The misnamed “oil shale” doesn’t really contain oil, and it isn’t usually shale but some other type of sedimentary rock. However, there are a number of industrial uses for oil shale.
A variety of sedimentary rocks can contain organic compounds known collectively as kerogen. While liquid hydrocarbons, approximating and able to be used similarly to crude oil, there isn’t any substance in oil shale that can truly be considered oil in the way it’s commonly known.
The oil shale industry consists of the mining of oil shale and processing for further use. While the United States is believed to have one of the most extensive oil shale deposits in the world, most of the industrial applications come from outside the country. Brazil, China, Estonia, Germany, Israel and Russia have progressed much further in the use of oil shale than the United States.
The first step in utilization of oil shale, in most cases, is to get it out of the ground. The majority of oil shale is mined through pit or strip mining methods. These surface mines involve the removal of the top surface, or overburden, exposing the desired layers. The oil shale is then broken up and carried off in trucks. In locations where the oil shale is deeper than is suitable for surface mining, underground mining using a room and pillar method is used.
Currently the primary use of oil shale is in direct combustion as fuel for thermal power plants. Dozens of power plants throughout the world use crushed oil shale producing over 3 gigawatts (3,000,000,000 watts!) of electricity. Most of that is produced in Estonia while Israel, China and Germany also have oil shale fired power plants.
The long-term goal of oil shale has been the extraction of the hydrocarbons for use as inputs to oil refineries. Many factors have limited this production but progress is being made. Pollutants in the hydrocarbons produced have been a concern. Also, environmental issues such as waste and water requirements have limited the economic production of liquid products from oil shale.
Extraction methods can either be ex situ, working with mined oil shale, or in situ, extracting liquids and gases while the oil shale is in the ground. In situ extraction can be more efficient, eliminating the need for mining while resulting in greater levels of production, but it can also threaten ground water supplies.
Whether extracting from in the ground or mined oil shale there are a number of methods used. Virtually all of these methods involve heating the oil shale to a high temperature and basically “cooking” the liquids and gasses from the rock. The resulting fluids are condensed and the spent shale must be disposed of. Extraction while the oil shale is in the ground consists of either true or modified in situ processes. Modified in situ extraction involves crushing the shale in the ground prior to initiation of extraction processes.
Oil shale is used in other industrial processes as well. Estonia, Germany and China operate plants creating cement from oil shale. Other chemical products can also be produced but the majority of these applications are still in experimental stages.
