Tax rise, but green fuels still cheaper: "The new excise rates are determined on the energy content per litre of different fuels. Normal petrol and diesel have a high energy content and already attract excise of about 38 cents a litre. Bio-diesel, also a high-energy fuel, will be taxed at half that rate. Mid-energy fuels - including LPG, LNG and ethanol - would attract a 25-cent excise on the basis of energy content, but would pay half that. Low-energy fuels such as methanol would pay 8.5 cents a litre rather than 17 cents."

Why is the tax rate not based on carbon emissions rather than the 'energy content'?

Tax rise, but green fuels still cheaper: "The new excise rates are determined on the energy content per litre of different fuels. Normal petrol and diesel have a high energy content and already attract excise of about 38 cents a litre. Bio-diesel, also a high-energy fuel, will be taxed at half that rate. Mid-energy fuels - including LPG, LNG and ethanol - would attract a 25-cent excise on the basis of energy content, but would pay half that. Low-energy fuels such as methanol would pay 8.5 cents a litre rather than 17 cents."

Why is the tax rate not based on carbon emissions rather than the 'energy content'?