The process is challenging and complex. First a synthetic gas is made from pure oxygen and methane, the main component of natural gas, which is cleansed of sulfur, metals and other impurities, under intense pressure and heat. Then the synthetic gas is put in giant reactors that make a synthetic crude through the Fischer-Tropsch process. The process essentially forces heated synthetic gas to react with a catalyst, typically cobalt, to convert into a liquid hydrocarbon. Finally that liquid is refined into one fuel or another. The process is far more complex than that at a typical refinery, so the plant is much more expensive to build and operate. Alfred Luaces, a refining specialist at the consultancy IHS, said a conventional oil refinery could be built for $50,000 per barrel of capacity, less than half of what Sasol says it is willing to spend on the proposed Louisiana plant.