Out of all the renewable energy sources, biomass contributed the most to U.S. energy consumption in 2008.

Out of all the renewable energy sources, biomass contributed the most to U.S. energy consumption in 2008.

Out of all the renewable energy sources, biomass contributed the most to U.S. energy consumption in 2008.

A gallon of gasoline contains about the same energy as 1 kg of hydrogen. Although fuel cells are expected to be twice as efficient as gasoline vehicles, hydrogen is very diffuse and storing an ample supply on board represents an engineering challenge.

A gallon of gasoline contains about the same energy as 1 kg of hydrogen. Although fuel cells are expected to be twice as efficient as gasoline vehicles, hydrogen is very diffuse and storing an ample supply on board represents an engineering challenge.

Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

Based upon the 2007 CAFE standards, the new average mpg required by 2020 is 35 mpg.

In 2008, wind accounted for 0.5% of America's energy portfolio.

In 2008, wind accounted for 0.5% of America's energy portfolio.

The average U.S. car gets 21.4 mpg. About 19 pounds of carbon dioxide are emitted for every gallon burned, or 0.9 lb/mile.

The average U.S. car gets 21.4 mpg. About 19 pounds of carbon dioxide are emitted for every gallon burned, or 0.9 lb/mile.

Oil, biofuels, natural gas, and coal are all used to generate electricity in the United States.

Oil, biofuels, natural gas, and coal are all used to generate electricity in the United States.

Oil, biofuels, natural gas, and coal are all used to generate electricity in the United States.

Oil, biofuels, natural gas, and coal are all used to generate electricity in the United States.

Nearly 80% of France's electricity is produced by nuclear power plants.

Nearly 80% of France's electricity is produced by nuclear power plants.

All of the above are emitted from coal-fired power plants and can be harmful to our health and the environment.

All of the above are emitted from coal-fired power plants and can be harmful to our health and the environment.

All of the above are emitted from coal-fired power plants and can be harmful to our health and the environment.

All of the above are emitted from coal-fired power plants and can be harmful to our health and the environment.

Less than 2% of the U.S. supply of natural gas is imported from outside North America.

Less than 2% of the U.S. supply of natural gas is imported from outside North America.