What are some disadvantages of ethanol?

EtOH has about two-thirds of the energy content of gasoline.
- Lower fuel economy
EtOH increases gasoline volatility when blended at low levels.
At 2-10 vol%, ethanol increases gasoline Reid Vapor Pressure by 1 psi (is greater than 1.0 psi at lower RVPs.)
- Leads to greater evaporative emissions.
- Increases the permeation of fuel hydrocarbons through the fuel storage and delivery systems of motor
vehicles contributing to the inventory of atmospheric ozone precursors.
EtOH increases emissions of some air toxics - notably aldehydes.
A 1999 National Research Council study concluded that while RFG leads to air quality improvements, the presence of the oxygen content requirement in RFG may have little overall impact on ozone formation.
Air quality modeling studies have shown the benefits of gasoline blended with 10% ethanol to be marginal at best.
In some areas, the use of 10% EtOH blends may actually increase ozone due to the local atmospheric conditions.

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