What is H-POWER to do with its ash?
Every day that it operates, H-POWER, Honolulu’s trash-to-energy plant, generates about 400 tons of ash in the process of burning about 2,000 tons of municipal solid waste. Almost all of the ash is hauled to the Waimanalo Gulch landfill, whose operator, Waste Management, Inc., is paid by the City and County of Honolulu about $16 a ton to place the ash in lined landfill cells, called monofills. That’s $6,400 a day, or about $2.4 million a year.
For more than two years, H-POWER’s operators have been looking for less expensive ways of dealing with the ash. In this connection, they have been pressuring officials at the state Department of Health to let them use the ash in a variety of applications: mixing it with asphalt for a paving material, making it into a construction material (something like cinder blocks), and using it as daily landfill cover (material that is spread over the refuse that arrives each day). In addition, they have asked the DOH to modify the landfill’s permit to allow the mining of ash for use as a landfill cover.
So far, the Department of Health has given its approval only for the first of these uses — and even then, for a pilot project on the grounds of H-POWER’s plant at Campbell Industrial Park. Nor does this use hold the promise of making great inroads into the ash supply: according to Colin Jones, H-POWER administrator for the City and County of Honolulu, the ash content in the asphalt mix is about 3 percent. “It appears that until we can develop a means of drying the ash better, this is about the best we can do,” Jones wrote in a memo last October to the Department of Health’s office of Solid Waste Management.
The request to use ash as landfill cover is poised to receive DOH approval — at least for a six-month or one-year demonstration project. But again, even if the DOH allows this use to continue indefinitely, that, too, would consume just a fraction of the volume H-POWER produces. The volume of daily cover that a landfill requires is typically 25 to 30 percent of the total volume of waste it takes in each day. At Waimanalo Gulch, the daily total (excluding H-POWER ash) is 900 to 1,000 tons, which would mean at most 250 tons of the 400 tons of ash H-POWER produces each day could be used in this application.
As for use of ash in construction material, a team of researchers at the University of Hawai`i is studying the chemical and physical properties of a masonry-type product made using ash. Among other things, the researchers are studying its strength, endurance, and the degree to which heavy metals may leach from the product.
With respect to the mining of ash, the Department of Health has indicated it has no interest in allowing this. And, according to Joe Fernandez, environmental manager for Waste Management at Waimanalo Gulch, given the volume of ash produced daily by H-POWER, mining the monofills where ash has been deposited since 1990 makes no sense. “We’ve got more than enough [ash] coming in each day to use as cover, plus we make our own cover on site,” he said, referring to Waste Management’s practice of crushing rock to meet present needs for daily cover.
Ash Faulted
According to H-POWER operators, the ash is a valuable resource that is being wasted so long as it is landfilled.
DOH officials counter that even though the ash may not meet the definition of hazardous waste (indeed, as a related article in this issue explains, it cannot, since hazardous waste regulations exempt waste-to-energy plants), the ash nonetheless contains concentrations of heavy metals and other materials (including dioxins) high enough to make the uncontrolled dispersal of large quantities of it into the environment a potential public health hazard. If ash is combined with asphalt and used on roads, made into construction materials, or shaped into artifical reefs and dumped at sea (as has been done elsewhere), the result over time would be to increase the background levels of lead and other hazardous substances to which the public is exposed on a daily, routine basis, the DOH argues.
In their efforts to avoid landfilling the ash, H-POWER’s contract operator, Ogden Environmental and Energy Services, prepared a risk assessment of the “beneficial use” of ash as landfill cover. The document concluded that this use would add a cancer risk of 3 in 100,000 to landfill workers and 5 in 100,000 to workers involved in ash mining — a level which the authors said compared favorably to target risk guidelines established by the Environmental Protection Agency for clean-up of Superfund sites. Superfund guidelines allow health risk levels after site clean-up to be as high as 1 in 10,000.
Leslie K.L. Au, a toxicologist with the DOH Hazard Evaluation and Emergency Response office, reviewed the risk assessment and took strong exception to the authors’ use of Superfund guidelines as a standard against which to judge the health risks associated with use of ash as landfill cover. As Au writes, “We disagree with this comparison. At the landfill, we are obviously not trying to clean up a number of hazardous-waste sites which have already been unaffordably contaminated. Rather, using ash as a daily cover is the deliberate adding of hazardous contaminants to a relatively uncontaminated site which is open to the public, while trying to prevent the creation of a site which is unhealthily contaminated. Another obvious thing to say is that the easiest way to avoid creating a hazardous-waste site is not to use ash as a daily cover.”
Despite his objections to the comparison, Au goes on to write, in a memo dated May 15, 1997, that, “in recognition of the conservative, health-protective overestimations of risk which the authors of this Risk Assessment used, the risk to landfill workers and visitors may be within acceptable levels.”
“The exposure assessment is the key element in the Risk Assessment,” Au writes. “The ash unquestionably contains substances which are hazardous to human health, so that the amount of human exposure and human intake must be tightly controlled below a certain threshold level. Failing to handle H-POWER ash at the landfill according to [the proposed method in the assessment] would increase the exposure of the workers and general public, which would then increase their added cancer risk to unacceptably high or significant levels, which would in turn reverse our verdict of ‘No objection.'”
The Dutch Experience
In some countries, ash from municipal waste incinerators is permitted to be used as building material, roadbed aggregate, and fill. In nearly every case, however, the uses are restricted to bottom ash. Fly ash normally contains higher levels of lead and other materials that can pose health risks and most of the European countries that allow use of incinerator ash prohibit use of combined bottom and fly ash. (H-POWER officials want to use combined ash.)
One country with extensive experience in the use of bottom ash is the Netherlands. In the last 10 years, nearly all the bottom ash produced by municipal solid waste incinerators has been used as fill in construction projects (especially embankments, where up to 1 million tons of ash can be used in a single project) and in road work.
Dutch law requires strict regulation of the bottom ash, with limits set on the percentage of metals the ash can contain. Before any of the ash can be used, it must undergo testing and be certified. In addition, the Dutch have developed guidelines for the use of ash. Among other things, the site where the ash is proposed to be used must be at least half a meter in elevation above the average maximum groundwater level, with use banned in specially protected groundwater reserves. Also, users are required to take steps to prevent rainwater infiltrating into the ash. This can be done by applying an asphalt top and side cover to ash used in a road base or by applying an impermeable clay layer over ash used as fill.
Cutbacks in Testing
For the Dutch, rigorous testing of incinerator ash is a keystone of the reuse program. To ensure that ash meets the certification standards, both with regard to its environmental properties as well as construction specifications, samples of bottom ash are taken for every 5,000 to 10,000 tons of ash intended for use. In addition, random inspections by certifying institutes make sure that the specifications are met at all times.
Yet in Honolulu, H-POWER officials have been seeking approval from the Department of Health to reduce the frequency of ash testing required by its permit. Most recently, in a letter dated February 8, 1999, Colin Jones, the city’s energy recovery administrator, asks the DOH to change the required frequency of ash testing from quarterly to annually.
Included with Jones’ request are summaries of analytical reports made on combined fly and bottom ash since 1989. One data set shows the parts-per-million content of various metals, including lead, mercury, arsenic, and cadmium. The other shows the results of tests on leachate extracted from the ash using the toxicity characteristic leachate procedure test (TCLP).
“The data,” Jones writes, “shows a bounded family of values which over tie have trended in the downward direction for all of the metals of interest except for barium. In the case of barium, the data appears to be stabilizing toward a value of 0.8 mg/l [milligrams per liter], which is below the drinking water standard for this material.”
“We believe,” he continues, “this TCLP data clearly characterize the H-POWER ash as a non-hazardous material and indicate that the benign qualities of this ash are improving with time… [W]e believe this evidence should be sufficient to justify reducing the frequency of TCLP testing of our ash from quarterly to annually.”
According to Gary Siu of the DOH’s Office of Solid Waste Management, no decision has yet been made on Jones’ request.
HAZARD.APR
State Exempts H-POWER Ash, ResidueFrom Regulation as Hazardous Waste
Could the lead, cadmium, arsenic, and other heavy metals in H-POWER ash ever reach such high levels that the ash is regulated as hazardous waste?
Absolutely, positively not.
That’s not to say the levels could not be high enough to justify concern over use of the ash in such applications as roadbeds, masonry, and landfill cover.
Nor is it to say that the metal content in the ash is always going to fall below the threshold of regulatory concern set in federal and state laws.
It is to say, however, that by definition, state regulations exempt H-POWER ash from being considered as hazardous waste, no matter how high the concentrations of such metals in either the ash itself or in the leachate produced when the ash is bathed with a mildly acidic wash, such as occurs in the standard Toxicity Characteristic Leaching Procedure (TCLP) test. (The acidity level of the TCLP wash is intended to be about the same as is found in landfills generally.)
According to Grace Simmons, head of the state Department of Health Hazardous Waste Section, the state regulations exempting H-POWER ash from consideration as hazardous waste have been in place since 1994. Simmons says the state regulations mirror federal Environmental Protection Agency language concerning ash from operations such as H-POWER, referred to in regulatory language as “resource recovery” facilities.
The EPA regulations were triggered following a U.S. Supreme Court decision in the spring of 1994. The case at issue involved ash from a Chicago trash-to-energy plant that flunked the TCLP test for lead, with one sample exceeding the EPA’s recommended action level for lead in drinking water (0.015 milligrams of lead per liter of water) by 100-fold.
For non-exempt materials, if a TCLP test shows lead concentrations in the leachate of at least 5 parts per million (more than 333 times the EPA action level for drinking water), the material is to be regulated as hazardous waste.
Low Standards?
The hazardous-waste standard of 5 ppm lead in leachate, even though it does not apply to H-POWER, has itself been criticized as overly lenient to polluters. As Peter Montague writes in Rachel’s Envirnment & Health Weekly of August 18, 1994, the TCLP test “does not identify the actual pollutants contained in the ash; it only identifies those pollutants that leach out under certain specific conditions. Since, sooner or later, all of the ash will be released into the environment (even ash that is monofilled), it is the total pollutant content that will affect communities, not merely what leaches out under TCLP conditions. Therefore, the TCLP test gives a misleading estimate of the ash hazard.” (Monofilling refers to the practice of placing ash in lined landfill cells intended to receive only ash. H-POWER’s ash is monofilled at the Waimanalo Gulch landfill.)
H-POWER is not required to measure the total lead content in its as a condition of its permit to operate. However, such tests have been done, most recently in connection with the desire of the City and County of Honolulu and H-POWER’s operator to see the ash re-used as landfill cover, building material, or in road construction. Under a contract issued by the federal Department of Energy’s National Renewable Energy Laboratory, H-POWER ash was analyzed for a number of different elements and compounds. One sample of combined bottom ash and fly ash found lead concentrations as high as 15,809 parts per million — in other words, the ash was 1.5 percent lead. For purposes of comparison, ash samples from a sister trash-to-energy plant in Connecticut, which were used as a control in the NREL study, had on average just 37 ppm lead. (The clean-up targets for lead in soils at Superfund sites are, by contrast, 400 ppm for residential areas and 1,000 ppm for industrial or commercial areas.)
Process Residue
In addition to ash, H-POWER produces what it calls process residue. This residue consists of glass, dirt, metal pieces, and other heavy materials, saturated with solvents and other wet wastes, that fall through a 2-inch screen intended to remove non-combustible items from the waste stream. A spokeswoman for Ogden Environmental and Energy, which operates the plant, told Environment Hawai`i that typically, 12 to 13 percent of the solid waste received by H-POWER falls out as process residue. Thus, on a day when 2,000 tons of waste are delivered to H-POWER’s front door, about 250 tons of process residue (in addition to 400 tons of ash) are taken out the back.
Much of this waste ends up being used to augment the daily cover at the Waimanalo Gulch landfill. Joe Hernandez, environmental manager for WMI, described how the residue is used: “Sometimes there are gaps and holes on the active face of the fill. When we have a homogeneous waste like this, it is used to fill the gaps in the daily face. Then after the face is smoothed out, we apply six inches of daily cover.” (Hernandez mentioned that “auto fluff” — the cushions, upholstery, and plastics removed from cars by metal recyclers — is also sometimes used to augment the daily cover.)
Under terms of H-POWER’s solid waste permit, the process residue must be tested periodically. Chemical analyses done in 1998 showed lead levels averaging 224.6 parts per million, with one sample showing concentrations as high as 650 ppm.
But once more, no matter how high the concentration of lead or other contaminant may be in process residue, it is exempted by state rules from regulation as hazardous waste.
— Patricia Tummons
Volume 9, Number April 1999