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Background on Quarterly Tracking of Emissions for Acid Rain Program Coal-Fired Units

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Since the start of the Acid Rain Program (ARP) in 1995, EPA has tracked on a quarterly basis emissions from facilities that are covered by this program. The vast majority of these emissions are from coal-fired electric generating units, which are the focus of this tracking status report.

Under the ARP, coal-fired electric generating units have made substantial progress in lowering emissions over time by changing dispatch patterns, switching to lower sulfur coals, and installing advanced emissions controls. This progress accelerated with EPA's promulgation of the Clean Air Interstate Rule (CAIR), implementation of state regulatory programs (such as North Carolina's Clean Smokestack legislation), and state and federal settlement agreements and will continue under the Cross-State Air Pollution Rule (CSAPR)*. EPA contacted various companies regarding plans for future controls and consulted other industry sources; based on this information, it is clear that some companies plan further action to install SO2 and NOx controls. Changes in Control Technologies (PDF 799 KB) displays changes that have occurred from 2000 to 2010 on a unit basis, as well as changes that EPA anticipates may occur in 2012 and 2014 based on the information obtained from major company contacts and industry sources.

Based on emissions monitoring data, EPA has observed substantial reductions in emissions from 2005 to 2011 as companies installed more controls, electric demand declined, and low natural gas prices made combined-cycle gas-fired units more competitive in several parts of the country. Thus, even after CAIR's vacatur and subsequent remand in late 2008, the controls in place generally have continued to operate, helping to drive continued progress in reducing emissions.

Allowance prices of SO2 and NOx have been relatively low since 2008. With the finalization of the CSAPR* in July 2011 and the start of a separate allowance system for the CSAPR* trading system, ARP and CAIR allowance prices for SO2 and NOx have been increasingly low. These low prices have raised concerns that coal-fired units could burn dirtier fuels, operate scrubbers or SCRs at reduced efficiency, or even bypass scrubbers or SCRs altogether, instead relying on banked allowances. For these reasons, EPA is tracking SO2 and NOx emissions closely each quarter to evaluate further progress and assess whether backsliding may be occurring and, if so, where it may be taking place.

* The United States Court of Appeals for the D.C. Circuit issued its ruling to stay the CSAPR pending judicial review. The court's decision is not a decision on the merits of the rule. EPA is ensuring the transition back to CAIR occurs as seamlessly as possible. Please see our Bulletins page for updates on CSAPR and the continuing implementation of CAIR.

In order to keep the public fully informed, EPA wants to share emissions data for coal-fired power facilities (which often have several generation units) on a quarterly basis. The data presented here are all four quarters of 2010, as compared to the same quarters of 2011, and for the full year of 2010 as compared to 2011. The data presented here are final data for 2010 and preliminary data for 2011 that are currently under review. As data are reviewed and verified, these materials will be updated. If a unit has not yet reported 2011 emissions data to EPA, its 2011 data are not included in the spreadsheet, maps, or motion chart presented here. While the information presented here is available in data and maps elsewhere on this web site, this report is intended to make it easier to see if, and where, progress is occurring. These quarterly updates will be posted on an ongoing basis. If you want more detailed emissions data, visit Data and Maps for an emissions history of individual units.

For each coal-fired facility in the ARP, we initially provide a spreadsheet titled Table of Emissions, Emission Rates, Heat Input: 2010 vs. 2011 (Excel 781 KB) covering 2010 final data and 2011 preliminary data for all four quarters of SO2 and NOx emissions, SO2 and NOx emission rate, and heat input. The data presented on this page show that, while a few facilities are emitting more SO2 and NOx or emitting at a greater rate in 2011 than in 2010, overall emissions are still declining substantially. This same information is displayed spatially on the previous page in an interactive, three dimensional format using Google Earth satellite maps, (KMZ 1.29 MB) (About KMZ). Additionally, substantial changes at faclities are displayed in a series of maps titled Maps of Emission Rates for Facilities with Substantial Changes: 2010 vs. 2011 (PDF 1.77 MB) which shows emission rate changes for facilities with substantial changes. Last year's data are all available at the annual aggregation level.

Changes in emissions and emission rates for all four quarters of 2010 versus the same quarters of 2011 can also be seen in these motion charts:

The circles representing various facilities are sized according to the change in emissions over time. This shows that facilities are exhibiting substantial changes (increases or decreases) in emissions beyond normal fluctuations that could result from routine operational changes or changes in coals among suppliers. It is important to note that the percent changes in rates can be misleading when rates are already very low. Therefore, when reviewing the quarterly information spreadsheet, it is important to consider both total emissions changes and emission rate changes. In addition, the heat input data demonstrate that some part of the improvement occurring today results from reduced electricity generation at many coal power facilities over the last year. We have also observed this emission reduction trend from 2005 to 2010 (see the Clean Air Interstate Rule, Acid Rain Program and Former NOx Budget Trading Program 2010 Progress Report).

To put recent data in context, four interactive motion charts show historically how coal-fired power facilities have responded to the Acid Rain Program:

In the first two of these four motion charts, as ARP implementation proceeds from 1990 or 1995 onward, emissions decrease at the majority of facilities while heat input either stays the same or increases, demonstrating that air pollution was reduced even as electricity generation increased. In the second pair of motion charts, this same trend can be seen from a different angle; most facilities exhibit a negative change in emissions as compared to 1990 or 1995 while heat input stays the same or increases.

Notably, in any quarter nearly every facility shows some variation in its emissions. Small changes (whether in emission rate or mass emissions) are likely due to normal variation in the sulfur content of fuels and/or operation of the facility. Larger changes can be due to various factors: changes in amount of operation of the facility, changes in fuel mix being used at the utility, or changes in controls (either addition of controls or operating existing controls less).

Quarterly Emissions Tracking

 

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