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Energy markets are once again in transition. We are now in the third wave of the fossil fuel era and in about 60 years all of the mined carbon will be gone. We must manage the transition to sustainable energy starting now to be prepared for the end of fossil fuel. Bio-energy is unique as a renewable fuel because it is renewable carbon and unlike wind, wave or solar power can be stored and used at our convenience in a way that we are used to with current fossil fuels. Therefore Bio-energy is and will remain the most important renewable form of energy. When you burn a log in your fireplace, you are using biomass energy. Because plants and trees depend on sunlight to grow, biomass energy is a form of stored solar energy. Although wood is the largest source of biomass energy, we also use corn, sugarcane wastes, and other farming byproducts. There are three ways to use biomass. It can be burned to produce heat and electricity, changed to a gas-like fuel such as methane, or changed to a liquid fuel. Liquid fuels, also called biofuels, include two forms of alcohol: ethanol and methanol. Because biomass can be changed directly into a liquid fuel, it could someday supply much of our transportation fuel needs for cars, trucks, buses, airplanes, and trains. This is very important because nearly one-third of our nation's energy is now used for transportation. Diesel fuel can also be replaced by biodiesel made from vegetable oils! In the United States, this fuel is now being produced from soybean oil. However, any vegetable oil—corn, cottonseed, peanut, sunflower, or canola—could be used to produce biodiesel. Researchers are also developing algae that produce oils, which can be converted to biodiesel. The most commonly used biofuel in the United States is ethanol, which is produced from corn and other grains. A blend of gasoline and ethanol is already used in cities with high air pollution. However, ethanol made from corn is currently more expensive than gasoline on a gallon-for-gallon basis. And even if we took all the corn that could possibly be grown in the United States and used it to produce ethanol, it would not make enough ethanol to power all our cars. So, it is very important for scientists to find less expensive ways to produce ethanol from other biomass crops. Today, we have found new ways to produce ethanol from grasses, trees, bark, sawdust, paper, and farming wastes. These processes could greatly increase the use of biomass energy in the United States. Imagine a new type of farm where energy crops, such as fast-growing trees or grasses, might be grown and harvested for their energy content! Of course, like many resources, we need to manage our use of biomass or we might consume it faster than we produce it. Also, like any fuel, biomass creates some pollutants when it is burned or converted into energy. What you may throw out in your rubbish today just might become fuel for someone else. That's right, whether you call it rubbish or waste, this municipal solid waste has the potential to be a large energy source. In 1993, the Environmental Protection Agency estimated that the United States generated 207 million tons (188 million metric tons) of waste. Out of all that waste, however, only 32 million tons (29 million metric tons) were converted to energy. Rubbish is also an inexpensive energy resource. Unlike most other energy resources, someone will collect waste, deliver it to the incinerator, and pay to get rid of it. This helps cover the cost of turning the waste into energy. Waste is also a unique resource because we all contribute to it. Municipal solid waste can be burned in large plants to generate electric power. Municipal waste-to-energy plants currently generate about 2500 megawatts of electricity—the equivalent of several large coal plants. There is also a way to use the energy trapped in landfill waste. When food scraps and other wastes decay, a gas called methane is produced. Methane is the main ingredient in natural gas. We can drill wells into landfills to release this gas. Pipes from each well carry the methane gas to a central point where it is cleaned. The gas can then be burned to produce steam in a boiler, or it can be used to power generators to produce electricity. However, as with burning any type of fuel, municipal solid wastes can produce air pollution when they are burned and turned into energy.
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