Natural gas vehicle gas has the highest energy/carbon ratio of any fossil fuel, and thus produces less carbon dioxide per unit of energy. 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. CNG is typically stored in steel or composite containers at high pressure (3000 to 4000 psi, or 205 to 275 bar). These containers are not typically temperature controlled,
Natural gas diesel, jet fuel and aromatic chemicals directly from natural gas via a single-loop process. In 2011, Royal Dutch Shell's per day F–T plant went into operation in Qatar. Natural gas can be "associated" (found in oil fields), or "non-associated" (isolated in natural gas fields), and is also found in coal beds (as coalbed methane). It sometimes contains a significant amount of ethane, propane, butane, and pentane—heavier hydrocarbons removed for commercial use prior to the methane being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as carbon dioxide, nitrogen, helium (rarely), and hydrogen sulfide must also be removed