A surge in government-backed ethanol blending credits has billionaire investor Carl Icahn worried that independent refiners like CVR Energy Inc., in which he owns an 82 percent stake, will be bankrupted by the “rigged” marketplace. “The RIN market will cause a number of refinery bankruptcies,” Icahn wrote in an Aug. 9 letter to Environmental Protection Agency administrators Gina McCarthy and Janet McCabe obtained by Bloomberg. “The domino effect of this will be that ‘big’ oil will sop up the bankrupt refineries, causing an oligopoly resulting in skyrocketing gasoline prices.” Merchant refiners that don’t own retail gas stations are expecting to pay $1.8 billion this year for Renewable Identification Numbers. They can’t generate the credits organically as their integrated counterparts can. As the EPA’s mandates to blend biofuels including ethanol or biodiesel have risen, supplies of the credits have been squeezed this summer. Refiners from Valero Energy Corp. to PBF Energy Inc. are crying uncle.