Cement Kiln Operators Better Hope That Their Control Technology Works: D.C. Circuit Vacates EPA’s Affirmative Defense Rule

Last week was hazardous air pollutant regulation week at the D.C. Circuit Court of Appeals. First, as we reported, the Court affirmed EPA's mercury air toxics rule, determining that EPA need not take cost into account in promulgating rules for electric generating units (EGUs) under § 112(n) of the CAA. On Friday, the Court affirmed the substance of EPA's revised hazardous air pollutant rules for cement kilns, but vacated EPA's affirmative defense based on unavoidable malfunctions. The decision is notable for two issues that will be of concern even outside the universe of cement kiln operators.

First, on the relevance of cost to EPA's standard-setting, the decision is a useful bookend to the mercury toxics decision for EGUs. Unlike § 112(n), § 112(d) specifically provides that EPA should take into account "the cost of achieving such emission reduction...." The environmental NGOs argued that EPA may only take cost into account if, as the Curt put it,