WASTE/ENERGY: NREL Identifies Means Of Reducing Mercury Emissions

Sue Darcey

Mercury emissions, a pollutant associated with incineration of municipal solid waste, could be reduced dramatically if batteries and fluorescent lamps are removed from the waste stream and wet scrubbers and carbon adsorption emissions controls are employed at resource recovery facilities, according to a study released by the Na-tional Renewable Energy Lab (NREL), Golden, Colo.

Mercury Emissions from Munici-pal Waste Combustors projected that MSW combustor emissions in the United States could decrease from about 97 metric tons in 1989 to four metric tons in 2000 - a 95 percent reduction in mercury. The authors doubted, however, if the incineration industry would adopt the pollution controls necessary to achieving the reductions.

The projections assume that:

* About 80 percent mercury emissions reduction control efficiency will be achieved with pollution control equipment likely to be employed by 2000;

* Most cylinder-shaped mercury-zinc batteries used in hospital ap-plications will be removed from the waste stream; and

* Either the amount of mercury used in fluorescent lamps is de-creased to an industry-wide average of 27 milligrams of mercury per lamp, or these lamps that contain mercury are diverted from the waste stream. (For estimates of mercury in the MSW stream, see chart.)

"No present consensus was found that ... emission control measures can be implemented in-dustry-wide within the U.S.," said the study. "Although the availability of technology is apparently not a limiting factor, practical implementation of necessary control technology may be limited by administrative constraints and other con- siderations, such as budgeting and regulatory compliance requirements."

Available data have identified MSW combustion as a major source of mercury emissions that do not occur naturally. For example, data recently developed for the construction of a MSW combustor in Los Angeles found that mercury emissions from the proposed facility, if constructed, could exceed all other known ambient sources of mercury emissions in the surrounding area.

According to the study, municipal refuse incineration is the second largest source of atmospheric emissions of mercury worldwide, at 140 to 2,100 metric tons per year, following coal combustion from industry and domestic sources, at 495 to 2,970 metric tons per year.

The authors warned that data regarding inventories from various types of emission sources are frequently incomplete or unavailable. This makes it difficult to establish a consensus on the amounts of mercury that derive from man-made vs. non-manmade activities.

Wet scrubbers have been used in Western Europe as control devices and, when coupled to MSW combustors, reportedly can achieve efficiencies of 80 to 90 percent. Resource recovery plant operators in the United States have been reluctant to use this technology, though, because of the possibility that dechlorination of chlorinated dioxins may shift the isomer distribution from octaform to the more toxic tetraforms, and because they do not want to treat the resulting wastewater produced when wet scrubbers are employed.

For a copy of the report, Mercury Emissions from Municipal Waste Combustors, contact Sally Evans, Document Distribution Service, NREL, 1617 Cole Blvd., Golden, Colo. 80401. (303) 231-1000.