Oil shale has been defined by the American Society for Testing Material (ASTM) AS: A compact rock of sedimentary origin, with ash content of more than 33 % and containing organic matter that yields oil when destructively distilled. Oil shale is a main source of energy of fossil origin having a high content of ballast material , it has been employed in the past as an alternative fuel.
Oil shale contains about 25 % of a solid organic material . the greater part of of this organic matter is called Kerogen and the rest are bitumen, also oil shale calorific value show considerable fluctuations just like the oil content . The heat content of oil shale are 1500- 2000 kcal/kg .