XtL refers to a collection of technologies that convert natural gas, biomass, coal, and petroleum coke (X) to liquid fuels, waxes, and chemicals (L). GtL (Gas-to-Liquids) is a class of XtL that refers specifically to natural gas, which includes producing syngas; removing sulphur compounds, metals, and other contaminants; and reacting the syngas to either Fischer-Tropsh fuels (FT), gasoline, alcohols, aldehydes, DME, or olefins. Converting natural gas continues to inspire academic research and industry as a means of tackling global warming, adding value to waste streams, and improving the environment. The Web of Science indexed 6400 papers regarding Fischer-Tropsch in the last 25 years (600 papers in 2014, which is a three-fold increase versus the late 1990s) and Derwent indexed 3500 patents.