A Midwest environmental group is questioning the ability of the country's largest coal producer to guarantee it has enough money for future cleanup of its Illinois mines. State regulators allow St. Louis-based Peabody Energy to pledge it has adequate assets to pay for the estimated $92 million needed to reclaim three southern Illinois mines once there's no coal left to extract. The Chicago-based Environmental Law and Policy Center says that arrangement puts Illinois taxpayers at risk should Peabody go bankrupt. Five other major coal companies have sought bankruptcy protection since 2014. The environmental group instead wants the state to require Peabody to purchase surety bonds from private insurers. The Illinois Department of Natural Resources says Peabody meets the state's required financial standards for the practice known as self-bonding.