"Our farm and forest lands can supply enough cellulosic feedstock to displace 30 percent of current U.S. petroleum consumption with biofuels by 2030, while meeting the nation's food, feed and export demands." U.S. Department of Agriculture

Biofuels include methanol, biocrude, methane, ethanol, and biodiesel, which are produced from organic material derived from plants or animals known as biomass. Along with transportation fuels, biofuels comprise plant residues that can be burned to create power. For instance, in the Fuels for Schools program, woody material that can prolong and intensify wildfires is removed from the forest and burned as fuel for heating school buildings.

Ethanol and biodiesel are the fastest growing renewable fuels today.

Ethanol is a form of alcohol made from plant material and other biomass-specifically, by breaking down the sugars in the fruit of the plants like corn, sugar cane, and sugar beets, as well as other parts of the plant like corn stover. Ethanol can be combined in varying percentages with gasoline to fuel automobiles configured to run on either ten percent ethanol and 90 percent gasoline or 85 percent ethanol and 15 percent gasoline. Research today focuses on developing commercially viable methods of producing ethanol from the massive amounts of cellulosic material present in crop residues and woody plants.

Biodiesel is made from vegetable oils, fats, or greases and low level blends can be used in existing biodiesel engines without making any modifications. Soybeans are commonly used to make this fuel.

Although burning biofuels does produce carbon emissions, they are far cleaner than fossil fuels because the plants grown for their production help to neutralize their carbon output by absorbing carbon dioxide and releasing oxygen.

For more information, please visit the U.S Department of Energy's Biomass Program or the U.S. Department of Agriculture's Energy Page or the U.S. Environmental Protection Agency's Methane Page.

"The amount of heat that flows annually from the Earth into the atmosphere is enormous-equivalent to ten times the annual energy consumption of the United States and more than that needed to power all nations of the world, if it could be fully harnessed." U.S. Geological Survey

Geothermal energy is produced from the heat constantly radiating from the Earth's interior. We've been enjoying this energy for centuries at hot springs and geysers. Modern technology allows us to drill deep into the earth's surface and harness the power of geothermal energy. Geothermal fluids at high temperatures can be utilized as high-pressure steam to drive turbine generators to produce electricity.

Geothermal energy is a clean, renewable source of power. Emissions from geothermal plants are low and sources of geothermal fluid can be replenished by pumping treated wastewater back into the reservoir.

For more information, please visit the U.S. Department of Energy's Geothermal Technologies Program and the U.S. Geological Survey's circular on geothermal energy; Clean Power from the Earth's Heat.

"Hydropower plants typically operate at 85 to 90 percent efficiency, more than twice the efficiency of fossil fuel plants." U.S. Department of Energy

The energy of water flowing downstream has been harnessed for ages through waterwheels. In the last century, this resource has been used to create electricity by channeling water through a turbine which turns a generator to produce electric energy.

This abundant source of renewable energy was providing as much as 40 percent of electrical generation in the United States in 1940.

Water used to produce hydropower is not reduced or used-up in the process, and the water cycle constantly refreshes the earth's water supplies, giving hydropower an endless, renewable source for energy production.

For more information, please visit the U.S Department of Energy's Wind and Hydropower Technologies Program.

"The sun's energy can be put to work in numerous additional ways. Solar thermal technologies provide electricity, hot water, space heating, and lighting. They can be very cost effective-solar water heating is the least expensive form of solar energy-and can even work in tandem with conventional energy sources to improve the flexibility and reliability of the electricity they produce." U.S. Department of Energy

The sun's rays are an abundant and unending source of energy. Technological advances have made it possible to use solar power to heat homes, buildings, and water. Solar lighting has moved beyond glass windowpanes to lens collectors, reflective light-pipes, and fiber-optic bundles that can power lamps through a hybrid of solar and electric light...

Solar energy can be converted into electricity through solar-thermal technology or photovoltaic systems. Solar-thermal technology concentrates the sun's rays to heat a liquid enough to create steam, which is then used to turn a generator. Photovoltaics convert light energy into electrical energy through the use of semiconductors.

For more information on the multiple uses of solar energy, please visit the U.S. Department of Energy's Solar Energy Technologies Program.

"Good wind areas, which cover 6% of the contiguous U.S. land area, have the potential to supply more than one and a half times the current electricity consumption of the United States." U.S. Department of Energy

Wind has been providing power for human tasks since 200 B.C. in the form of simple windmills used to pump water and grind grains for food. Turbines were developed as early as 1890 to use wind power to generate electricity. As the wind turns the turbine blades, a shaft connected to a generator spins and produces electricity.

With no harmful emissions and a power supply that is not dependent on finite natural resources, wind energy is the fastest growing source of renewable energy across the globe.

For more information, please visit the U.S Department of Energy's Wind and Hydropower Technologies Program.