FILE PHOTO: Dump trucks haul coal and sediment at the Black Butte coal mine outside Rock Springs, Wyoming, U.S.

FILE PHOTO: Dump trucks haul coal and sediment at the Black Butte coal mine outside Rock Springs, Wyoming, U.S.

FILE PHOTO: Dump trucks haul coal and sediment at the Black Butte coal mine outside Rock Springs, Wyoming, U.S. April 4, 2017. REUTERS/Jim Urquhart/File Photo GLOBAL BUSINESS WEEK AHEAD – SEARCH GLOBAL BUSINESS 2 OCT FOR ALL IMAGES