Disadvantages of Ethanol
There are a few disadvantages to ethanol when compared to gasoline, including:
1. Lower energy density in ethanol is the most significant disadvantage. A kilogram of ethanol has about 66% of the energy that a kilogram of gasoline has. This will translate as lower miles per gallon when ethanol is substituted for gasoline in automobiles.
2. Ethanol is hygroscopic and tends to absorb moisture.
3. Ethanol may have corrosive effects on some older vehicles with steel fuel tanks and fuel piping, which
were manufactured before the 1980s; some older plastic fuel pipe lines may also be affected by ethanol.
4. Low vapor pressure of ethanol can make cold starts difficult.
5. Ethanol increases exhaust emissions of acetaldehyde.
Ethanol can be used in various proportions as a transportation fuel. It can be used directly as a transportation fuel or it can be blended with gasoline. Ethanol is most commonly blended with gasoline in concentrations of 10% bioethanol to 90% gasoline, known as E10 and nicknamed "gasohol." Ethanol is blended with gasoline up to 15% and can be burned in traditional combustion engines with virtually no modifications. E10 is the most commonly used gasoline-ethanol blend in the United States, whereas E20-E25 blends are common in Brazil. A more detailed discussion on ethanol-gasoline blends is in Chapter 16.