Continuing the Momentum on Air Toxics Rules – Utility MACT

In the midst of a tug of war between environmental groups, state agencies, and industry, the U.S. Environmental Protection Agency (U.S. EPA) remains bullish on the issuance of its proposed revisions to the Utility Maximum Achievable Control Technology (MACT) standards. The Utility MACT, also known as the Mercury and Air Toxics Standards (MATS), includes emission limits for mercury, particulate matter (PM), acid gases, and certain individual metals, and affects only coal‐ and oil‐fired power plants that will be built in the future.

The proposed revisions include a relaxation of the mercury limit for bituminous and sub-bituminous coal (“non-low rank virgin coal”) from 0.0002 pounds per gigawatt-hour output (lb/GWh) to 0.003 lb/GWh, in response to industry concerns. Non-low rank virgin coal is defined as having a heat value above 8,300 British thermal units (Btu) per pound (note that this heat value would exclude lignite coal from the definition of non-low rank virgin coal). The proposed revisions also include raising the filterable PM limits for most coal plants from 0.007 pounds per megawatt-hour output (lb/MWh) to 0.09 lb/MWh, and acid gas limits for most coal plants from 0.0004 lb/MWh to 0.01 lb/MWh.

Not surprisingly, environmental groups oppose the proposed revisions that relax the emission limits, contending that the limits will not be as stringent as those in current practice. State agencies are aligned with environmental groups, declaring U.S. EPA does not always set limits “on the basis of the unit that demonstrates the lowest calculated emission rate.”

To date, industry concerns with the MATS have been largely related to the technical challenges related to demonstrating compliance with limits that are as low as the levels of quantitation for instruments that are currently available to measure emissions (e.g., CEMS). However, industry has indicated that U.S. EPA has properly included available data in its evaluation and is generally supportive of the proposed revisions. It is interesting to note that despite the general public agreement with the proposed revisions, utilities are suing over the MATS in federal appeals court (though the case is currently suspended pending the final outcome of the reconsideration process).

To keep up with the status of the MATS, you can visit U.S. EPA’s website at http://www.epa.gov/airquality/powerplanttoxics/actions.html. ALL4 also will follow-up with a summary blog regarding the rule when it is issued.