Introduction

For a number of years, EPA SARA 313 reporting requirements for dioxin emissions and releases to the environment have caused confusion and difficulties among those attempting to comply with the rule.  Default emission factors as well as site-specific data have been used in an attempt to comply, but because of confusion over the specific requirements, over-reporting of dioxin emissions has been a common result.  The following provides specific guidance on how to properly perform these calculations and avoid or minimize the negative publicity that can result from over-reporting dioxins.

Which Dioxins Are To Be Reported?

“Dioxins” or polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) include a large number of individual compounds.  Most stack test reports provide two different emission levels based on different ways of summarizing the data.  One is “total dioxins” or, more specifically, total tetra through octa PCDDs and PCDFs.  The other is “TEQ dioxins.”  Unfortunately, for ease of use, neither of these approaches provide the correct value required for SARA 313 reporting.  If “total dioxins” is used, the level will generally be one to two orders of magnitude too high.  If “TEQ emissions” are used, the value will be too low. 

SARA 313 reporting requires use of only the seventeen (17) PCDD/PCDF congeners used for the TEQ method of reporting, but without applying the TEQ factors.  The seventeen congeners required to be used for SARA 313 calculations appear in Table 1 in the order commonly found on laboratory reports.  Care must be exercised, however, as some laboratories may use a slightly different order, especially a reversal within the HxCDF group. The SARA 313 Number column lists the order in which the congeners appear on the SARA 313 Form R.

SARA 313 reporting uses a very specific process for calculating dioxin values that is different from the total or TEQ process.  Accomplishing this generally requires a recalculation of the emission rate based on the raw lab data and stack sampling parameters recorded during the test.  This recalculation in turn requires a significant level of familiarity with understanding dioxin lab reports and using stack sampling parameters to calculate emission rates – both of which are beyond the scope of this brief write-up, but should be sufficiently familiar to those technically proficient in dealing with D/F stack test reports. 

 Table 1

SARA 313 Dioxin Congeners of Interest

 The simplified calculation is as follows and must be converted to grams/year:

[congener (mass)] / [sample volume] x [stack gas flow rate] x [annual kiln operating hours]

A few notes of caution are in order:

1.      Be careful with all units.  Laboratories generally report individual congeners in either picograms (pg) or nanograms (ng).  Gas flow rates may sometimes be  reported in minutes or in hours.  SARA 313 requires converting the result to grams/year.

2.      When using gas flow rates and sample volumes, be certain that all of the units are the same, including wet vs. dry and Standard Temperature and Pressure (STP) corrections. 

3.      EPA generally considers Estimated Maximum Potential Concentrations (EMPCs) to be zero.  There is no guidance specific to SARA 313 suggesting anything different for this particular report.  Use zero for all EMPC values and gain the benefit of a lower emission level.

4.      Sometimes back half and front half catches may be reported separately.  In this case, the two halves must be combined, properly accounting for EMPCs.

Yet Another EPA SARA 313 Reporting Requirement

Individual emission rates for the congeners are not reported under SARA 313.  Instead, a single total grams/year of dioxin emissions for the total of the seventeen specified congeners is reported.  It is then necessary to calculate a percentage breakdown for each of the seventeen congeners on the SARA 313 reporting form whenever the data is available to do so.  If there is more than one source of dioxin emissions or releases, a weighted average will need to be used to calculate the total congener percentage breakdown.

Conclusion

Dioxin reporting under SARA 313 is not a simple proposition.  Nevertheless, proper calculation and reporting can lower a plant’s emission profile in this very public database.