The amount of hazardous waste which is incinerated in the United States has increased substantially since the mid-nineteen eighties, when federal regulations began requiring that hazardous waste be treated to render it safe for disposal in landfills. Under ideal conditions, good combustion destroys most of the non-metallic, toxic organic compounds in hazardous waste and leaves ash residues which are easier to dispose than raw, untreated waste.
It may be surprising to learn that only about 40 per cent of the 5 million tons of hazardous waste burned annually is incinerated in licensed hazardous waste incinerators. The other 60 per cent is burned in boilers and industrial furnaces (BIFs) which use waste as an auxiliary fuel. Virtually all BIFs which burn hazardous waste on a commercial basis are cement kilns or lightweight aggregate kilns. By May, 1994, 37 cement and aggregate kilns were authorized to burn hazardous waste. It is estimated that cement kilns now burn about 90% of all commercially incinerated liquid hazardous waste in this country, and a growing percentage of solid hazardous wastes.
Since cement and aggregate kilns currently play such a large role in hazardous waste combustion, the use of hazardous waste in these facilities deserves close scrutiny. Using hazardous waste to fire cement kilns concerns some public health and environmental advocates because it can expose humans and the environment to increased risks from toxic and hazardous metals and chemicals.
Hazardous waste fuels can include paint thinners, paint sludges, waste oil, chemical production process byproducts, spent and off-specification solvents and other petrochemical byproducts. Solids and liquids from the cleanup of past uncontrolled hazardous waste dump sites may also be blended into hazardous waste fuel streams. Some of these types of waste can contain toxic heavy metals such as lead, arsenic, cadmium, mercury and chromium.
Combustion of wastes that contain chlorine, including chlorinated solvents and chlorine containing organic and inorganic chemical compounds, can cause the formation and emission of toxic organic compounds known as poly-chlorinated dibenzo-dioxin (PCDD) and poly-chlorinated dibenzo-furan (PCDF) compounds.
People can be exposed to these hazardous substances, not only from air pollution from waste burning operations at kilns, but also from cement kiln dust (CKD) disposal, reuse and management. Occupational contact with cement products produced by the kilns may also lead to exposure to hazardous substances. There is evidence that kilns which use hazardous waste fuel emit solid particulate matter and chlorinated dioxin compounds at higher stack gas concentrations and in greater volumes than state-of-the-art commercial hazardous waste incinerators, and that cement products and kiln dust from waste burning kilns contain higher concentrations of these hazardous substances than from kilns which burn only conventional fossil fuels.
The potential risks to public health posed by burning hazardous waste in cement kilns may be increased by the location of many of the kilns. Much of the hazardous waste is burned in older wet-process kilns traditionally located in or near to rural and small town population centers. Zoning restrictions are traditionally a matter left to local governments, very few of which have enacted restrictions specifically dealing with hazardous waste combustors. Federal law imposes specific requirements on hazardous waste-burning kilns located within municipalities with populations of at least 500,000, but all kilns currently burning hazardous waste are located in or near far smaller communities.
Congress and the EPA initially exempted BIFs from obtaining hazardous waste operating permits under regulations implementing the Federal Resource Conservation and Recovery Act ("RCRA") issued in 1980. Congress and the EPA believed that the high combustion temperatures of cement kilns and other BIFs made them desirable - and safe - for hazardous waste processing. Allowing BIFs to recover the energy value of hazardous waste would also theoretically conserve fossil fuel.
In addition, Congress exempted cement kiln dust from hazardous waste regulations until after completion of a U.S. Environmental Protection Agency study of the environmental and human health hazards posed by CKD. This gave the cement kilns a significant economic advantage over commercial hazardous waste incinerators, which are required to dispose of process residues in RCRA-licensed hazardous waste landfills with extensive requirements to control fugitive emissions, groundwater contamination and other environmental hazards. EPA's kiln dust study and Report to Congress (RTC) have lead to publication of an EPA decision to regulate cement kiln dust under the hazardous waste authority of the Resource Conservation and Recovery Act, but with a tailored regulation which does not provide all features of full hazardous waste regulation.
The 1984 Hazardous and Solid Waste Amendments (HSWA) to RCRA provided a major stimulus to burning hazardous waste in BIFs by prohibiting the land disposal of many hazardous wastes without treatment to specified standards. Thermal destruction was an obvious method for treatment or destruction of many RCRA regulated wastes. Cement kiln operators were able to offer an inexpensive alternative to RCRA licensed incinerators during the 1980s because kilns were not subjected in practice to the same stringent standards and performance requirements under state and federal regulation that applied to other hazardous waste combustors.
The trend toward sending hazardous waste to cement kilns was also encouraged by EPA's decision to exclude hazardous waste sent to BIFs for use as fuel from the reporting requirements of the Emergency Planning and Community Right to Know Act of 1986. Prior to 1988, hazardous waste generators were required to report wastes shipped off-site for "reuse as fuel/fuel blending" on EPA's Toxics Release Inventory (TRI) forms. In that year, however, EPA decided that wastes which were "recycled" (including wastes used as fuel) would no longer have to be reported in the TRI forms. Generators could thus ship wastes to BIFs or to fuel blending operations and claim credit for reducing the amount of waste "released" to the environment. This provided a strong incentive to send wastes to BIFs for "reuse as fuel."
The EPA did not issue final regulations covering hazardous waste-burning cement kilns and other BIFs until 1991. Even then, the EPA allowed existing BIFs to seek "interim status" which would authorize them to burn hazardous waste without a federal permit under less stringent overall regulation and performance than what is achieved in practice for fully permitted RCRA hazardous waste burning incinerators under federal and typical state regulations. Waste burning cement kilns were not required to upgrade the performance of their particulate emission controls at these sites to what would generally be achievable by existing hazardous waste incinerators using best available control technology. Waste burning cement kilns were not subjected to stringent discharge "opacity" regulations that applied to most waste incinerators under state and federal requirements. Waste burning cement kilns were not subjected to requirements to immediately report all RCRA violations which may occur at a site that would be required at a permitted facility. Waste-fuel derived cement kiln dust was not subjected to hazardous waste regulation, unlike residues from hazardous waste incinerators which had to be placed in a secure hazardous waste landfill.
Although several waste burning cement kilns have applied for final Part B RCRA permits, none of these facilities has obtained such a federally-required hazardous waste permit. Interim status facilities may continue to burn hazardous waste indefinitely until EPA acts on Part B permit applications.
These regulations and policies have provided major financial benefits to the waste burning cement industry. Instead of paying for all of their fuel, cement and aggregate kilns are now earning large fees for accepting hazardous waste for energy recovery or destruction.
Cement industry trade groups argue that using hazardous waste fuel poses no major environmental problems and is actually more beneficial to the environment than burning coal or oil.
Critics of the current BIF regulations, including environmental and public health groups, community organizations, and representatives of the hazardous waste incineration industry argue that:
the regulations are not adequate to assure protection of human health and the environment
that the cement kiln industry has a poor record of compliance with the BIF standards
that current regulations allow many kilns to receive hazardous waste even though their air pollution controls are antiquated and do not reflect state-of-the-art, best available control technology
that lax regulation of fuel blending operations allows kilns to receive metal-bearing hazardous wastes with little energy value leading to poorly regulated waste combustion and dispersal of toxic metals to the environment, all disguised as a form of energy recovery.
The U.S. EPA is currently evaluating its BIF regulations as part of a major reassessment of its hazardous waste policy. The EPA has announced it intends to strengthen BIF emissions standards and operating requirements as part of its combustion strategy. EPA has, for example, briefed stakeholders on its intention to issue stringent regulations that would regulate dioxin and furan stack gas emission concentrations in a standard that would be identical for hazardous waste incinerators and hazardous waste-burning cement kilns. In other areas, such as proposals for particulate emission regulation and EPA's long delays in dealing with the fuel blending issue, EPA seems less committed to a level playing field for cement kilns and hazardous waste incinerators. EPA's own attempts to foster pollution prevention and waste minimization policies are undermined by the weste-burning kiln industry's approach to waste management policy whose emphasis on combustion eclipses material re-use and recycling.
Future regulation of hazardous waste-burning cement kilns and industrial boilers and hazardous waste incinerators has important implications for the management of hazardous waste in this country. Stringent regulation of hazardous waste combustion should not only provide increased environmental protection at the site of the combustion unit; such stringent regulation and the resulting increased disposal costs should also create additional incentives for industry to reduce the generation of hazardous waste at the source. In the long run, reducing the amount of hazardous waste generated is the most desirable and environmentally beneficial strategy for dealing with the hazardous waste problem.
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