Lighting is also contributing to an increase in greenhouse gases. To generate 1 kW/hr of electricity uses about 1lb (0.5 kg) of coal and produces 2lb (1 kg) of carbon dioxide emissions (the chemical equation is C+H2->CO2+Energy, where C=carbon=coal, H=hydrogen & CO2=carbon dioxide) (for more details, see the
"How stuff works!" internet page.). Imagine a 500W light is on throughout the night all year: 500W * 4400 hrs/year * 2lb = 4,400 lb of CO2 emission per year! (equal to 312 stones/year, or 2,000 kg/year, or 2 tonnes per year!)
A new diesel car would produce the same amount of pollution in 13,000 km (150g CO2 per km), and an older car in about 4,000 km (figures from The Society of Motor Manufacturers and Traders limited). Lighting can be more polluting than most cars!
The mean generating capacity of a power large power station is 1Gwatt (1000 MegaWatts), and the typical running generation rate is 0.5 G Watt (PowerGen figures). There are 7.5 Million street lights in the UK, mean power 100W (ILE figures), that typically waste 15% of their light directly upwards, above the horizontal (older lights). A further 30% of the light is spilt where it is not needed or not wanted. Hence, the total amount of power wasted above the horizontal is 110 MW, and including the further 30%, some 330 MW are wasted. This is equivalent to 70% of a power station.
If other sources of lighting are included (e.g. floodlights, etc.), this is far greater that 1 power station worth of wasted energy, money and atmospheric pollution.
For coal fired power stations, 7 tonnes of CO2 are produced to generate a kilowatt of electricity per year. Considering just the wasted light from street lights, this amounts to dumping over a million tonnes of unnecessary carbon dioxide into our atmosphere per year.
  