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March 23, 2018  |  Login
What about Ethanol Fuel?

By Dan Chiras

Another liquid fuel that's already being used in the transportation sector is ethanol or ethyl alcohol. Derived from corn and other sugar-rich crops such as sugar cane, ethanol is the same chemical substance that's found in alcoholic beverages. Today, many states in the United States add small amounts of ethanol (ten percent) to gasoline in the winter to help reduce air pollution during winter months.

Ethanol's Low Net Energy

Unfortunately, corn ethanol has a low net energy efficiency. In fact, for many years, it actually took more energy to make a gallon of ethanol than you got out of burning it. It had, in other words, a negative net energy efficiency. That, of course, rendered ethanol a highly questionable fuel source.

Ethanol's early performance has given it a black eye and many folks still continue to dismiss it for this reason. Fortunately, ethanol's prospects are changing. Research over the past 20 years has helped ethanol claw its way into the positive net-energy yield category. According to Marc Franke, corn ethanol currently yields 1.67 units of energy for every unit invested. That's still not great, but don't count ethanol out. Sugar cane ethanol has a net energy efficiency of 7.

Using By-Products for Energy

New processes are under development that could dramatically boost the net energy efficiency of ethanol production. One Canadian company, for instance, has developed a way to generate ethanol from cellulose in corn stalks and wheat straw, both of which are considered waste materials. By using waste products from the production of corn and wheat, manufacturers could dramatically improve the net energy efficiency. Although it is too early to tell, some think that the net energy efficiency could be as high as seven. Translated, that means that for every unit of energy invested in the production of ethanol, you'd get back seven.

Making ethanol production more energy efficient is one of the goals of the US Department of Energy's National Renewable Energy Laboratory (NREL) in Golden, Colorado. It is part of their program to study and develop ways of obtaining energy from biomass. Biomass refers to biological materials, principally plant matter, that can be used to produce energy, either by direct combustion or by processing (fermentation, for instance) to create liquid or gaseous fuels such as ethanol or methane.

Much of NREL's biomass program focuses on ethanol. And much of NREL's research on ethanol concentrates on using "corn stover" - stalks, leaves, and corn cobs, the leftover by-products of corn harvest. NREL scientists have concluded that manufacturers could use about one-third of the nation's corn stover to produce ethanol for fuel without harming North America's agricultural soils.

Although ethanol production currently costs approximately twice as much as gasoline, primarily because of its low net energy yield, NREL scientists are confident that they can lower costs. To do so, they're working with specially developed enzymes plucked from bacteria that grow in hot springs. It's their hope that by manipulating these enzymes they'll be able to dramatically increase ethanol production and lower energy input - lowering the cost to the general public.

Flex Cars and Ethanol's Future

If these and other efforts are successful, ethanol could someday join vegetable oil and biodiesel as a major component of North America's liquid transportation fuel supply. It can be mixed with gasoline, as noted above, and can be burned at nearly full strength, for example, in mixtures containing 85 percent ethanol and 15 percent gasoline. more




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