A milder winter and cheaper natural gas prices have taken a toll on coal mining with a number of coal mines either cutting back on production or shutting down completely.

Patriot Coal Corp. was one of the most recent companies to take measures because of decreased demand as it announced plans to idle its Freedom underground mine in the Bluegrass complex near Henderson, KY. Employees were given a 60-day notice that they will lose their jobs, the St. Louis Business Journal reported.

The mine produced 1.1 Mt (1.2 million st) of thermal coal in 2011. Following the most recent idling, Patriot will have no remaining uncommitted Illinois Basin thermal coal for 2012 delivery, the company said.

“Thermal coal markets remain weak as a result of the mild winter, coupled with low natural gas prices and reduced demand for electricity related to the economic downturn,” Patriot Executive Vice President and Chief Operating Officer Bennett Hatfield said in a statement. “We are taking this step to align production with committed sales.”

During the first quarter, Patriot idled three smaller Central Appalachian thermal coal mines that together produced about 1.1 Mt (1.2 million st) of coal in 2011.

“In total, including today’s announcement and the previously announced closure of the Big Mountain complex, we have reduced Patriot’s annual thermal production by more than 3.6 Mt (4 million st) compared with 2011,” Hatfield said.

St. Louis-based Patriot Coal Corp. reported a loss of $115.5 million on revenue of $2.4 billion for 2011.