What does a catalytic converter do anyway?
In the days before catalytic converters, cars spewed lots of smoke. Laws governing emissions have helped to clean up the air.
The Clean Air Act
The Clean Air Act of 1970 and the amendments since then have done a great job in requiring people to clean up the air over the United States. Emissions of the six major pollutants regulated by the Clean Air Act — carbon monoxide, lead, nitrous oxides, ozone, sulfur dioxide, and particulates — have decreased by more than 50%. Cars, power plants, and factories individually release less pollution than they did in the mid-20th century. But there are many more cars, power plants, and factories. Many pollutants are still being released and some substances have been found to be pollutants that were not known to be pollutants in the past. There is still much work to be done to continue to clean up the air.
Reducing air pollution from vehicles can be done in a number of ways.
- Breaking down pollutants before they are released into the atmosphere. Motor vehicles emit less pollution than they once did because of catalytic converters (Figure below). Catalytic converters contain a catalyst that speeds up chemical reactions and breaks down nitrous oxides, carbon monoxide, and VOCs. Catalytic converters only work when they are hot, so a lot of exhaust escapes as the car is warming up.
Catalytic converters are placed on modern cars in the United States.
- Making a vehicle more fuel efficient. Lighter, more streamlined vehicles need less energy. Hybrid vehicles have an electric motor and a rechargeable battery. The energy that would be lost during braking is funneled into charging the battery, which then can power the car. The internal combustion engine only takes over when power in the battery has run out. Hybrids can reduce auto emissions by 90% or more, but many models do not maximize the possible fuel efficiency of the vehicle.
A plug-in hybrid is plugged into an electricity source when it is not in use, perhaps in a garage, to make sure that the battery is charged. Plug-in hybrids run for a longer time on electricity and so are less polluting than regular hybrids. Plug-in hybrids began to become available in 2010.
- Developing new technologies that do not use fossil fuels. Fueling a car with something other than a liquid organic-based fuel is difficult. A fuel cell converts chemical energy into electrical energy. Hydrogen fuel cells harness the energy released when hydrogen and oxygen come together to create water (Figure below). Fuel cells are extremely efficient and they produce no pollutants. But developing fuel-cell technology has had many problems and no one knows when or if they will become practical.
A hydrogen fuel-cell car looks like a gasoline-powered car.
Reducing Industrial Air Pollution
Pollutants are removed from the exhaust streams of power plants and industrial plants before they enter the atmosphere. Particulates can be filtered out, and sulfur and nitric oxides can be broken down by catalysts. Removing these oxides reduces the pollutants that cause acid rain.
Particles are relatively easy to remove from emissions by using motion or electricity to separate particles from the gases. Scrubbers remove particles and waste gases from exhaust using liquids or neutralizing materials (Figure below). Gases, such as nitrogen oxides, can be broken down at very high temperatures.
Scrubbers remove particles and waste gases from exhaust.
Gasification is a developing technology. In gasification, coal (rarely is another organic material used) is heated to extremely high temperatures to create syngas, which is then filtered. The energy goes on to drive a generator. Syngas releases about 80% less pollution than regular coal plants, and greenhouse gases are also lower. Clean coal plants do not need scrubbers or other pollution control devices. Although the technology is ready, clean coal plants are more expensive to construct and operate. Also, heating the coal to high enough temperatures uses a great deal of energy, so the technology is not energy efficient. In addition, large amounts of the greenhouse gas CO2 are still released with clean coal technology. Nonetheless, a few of these plants are operating in the United States and around the world.
Ways You Can Reduce Air Pollution
How can air pollution be reduced? Using less fossil fuel is one way to lessen pollution. Some examples of ways to conserve fossil fuels are:
- Riding a bike or walking instead of driving.
- Taking a bus or carpooling.
- Buying a car that has greater fuel efficiency.
- Turning off lights and appliances when they are not in use.
- Using energy efficient light bulbs and appliances.
- Buying fewer things that are manufactured using fossil fuels.
All these actions reduce the amount of energy that power plants need to produce.
Developing alternative energy sources is important. What are some of the problems facing wider adoption of alternative energy sources?
- The technologies for several sources of alternative energy, including solar and wind, are still being developed.
- Solar and wind are still expensive relative to using fossil fuels. The technology needs to advance so that the price falls.
- Some areas get low amounts of sunlight and are not suited for solar. Others do not have much wind. It is important that regions develop what best suits them. While the desert Southwest will need to develop solar, the Great Plains can use wind energy as its energy source. Perhaps some locations will rely on nuclear power plants, although current nuclear power plants have major problems with safety and waste disposal.
Sometimes technological approaches are what is needed.
National Geographic videos exploring energy conservation are found in Environment Videos, Energy: http://video.nationalgeographic.com/video/environment/energy-environment.
- Alternative Energy
- Fuel Cells
- Solar Power
What you can do to your home to help reduce energy use: http://www.youtube.com/watch?v=6h8QjZvcp0I&feature=related.
A very simple thing you can do to conserve energy is discussed in “This Bulb”: http://www.youtube.com/watch?v=FvOBHMb6Cqc.
- Catalytic converters break down some pollutants, but only when they are hot.
- Hybrid vehicles use the energy that is usually wasted as a car slows to charge a battery that then powers the car.
- Different types of clean energy can be developed for different locations, such as solar for the desert southwest and wind for coastal regions.
Use this resource to answer the questions that follow.
1. How have lead levels changed in ambient air?
2. How has reducing acid rain helped the environment?
3. How much has acid deposition been reduced?
4. How much have toxic emissions from industry been reduced?
5. Explain the technologies that have improved vehicle emissions.
1. How do fuel cells work, what are their advantages, and why are they not used in every vehicle?
2. What is gasification technology and what role could it play in reducing air pollution?
3. What can you do to reduce the amount of air pollution you produce?