Warning signs are displayed as gas is produced in the tri-generation power and hydrogen system at the Orange County Sanitation District waste-treatment facility in Fountain Valley, California, U.S., on Wednesday, Feb. 5, 2014. California plans to spend $20 million a year for a decade for dozens of new hydrogen stations as carmakers including Hyundai, Toyota, Honda and Daimlers Mercedes-Benz try to entice Californians to buy fuel cell vehicles. Photographer: Patrick T. Fallon/Bloomberg via Getty Images
水素は、燃料電池を使用するか、または燃焼させることによって、電力を生み出すことができる。写真は、ダイムラー社の燃料電池車「メルセデス・ベンツF-CELL」が、公共の水素供給ステーションで燃料を補給しているところ。このステーションは、カリフォルニア州ファウンテン・バレーにあるオレンジ郡衛生地区の廃棄物処理施設の外に設置されている。(Patrick T. Fallon/Bloomberg via Getty Images)
Top U.S. Renewable Energy Sources - 2011 (MOST RECENT DATA)
Top Renewable Energy Sources(01 of08)
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Renewable energy made up 9 percent of all energy consumed in 2011, according to the U.S. Energy Information Agency, and that number is predicted to grow throughout the next decade.\n\nHere\'s a breakdown of the top sources of renewable energy in the country, from wind to water and everything in between.\n\nInformation courtesy of the U.S. Energy Information Agency. (credit:Getty Images)
Solar Power - 2 Percent(02 of08)
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Solar power and photovoltaic cells make up the smallest percentage of U.S. renewable energy production, but its future looks fairly promising. Warren Buffett\'s Berkshire Hathaway invested $2.5 billion in Calif. solar company SunPower earlier this year.\n\nAlso, unlike other sources of renewables, energy can also be generated by small-scale solar installations (like on the rooftop of a home or business), and declining costs have made solar much more affordable.\n\nInformation courtesy of the U.S. Energy Information Agency. (credit:Getty Images)
Geothermal - 2 Percent(03 of08)
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Geothermal power captures naturally occurring heat from the earth to turn it into power. The renewable source is geographically dependent, but the Western half of the U.S. has many promising locations for power plants, like The Geysers in Calif., the largest geothermal power plant in the world.\n\nThe U.S. is the largest producer of geothermal power on the planet, but growth hasn\'t kept up with wind or solar development in recent years.\n\nInformation courtesy of the U.S. Energy Information Agency. (credit:WikiMedia:)
Waste - 5 Percent(04 of08)
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Believe it or not, burned garbage accounts for 5 percent of all renewable energy created in the U.S. each year. More than 29 million tons of municipal solid waste was burned in 2010 to create steam to spin turbines and generate power, and there are more than 75 waste-to-energy plants in the country.\n\nEmissions regulations have been in place at waste incineration plants since the 1960s, but the EPA warned in a 2006 report that the toxins released during the process could pose a serious environmental risk if not strictly enforced.\n\nInformation courtesy of the U.S. Energy Information Agency. (credit:Getty Images)
Wind - 13 Percent(05 of08)
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The amount of wind power has grown for each of the past three years throughout the U.S. and accounted for the largest growth in capacity of any energy resource in the country last year. Wind turbines now supply more than 50,000 megawatts a year, enough to power 13 million homes, according to Reuters.\n\nFederal tax credits, which were set to expire at the end of 2012, have made wind farms an attractive form of renewable energy. Congress approved an extension of the credits through the end of 2013.\n\nAfter production, wind turbines are net zero, meaning they require no energy and produce no emissions. The only problematic thing generated in some cases other than clean power has been a whole lot of noise. \n\nInformation courtesy of the U.S. Energy Information Agency. (credit:AP)
Biofuel - 21 Percent(06 of08)
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Biofuels, like ethanol, are created from organic matter like corn or soybeans. Gasoline in the U.S. contains 9 percent of the resource by federal mandate under the Renewable Fuel Standard program, and more than 40 percent of the corn crop last year was turned into biofuel.\n\nThe resource is slightly more unstable than other renewables because it depends on the productivity of farms - drought or other environmental problems can significantly lower yields and increase prices.\n\nOn average, ethanol has 20 percent fewer emissions than traditional gasoline but some types, like cellulosic ethanol, cut greenhouse gas emissions more than 85 percent, according to the U.S. Department of Energy.\n\nInformation courtesy of the U.S. Energy Information Agency. (credit:Getty Images)
Wood - 22 Percent(07 of08)
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Timber accounts for nearly a quarter of all renewable energy created in the country. Rising energy costs have led to an upswing in wood burning over the past decade, and nearly 20 percent of New England homes use wood for heating, according to a National Geographic report.\n\nAlthough it may be a cheaper alternative, wood burning stoves and fireplaces release more emissions of fine particles than other home heating methods, according to the EPA. Burning good wood in an efficient burner lowers toxic emissions and lost energy. Oh, and always have working smoke and carbon monoxide detectors handy.\n\nInformation courtesy of the U.S. Energy Information Agency. (credit:AP)
Hydroelectric - 35 Percent(08 of08)
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Almost all of the current hydroelectric power plants in the U.S. were built before the mid-1970\'s, but it\'s still the highest producing renewable energy source in the country. \n\nIn 2011, 8 percent of all power created in the U.S. came from hydroelectric sources, but it\'s also one of the most geographically dependent sources of energy. The Pacific Northwest gets more than half of all power via hydroelectric due to prime geography.\n\nInformation courtesy of the U.S. Energy Information Agency. (credit:AP)