combustion resources worked under a grant from the us department of energy to research and optimize current designs of shale oil extraction. it sought to eliminate carbon dioxide emissions from the shale oil production process. pyrolysis occurs in a rotating kiln heated by hot gas flowing through an outer annulus. the hot gas is created by burning hydrogen generated in a separate unit by coal gasification followed by carbon dioxide separation. the geometry of the annulus enables the transfer of heat to the moving shale through a wall.