The White House is considering imposing restrictions on trading of biofuel credits, hoping to discourage speculation and reduce costs for oil refiners to comply with U.S. biofuels policy, according to three sources familiar with the discussions.  The sources, who asked not to be named because they are not authorized to comment on the discussions, said an announcement could be made in coming weeks. The move would be part of a widely anticipated deal to help U.S. corn farmers and biofuels producers by lifting a ban on summer sales of higher ethanol blends of gasoline. U.S. President Donald Trump has repeatedly said he supports lifting that ban on so-called E15 gasoline to help expand the market for corn. This could also bolster vulnerable Midwest […]