Impacts of Power Generation

The term air pollution describes any harmful substances in the air we breathe. The largest sources of air pollution in the UK are transport and industry (including power generation).

Power stations are responsible for releasing large amounts of harmful pollutants into the air. The world emits approximately 69 tonnes of sulphur dioxide (SO₂) and 24 million tonnes of nitrogen oxide (NO_x) into the atmosphere each year. SO₂ and NO_x can cause respiratory disorders, with children and asthmatics being particularly vulnerable.

In the past, air pollution was dominated by thick black smoke, which was emitted from the burning of coal by power stations, industries and homes. The famous London Smog of December 1952, which caused thousands of deaths, prompted the introduction of the 1956 Clean Air Act. This created smokeless zones, where no pollution from the burning of coal could be produced. The Act focused on reducing smoke pollution, but the measures taken helped to reduce SO₂ levels at the same time. Air pollution in cities dramatically reduced in the following ways:

• domestic emissions reduced due to smokeless zones;
• electricity and gas usage increased and the use of solid fuels decreased;
• cleaner coals were burnt, which had a lower sulphur content;
• taller chimney stacks were used on power stations to help the pollution disperse;
• there was a continuing decline in heavy industry.

Acid Rain

Acid rain is the term used to describe the acidity of wet and dry deposition. This includes acidity falling as rain, snow, sleet, hail, mist or fog (wet deposition) and the dry deposition of gases and particles. Rain water is naturally acidic as a result of carbon dioxide (CO₂). However, anthropogenic (man-made) emissions of pollutants make acid rain a large problem.

The main pollutants responsible for acid rain are sulphur dioxide (SO₂) and nitrogen oxides (NO_x). Both are produced from the burning of fossil fuels for power generation. Once emitted, they combine with water in the atmosphere to form sulphuric and nitric acid. The acid then falls to the Earth's surface, causing damage to plants and animals.

Emissions of SO₂ and NO_x in the UK contribute significantly to problems of acid deposition in other parts of Europe, e.g. Scandinavia. This occurs because the pollutants remain suspended in the atmosphere, where they can travel long distances before falling back to the ground.

To reduce the problem of acid rain throughout the world, it is necessary for all countries to work together in reducing their pollutant emissions.

Greenhouse gases such as water vapour, carbon dioxide (CO₂), methane, and nitrous oxide (N₂O) keep our planet warm. They exist naturally in the atmosphere, heating it by trapping energy that originally came from the Sun. This process is called the greenhouse effect. Without the greenhouse gases, the surface of the Earth would be about -18°C, rather than the typical surface temperature of about 15°C.

Increasing concentrations of the greenhouse gases trap more terrestrial radiation in the lower atmosphere (troposphere), enhancing the natural greenhouse effect. Over the last 200 years, mankind has increased the amount of greenhouse gases in the atmosphere through processes such as fossil fuel burning. Fossil fuels are made up of carbon and hydrogen, which are changed to water and CO₂ when they are burned.

By the end of the 21^st century, global average temperatures could be several degrees higher than today. In an effort to reduce or remove the threat of global warming, nations around the world have adopted the Framework Convention on Climate Change. The objectives of this framework are to prevent "dangerous interference with the climatic system". The aim is to reduce global greenhouse gas emissions by 5.2% from 1990 levels by 2012.

Renewable and nuclear power are alternative energy resources that do not produce CO₂ and may therefore be used to reduce the threat of global warming. As the world aims towards a sustainable energy future, the use of renewables will increase and hence pollution from the burning of fossil fuels will reduce.