Fossil-fuel power is generated from non-renewable energy sources including oil, natural gas and coal. Fossil fuels used in thermoelectric power plants require significant amounts of water for the generation of steam, which is turned into electricity. Water is also used in cooling towers at thermoelectric plants, which when discharged to receiving waters can pose temperature and water quality-related impacts on the environment. Thermoelectric plants require significant land area, impacting surrounding land-use options. Fossil-fuel power also includes diesel generators, which are often used for back-up power supply or in remote locations.