EIA: Clearing the Air

Ed Repa

In June, the comment period ended on the U.S. Environmental Protection Agency's (EPA) proposed supplement to the pending national emission standards for hazardous air pollutants (NESHAP) for municipal solid waste (MSW) landfills.

NSWMA's Landfill Institute submitted comments that questioned whether sufficient information on bioreactor emissions existed to develop the NESHAP. The comments also suggested that the EPA delay regulatory decision on the air emissions from bioreactor landfills until data becomes available.

The 1990 Clean Air Act Amendments required the EPA to identify source categories that emit any of the 188 listed toxic air pollutants. MSW landfills emit approximately 30 of the pollutants.

For major sources within each source category, the act required the EPA to develop standards that restrict emissions to levels consistent with the lowest-emitting facilities. Major sources are those that emit 10 or more tons per year (t/yr) of a single air toxic or 25 or more t/yr of a combination of air toxics. Approximately 10 percent of landfills in existence since 1987 are capable of emitting toxic air pollutants at levels that classify as major sources. These facilities are required to install collection and control systems required by the existing new source performance standards (NSPS) and emission guidelines (EG).

On March 12, 1996, the EPA promulgated NSPS/EG for MSW landfills. The NSPS for new landfills and EG for existing landfills required large new and existing landfills to collect and control landfill gas (LFG) emissions. The regulations required these facilities to install equipment to collect and control LFG when emissions levels of nonmethane organic compounds reached 50 megagrams year (Mg/yr.) When emissions reach this level, the facility is required to install a gas collection and control system within 30 months for closed landfill areas where waste is at least two years old and for active areas where waste is at least five years old.

The supplemental proposed rule published on May 23 is based on the existing EPA NSPS/EG. Both require LFG collection and control technology installation. The proposed supplement is intended to reduce toxic air pollutants from MSW landfills employing bioreactor operations. The supplemental proposal defined bioreactor landfill operations as when liquids are added to waste to increase waste's moisture content and subsequently speed up the biodegradation rate.

The supplemental proposal requires bioreactor landfills to install the same collection and control systems required by the existing NSPS/EG earlier than conventional landfills are required to. The EPA considers earlier installation of controls for bioreactor landfills as timely in terms of environmental protection because waste degrades more quickly in a bioreactor landfill than in a conventional landfill.

The EPA believes that within 90 days of adding liquid, a bioreactor landfill generates the same amount of LFG that a conventional “dry tomb” landfill generates in two years. Requiring bioreactor landfills to operate a control system on an alternative timeline from what is required under existing NSPS/EG effectively accounted for the LFG generation difference. The EPA expects that the timely LFG collection and control will potentially reduce emissions of air toxics ranging from 60 to 240 megagrams at a single, medium-sized bioreactor landfill. Another benefit of timely gas controls may be the ability to capture higher quality LFG for alternative fuel use, according to the EPA.

The proposed rule affects MSW landfills with a design capacity greater than or equal to 25 million megagrams and 25 million cubic meters. The rule applies if all or a portion of the landfill operates as a bioreactor. Within 90 days of adding liquids, these facilities would be required to install and operate a LFG collection and control system equivalent to the controls required by the NSPS/EG for MSW landfills. Affected MSW landfills will be required to conduct a control system performance test within 180 days of LFG control system startup.

Ed Repa is the director of environmental programs for the National Solid Wastes Management Association. E-mail the author at: [email protected]