Ethanol as Fuel for Combustion

Ethanol
Ethanol fuel is simply ethanol, or ethyl alcohol, the same type of alcohol found in alcoholic beverages. It is most often used as a bio-fuel additive for gasoline and automobiles. Ethanol fuel has a "gasoline gallon equivalency", or GGE value of roughly 1.5 gallons, or is roughly 66% as powerful as gasoline. In 5-10% fuel blends with gasoline the fuel efficiency only seems to be decreased marginally, if at all. The Ford Model T, produced August 12, 1908 was capable of running on ethanol, kerosene or gasoline, and is generally considered to be one of the first widely commercially available cars.

Several full life cycle ("Well to Wheels" or WTW) studies have found that corn ethanol reduced greenhouse gas emissions when compared to gasoline. In 2007 a team led by Farrel from the University of California, Berkeley, evaluated six previous studies and concluded that corn ethanol would only reduce greenhouse emissions by 13% . Despite this, a more commonly cited figure is 20 to 30 percent, and it is considered to possible to produce an 80 to 85% reduction if cellulosic ethanol was used. Both of these figures were estimated by Wang from the Argonne National Laboratory, based on review of 22 studies conducted between 1979 and 2005, and simulations with Argonne's GREET model; all of these studies included direct land use changes. None of these studies considered the effects of indirect land-use changes, and while their impact was recognized, its estimation was considered too complex and far more difficult to model than direct land use changes.


The reduction estimates on carbon emissions for a given biofuel depend on many assumptions regarding several variables, including crop productivity, agricultural practices, and distillery power source and energy efficiency. The primary problem associated with ethanol is land usage. Modern gasoline engines are already capable of using a small percentage of ethanol fuel blends, and early gasoline engines were capable of using multiple types of fuels with relatively little difficulty. With a few changes in engine function, ordinary engines could be converted into ethanol engines or be integrated into ordinary cars quite easily. Many race cars use ethanol, and ethanol has a lower ignition point than gas. Ethanol generally has about 115 octane and E85 fuel (85% ethanol, and 15% other hydrocarbon by volume) has about 105 octane. It burns cooler than gasoline and will generally extend engine life by preventing the burning of engine valves and prevents the build-up of olefins in fuel injectors, keeping the fuel system clean. Ethanol by itself can currently be used with 10% water blends and still retain a roughly equal fuel efficiency to 100% ethanol.

However a large amount of land would be required to produce the ethanol, potentially taking away from farmland. The concerns about the amount of land required has been reduced some, as cellulosic ethanol has been shown be capable of producing more ethanol than previously believed possible. Cellulosic ethanol offers promise because cellulose fibers, a major and virtually universal component in plant cells walls, can be used to produce ethanol. According to the International Energy Agency, cellulosic ethanol could allow ethanol fuels to “play a much bigger role in the future than previously thought”. An alternative process to produce bio-ethanol from algae is supposedly being developed by the company Algenol. Rather than grow algae and then harvest and ferment it, the algae grows in sunlight and produces ethanol directly which is supposedly removed without killing the algae. Algenol claims the process can produce roughly 6,000 US gallons per acre per year compared with 400 US gallons per acre from corn production.

Of course, as with any potential bio-fuel, the bio-mass burned and released into the atmosphere will have trouble getting back into the soil, meaning that the long term use of bio-fuels and it’s potential detraction of nutrients from local or potentially farmland growing soil remains an issue. Even if high efficiencies were achieved it’s difficult to ascertain how much bio-mass that could be used for food production would be wasted. If within a closed system, such as an ethanol burning steam turbine device with high efficiency feeding the exhaust into algae, it may be possible to reduce much of this problem, although how much so is uncertain.