(comprising a mine, retorting plant, upgrading plant, supporting utilities, and spent shale reclamation), would range between US$70–95 ($440–600/m3, adjusted to 2005 values). , industry uses oil shale for shale oil production in Brazil, China and Estonia. Several additional countries started assessing their reserves or had built experimental production plants. In the US, if oil shale could be used to meet a quarter of the current demand, of recoverable resources would last for more than 400 years. Thermal depolymerization Thermal depolymerization (TDP) has the potential to recover energy from existing sources of waste such as petroleum coke as well as pre-existing waste deposits. This process, which imitates those that occur in nature, uses heat and pressure to break down organic and inorganic compounds through a method known as hydrous pyrolysis. Because energy output varies greatly based on feedstock, it is difficult to estimate potential energy production. According to Changing World Technologies, Inc., this process even has the ability to break down several types of materials, many of which are poisonous to both humans and the environment. Coal and gas conversion Using synthetic fuel processes, the conversion of coal and natural gas has the potential to yield great quantities of unconventional oil and/or refined products, albeit at much lower net energy output than the historic average for conventional oil extraction. In its day - prior to the drilling of oilwells to tap reservoirs of crude oil- the pyrolysis of mined solid organic-rich deposits was the conventional method of producing mineral oils. Historically, petroleum was already being produced on an industrial scale in the United Kingdom and the United States by dry distillation of cannel coal or oil shale in the first half of the 19th Century. Yields of oil from simple pyrolysis, however, are limited by the composition of the material being pyrolysed, and modern 'oil-from-coal' processes aim for a much higher yield of organic liquids, brought about by chemical reaction with the solid feedstuff. The four primary conversion technologies used for the production of unconventional oil and refined products from coal and gas are the indirect conversion processes of the Fischer–Tropsch process and the Mobil Process (also known as Methanol to Gasoline), and the direct conversion processes of the Bergius process and the Karrick process. Sasol has run a coal-to-liquids plant based on Fischer Tropsch conversion in South Africa since the 1970s. Because of the high cost of transporting natural gas,