equipment are not necessarily safe for ethanol blends higher than E10 or E15.
This is especially troublesome when you consider the 595,000 underground storage tanks in the U.S. While the Environmental Protection Agency requires leak detection technology for fuel storage tanks to prevent groundwater contamination, these systems were not designed with biofuels in mind. There are thousands of tanks across the country in which the capacity to handle ethanol blends higher than E10 without causing corrosion and leaks is unknown. Changes in ownership and lack of records of the specific materials comprising all the components of the tanks makes it very difficult to determine if they are appropriate for storage of ethanol blends.
Furthermore, leakage of ethanol blends may actually result in more environmental damage than the spill of a comparable amount of petroleum fuel, because of ethanol’s capacity to extend the reach of the toxic components in the ethanol-gasoline blend. The BTEX plume (comprised of volatile organic compounds benzene, toluene, ethylbenzene, and xylene) can spread farther and cause its toxic and carcinogenic components to persist longer in soil and groundwater, according to a 2009 report from the Government Accountability Office.
For better or for worse, it’s important to recognize how the overall impacts of ethanol use depend on many factors throughout the supply chain (which are often difficult to strategically assess). Later in our blog series, we will address the next aspect in the “life cycle” of ethanol: tailpipe emissions from corn ethanol and how they differ from gasoline emissions.
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