Energy Use and Air Pollution
Americans are the biggest energy consumers in the world. We use energy to create electricity, transport us, power our industries, and run our homes. About 83% of the energy we use comes from fossil fuels oil, coal, and natural gas. The remainder comes from nuclear power and renewable energy sources such as hydroelectric, wind, and solar power.
Energy consumption is at the root of many environmental problems, especially those relating to air pollution. Automobile exhaust and the burning of oil and coal by industry and by electric power plants are primary causes of smog, acid precipitation, and the greenhouse effect. The mining of coal and the extraction and transportation of oil cause pollution on land and in the water; the 2010 oil spill in the Gulf of Mexico was the worst environmental disaster in American history and one of the largest oil spills ever to occur. Nuclear power generation creates hazardous wastes and carries the risk of dangerous releases of radiation.
Two key strategies for controlling energy use are conservation and the development of nonpolluting, renewable sources of energy. Although the use of renewable energy sources has increased in recent years, renewables still supply only a small proportion of our energy, in part because of their cost. Some countries have chosen to promote energy efficiency by removing subsidies or adding taxes on the use of fossil fuels. This strategy is reflected in the varying prices drivers pay for gasoline. Despite increases in U.S. consumer gas prices, more than 70% of commuters drive alone to work, and low fuel-economy sport utility vehicles
The Fukushima Daiichi nuclear disaster of March 2011 occurred when a tsunami, following a massive earthquake, flooded the low-lying rooms in which the plant’s emergency generators were housed. The plant overheated, causing full meltdown in three of the six reactors.
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(SUVs) remain popular. The largest SUVs increase greenhouse gas emissions by six or more tons per year more than an average car.
Alternative Fuels The U.S. Department of Energy (DOE) is encouraging researchers and automobile manufacturers to produce vehicles that can handle alternative fuels such as ethanol. Ethanol, a form of alcohol, is a renewable and largely domestic transportation fuel produced from fermenting plant sugars such as corn, sugarcane, and other starchy agricultural products. Ethanol use reduces the amount of imported oil required to produce gasoline, reduces overall greenhouse gas emissions from automobiles, and supports the U.S. agricultural industry.
Another type of alternative fuel is E85, which is a mixture of 85% ethanol and 15% gasoline. E85 is becoming more popular in the Midwest region (the “corn belt”) of the United States. E85 provides lower mileage than gasoline, though it typically costs the same as regular gasoline. Ethanol has been mixed with gasoline for years in the United States, but several other countries (such as Brazil) use ethanol much more extensively.
Ethanol, however, has its critics, who say the alternative fuel may do more harm than good. For one thing, some reports show that corn-based ethanol requires more energy to produce than it yields when burned as fuel. Other reports dispute this point, and improvements in manufacturing processes may reduce the amount of energy required to make the fuel. Regardless, ethanol made from sugarcane and other plant matter may be far more energy-efficient, say some experts.
One huge potential drawback of ethanol is the diversion of corn crops from the food supply to produce the fuel. Food-related concerns prompted the United Nations to call for a moratorium on food-based ethanol production until nonfood sources of alternative fuels could be developed.
Another alternative fuel is biodiesel, a fuel made primarily from vegetable oils, fats, or greases. It is the fastest-growing alternative fuel in the United States, is biodegradable, and produces lower levels of most air pollutants than petroleum-based products. Biodiesel, like ethanol, can be problematic depending on its material source. If it is produced from waste animal fat and grease or as a by-product of other agricultural processes, it can be carbon-neutral. But in some parts of the world, natural vegetation and forests have been cleared and burned to grow soybeans and palm oil trees to make biodiesel, and these negative environmental and social effects can outweigh any benefit.
Hybrid and Electric Vehicles Hybrid vehicles use two or more distinct power sources to propel the vehicle, such as an on-board energy storage system (batteries, for example) and an internal combustion engine and electric motor. The hybrid vehicle typically realizes greater fuel economy than a conventional car does and produces fewer polluting emissions. Hybrids also tend to run with less noise than conventional vehicles. Several hybrid models are currently available in the United States, but they typically cost several thousand dollars more than their conventional gas-powered counterparts. Still, hybrids are gaining popularity with consumers and are being more commonly used in both corporate and government vehicle fleets.
Researchers hope that hybrid technology can be extended to all classes of vehicles and that Americans can be convinced to use more fuel-efficient vehicles and to travel more frequently on public transportation, in carpools, or on foot.
Another type of alternative vehicle is all-electric. In these vehicles, electricity is stored in battery packs and then converted into mechanical power that runs the vehicle. After a given number of miles, the batteries must be recharged. These vehicles do not produce tailpipe emissions, but generators that produce the electricity for the batteries do emit pollutants. All-electric vehicles are gaining credibility and popularity. A new generation of all-electric vehicles has recently been introduced to consumer markets, taking advantage of better battery storage performance, “quick-charging station” infrastructure, and changing consumer perceptions of trip use and distance. Researchers hope that hybrid and battery technologies can be extended to all classes of vehicles.