From Greenlivingpedia, a wiki on green living, building and energy
Fossil fuels such as coal, natural gas and oil are derived from organic matter and contain carbon. When burnt, fossil fuels emit carbon dioxide which is a greenhouse gas. There is no such thing as "clean fossil fuel", although some (such as natural gas) emit less carbon dioxide than others (such as coal).
Coal was the first fossil fuel used by humans, followed by oil and gas.
Renewable energy with zero carbon emissions derived directly from the wind and sun is preferable.