Environmental Problems, Their Causes, and Sustainability 1

source. These systems have an energy efficiency of80–90% (compared to about 30–40% for coal-fired boilersand nuclear power plants) and emit two-thirds lessCO 2 per unit of energy produced than conventionalcoal-fired boilers do.Cogeneration has been widely used in westernEurope for years. Its use in the United States (where itnow produces 9% of the country’s electricity) andChina is growing.Another way to save energy and money in industryis to replace energy-wasting electric motors, which consumeabout one-fourth of the electricity produced inthe United States. Most of these motors are inefficientbecause they run only at full speed with their outputthrottled to match the task—somewhat like driving acar fast with your foot on the brake pedal. Each year aheavily used electric motor consumes 10 times its purchasecost in electricity—equivalent to using $200,000worth of gasoline each year to fuel a $20,000 car! Thecosts of replacing such motors with new adjustablespeeddrive motors would be paid back in about 1 yearand save an amount of energy equal to that generatedby 150 large (1,000-megawatt) power plants.A third way to save energy is to switch from lowefficiencyincandescent lighting to higher-efficiency fluorescentlighting.Average fuel economy(miles per gallon, or mpg)30252015101970 1975 1980 1985 1990 1995 2000 2005Model yearCarsBothPickups, vans, andsport utility vehiclesFigure 18-7 Average fuel economy of new vehicles sold in theUnited States, 1975–2004. The largest and most inefficient vehicles,like the Hummer, are not covered by fuel economy regulations.(U.S. Environmental Protection Agency and NationalHighway Traffic Safety Administration)Dollars per gallon (in 1993 dollars)2.22.01.81.61.41.21.00.819201930194019501960Year19701980199020002010Figure 18-8 Real price of gasoline (in 1993 dollars) in theUnited States, 1920–2004. The 225 million motor vehicles in theUnited States use about 40% of the world’s gasoline. Gasolineis one of the cheapest items American consumers buy andcosts less per liter than bottled water. (U.S. Department ofEnergy)How Can We Save Energy in Transportation?Replace Gas Guzzlers with Gas SippersThe best way to save energy in transportationis to increase the fuel efficiency of motor vehicles.Good news. Between 1973 and 1985, the average fuel efficiencyrose sharply for new cars sold in the UnitedStates and to a lesser degree for pickup trucks, minivans,and sport utility vehicles (SUVs) (Figure 18-7).This occurred primarily because of government-mandatedCorporate Average Fuel Economy (CAFE) standards.Bad news. Between 1985 and 2004, the averagefuel efficiency for new passenger cars sold in theUnited States leveled off or declined slightly.Fuel-efficient cars are available, but account forless than 1% of all car sales. One reason is that the inflation-adjustedprice of gasoline today in the UnitedStates is low (Figure 18-8 and Connections, p. 384). Asecond reason is that two-thirds of U.S. consumers preferSUVs, pickup trucks, minivans, and other large, inefficientvehicles. A third reason is the failure of electedofficials to raise CAFE standards since 1985 because ofopposition from automakers and oil companies.Suppose that Congress required the average motorvehicle in the United States to get 17 kilometers perliter (kpl) [40 miles per gallon (mpg)] within 10 years.According to energy analysts, this would cut gasolineconsumption in half, save more than three times theamount of oil in the nation’s current proven oil reserves,and also save more than enough oil to eliminateall current oil imports to the United States from theMiddle East. In 2003, China announced plans to imposemuch stricter fuel-efficiency standards than theUnited States. The goals are (1) to enourage car companiesto develop hybrid, fuel cell, and other fuel-savingvehicles, (2) reduce the country’s dependence on oilimports, and (3) reduce carbon dioxide emissions.http://biology.brookscole.com/miller14383