Such an experiment would teach you a lot. First, you'd learn that there's three times more energy in a pound of split pine or recycled phone books or cattle manure or Cap'n Crunch than in a pound of oil shale. Next, you'd learn that 85 percent of oil shale is inert mineral matter.
This means that on a cold winter day you'd have to shovel about pounds of rocks into your oil shale furnace and remove pounds of ash.
If, during the course of the winter, you burned 40 tons about what you'd need , come spring you'd have 36 tons of hazardous waste, enough to fill three dump trucks. The organic matter of oil shale typically has a higher hydrogen and lower oxygen content than that of lignite and bituminous coal.
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Oil shale can be mined and processed to produce oil similar to oil pumped from conventional oil wells; however, extracting oil from oil shale is more complex than conventional oil recovery and currently is more expensive. The kerogen in oil shale is a solid and cannot be pumped directly out of the ground. The oil shale can be mined and then heated to a high temperature a process called retorting ; the resultant liquid can then be separated and collected.
An alternative but currently experimental process referred to as in situ retorting involves heating the oil shale while it is still underground and then pumping the resulting liquid to the surface. Oil shale should not be confused with shale oil. In shale oil, the strata were buried deeply enough that the temperature was sufficiently high to naturally convert the kerogen into oil.
In shale oil plays, such as the Bakken in North Dakota and Montana, the objective is to find brittle layers in the shale, drill horizontal holes along those brittle layers, artificially fracture the rock, and produce the resulting oil. While oil shale is found in many places worldwide, by far the largest deposits in the world are found in the United States in the Green River Formation, which covers portions of Colorado, Utah, and Wyoming.
Estimates of the oil resource in place within the Green River Formation range from 1. Not all resources in place are recoverable; however, even a moderate estimate of billion barrels of recoverable oil from oil shale in the Green River Formation is three times greater than the proven oil reserves of Saudi Arabia.
Present U. If oil shale could be used to meet a quarter of that demand, the estimated billion barrels of recoverable oil from the Green River Formation would last for more than years 1. Extracting and processing shale oil is an expensive and difficult process. Coal, petroleum, and natural gas are less expensive to extract. Australia, Brazil, Switzerland, Sweden, Spain, and South Africa began mining oil shale in the 19th and 20th centuries, but they all stopped production by the s.
The U. Many nations, including Estonia, China, and Brazil, continue to rely on oil shale for fuel. It is burned to generate electricity , is a component in chemical industries, and byproduct s are used in cement production. Obtaining shale oil from oil shale involves heating kerogen in a process called pyrolysis. Pyrolysis is a form of heating without the use of oxygen. Pyrolysis can either be done ex situ above ground or in situ below ground.
During the ex situ process, oil shale is first extracted from the earth by surface or underground mining. The rock is crushed, and then retort ed heated to release the shale oil. The shale oil is then refined of impurities, such as sulfur.
During the in situ process, oil shale is not mined or crushed. Instead, the rock is heated to its oil window while it is still underground. One technology used for in situ oil extraction is known as volumetric heating. In this process, the rock is heated directly with an electric current.
The heating element is injected either directly in a horizontal well or into a fractured area of the rock, until the oil shale begins producing shale oil. The oil could then be pumped directly from underground. The internal combustion process uses a combination of gas, steam and spent shale produced by ex situ processing. These compounds are burned for pyrolysis. The hot gas is continually cycled through the oil shale, pyrolyzing the rock and releasing oil.
Unfortunately, substances in the oil shale, such as sulfides, react with water to form toxic compounds that are harmful to the environment and to us. Sulfides can cause effects from eye irritation to suffocation. Water containing toxic substances is unusable, and expensive to decontaminate. The process also produces heaps of ash. This ash can pollute ground, air, and water sources.
Another method that can be used either in situ or ex situ involves chemically reactive fluids. The fluids are injected directly into the retort zone where the rock is being heated. High-pressure hydrogen is one of the most common chemically reactive fluids. It simultaneously heats the rock, removes sulfur, and upgrades the quality of the extracted oil. When shale oil is combusted heated , it releases carbon dioxide into the atmosphere.
Carbon on the earth is contained in plants, soil, fossil fuels, and all living things—including us! The carbon in fossil fuels including coal, petroleum, natural gas, and oil shale has been sequester ed, or stored, underground for millions of years. Burning fossil fuels releases carbon into the atmosphere at a much quicker rate than the trees, water, and ground can reabsorb it. Sometimes, climates can rise faster than organisms can adapt.
Another environmental disadvantage to extracting shale oil is the enormous amounts of freshwater required. Water is necessary for drilling, mining, refining, and generating power. Some experts estimate that three litres. Some of this water is contaminated by toxic compounds, and is costly to decontaminate.
Mining can also contaminate groundwater. During in situ processing, toxic byproducts are left underground. They can leach into other sources of water, making them unsafe for drinking, hygiene , or development. The United States has enormous proven deposits of oil shale. A source of oil in the United States would reduce the need for importing oil from other countries.
This would put people to work and make the U. However, not all of oil shale is recoverable. This determines whether they are economically worth recovering. They have fewer impurities and are less complex than the carbonate-based oil shales in the Western United States, and thus cost less to extract and process.
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