The net energy gain (or loss) of ethanol production under various conditions is an important consideration that directly impacts the environmental benefits that can be achieved through the use of ethanol.
Critics of ethanol production cite studies showing a net energy loss. One of the most prominent of these is a study by David Pimental. Some argue that, if ethanol production consumes more energy than it produces, the result is an overall increase in fossil fuel consumption, with simply a shift in the polluting effects away from urban centres (where ethanol-blended is consumed) to rural areas, where fossil fuels are consumed to produce ethanol.
Others have raised questions have been raised about the relevance of the net energy balance. It is argued that issues of fuel security, trade deficits created by importing oil, and environmental degradation due to fossil fuel use make ethanol attractive whether or not it provides a net energy gain.
The American Coalition for Ethanol states that gasoline has an energy balance of only 85%. In other words, it takes more energy to produce gasoline than it contains. Proponents of ethanol production say that if we can use a harmful fossil fuel at a net energy loss, we can certainly use a renewable source of liquid fuel that is less harmful to the environment and better for the domestic economy.