Power stations collectively are the largest suppliers of electricity. Although some electricity comes from nuclear power, hydroelectric power and other renewable forms of energy, on the whole most power generation in the world is still reliant on the burning of fossil fuels. Fossil fuel power stations are a major source of air pollution, from poor air quality and acid rain, to global warming.
The burning of coal, oil and gas in power stations releases a number of air pollutants, including sulphur dioxide, nitrogen oxides and carbon dioxide. Sulphur dioxide and nitrogen oxides can cause respiratory disorders, with children and asthmatics being particularly vulnerable. In addition, these two primary pollutants are converted to acids in the atmosphere which can damage a range of ecosystems, including freshwater lakes and forests, when they are returned to Earth as acid rain. Fortunately, international action aimed at reducing the threat of acid rain and air pollution from power generation has, over the last 20 years, led to a reduction in the amount of pollutants coming from power stations.
Fossil fuel power stations however, remain a significant source of carbon dioxide, a major greenhouse gas. Whilst carbon dioxide exists naturally in the atmosphere, contributing to the natural greenhouse effect, man-made emissions of carbon dioxide through power generation may be contributing to global warming. Nuclear power releases neither carbon dioxide nor other acidic air pollutants. However, there remain public concerns over the safety issues surrounding nuclear plants, and the disposal of radioactive waste. Renewable energy, including hydroelectric, solar, wind, wave, tidal and geothermal energy, offers perhaps the most sustainable form of power generation in the 21st century.