Thanks to cheap natural gas, regulatory pressures and an increasingly diversified energy market, the U.S. coal industry is suffering its worst downturn in decades. More than three dozen coal companies have declared bankruptcy since 2012, and the situation has gotten so bad for coal workers that presidential candidate Hillary Clinton proposed a $30 billion aid plan earlier this month.

The coal companies face a particular challenge in navigating Chapter 11: Unlike other bankrupt businesses whose assets can be bought and repurposed by other industries, the mining companies’ chief holdings are their mines. Without sufficient demand for new coal, those mines—especially if they’re depleted or saddled with environmental concerns—are a tough sell.