Coalition for Responsible Waste Incineration

Technical Issue

Particulates are emitted in the exhaust air from an incinerator system. "Particulate matter" means any airborne finely divided solid or liquid material with an aerodynamic diameter smaller than 100 micrometers (1). A micrometer is one millionth of a meter or about 0.00004 inches. The human eye cannot see particles smaller than about 50 micrometers or 0.002 inches. The issue is whether particulates are controlled sufficiently to protect human health and the environment.

Technical Background

Under the Clean Air Act, EPA has set an ambient air standard for particulates of 50 micrograms per cubic meter, ug/m3, annual arithmetic average (2). As of July 1987, this standard is measured using "PM10" as the control. PM10 means particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers as measured by a reference method.(1). The "PM10" standard replaces the "particulate matter" standard because the finer particles can penetrate further into the respiratory tract and have more potential to adversely affect human health. The 50 ug/m3 PM10 standard was determined from long-term epidemiological studies that indicate health effects likely when the PM10 concentration is greater than 80-90 ug/m3, health effects possible at PM10 concentrations between 40-80 ug/m3 and no significant effects at PM10 concentrations less than 40 ug/m3 (3).

The EPA has recently announced plans to drastically tighten it air quality standards by the year 2003. EPA cites new health studies indicating that particles smaller than 2.5 micrometers (PM2.5) are the major contributor to serious health problems like respiratory illness and premature mortality. These standards, however, are global. They apply to the ambient air in a community. The exhaust stack from a hazardous waste incinerator is only one of many sources that emit particulates to the environment. Consequently, specific regulations apply to the incinerator emissions to ensure that the ambient air concentrations in the community are safe.

All hazardous waste incinerators are currently required to control particulate emissions to 0.08 grains per dry standard cubic foot (dscf) of air emissions (4). This standard equals 0.000011 lb./dscf. For a small incinerator (3000 dscf/min.), this emission rate would be about 2 lb./hr.; for a larger incinerator (22,000 dscf/min.), it would be about 15 lb./hr. It is expected that the EPA will finalize a reduced particulate emissions standard during 1998 as a Maximum Achievable Control Technology (MACT) standard. The expected standard is 0.015 grains/dscf or less than 1/5 th of the present standard. The EPA is reducing the PM standard for incinerators in order to control emissions of hazardous air pollutants (HAPs) that are emitted as particulate (e.g. metals). MACT standards are based upon the performance of the best operating incinerators. Once finalized, most incinerators will be required to be in compliance with the new standard within 3 years.

When the average emissions exceed about 6 lb./hr. of "particulate matter" or a 4 lb./hr. of "PM10," certain provisions in the Clean Air Act are triggered (5). These provisions, again, are to ensure that the ambient air concentrations in the community remain safe. Under them, a study of ambient air conditions may be required, the use of best available control technology would be required, and there may have to be emission reductions somewhere else in the community to offset the incinerator emissions. Best available control technology would include such devices as high efficiency scrubbers, fabric filters and electrostatic precipitators.

Before an incinerator can operate, it must pass a trial burn (6). The trial burn is run at the most difficult conditions under which the incinerator is expected to operate. If it meets permit conditions during the trial burn, the incinerator is given a permit to operate under conditions specified in the permit. Most of the time the incinerator will be operating at conditions significantly less difficult than the trial burn conditions. Consequently, most hazardous waste incinerators emit less than the permitted 0.08 grains/dscf.

Conclusion

Considering the particulate controls on hazardous waste incinerators and the current PM10 standards, the combination of technology-based and health-based standards will protect the environment.

References

1. 40 CFR 51.000
2. 40 CFR 50.6(b)
3. Federal Register, Vol. 52, No. 126, July 1, 1987, p. 24663
4. 40 CFR 264.343
5. 40 CFR 51.166
6. 40 CFR 270.62

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