Jetty at liquefied natural gas terminal. An old jetty at a gas terminal in Milford Haven, Wales. The jetty is to be demolished as the terminal undergoes construction work to equip it to supply liquefied natural gas (LNG) to other parts of the UK. LNG is natural gas that has been processed to remove impurities and then cooled to condense it into a liquid. Its production cost is high, but it is cheap to transport because of its low volume.