A Particulate Mess: The Proposed NAAQS PM2.5

In response to a court order under the Clean Air Act in June, the U.S. Environmental Protection Agency (EPA) proposed updates to its national air quality standards for fine particle pollution, including soot (known as PM2.5). The proposed standard has the potential to create a tangled, regulatory mess as power producers sort through the remnants of the Cross State Air Pollution Rule (CSAPR) and consequently make both gas and coal compliance more challenging.

EPA has proposed to limit PM2.5 to a level within a range of 13 micrograms per cubic meter to 12 micrograms per cubic meter. The current annual standard is 15 micrograms per cubic meter. EPA has said the proposal has no effect on the existing daily standard for fine particles or the existing daily standard for coarse particles (PM10), both of which would remain unchanged. EPA plans to issue the final standards by Dec.14, 2012 and expects affected counties to achieve attainment by 2020.

Reductions in both PM10 and PM2.5 over the past couple decades have been dramatic. PM10 saw a reduction of 37 percent nationwide from 1990 to 2010, and PM2.5 was cut by 29 percent from 2000 to 2010, according to data from the EPA.

In fact, not just PM, but every major emission type, including carbon, nitrogen dioxide (NOX) and sulfur dioxide (SO2), has encountered impressive decreases. But despite major efforts by power producers to limit emissions, EPA has increased its number of non-attainment areas as a result of the agency redefining what is “healthy air.” So while the air is getting cleaner, the standards are also becoming more stringent.

Part of the emissions squeeze, so to speak, came in 1997 when EPA decided to add PM2.5 as a National Ambient Air Quality Standards (NAAQS) pollutant. EPA is required under the Clean Air Act to re-examine the standards once every five years.

In February, the American Lung Association and the National Parks Conservation Association sued EPA for not completing the review of the standards within five years – by October 2011. The states of California, Connecticut, Delaware, Maryland, Massachusetts, New Mexico, New York, Oregon, Rhode Island, Vermont and Washington also filed a separate suit. Obviously, EPA had no choice but to review the standards. However, proposing to enforce relatively stricter standards on PM2.5 is likely in part an effort to appease the opposing groups.

Controlling fine particle emissions can be particularly challenging, as PM2.5 can be formed both directly and indirectly. The pollutant can be emitted directly from a source, but it can also be formed miles away from a source when pollutants like SO2 and NOx chemically interact in the atmosphere.

The proposed soot rule may not have a huge impact on coal-fired power plants since those facilities are already facing stringent compliance under other regulations like the Mercury and Air Toxics Standard (MATS). However, the proposed rule could have a more significant impact on gas power plants, since gas turbines have less control on particulate emissions, and their NOx emissions are frequently low enough that they may not have many pollution control devices already installed.

EPA says that depending on the final level of the standard, estimated benefits will range from $88 million a year, with estimated costs of implementation as low as $2.9 million, to $5.9 billion in annual benefits with a cost of $69 million.

“It is not a significant cost rule because of all of the reductions that have already been achieved,” said Gina McCarthy, assistant administrator for EPA’s Office of Air and Radiation.

Implementation of actual PM limitations could be a lengthy process, however, since the EPA must reevaluate PM limitations under CSAPR, which was rejected by a federal court in August. Because of CSAPR and MATS, most areas are already in compliance, McCarthy said. “That’s why 99 percent of U.S. counties are already on a path to meet these standards.”

However, since CSAPR has now been replaced by its predecessor, the Clean Air Interstate Rule, the proposed PM2.5 NAAQS and CAIR being reinstated could cause some compliance overlap. Once the PM2.5 NAAQS is final, EPA will have to reexamine CSAPR allowances in 2013 to see if a reallocation is needed.  That reallocation could impact coal and gas-fired facilities two to three years after the rule is final, or in the 2015/2016 timeframe.

However, if CSAPR is totally rejected by the D.C. Court (EPA filed for an en banc rehearing of CSAPR on Oct. 5), it could take EPA two to three years to re-propose a new transport rule – a year to finalize and additional years to get through the inevitable legal challenge.  Reconfiguring CSAPR could subsequently cause implementation of a new NAAQS PM2.5 to be postponed until 2017 or later.

Be sure to read the article in the upcoming November issue of Power Engineering magazine.