It takes energy to produce energy. The key is to “get” more energy from the final product than it “takes” to make it. Traditionally, there have been concerns that it takes more energy to produce ethanol than the fuel yields. However, thanks to developments in technology and agriculture, ethanol production has become an energy efficient process.

• Ethanol has a positive net energy balance (NEB is the ratio of the energy produced from a production process relative to the energy used in the production process.), while gasoline has a negative NEB.

• The degree of ethanol’s positive energy balance depends on the feedstock from which it is produced.

• A 2004 life cycle analysis completed by the U.S. Department of Agriculture concluded that corn-based ethanol produces approximately 67% more fossil energy than is used to grow, harvest and refine the grain and transport the ethanol to gasoline terminals for distribution.

• This means that corn-based ethanol had a NEB of 1.67 in 2004, compared to gasoline’s negative NEB of 0.81.

• Sugarcane-based ethanol is extremely energy efficient, producing 8 times more energy than is put into it.

• The energy balance of cellulosic ethanol is also extremely promising. According to National Geographic, cellulosic ethanol can have an energy output of 2 to 36 times the input, depending on the production method.
  

• Initial analysis of switchgrass revealed a net energy balance of 343% when used to produce biomass ethanol, and more recent energy model analyses that used simulated biomass yields and estimated agricultural inputs indicate that switchgrass could produce 700% more output than input energy.

• According to estimates from a large on-farm study by researchers at the University of Nebraska-Lincoln, switchgrass grown for biofuel production produced 540 percent more energy than needed to grow, harvest and process it into cellulosic ethanol.

Source: Unica (2007)

Click here for an interactive comparison of ethanol’s energy balance from National Geographic.

Click here for a University of Nebraska-Lincoln study on the net energy of cellulosic ethanol from switchgrass.