America’s second-largest coal producer, Arch Coal, has filed for Chapter 11 bankruptcy protection under a heavy debt load and halving coal prices. The Wall Street Journal reports that more than a quarter of US coal production is now in bankruptcy, battered by competition from natural gas and new environmental rules. The biggest coal company to fall so far, the NYSE-listed Arch Coal, is trying to trim debt of $4.5-billion off its balance sheet, which was put under strain when it bought International Coal Group for $3.4-billion in June 2011. The company’s $5-billion-plus outstanding debt and $360-million in yearly debt service proved unsustainable in the currently depressed coal market.