BILLINGS, Mont. — U.S. coal exports reached their highest level in two decades last year as strong demand from Asia and Europe offered an outlet for a fuel that is falling from favor at home.

U.S. Department of Energy data analyzed by The Associated Press reveal that coal exports topped 107 million tons of fuel worth almost $16 billion in 2011. That’s the highest level since 1991, and more than double the export volume from 2006.

Much of the increase went to slake the thirst of power-hungry markets in Asia, where development has sparked what mining company Peabody Energy calls a “global coal super cycle” that heralds renewed interest in the fuel. The AP’s analysis showed coal exports to South Korea leapt 81 percent last year to more than 10 million tons. India saw a 65 percent jump, to 4.5 million tons. And Japan bought almost 7 million tons of U.S. coal last year — a 119 percent increase — as the nation sought alternatives to nuclear power after an earthquake and tsunami prompted the Fukushima nuclear complex meltdown.

Coal faces a tougher outlook in the U.S., where competition from cheap natural gas and costly new rules for power plants are eroding its historic dominance in electricity generation. Coal’s share of the domestic power supply has fallen by more than 20 percent in the past several years, forcing companies to search out new customers or risk having to cut production from U.S. mines that produced almost 1.1 billion tons last year.

Government projections said domestic power sector demand for could dip another 10 percent in 2012. That would drive total U.S. coal use below a billion tons annually for only the second time since 1995.