Gas together with other fossil fuels will continue to be an indispensable part of the energy mix for the next thirty years. From an environmental viewpoint, natural gas has the best credentials, because it emits the least CO2 when it is burnt (half the CO2 emissions of coal for example). Through the commercial input of biogas ("green gas") in the network today, CO2 emissions per cubic metre can only continue to fall. Finally, gas is the natural partner of renewable energy, the reason being that wind, solar power and other renewables are not constantly available to meet the demand for electricity. To continue to give consumers the certainty that the lights will always come on, we need a constant source of energy to serve as a back-up if the sun does not shine or the wind stops blowing. Natural gas can fulfill this role perfectly.