Coal companies want to bring a controversial practice to the state of Wyoming. The United States experimented with underground coal gasification – a process by which coal is turned to synthetic gas without being removed from the ground – in the 1970s and it cost the government $10 million dollars to clean up the mess.

Coal gasification is the process of making synthetic natural gas from coal by lighting the coal on fire and injecting it with oxygen and water. Underground coal gasification (UCG) is the process of setting the coal on fire while it’s still hundreds to thousands of feet underground.

In the 1970s, the Lawrence Livermore National Laboratory experimented with UCG in the Hoe Creek project in Wyoming. The project gasified around 6,500 tons of coal in three phases: 1976, 1977, and 1979. Afterward, groundwater testing revealed contaminates such as benzene, toluene, and ethylbenzene at the site.

The government began aquifer restoration work in 1989 and announced its completion last year, 24 years later. The restoration cost the Department of Energy $10 million, according to SF Gate.

Now, an Australian company, Linc Energy, wants to bring the experimental process back to Wyoming to the Wyodak coal seam 1,100 feet underground. The Wyoming Environmental Quality Council is set to review a development license for Linc Energy this month, due to protests from the Powder River Basin Resource Council, residents, and environmental groups.

UCG could contaminate the Fort Union Aquifer, a major regional aquifer that supplies water to Wyoming cities. The Department of Environmental Quality has already reviewed Linc’s application, deemed it “technically complete,” and forwarded it to the EPA for exemption under the Safe Water Drinking Act.

Coal companies like Linc Energy refer to the experimental process as “a cleaner, more affordable and safer energy alternative.” Proponents argue that it is a clean coal technology that combats climate change by trapping underground harmful gases emitted by coal burning, ClimateProgress reports.

The process ultimately results in carbon dioxide, which can be captured and stored using CCS, or the process of capturing carbon dioxide emissions before they are emitted into the atmosphere. The captured emissions would then be stored deep underground, similar to wastewater from hydraulic fracturing.

While CCS, or carbon capture and storage, can mitigate the effects of carbon dioxide emissions from UCG, underground gasification is extremely likely to contaminate groundwater with benzene – a volatile organic chemical that is highly flammable. Benzene is a natural component of crude oil, gasoline, and cigarette smoke.

For Wyoming, potentially endangering any fresh water resource seems foolish, as the state is one of the driest in the country, and is under the constant threat of drought. Much of the state has been experiencing moderate to severe drought since 1999, according to the Wyoming State Climate Office.

Alisha is a writer and researcher with Ring of Fire. Follow her on Twitter @childoftheearth.