U.S. merchant oil refiners like Monroe Energy and PBF Energy Inc (PBF.N) are playing chicken with the White House, taking moves in the biofuels credit market that could force them to close plants and fire union workers unless the Biden administration bails them out by changing the rules on blending biofuels in gasoline. Merchant refiners have long tried to dismantle a U.S. law requiring them to blend biofuels like ethanol into their fuel or buy credits from competitors who do. But until very recently, they largely continued to participate in the multibillion-dollar credit market by buying credits to offset their production, a Reuters analysis of earnings releases shows. Now, some of these refiners are building up record short positions in the credits. […]