Liquefied natural gas or LNG is natural gas that has been processed to remove impurities and heavy hydrocarbons and then condensed into a liquid at atmospheric pressure by cooling it to approximately -163 degrees Celsius. LNG is transported by specially designed vessels and stored in specially designed tanks. LNG is about 1/600th the volume of natural gas at standard temperature and pressure (STP), making it much more cost-efficient to transport over long distances where pipelines do not exist. Where moving natural gas by pipelines is not possible or economical, it can be transported by LNG vessels, where the most common tank types are membrane(prismatic) or Moss Rosenberg(spheres).