Incineration can greatly reduce waste volume and thus help to solve a nationwide dilemma—shrinking landfill space to accommodate burgeoning levels of municipal solid waste. But critics are worried about its health effects, especially possible risks from the ash it produces. How risky is ash?
By the turn of the century, say some experts, as much as 30 percent of municipal solid waste in the United States may be burned using large incinerators known as municipal waste combustors. Though other experts dispute this figure as too high—it is triple the current rate—they agree that incineration technology will be very much in the minds of local and regional decisionmakers during the next ten years.
Municipal waste combustors have had a very short history. Until recent decades, solid waste either was burned in backyards or transported to local garbage dumps. There it was buried or piled onto open heaps of other previously deposited solid waste. All this changed about twenty years ago when the amount of solid waste being generated, including paper, glass, plastic, metals, and food wastes, began to skyrocket.
Despite the hefty cost of these combustors (the price tag for one plant can be as much as $135 million) and growing concern about the potential health effects of incineration, some municipalities and regional authorities have issued bonds and made the purchase. More are considering following suit. If the volume of incinerated waste does triple over the next ten years, the number of communities that choose incineration will have to be considerable. Why the appeal?
It seems mostly to come down to the issue of bulk. Incineration can reduce the volume of municipal waste by about 90 percent, a figure that is not lost upon local government officials confronted by rapidly diminishing landfill capacity and rapidly mounting heaps of community garbage. Moreover, incineration produces energy in the form of heat that can be harnessed to produce steam, which in turn can generate electricity. Most waste combustors in this country are currently being used in this dual-purpose capacity.
Concern over ash
Public opposition to municipal combustors has grown and become more vocal over the past several years. While criticism at first focused on airborne emissions of toxic substances produced during incineration, many experts have since come to believe that technologies now available can adequately control these emissions. Attention has now shifted from airborne emissions to ash. Municipal combustor ash consists of the residual material that is trapped in the stack—fly ash—and other combustion products and noncombustible residues that remain behind in the combustion chamber: bottom ash. In most waste combustors, the two types of ash are combined for easier handling.
This combined ash may contain considerable quantities of toxic materials, including lead and cadmium. If present in sufficient concentrations and not properly disposed of, these materials may leach from the ash and contaminate ground or surface water supplies. Besides water contamination, the public also is concerned about human exposure to ash and ash dust at combustor plants and landfills. In addition, critics point to possible risks to area residents from ash dust blowing off solid waste trucks en route from incineration to disposal.
Yet clear guidance for appropriately managing incinerator ash remains elusive. The debate over ash persists because government, builders and vendors of incinerators, and the public cannot agree on what risks are presented by ash and whether or how these risks can best be managed. This failure to reach a consensus has caused cancellation of plans to install some combustor plants and has greatly prolonged the permit approval process and construction of others. It also has stymied needed improvements in the existing ash management system.
Regulation
Current management practices are based on adhering to federal regulations directed at solid wastes in general, not at ash in particular. Ash and all other solid wastes are regulated by the U.S. Environmental Protection Agency (EPA) under the Resource Conservation and Recovery Act (RCRA) of 1976. Under the terms of RCRA, solid wastes are categorized as either hazardous or nonhazardous. Subtitle C of RCRA lays out strict requirements for managing the hazardous wastes. Subtitle D addresses the nonhazardous wastes.
Whether incinerator ash should be considered hazardous or not remains very much open to question. RCRA enumerates four traits that are characteristic of hazardous materials: corrosiveness, ignitability, reactiveness, or toxicity. Toxicity is the only one of the four that could apply to ash. A toxicity test developed by EPA has been used on selected samples of ash with mixed results: some samples clearly indicate toxicity while others do not.
Categorizing ash as hazardous or nonhazardous is further complicated by a provision of RCRA known as the household waste exclusion. This provision states that household waste cannot be declared hazardous. Since the exclusion does not specifically include ash, some observers have argued that ash can be declared a hazardous substance; others argue that the exclusion encompasses the entire household waste system and that ash is included. EPA, however, has said that if incinerator ash is tested and found to possess traits of a hazardous waste, it should be regulated as such. To date, the agency has not enforced this position. The former administrator of EPA, Lee M. Thomas, has said that the agency is looking to Congress for clarification of the household waste exclusion as it applies to waste combustors and that EPA will await its decision.
In practice, because its regulatory status is uncertain, ash usually is managed and disposed of as a nonhazardous waste. Yet existing requirements for nonhazardous landfills are weak. In August of 1988, EPA proposed substantive revisions to these requirements that have generated substantial debate. It now seems unlikely that final revisions will become effective before at least 1992. Meanwhile, arguments about the appropriate disposal of ash continue.
Views from Congress, the courts
Congress has not yet acted to clear up the confusion, although the 100th Congress considered several bills that would have declared ash from waste combustors to be nonhazardous. Although they differed in detail, all of the bills would have required that most ash from incinerators be disposed of in lined—not unlined—landfills. (As many as 80 percent of existing landfills are believed to be unlined.) The bills also would have required less rigorous containment for ash monofills than for disposal sites. Ash in monofills is believed to be relatively less risky because leaching of toxic substances is encouraged by acidic conditions, while ash is alkaline and therefore conditions at monofills tend to be alkaline.
"But none of these issues excites so much opposition as the perceived health threats from ash."
So far in the present legislative session, one new bill that applies to incinerator ash has been introduced. Others are likely to follow. All of the bills are expected to resemble those considered by the previous Congress and to stipulate that municipal waste incinerator ash be regulated as a non hazardous waste.
The likelihood of any of these bills becoming law in 1989 is not great. The general view is that other environmental priorities such as revising the Clean Air Act amendments of 1977 may have greater claims on lawmakers' attention in the near term. Early 1990 is seen as a more likely time for moving forward on new legislation that affects the ash issue. Even if a bill were to be passed into law quickly, it would be several more years before design regulations could become final and EPA could begin to enforce them.
In the meantime, the Environment Defense Fund (EDF) is suing two owners and operators of municipal waste incinerators. EDF charges that because ash from the two facilities failed EPA's toxicity test, it should be managed as hazardous waste and disposed of accordingly. Trial dates have not yet been set. An EDF victory may well spur Congress on to enact legislation that nullifies the court ruling and confirms its own view, which appears to be that ash should be considered a nonhazardous, albeit special, waste. An EDF loss might well help maintain the status quo.
Notwithstanding the hiatus in regulation, legislation, and the courts, local and regional authorities must continue to choose destinations for municipal solid waste and make decisions about incineration. These decisions vary widely from locale to locale, but generally states in the Northeast with high population densities and little landfill capacity to use incineration to a greater extent than Midwestern and western states with more landfill capacity (Connecticut already incinerates roughly one-third of its trash). Many states already have or are developing their own requirements for ash disposal. For instance, regulations in New York State echo many of the special handling requirements in the bills introduced during the 100th Congress.
Technology
Much of the debate over how incinerator ash should be regulated boils down to the issue of containment technology. Questions revolve around the rigorousness of engineering controls such as the number of liners that should be installed for different types of facilities, methods for collecting any leachate that escapes through the liners, and strategies for monitoring groundwater contamination.
One strategy being considered to ease concern over the adequacy of containment technology is to solidify or otherwise treat the ash before landfilling. Some companies offer chemical treatments designed to reduce the leachability of toxic substances from ash. However, treatment is not being widely carried out because it is not currently a prerequisite for disposal at nonhazardous landfill sites. In essence, it adds a cost that can be avoided.
Though many critics focus on toxic components of ash such as lead and cadmium, concern is also being voiced about another component, salt. Incinerator ash contains extremely large concentrations of common table salt and other nontoxic salts that present problems of their own. Though they are unlikely to directly harm human health, they could adversely affect the environment by contaminating ground and surface water.
Incineration techniques also enter into the debate over ash. In general, these techniques have been improved in recent years both to increase the efficiency of power generation and to better control emissions of toxic substances. Airborne emissions from waste combustors have been reduced to a level where many, but not all, observers say that the emissions are acceptable. To a lesser extent, environmentalists and some commercial firms are looking at ways to control the entry of toxic substances into the combustor. Even so, opponents of incineration argue that current provisions and practices are not sufficiently health-protective; such opponents often garner strong resistance to the installation of waste combustors in their communities.
Labels matter
What are the implications of regulating incinerator ash as a hazardous waste? Of singling it out for special handling and disposal? Of considering it nonhazardous?
Michael Gough, senior fellow in the Center for Risk Management at Resources for the Future and director of a research project on managing ash from municipal waste incinerators, says classification could have significant effects: "Clearly, labeling incinerator ash as a hazardous waste would impose higher costs on its disposal because the costs of constructing and maintaining a hazardous facility are greater than those for nonhazardous facilities.
"In the more likely event that Congress declares ash to be a non hazardous waste that requires special handling, disposal costs undoubtedly would be greater than for other nonhazardous wastes and probably less than those for hazardous wastes," Gough continues. "More important, however, labeling ash as a 'special waste' probably would make its management somewhat easier because it would avoid the stigma attached to 'hazardous waste.'"
"Clear guidance for appropriately managing ash remains elusive."
According to Gough, a partial solution to ash disposal could be achieved by using ash in construction fill and roadbeds, as it is used in Europe. Furthermore, he explains, ash has been used to fabricate building blocks and concrete. Firms that have begun to investigate the possible reuse of incinerator ash in these materials say they pass the toxicity test after treatment. "But no matter what test results are available," he says, "they would be given little credence if ash is declared to be hazardous."
Casting the die
"By the year 2000, the volume of municipal solid waste that will be disposed of, incinerated, or recycled in the United States is expected to rise almost 20 percent," Gough says. "Even more telling is EPA's estimate that landfill capacity will be exhausted in 27 states within the next five years. Although additional landfills may be opened up, they surely will be more expensive to site, maintain, and monitor."
Gough says that recycling is becoming a more attractive option because waste combustors are expensive and landfilling costs for both ash and other municipal solid wastes are rising. He says proponents of recycling cite cases such as the city of Seattle, Washington, which recycles about 30 percent of its waste, a rate comparable to that in Japan.
But in the near term, he says, states with relatively low-cost, bounteous land available at the right price could find themselves becoming multistate dumping grounds. Such a trend already has begun, with private interests buying up thousands of acres of land for future landfill sites. The New Mexico legislature already has passed a moratorium on new landfills as a result of such activities. On the other hand, at least one railway engineering firm is said to be designing cars to carry trash interstate.
According to a background document prepared for the EPA 1988 Agenda for Action, if current recycling and disposal methods are not stepped up and if the amount of garbage produced annually continues to grow at the current rate, the United States may have as much as 56 million tons of garbage "left over" with no provisions for disposal in the year 2000. Will local authorities turn to incineration to the degree some experts predict and use this technology to offset the excess garbage figure?
"The answer depends to a great extent on resolution of the ash controversy," Gough says. "Undoubtedly, disagreements will continue over whether or not to install waste combustors. First, they are expensive. Second, they may have local impacts such as lowering property values and increasing truck traffic.
"But none of these issues excites so much opposition as the perceived health threats from ash," he continues. "The number of waste combustors in the year 2000 will directly reflect whether policymakers and the public deem risks from ash to be acceptable."
Elaine M. Koerner is staff writer for Resources for the Future. Michael Gough is senior fellow in the Center for Risk Management at Resources for the Future. The Center will shortly release a report on municipal waste combustor ash; the report contains recommendations for improving the management of ash.
A version of this article appeared in print in the May 1989 issue of Resources magazine.
