Beneficial Use and Recycling of Municipal Waste Combustion Residues--a Comprehensive Resource Document

This paper summarizes some of the information contained in a comprehensive document about the beneficial use of municipal waste combustion (MWC) residues. The document entitled "Beneficial Use and Recycling of Municipal Waste Combustion Residues A Comprehensive Resource Document", presents information from world-wide sources and contains numerous references. Information is presented on ash characteristics, environmental considerations when using ash, guidelines for selected use applications, information on federal and state regulations concerned with ash, and many other topics important to consider when implementing ash use projects. Results of several studies evaluating risks associated with ash use are presented including potential environmental and human health exposure pathways that should be considered when evaluating the acceptability of alternative uses. Information presented on ash use practices in several other countries show that ash use is much more prevalent in some of these countries than in the United States. Information presented in the document, including results from numerous studies, demonstrates that ash can and is being used safely. The document was produced at the National Renewable Energy Laboratory (NREL) with support from the U.S. Department of Energy. Copies may be obtained by calling NREL Document Distribution 303.275.4363 and requesting publication NRELIBK-570-25841. This paper briefly describes what is in each chapter and summarizes some of the key information in the document. CHAPTERS IN THE DOCUMENT The following presents the title and a brief description of the contents of each chapter: Chapter 1 Background This chapter provides an historical overview of ash management in the United States, some information on the sources of various ash streams, and discusses some earlier studies. 89 Chapter 2 the Nature of Ash Chapter 2 presents detailed data on the physical and chemical properties of MWC ash. Results of characterizing ash and ash products for use in selected projects is also presented. Chapter 3 Productive Use of Ash This chapter discusses potential uses for the ash, commercial experiences, and guidelines for some specific uses. Chapter 4 Research and Demonstration Projects Chapter 4 presents a compilation of and discusses MWC ash demonstrations. Discussions of selected research projects are included. Chapter 5 Management of Municipal Waste Combustion Ash in Other Countries In this chapter, information is presented on ash management and use in Bermuda, Japan, the Netherlands, Denmark, Germany, France, Sweden, and the United Kingdom. Chapter 6 Environmental Considerations This chapter discusses issues that are important to human health and the environment when implementing ash use projects. Fugitive dust, laboratory and field leaching of ash, leaching tests and similar topics are discussed. Results of TCLP testing of ash from several WTE facilities are included. Results of several risk assessments conducted for ash use projects are presented. Chapter 7 Regulations and Policies Federal and state regulations and policies that affect MWC ash use are presented. Potential liability issues and how they can be managed are discussed. RESULTS OF SELECTED RISK ASSESSMENTS Risk assessments discussed in the document include the following uses: • combined ash as landfill daily cover • combined ash as final cover (bottom layer) • use of Treated Ash Aggregate (T AA) as a roadway base, as a structural fill, as daily and fmal landfill covers, as an aggregate substitute in asphalt concrete paving, and reuse and final disposal of paving material containing T AA. Production of asphalt containing T AA, storage in stockpiles, loading and unloading, and transporting of T AA were also evaluated. A brief description of T AA is provided later in this paper. Boiler AggregateTM used to produce asphalt, placement of the Boiler AggregateTM asphalt product, use as an unregulated fill, and milling and excavation for reuse of Boiler AggregateTM asphalt. Stockpiling, handling and transporting operations were also evaluated. A brief description of Boiler AggregateTM is provided later in this paper. Combined ash as a 30% substitution in bituminous pavement. Although each risk assessment covered a specific situation, they generally evaluated the non-carcinogenic and carcinogenic effects on receptors from exposure to As, Ba, Cd, Cr, Pb, Hg, Ni, Se, Ag, and dioxin and furan congeners. Key receptors included nearby residents, workers, adults and children visiting a site, those that could be exposed to runoff, fugitive dust, etc. Direct and indirect exposure pathways evaluated included inhalation of fugitive ash dust onand off-site, incidental ingestion and dermal contact with ash and ash products, residential exposure to soils potentially contaminated with particulates and/or leachates from ash and ash products, and similar pathways. In the case of landfill final cover, exposure pathways also included incidental ingestion and dermal contact with surface water and sediment while swimming in a nearby harbor and consumption of fish from the harbor. Exposure from ingestion of food grown in soils potentially contaminated with TAA was also evaluated. Also included was ingestion of drinking water containing leachate from Boiler AggregateTM stockpiles, a road base and a recycled asphalt product pile. Results of these risk assessments were favorable to ash use. Using EPA and other approved methods for conducting risk assessments, results in all cases showed that use of the ash would pose no unacceptable risks to human health or the environment. Hazards evaluated were below all applicable health criteria and non-carcinogenic and carcinogenic risks were well within US EPA recommended goals. GUIDELINES FOR ASH BENEFICIAL USE The document reviews several different sources for information on experiences and guidelines useful for the development of ash use applications. Specific guidance is provided for such items as mix design, material processing 90 (ash segregation, metals removal, blending, etc), engineering properties, environmental considerations, and similar items important for asphalt paving, granular base for roadways, formulation of concrete products, and similar uses. Although the sources differed somewhat in their content, there were no substantial contradictions among them. The document also contains numerous references to ASTM methods and standards applicable to the testing of ash and ash products. This information will be useful to readers in the development of draft specifications and practices applicable to their desired use, ash source, and market circumstances. LEACIDNG OF MWC ASH In preparing the document, the authors reviewed numerous sources on the leaching of ash. Data is presented from several field studies that characterized the leachates from ash monofills, TCLP testing of ash from several waste-to­ energy (WTE) facilities, and leaching of products containing ash. Several points are clear from reviewing this data. These include: • No single leach test, including the TCLP, is adequate to fully and accurately predict the potential for an ash or an ash product to release constituents of concern under field disposal and beneficial use conditions. • Laboratory leach test routinely overestimate the potential for constituents of concern to leach from an ash and ash product when compared to actual leaching from ash monofills and ash use in field applications. • Modem waste-to-energy facilities routinely pass the requirements of the TCLP. Metal concentrations in leachates from ash monofills evaluated over time have routinely met ground water standards and often meet drinking water standards. • Although leachates from combined ashes in monofills have low concentrations of heavy metals; the total dissolved salts concentrations may be several orders of magnitude above drinking water standards. • If detected at all, levels of dioxins/furans in ash and ash leachates were extremely low and considered not to be a concern when evaluating the environmental and health consequences of using ash. TCLP TESTING OF ASH FROM THE H-POWER