Pounds of CO2 emitted per million Btu of energy for various fuels: gasoline 157.2, propane 139.0, natural gas 117.0. The amount of CO2 produced when a fuel is burned is a function of the carbon content of the fuel. The heat content or amount of energy produced when a fuel is burned is a function of primarily the carbon (C) and hydrogen (H) content of the fuel. Heat is produced when C and H