# Risk glossary

## Compressed natural gas (CNG)

A product consisting of natural gas that has been compressed under high pressures, typically between 2,000 and 3,600psi, and is held in a hard container. It is used mainly as an alternative fuel for internal combustion engines (such as automobile engines). It generates low hydrocarbon emissions but a significant quantity of nitrogen-oxide emissions. CNG’s volumetric energy density is about 42% of liquefied natural gas’s (LNG) and 25% of diesel’s.