the previous four years into the industrial market, and is continuing to add new customers. Motorcycles Scooters can also use CNG as a fuel source. Ships The was the world's first LNG powered container ship. LNG carriers are sometimes powered by the boil-off of LNG from their storage tanks, although Diesel powered LNG carriers are also common to minimize loss of cargo and enable more versatile refueling. Aircraft Some airplanes use LNG to power their turbofans. Aircraft are susceptible to weight; much of an aircraft's weight goes into fuel carriage. Liquified natural gas has a high specific energy (MJ/kg), a useful optimization for flight applications. Chemical composition and energy content Chemical composition The primary component of natural gas is methane (CH4), the shortest and lightest hydrocarbon molecule. It may also contain heavier gaseous hydrocarbons such as ethane (C2H6), propane (C3H8) and butane (C4H10), as well as other gases, in varying amounts. Hydrogen sulfide (H2S) is a common contaminant, which must be removed prior to most uses. Energy content Combustion of one cubic meter yields 38 MJ (10.6 kWh). Natural gas has the highest energy/carbon ratio of any fossil fuel and thus produces less carbon dioxide per unit of energy. Storage and transport Transport The major difficulty in the use of natural gas is transportation. Natural gas pipelines are economical and common on land and across medium-length stretches of water (like Langeled, Interconnector and Trans-Mediterranean Pipeline), but are impractical across large oceans. Liquefied natural gas (LNG) tanker ships, railway tankers, and tank trucks are also used. Storage CNG is typically stored in steel or composite containers at high pressure (). These containers are not typically temperature controlled but are allowed to stay at local ambient temperature. There are many standards for CNG cylinders. The most popular one is ISO 11439. For North America the standard is ANSI NGV-2. LNG storage pressures are typically around 3 to 10 bar. At atmospheric pressure, LNG is at a temperature of -162 °C. However, in a vehicle tank under pressure, the temperature is slightly higher (see saturated fluid). Storage temperatures may vary due to varying composition and storage pressure. LNG is far denser than even the highly compressed state of CNG. As a consequence of the low temperatures, vacuum-insulated storage tanks typically made of stainless steel are used to hold LNG. CNG can be stored at lower pressure in a form known as an ANG