Natural gas liquids (NGLs) are playing a greater economic role than ever before. In 2010, domestic production of NGLs reached 2 million barrels per day.
The 4 primary NGLs in the U.S. market are ethane, propane, butane, and iso-butane. Ethane accounts for 40% and propane accounts for 30% of the total NGL production each year by volume, and also account for most of the increase in NGL production.
All 4 of these NGLs have limited roles as residential fuels. Propane and butane are petrochemical feedstocks, while ethane can be used to produce ethylene, another petrochemical feedstock. Iso-butane is a refining feedstock, and is also used in some gasoline octane blends. Ethane can also be used as a petrochemical building block.
Liquified natural gas
Natural gas is a hydrocarbon gas mixture which consists mostly of methane. It can also include other hydrocarbons, as well as impurities such as carbon dioxide or helium. It is widely used for domestic heating and industrial power.
Economics has encouraged a shift from delivering gaseous natural gas by pipeline to producing liquified natural gas (LNG). The conversion from gas to liquid is done by cooling the natural gas. Most of the impurities in natural gas are removed in the process.
As a liquid, natural gas occupies just 1/600 of the space that the gaseous form does. This vastly reduces the cost of transportation and will increase the role natural gas plays in the world's future energy supply.
= Safety =
There is serious concern about the safety of the transportation of LNG. LNG must be kept cool or under pressure to remain in liquid form. There is no danger in its liquid form.
However, every time a valve is opened, some of that natural gas escapes in gaseous form. Careless handling can result in a highly explosive, invisible cloud of natural gas surrounding the entire region around the vessel carrying LNG. Even the cold temperatures at which LNG must be stored are capable of making containers brittle if they are not made of a high-quality steel with sufficient nickel content.
There are few ways to know from a safe distance if such a situation has occurred unless a spark ignites the natural gas fumes. This is why all ships transporting LNG must be registered by their cargo. However, ships transporting LNG have been known to travel thousands of miles without experiencing a single incident.