The Mossmorran NGL (natural gas liquids) fractionation plant is part of the North Sea Brent oil and gas field system located on the outskirts of Cowdenbeath, Fife.

After the gas is separated from oil on the platforms offshore, the gas is then pumped ashore in the FLAGS and Fulmar pipelines to a terminal at St Fergus operated by AvantiGas. At the St Fergus Gas Plant the methane is separated from the rest of the gas product. The methane is then sent to a neighbouring national grid plant, leaving the remaining NGL to be piped south via a 223 kilometres (139 mi) pipeline to the Mossmorran site in Fife. At the Mossmorran NGL fractionation plant natural gas fluid is separated by distillation (in a number of fractionation columns) into ethane (C2H6), propane (C3H8), butane (C4H10) and natural gasoline (C5H12). The ethane is then piped to an adjacent ethylene cracker plant operated by ExxonMobil for further processing and cracking. The propane and butane is chilled, liquefied and stored on site within double integrity tanks, the gasoline is also stored on site within floating roof tanks. These liquids are then transported via pipeline to the marine terminal at Braefoot Bay on the Firth of Forth for loading onto ships for export. Mossmorran also has an adjacent road tanker terminal for road transportation of propane and butane.

The plant originally operated using two identical process modules (each with three columns) with a capacity of approximately 10,000 tonnes per day. This was later increased to 15,000 tonnes per day by the addition of a third process module and a few other up grades in 1992 at a cost of roughly £100 million. As well as the Brent fields the plants at St. Fergus and Mossmorran also process gas from the recently installed Goldeneye Gas Platform.

The flare from the Mossmorran site is clearly visible, day and night, from any elevated point in the city of Edinburgh at normal levels and can be seen from many tens of miles away when it is in full flow.

Coordinates: 56°5′50″N 3°18′12″W / 56.09722°N 3.30333°W / 56.09722; -3.30333