The Role of Waste-to-Energy in the U.S.A.

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1 The Role of Waste-to-Energy in the U.S.A. Prof. Nickolas Themelis Chair, Waste-to-Energy Research and Technology Council (WTERT) Director, Earth Engineering Center, Columbia University (Paper presented at 3 rd Congress of the Confederation of European WTE Plants (CEWEP), Vienna, May 2006) Generation and disposition of municipal solid wastes in the U.S. The generation of municipal solid wastes (MSW) in the U.S. has grown steadily. Every two years, the Earth Engineering Center of Columbia University conducts a survey of MSW generation and disposal in the U.S. on the basis of information solicited from the waste management departments of the fifty states of the union. This survey is made in collaboration with BioCycle Journal and is called the State of Garbage in America (SOG). The most recent survey (BioCycle, April 2006; to be made available during the 3 rd CEWEP Congress) showed that the generation of MSW increased from 369 million short tons (1.1 short tons = 1 tonne) in 2002 to 388 million tons in 2004, i.e., at the rate of 2.5% per year. Landfilling accounted for 249 million tons or 64% of the MSW generated. The MSW generation per capita remained at 1.3 tons/year (3.2 kg/day), by far the highest in the world. A comparison of the BioCycle/EEC data for 2002 and 2004 data (Table 1) shows that in the intervening two years, recycling plus composting increased by 11.8 million tons, landfilling by 6.3 million tons and WTE by 0.5 million tons. Table 1. U.S. MSW generation and disposal in 2002 and in 2004 MSW Generated Recycled or composted Waste-to- Energy Landfilled 2004, million tons , percent 100% 28.5% 7.4% 64.1% 2002, million tons , percent 100% 26.7% 7.7% 65.6% BioCycle/EEC surveys (BioCycle, Jan and April 2006) Figure 1 shows that most of the recycling is done in coastal states and that many of the WTE facilities are on the East coast. 1

2 Figure 1. Breakdown of disposition of MSW by region (BioCycle/EEC SOG, April 2006) Overview of WTE Industry in the U.S. There are 89 waste-to-energy power plants operating in 27 states. They are fuelled by 29 million tons of MSW and have a generating capacity of 2,700 megawatts of electricity. They recover about 0.7 million tons of ferrous and non-ferrous metals; also, three million tons of WTE are used in place of soil or stone aggregate in the maintenance of landfills. The major WTE companies in the U.S. are Covanta Energy (31 plants), Montenay Power ( 17 U.S. plants) and Wheelabrator Technologies (9 plants). The organization corresponding to CEWEP in the U.S. is the Integrated Waste Services Association ( and is headed by Mr. Ted Michaels. The U.S. WTE facilities can be classified in three broad classes (Table 2): Mass burn plants generate electricity and/or steam from trash by feeding MSW as received into large furnaces dedicated solely to burning trash and producing power. Refuse-derived fuel (RDF) plants shred the MSW, recover some recyclable materials, and combust the homogenized fuel in a combustion chamber. The RDF producing facility may be next to the furnace or at another location. Modular waste-to-energy plants are similar to mass burn facilities but are smaller and typically pre-fabricated off site and assembled where they are needed. 2

3 Table 2. Operating U. S. Waste-to-Energy Plants Technology Number of plants Capacity, tons/day Capacity, tons/year Mass burn 65 71, Refuse derived fuel (RDF) 15 20, Modular 9 1, Total 89 92, J. V. L. Kiser and M. Zannes, Integrated Waste Services Association, April 2004 One can estimate the population served by WTE by assuming that in the communities that have WTE facilities all the non-recycled wastes (i.e. 71.5% of the total using the national average) are combusted. Therefore, the total MSW in those communities amounts to 28.9x100/71.5 = 40.4 million tons. Dividing this number by the average national generation rate of 1.3 tons per capita, indicates that the U.S. WTE facilities serve 31 million people. Energy and Greenhouse Gas Benefits of Waste-to-Energy Combusting one ton of MSW in a modern WTE power plant generates a net of 550 kilowatt-hours of electricity, thus avoiding mining a quarter of a ton of coal or importing one barrel of oil. Also, WTE is the only alternative to the landfilling of non-recyclable wastes, where the decomposing trash generates methane, a potent greenhouse gas, an estimated 40% of which escapes to the atmosphere even in the modern sanitary landfills. The non-captured methane has a greenhouse gas (GHG) potential 23 times that of the same volume of carbon dioxide (Intergovernmental Panel on Climate Change). Taking into account the electricity generated and the methane emissions avoided has led several independent studies to conclude that waste-to-energy reduces U.S. greenhouse gas emissions by an estimated tons of carbon dioxide per ton of trash combusted rather than landfilled. Therefore, in addition to the energy benefits, the combustion of MSW in WTE facilities reduces U.S. greenhouse gas emissions by about forty million tons of carbon dioxide. Source of Renewable Energy As stated earlier, in 2004, 28.9 million tons of trash were combusted in America's wasteto-energy power plants and generated a net of 13.5 billion kilowatt-hours of electricity, equal to geothermal energy and greater than all other renewable sources of energy, with the exception of hydroelectric and geothermal power. For comparison, wind power amounted to 5.3 billion kwh and solar energy to 0.87 billion kwh (Table 3, DOE 2000 data). 3

4 Table 3. Generation of renewable energy in the U.S. in 2002, excluding hydropower ( DOE-EIA, Annual Energy Outlook 2002) Energy source Billion kwh generated % of renewable energy Geothermal % Waste-to-Energy* % Landfill gas* % Wood/biomass % Solar thermal % Solar photovoltaic % Wind % Total % * If it is assumed that the Rubber, Leather and Textiles category of MSW, as reported by USEPA in its 1997 characterization of U.S. MSW, is divided equally between natural (cotton, wool, leather, rubber) and man-made (plastics, synthetic rubber and fabrics) organics, the combustible materials in MSW consist of 82% biomass (paper, food and yard wastes plus half of rubber, etc.) and 18% petrochemical wastes (Table 4),. Therefore, MSW is a renewable source of energy and, rightly so, is included by the U.S. Department of Energy in the biomass fuel category of renewable energy sources. Table 4. Concentration of combustible materials in U.S. MSW (USEPA, 1997 data) Biomass combustibles Paper/cardboard Wood Cotton/wool Leather Yard trimmings Food wastes Total biomass content % Petrochemical combustibles % % Plastics Rubber Fabrics Total petrochemical content % Biomass constitutes 82% of the combustibles in MSW; petrochemicals 18% WTE emissions and public health issues In the distant past, there were thousands of incinerators without any air pollution controls. For example, at one time New York City had an estimated eighteen thousand residential 4

5 incinerators and thirty two municipal incinerators. The environmental impacts can still be detected in deep lying cores of the Central Park soil. Understandably, this has left a bad image of incineration in New York City that persists to this day, so that New York transports most of its MSW to distant landfills in other states. Yet, the adjacent New Jersey and Long Island Sound communities depend largely on waste-to-energy and most of the Manhattan MSW is combusted in the Essex County WTE of Covanta Energy. At this time, there are over 1500 incinerators of all types in the U.S. but less than one hundred Waste-to-Energy plants (WTE). In the past, when the effects of emissions on health and the environment were not well understood, all high temperature processes, including metal smelting, cement production, coal-fired power plants and incinerators were the sources of enormous emissions to the atmosphere. In particular, incinerators were the major sources of toxic organic compounds, called dioxins and furans, and mercury. However, in the last fifteen years and at the cost of about one billion dollars, the 89 WTE facilities operating in the U.S. have implemented air pollution control systems that has led USEPA to recognize them publicly as a source of power with less environmental impact than almost any other source of electricity ( In 1995, the USEPA adopted new emissions standards for WTE facilities pursuant to the Clean Air Act. Their maximum achievable control technology (MACT) regulations dictated that waste-to-energy facilities with large units (i.e., >250 tpd) should comply with new Clean Air Act standards by December 19, Small unit facilities (i.e., 35 tpd to 250 tpd) represent only 5% of the U.S. WTE capacity and by 2005 also met similar MACT rules. MACT includes dry scrubbers, fabric filter baghouses, activated carbon injection and other measures that were implemented at the cost of over one billion dollars. Waste-to-energy facilities now represent less than 1% of the U.S. emissions of dioxins and mercury, as discussed below. Decrease in WTE Dioxin emissions The toxic effects of dioxins and furans were not realized, both in the U.S. and abroad, till the late eighties. Thanks to the implementation of MACT regulations, the toxic equivalent dioxin emissions of U.S. WTE plants have decreased since 1987 by a factor of 1,000 to about 12 grams TEQ total (Figure 2). In comparison, the major source of dioxin emissions reported by EPA is backyard trash burning that emits close to 600 grams annually. Also, Federal Emergency Management Administration (FEMA, May 2002) reports that thousands of landfill fires result in dioxin emissions of 1000 grams TEQ annually ( Mercury emissions The use of mercury in U.S. processes and products reached a high of 3,000 tons per year in the seventies. It decreased to less than 400 tons by 2002, due to the phasing out of most applications of this metal, as mandated by USEPA. For example, mercury activated switches and thermostats have been substituted and the mercury content of fluorescent lamps has been reduced substantially. Also, many communities have put in place strong recycling programs that keep older mercury-containing products out of the MSW sent to 5

6 WTE facilities. This trend, plus the implementation of the MACT regulations have decreased the mercury emissions of the WTE facilities from 89 tons of mercury in 1989 to less than one ton by now (Figure 3). By now the major sources of mercury in the atmosphere are the global coal-fired power plants. Figure 2. Dioxin emissions in the U.S. (P. Deriziotis, MS Thesis, Columbia University, 2003; data by U.S. EPA) 6

7 Figure 3. Reduction of WTE mercury emissions (N.J. Themelis and A. Gregory, Mercury Emissions from High Temperature Sources in the NY/NJ Hudson Raritan Basin, Proceeding of NAWTEC 10, American Society of Mechanical Engineers, p , May 2002) The only remaining WTE emissions of concern are nitrogen oxides. However, the total WTE emissions correspond to only 0.22% of the total U.S. NOx emissions. For comparison, coal-fired power plants contribute 19.5% of the U.S. NOx emissions (D. Albina; The Waste-to-Energy Research and Technology Council (WTERT) Because of competition with low-cost landfills, the U.S. WTE companies have not been profitable enough to support a substantial R&D function. In recognition of this need, the Waste-to-Energy Research and Technology Council (WTERT) was co-founded in 2002 by the Earth Engineering Center of Columbia University ( and the Integrated Waste Services Association (IWSA; that represents most of the waste-to-energy facilities in the U.S. WTERT brought together engineers and scientists from industry, government, and universities from all over the U.S. and other countries. WTERT believes that responsible and management of wastes must be based on science and best available technology and not on emotion or what seems to be inexpensive now but may not be sustainable even for the next hundred years. In general, the mission of WTERT is to increase the global recovery of materials and energy from used solids and, in particular, to advance both the economic and environmental performance of waste-to-energy technologies. WTERT conducts academic research that involves both M.S. and doctoral students, investigates existing and developing technologies. The findings are reported through presentations, publications, the WTERT meetings, and the WTERT web page ( This page includes the database SOFOS and has become 7

8 one of the best sources of information on R&D on the recovery of energy and materials from wastes and the environmental impacts of waste processing technologies. On the basis of several studies by graduate students in the Department of Earth and Environmental Engineering of Columbia University and other researchers, WTERT has concluded that waste-to-energy technologies are an indispensable tool in the integrated management of municipal solid wastes. Both recycling and WTE conserve nonrenewable minerals and fossil fuels. The environmental benefits of WTE derive from reducing the greenhouse gas emissions associated with landfilling putrescible materials, avoiding the conversion of greenfields to landfills, conserving fossil fuels, and recovering metals. As noted above, U.S. WTE facilities recover 0.7 million of metals; in contrast, an estimated 10 million tons of metals are buried annually in U.S. landfills. Current WTERT Research Reducing corrosion in WTE combustion chambers: Because the WTE combustion gases, before gas cleaning contain a relatively high concentration of HCl, corrosion is more acute than in coal-fired power plants and represents a major item of maintenance. Research efforts to overcome this problem include superior metal alloys and methods of application; sequestering of HCL at high temperatures; and reducing the superheater metal temperatures. Thermogravimetric analysis (TGA) of the kinetics of drying, volatilization, and combustion of various components of MSW, particle size and shape factor. Study of transport and chemical rate phenomena on WTE grates: The objective is to reduce the capital cost of future WTEs by understanding the effect of MSW size distribution and grate design on the combustion capacity of WTE units, in terms of thermal energy released (in MWh) per square meter of grate surface. Improving the quantity and quality of metal recovery in WTE plants: On the average, only 50% of the input metal is recovered in U.S. WTEs; also in many plants ferrous and non-ferrous metals are not separated, thus reducing the value of the metal collected. Means to increase the beneficial use of WTE ash: For example, removal of chlorine from fly ash can increase the use of combined ash for the remediation of land used in the past for coal strip mining. Critical analysis of existing waste management system and technical economics studies on the potential for WTE implementation in Brazil, Chile, Greece, and New York City. Comparison of health effects, Life Cycle costs and benefits, and greenhouse effects of MSW disposal by WTE and by landfilling. WTERT Annual Meetings The WTERT Annual Meetings are held at Columbia University in the fall and in 2004 and 2005 included presentations on waste management in Brazil, China, Germany, Finland, France, India, Israel, Italy, Japan, the Netherlands, Singapore, Taiwan, and other 8

9 nations. WTERT is also a partner of SWANA and ASME International in organizing the North American Waste-to-Energy Conference (NAWTEC) held each spring in Florida. WTERT Awards for Outstanding Contributions the management of solid wastes In 2004, the first WTERT awards for Outstanding Contributions to Waste Management were awarded at a gala dinner to Martin GmbH of Germany, a company that has continually improved the reverse grate technology used in over 300 WTE facilities worldwide (Industry Award); and to Prof. George Tchobanoglous of the University of California-Davis for his pioneering textbooks and handbooks on waste management (Education Award). The 2006 WTERT Industrial Award will be presented to an operating WTE facility that is judged by an international committee to be amongst the best in the world, on the basis of the following criteria, but not limited to: Esthetic appearance of facility; energy recovery, in terms of kwe plus kwh recovered per ton of MSW and as % of thermal energy input in the MSW feed; level of emissions achieved; optimal resource recovery and beneficial use of WTE ash; acceptance of facility by host community The WTERT 2006 Education Award will be given to a person who has made an outstanding contribution to integrated waste management through his/her publications, inventions or other activity. Nominations by CEWEP members are most welcome and can be submitted by with brief description of the reasons for nomination to Prof. Marco J. Castaldi of WTERT at Columbia University, (mc2352@columbia.edu). 9