WASHINGTON — When the companies that supply motor fuel close the books on 2011, they will pay about $6.8 million in penalties to the Treasury because they failed to mix a special type of biofuel into their gasoline and diesel as required by law. But there was none to be had. Outside a handful of laboratories and workshops, the ingredient, cellulosic biofuel, does not exist. In 2012, the oil companies expect to pay even higher penalties for failing to blend in the fuel, which is made from wood chips or the inedible parts of plants like corncobs. Refiners were required...