The California Air Resources Board has conditionally approved a slate of regulatory amendments intended to more closely monitor the additives blended into B-20 biodiesel that so far have not been deemed effective at mitigating oxides of nitrogen in the alternative diesel fuel. However, opposition from biodiesel industry representatives persuaded the board to invoke its 15-day rule, giving Carb Executive Officer Richard Corey discretion to tweak the rule before it becomes official. In a presentation to the Carb board April 23rd, staff members said that recent testing conducted by the University of California at Riverside on six additives to B-20 biodiesel showed they failed to effectively mitigate oxides of nitrogen to the regulatory standard.