GCI TECH NOTES ©

Introduction

On September 9, 2010, EPA published in the Federal Register a new final set of Portland Cement MACT limitation for new and existing cement plants. On March 21, 2011, EPA published in the Federal Register a final rule which establishes MACT emission limits for cement kilns that burn solid waste. Table 1 provides a summary of the emission limits established for new cement kilns.

Table 1 - Limits from 2010/2011 Portland Cement MACT Regulations

Comparison

Ignoring the technical flaws that exist in both of these regulations and the way the limits were developed, it is worth looking at a comparison of the two sets of limits. Looking at Table 1, such a comparison appears to be almost impossible. It is as though the two EPA groups working on these regulations never talked or looked at the other’s work. Limits are so totally different even with regards to units as to be incomparable upon initial examination. Table 2 provides a “normalized” comparison based on typical preheater/precalciner relative gas flows and clinker production rates combined with standard unit conversions.

Table 2 - Standardized Limits from 2010/2011 Portland Cement MACT Regulations

Analysis

It must be first noted that cement kiln emissions are relatively unaffected by the fuels that they use. Generally emissions from cement kilns are primarily impacted by the raw materials fed to the kilns to make cement. Both the industry and EPA have generally acknowledged this fact. One is then forced to wonder how two rules setting MACT limits could be so different, not just in the way that they set limits but on what parameters are limited and the numerical values of those limits. A pollutant by pollutant analysis follows.

Lead (Pb) and cadmium (Cd) are limited in the PC Solid Waste MACT rule. It is not clear why. The PC MACT rule established the precedent for using particulates as a surrogate for toxic metals other than mercury (Hg). There is no reason that this same logic would not apply under the solid waste MACT rule. It is possible that some solid waste incinerators cannot use particulates as a surrogate because of high exit temperatures but that is not a reason to impose limits on cement kilns for these same parameters since the rule already subcategorizes and establishes different numerical limits. Strictly based on the raw materials used at cement plants and unrelated to the use of solid waste as fuel this aspect of the rule could prevent some cement kilns from entering the solid waste fuel combustion market without regard to emissions of the metals from the solid waste combustion.

The mercury (Hg) limit for cement kilns using solid waste fuel is somewhat higher than that established in the PC MACT rule. This is likely a statistical aberration brought on by a more limited set of kilns being used to establish the limit. There is no technical reason for a difference.

EPA has known and acknowledged for many years that CO is not a good surrogate for establishing good combustion conditions in a cement kiln. Apparently the EPA group (or contractor) that drafted and finalized these regulations were unaware of that body of knowledge. PC MACT establishes a THC limit as a surrogate for organic HAPs and provides an alternative limit for speciated organic HAPs. There is no reason this should not have been done in the same manner with the same limits for the cement kiln solid waste MACT, especially since organic emissions from cement kilns come entirely from the raw materials, not the fuels.

SO₂ and NO_x limits are notably similar. It is not clear why EPA did not just establish the same limit as was done for HCl. It might at first seem that the SO₂ limit should be lower for plants burning solid wastes as fuel since these fuels tend to have lower sulfur levels than coal. Again it needs to be noted that these emissions arise from the raw materials, not the fuel.

The difference in the dioxin (PCDD/PCDF) limits is both remarkable and disconcerting. There is no conceivable reason that there should be any such differences in the two groups of cement kilns relative to this pollutant. Further, the lower limit established in the cement solid waste MACT as well as the other associated dioxin limits for other solid waste combustors suggests that EPA did not take into proper account the quantitation limit for dioxins from stacks using the required test method. It is likely that the developers of this regulation mistakenly used quantitation values from the lab test data ignoring that the sampling itself creates much higher quantitation limits. Rigo and Chandler found in a study published by the Journal of Air and Waste Management¹ that the Reference Method Quantitation Limit for PCDD/PCDF TEQ in a municipal waste combustor may be as high 0.51 ng/dscm. Establishing a limit at 0.2 ng/dscm as was done in the PC MACT rule is therefore at least conceivable. Setting the limit at 0.003 ng/dscm for cement kilns using solid waste as fuel cannot be reliably verified using the required stack test method based on this information.

For particulates the cement solid waste MACT establishes a limit almost 4 times lower than the already extremely low limit set in PC MACT for new cement kilns. It is unclear how such a limit would be possible or could be complied with. There was no apparent effort on EPA’s part to verify that the required particulate CEMs can reliably determine values at this low a level, or how such a CEM could be certified given the required procedures for doing so.

Conclusion

EPA has invited attack on both sets of MACT limits by both industry and environmental groups by establishing radically different limits for cement kilns that should be unaffected by using different fuels. There is little doubt that these limits will change in response to the legal challenges that arise. Further, the lack of a sound technical evaluation of some of these limits, especially the radically low limit of dioxins, well below any conceivable quantitation limit using established and required stack test methods, suggests either an unusually high level of incompetency on the part of those who developed the standard or an agenda designed to stop the combustion of solid wastes altogether.

¹Rigo, H.G. and A.J. Chandler. 1999. “Quantitation Limits for Reference Methods 23, 26 and 29,” J. Air & Waste Manage. Assoc. 49:399-410