Complex sentence: Although there are several oil shale retorting technologies, only five technologies are currently in commercial use, which are Kiviter, Galoter, Fushun, Petrosix, and Alberta Taciuk.
Split into simpler sentences: Although there are several oil shale retorting technologies, only five technologies are currently in commercial use. These are Kiviter, Galoter, Fushun, Petrosix, and Alberta Taciuk.