"The Tosco II retorting process, which has been successfully tested in a 1,000 ton per day semi-works, is equally adaptable to rich or lean oil shales. At present, Tosco Corporation and Exxon are constructing a 66,000 ton a day commercial facility to utilize the process at the Colony Project in northwestern Colorado. The Tosco II process involves the indirect heating of finely crushed shale in a rotating retort, using ceramic balls as a heat carrier. The process recovers all the assay hydrocarbons in the shale, producing a high-caloric-value gas and a C5 oil stream. The spent shale produced in retorting still contains some organic carbon. For high quality U.S. shales the percentage of organic carbon is small, approximately 4%, and in the past was considered to have, little economic consequence as a source of heat energy. However, the drastic increase in energy prices and a growing interest in non U.S. oil shale deposits, whose spent shales typically contain higher percentages of residual organic carbon, has caused Tosco to accelerate its development of technology to utilize this source of energy. The product of that development work combines the Tosco II process with well known fluidized bed technology for combustion or gasification of spent shale. The heat recovered from the fluid bed can be integrated into the retorting process or is utilized to produce steam for turbine drivers or power generation."