Like the millipedes, centipedes are highly segmented (15 to 177 segments), but with only one pair of walking legs per segment (millipedes have two legs per segment). The head of a centipede has a pair of antennae, jaw-like mandibles (called forcipules) and other mouthparts.
Although compressed natural gas (CNG) is a fossil fuel like diesel, gas and coal, it is far different in terms of its impact on the natural environment.
How Natural Gas is Sold as Transportation Fuel. Compressed Natural Gas or CNG is sold at the retail level either by mass, energy units or gasoline gallon equivalents or gge. The National Conference of Weights & Measurements (NCWM) has developed a standard unit of measurement for compressed natural gas.