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Encyclopedia Dubuque


"Encyclopedia Dubuque is the online authority for all things Dubuque, written by the people who know the city best.”
Marshall Cohen—researcher and producer, CNN

Affiliated with the Local History Network of the State Historical Society of Iowa, and the Iowa Museum Association.


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COAL TAR PITS. Coal is best known for supplying electricity throughout the United States—nearly half of the country's electricity comes from coal. While the majority of it is burned at conventional coal-fired power plants, coal is also turned into a gas for conversion into electricity, hydrogen, and other energy products. (1)

Coal gasification is a thermo-chemical process in which the gasifier's heat and pressure break coal down into its chemical parts. The resulting "syngas" is comprised primarily of carbon monoxide and hydrogen, and occasionally other gaseous compounds. (2)

Supporters of coal gasification say that syngas can be used for electricity production, used in energy-efficient fuel cell technology, or as chemical "building blocks" for industrial purposes. Hydrogen can also be extracted for use in fueling a hydrogen economy. But these developments are ongoing, and researchers continue to focus on improving coal gasification technology to realize these and other potential applications for the future. (3)

Coal gas can also be converted into a transportation fuel as a substitute for gasoline in vehicles, but it is far less efficient than the current production and burning of petroleum-based gasoline. (4)

Coal gasification is said to have greater efficiency than conventional coal-burning because it can effectively use the gases twice: the coal gases are first cleaned of impurities and fired in a turbine to generate electricity. The exhaust heat from the gas turbine can be captured and used to generate steam for a steam turbine-generator. This is called a combined cycle, and Department of Energy says a coal gasification plant using this dual process can potentially achieve an efficiency of 50 percent or more, compared with a conventional coal power plant, which is often just above 30 percent. (5)

In 1987 two coal tar pits, remains of the coal gasification process used until the development of natural gas after WORLD WAR II, were discovered near the path of the U.S. 61 relocation project. The pits were both KEY CITY GAS COMPANY coal gasification sites. One pit, located at 11th Street and Kerper Boulevard, was found on city garage property. The second pit was near an Amoco service station west of the JULIEN DUBUQUE BRIDGE at Dodge and Bluff. (6) This had been the site of a gasification plant during the turn of the twentieth century.

The cleanup of the coal tar block construction of U. S. 61 was scheduled to begin in June, 1990 at an estimated cost of $3 million. The Environmental Protection Agency determined that Midwest Gas of Des Moines, the company which purchased the industry responsible for burying the coal tar, was responsible for cleanup costs. An estimated 10,000 cubic yards of contaminated soil would be hauled by rail to its coal-fired power plant 12 miles south of Sioux City, Iowa. The material would be mixed with coal and burned. The material was tested and found to potentially cause cancer if it came into contact with human skin or was eaten. (7)

The site at 11th Street and Kerper became more difficult to handle as liquid coal tar was discovered. While more difficult to remove, it was easier to transport and burn. (8)



1. Cernansky, Rachel. What is Coal Gasification?" Online: https://science.howstuffworks.com/environmental/energy/coal-gasification.htm

2. Ibid.

3. Ibid.

4. Ibid.

5. Ibid.

6. Kirchen, Rich. "Coal Tar Pits," Telegraph Herald, December 2, 1987 p. 3

7. Pritchard, Ken. "Coal Tar Cleanup Cost: $3 Million," Telegraph Herald, April 13, 1990, p. 3

8. Pritchard, Ken. "Underground Gas Tanks Could Delay Highway Work," Telegraph Herald, October 6, 1990, p. 2