Because of the concentration of heavy metals and other toxics in incinerator ash, it may be the one thing on Earth that is truly non-recyclable. The City’s biggest concern, however, is to avoid having the ash characterized as hazardous. Were that to occur, the ash would have to be shipped to a hazardous waste disposal site. The closest one is on the Mainland.
Tests were conducted on the ash in December 1989 and February 1990. One sample showed lead in excess of the Evironmental Protection Agency’s standard for non-hazardous waste. That was the only exceedance noted.
The State is seeking to require monthly ash tests for metals and yearly tests for the certain organic chemicals. Although fly ash (from the electrostatic precipitations) contains far higher levels of metals, no separate tests will be required for it, since it is mixed with the bottom ash before leaving the plant.
If the ash regularly tests out as non-hazardous, the State and the City may renegociate test frequency. But Arlene Kabei, Director of the Division of Solid and Hazardous Waste in the State Department of Health, wants to make certain “front-end” controls are working before cutting back on test frequency. “Front-end” control means pulling out sources of heavy metals and other toxics before they land in the boiler.
Anyone who has seen H-POWER’s tipping floor might be skeptical of the effectiveness of any plan for “front-end” control. Some 2,000 tons of material are dumped each day, and sorting occurs on the floor at only the grossest level. Frank Doyle, Direcort of the City’s Division of Refuse, noted that “as the conveyors go up to the shredder, there are people picking things off.” Some items are plucked out manually, Doyle said, adding: “But, let’s say they had a drum? And they couldn’t pick it out manually? There’s a hoist there, so theos things you can save, too.” (The drum evidently would have slipped past the keen eye of the sourter on the tipping floor.)
Doyle said also that haulers were being instructed on what was appropriate to bring to H-POWER, and what was not.
H-POWER’s ash is taken to Waimanalo Gulch, where it is placed in an ash monofill – a separate area of the landfill lined with heavy plastic. THe site is probably no worse than any other in the state. It is on the dry Waianae Coast, upstream only from the new resort of Ko Olina. Ground water is brackish. If leachate tests show levels of contaminants high enough to prevent legal discharge into the channelized stream that drains the valley, the leachate is sprayed back over the ash. Over the years, this might cause the concentration of contamination in the leachate to soar. For now, no one seems worried.
But is Waimanalo Gulch filling faster than planned? H-POWER had been expected to generate ash, residue and other material equal to about 25 percent, by weight, of what was delivered. Figures for June were closer to 34 percent. Doyle said that those figures did not account for the water in the ash. Adjust for that, he said, and the latest figures show that what goes out H-POWER’s back end is just 21.8 (by weight) of what comes in the front. (Doyle provided these figures for July: 2,000 tons per day delivered; landfilled were 120 tons per day of “residue,” or noncombustible material; 70 tons of ferrous metal; 40 tons of “unacceptable waste” – refrigerators and the like – and 460 tons of wet ash. With water accounting for 30 percent of the ash weight, the dry ash would amount to 322 tons. Our calculations show all this totals 27.5 percent of the delivered weight.)
In any event, Doyle said reductions would come. Tires now being landfilled will eventually be disposed of in some other fashion (possibly at H-POWER), Doyle said, and a market will be found for the scrap metal now being dumped.
Doyle believes that ash will one day be used in roadbeds and other construction applications: “We’re going to get over this business of what really happens with the metals and the dioxins.”
But before ash can be used responsibly in any application, problems arising from its potential dispersal into media where the metals can be inhaled or ingested must be overcome.
Doyle’s concern for dioxins in ash is singular. Most people believe dioxins are created in the stack. Dioxins are not generally found in ash.
Volume 1, Number 4 October 1990