Soil microbiology

Manufacturers are also experimenting with the gas turbine engine, which is widely used in airplanes. Like traditional gasoline engine, this engine combusts a fuel-air mixture. The advantages of gas turbines include the potential for operating at 1ow emission levels, a simple design, reduced fuel consumption, and animal maintenance.

Finally, the high performance levels sought for advanced engines requires engineers to develop materials that not only will remain strong under high temperatures in corrosive environments but also will be inexpensive to purchase and mold. Ceramics may meet these goals. For example, a ceramic coating applied to engine components that get very hot will act as a thermal barrier, reducing the amount of wasted heat and minimizing the engine’s cooling needs. Plastics reinforced with graphite fiber, which have been used in the hot engines of racing cars, also are likely to find their way into passenger automobile engines. Such high-temperature materials could help reduce emissions by keeping heat in the cylinder, where it can do the job of pushing down the pistons.

 

 

While some researchers concentrate on the car and improving its systems and materials, others focus on the fuel that feeds the car, On at least one occasion, car improvements and fuel refinements went hand in hand. When catalytic converters were developed, the petroleum industry had to make gasoline lead-free. Leaded gasoline produces emissions containing lead, which coats the metals in the converter, rendering them ineffective. Because lead has been linked to cancer and can cause nervous-system damage in children, lead-free gasoline was an important development against automobile pollution.

Researchers continue to search for ways to make better gasoline. Refining crude oil to produce gasoline involves heating the oil and drawing off various types of hydrocarbons as they evaporate. Some hydrocarbons, such as butane, are lightweight molecules that evaporate easily. Others, such as benzene, are heavier, have a tendency to form deposits and particulates, and may be cancer-causing.

Petroleum companies can create gasolines that pollute less by using more hydrocarbons from the middle the weight spectrum - those that are neither very light nor very heavy. Refiners can also break down or «crack» some of the heavier hydrocarbons to yield lighter compounds. Some gasoline additives, such as methyl tertiary butyl ether - commonly known as MTBE - include oxygen atoms in their structure. This helps promote more complete fue1 combustion.

Researchers are also investigating fuels other than gasoline. Methanol (an alcohol made from ingredients derived from such sources as natural gas, wood, coal, sewage, or garbage) emits smaller quantities of pollutants normally associated with gasoline combustion. But it has less potential energy than does gasoline, a d it is more difficult to ignite. Methanol also can corrode (eat away) any of the metals, sealants, and resins used in automobiles. Finally, methanol produces formaldehyde, a toxic compound that can irritate the eyes, nose, and throat, and which is thought to cause cancer. On the positive side, methanol burns more completely than does gasoline, arid when mixed with 15 per cent gasoline to form a fuel called M-85, it- achieves satisfactory starting performance. A «flexible fuel» engine can run on either gasoline or methanol or a combination of both. Special sensors determine the type of fuel in use and relay this information to the central computer system.

Natural gas is another abundant fuel that experts consider an alternative to gasoline. It is composed mainly of methane gas and is cheaper and much cleaner than gasoline. This fuel’s major drawback is that, unlike gasoline and methanol, it is not available as a liquid at normal air temperatures and pressures. Natural gas must be carried in a pressurized tank, or, as a liquid, in an insulated tank - unfamiliar additions to a car’s design that consumers may reject. Refueling with natural gas could take up to several hours.

Some scientists are interested in hydrogen as the fuel of the future. Hydrogen burns much more cleanly than do either fuels and is easy to produce. But complex technical problems must be solved before it can be widely used in cars.

Electric vehicles are quiet and virtually emission-free. However, the batteries from which they draw energy usually contain toxic chemicals, which become pollutants when the batteries ate disposed of. Today’s electric cars cannot go as far or as fast as gasoline-driven vehicles because the battery does not offer the same amount of energy as does gasoline combustion. Furthermore, the battery must be recharged regularly, and the energy to do this comes from power plants that are also a source of pollution. Nevertheless, electric vehicles are the likely choice for meeting zero-emission laws that have been established in some areas, such as California.

The ongoing search for ways to make cars cleaner poses a demanding challenge to engineers, as well as chemists, materials scientists, and technicians. The widespread research reflects our newly heightened concerns for the environment along with our old desire to maintain the freedom of movement that the automobile has brought to the developed world.

 

 

1. Bilger, Burkhard. Global Warming. Chealsea House, 1992.

2. Schneider, Stephen H. The Greenhouse Effect: Science and Policy. Science. Feb. 10, 1989.

3. Seiffert, Ulrich, and Walzer, Peter. The Future for Automotive Technology. Frances Pinter Ltd., 1984.

4. Stockel, Martin W., and Stockel, M. T. Auto Mechanics Fundamentals. The Good-heart-Willcox Co., Inc. 1990.

5. White, Robert W. The Great Climate Debate. Scientific American. July, 1990.