How much energy does Compressed Natural gas release compared to petrol?
A direct answer to your question is that the energy content of natural gas (NG) is about 47 MJ/kg or 40 MJ/m3. (gross heating value). The values for a typical petrol are 60 MJ/kg and 44 MJ/litre. Another comparison on an energy basis is that 1 kg of NG is equivalent to about 1.33 litre of petrol or 1.22 litre of diesel. Or on a volume basis 1 m3 of NG is equivalent to about 1.10 L of petrol or 1.0 L of diesel. When making comparisons you may also need to take into account the relative energy efficiency of the engines that use the various fuels. Generally engines that are designed for natural gas fuel are slightly more efficient than a similar petrol engine (because they can run at a higher compression ratio). The NG and diesel engines of similar size will have a much the same thermal efficiency.
