A federal appellate court didn't fully satisfy industry or environmentalists with its ruling in a case concerning federal rules that govern cement kilns' air emissions.

In its Dec. 9 decision, the U.S. Court of Appeals for the District of Columbia Circuit sided partly with the petitioner, Portland Cement Association (PCA), by blocking one Environmental Protection Agency standard. The court also agreed partly with EPA by letting two other rules stand.

The ruling by a three-judge panel deals with two final EPA rules issued in 2010: National Emission Standards for Hazardous Air Pollution (NESHAP) and New Source Performance Standards. NESHAP applies to particulate matter, mercury, hydrochloric acid and hydrocarbons; the new-source rule covers nitrogen oxide and sulfur dioxide and revises the federal limit for particulates.

However, while EPA was working on the NESHAP rule, it also was developing a regulatory definition for solid-waste incinerators. Under that definition, some cement kilns would be reclassified and subject to the incinerator rule's standards, which differ from NESHAP's.

The court issued a stay on one part of NESHAP—that is, its standards for clinker storage piles—while EPA reconsiders them. The court also faulted EPA's handling of how the NESHAP and incinerator rules interact and directed EPA to review that issue.

But the judges denied other PCA challenges to NESHAP and objections to the new- source standard, letting both rules remain in place.