The use of waste-to-energy (WTE) as a mechanism for solid waste reduction has been the subject of debate for as many years as WTE facilities have been in operation. WTE facilities are often viewed as a source of pollution that can cause serious health and environmental effects. On the other hand, WTE facilities are also viewed as a viable recycling mechanism that reduces the volume of solid waste requiring ultimate disposal and reduces the impact of landfill leachate and gas on the environment while creating electricity. Over time, increasingly stringent regulations have been promulgated to reduce the air emissions from these facilities, including the federal performance standards 40 CFR 60 Subpart Eb and Subpart Cb. On December 19, 2000, all facilities with units designed to combust greater than 250 tpd were required to comply with these regulations. For this reason many facilities were obligated to retrofit to add air pollution control equipment to enable them to comply with the more stringent limits. To determine how effectively WTE facilities are operating as the industry has evolved from an environmental performance standpoint, the Delaware Solid Waste Authority retained the services of HDR Engineering Inc., Cambridge Environmental Inc., and Eden Environmental Inc. This collective group, HDR team, evaluated 12 of the most recently constructed and/or permitted WTE facilities and the public health and environmental impacts associated with WTE facilities. The HDR team was also asked to identify concerns expressed by WTE opponents at the time of the permitting of these facilities and to provide a long-term assessment of those concerns.
The WTE evaluation involved obtaining information on specific performance criteria for 11 facilities in the United States and one facility in the Netherlands. Performance information was obtained through issuing Freedom of Information requests, interviewing state regulatory officials, visiting state regulatory agencies to conduct file reviews (where necessary and where day visits were possible), interviewing agencies that oversee operations of the WTE facilities, and interviewing facility operators.
The Delaware Solid Waste Authority requested that the 12 facilities evaluated include mass-burn and refuse-derived fuel (RDF) technologies (including fluidized-bed combustion). Therefore, of the 11 facilities evaluated in the US, eight are mass-burn waterwall combustors and three are RDF processing facilities. Two of the RDF facilities use spreader stokers and one uses a fluidized-bed combustor. The facility in the Netherlands is a mass-burn waterwall combustion facility. Data collected for each of the 12 WTE facilities included combustion technology; air pollution control technology; general facility design data; compliance with air, ash, and water discharge limits; community and facility recycling data; and area demographics.
The following 12 WTE facilities were evaluated:
- Robbins Resource Recovery Facility, Robbins, IL
- Montgomery County Resource Recovery Facility, Dickerson, MD
- Onondaga County Resource Recovery Facility, Jamesville, NY
- Wheelabrator Falls Energy Recovery Facility, Morrisville, PA
- Lee County Solid Waste Resource Recovery Facility, Fort Myers, FL
- Union County Resource Recovery Facility, Rahway, NJ
- AVI Amsterdam, Amsterdam, Holland
- Delaware County Resource Recovery Facility, Chester, PA
- Montgomery County Resource Recovery Facility, Conshohocken, PA
- Southeastern Connecticut Resource Recovery Facility, Preston, CT
- Palm Beach County Resource Recovery Facility, West Palm Beach, FL
- Semass Facility, Rochester, MA
The data developed for each facility included utilization, demonstrated combustion technology, facility age, exceedances, maximum achievable control technology (MACT), location in a coastal zone, zero water discharge, use of an air-cooled condenser, ash reuse, front-end separation of waste received, recycling rates in excess of national average, bypass landfill, host community benefits, high-pressure design vs. low-pressure design, and demographics.
General information regarding the location, date of facility start-up, facility operator and owner, combustion system used, the number of boilers, facility rated capacity, location in a coastal zone, and host community zoning is included in Table 1.
Tables 1 through 5 can be viewed as a pdf by clicking here. You will need Acrobat Reader in order to view this version. If you do not have Acrobat please download it now.
Table 2 contains facility operating data. The operating data include the facility rated capacity, the average utilization, the tip fee charged based upon the December 1998 issue of Solid Waste Digest, the rated steam production, the boiler exit temperature and pressure design values, and the turbine generator rated capacity. Facility capacity utilization ranges from 52.7% to 100% of facility rated capacity for each of the facilities surveyed. There are four low-pressure design facilities with pressures that range from 625 to 675 psig. The remaining eight facilities are high-pressure design facilities with pressures ranging from 750 to 900 psig.
Table 3 indicates the types of air pollution control equipment used at each of the facilities. Seven of the 12 facilities have air pollution control equipment considered MACT by the Environmental Protection Agency (EPA): carbon injection, selective noncatalytic reduction (SNCR), semidry reactor (SDA), and fabric filter (FF). These facilities are RRRF-Illinois, MCRRF-Maryland, ORRF-New York, WFERF-Pennsylvania, LCSWERF-Florida, UCRRF-New Jersey, and AVI-Holland. Of these facilities, RRRF-Illinois has exceeded the current permit limits and future enforceable Subpart Eb emission limits. Three additional facilities (DCRRF-Pennsylvania, MCRRF-Pennsylvania, and SCRRF-Connecticut) have an SDA and an FF. MCRRF-Pennsylvania and SCRRF-Connecticut have Hg stack emissions that exceed the future enforceable Subpart Cb emission limit. MCRRF-Pennsylvania has started using Sorbalit for control of mercury emissions. The most recent stack tests conducted indicate that this facility is operating well below the mercury emission limits. SCRRF-Connecticut also intended to use Sorbalit starting in December 2000 to control mercury emissions. SCRRF-Connecticut does not plan to install an SNCR system for NOx controls. Rather, the facility will continue to purchase emission credits to ensure compliance with the NOx limit.
The Semass-Massachusetts facility has two units with an SDA and an ESP (electrostatic precipitator) and one unit with an SDA, FF, and SNCR system. This facility also has added Compact Hybrid Particulate Collectors (COPAC) downstream of the ESPs on Units 1 and 2. The COPAC system acts as a final particulate-matter collection system and is expected to reduce mercury emissions by 90%. A carbon injection system was added to Unit 3 to control mercury emissions. PBCRRF-Florida has an SDA and an ESP. The NOx emissions based upon the stack test results exceed the future enforceable Subpart Cb emission limits. PBCRRF-Florida reported that recent test data indicates that both NOx and mercury emissions are below the respective limits and therefore there is no plan to add air pollution control equipment at this time.
Table 4 contains information on the total quantity of materials recycled and the recycling rates for each of the WTE host communities. Because various states allow different materials to be counted when calculating recycling rates, caution should be used in making comparisons with the recycling rates. The national average recycling rate published in the April 1999 issue of Biocycle is 30%. Based on the information provided in Table 4, seven of the 10 communities for which information could be gathered had recycling rates exceeding the national average. This is consistent with surveys conducted by various trade organizations that have concluded that communities with WTE facilities generally have higher recycling rates, showing that WTE and recycling work hand in hand.
Table 5 contains information related to nuisance issues reported for each of the 12 WTE facilities. This table also contains information on the issues raised by opponents to WTE during the siting, permitting, and construction phases of each of the 12 WTE facilities. The names of the opponents are also provided.
Tables 1 through 5 can be viewed as a pdf by clicking here. You will need Acrobat Reader in order to view this version. If you do not have Acrobat please download it now.
The evaluation also included a review of information regarding the public health and environmental impacts both perceived and real in relation to WTE facilities. The major public health issues of concern include asthma and cancer, dioxin toxicity, metals toxicity, ash handling and disposal, and environmental justice.
Asthma and Cancer
Asthma is a disease that affects the immune system and therefore involves allergens, not simple chemical pollutants. Certain outdoor air pollutants exacerbate symptoms in those already afflicted with asthma. Because solid waste combustors are a source of criteria pollutants, such as fine particulate and sulfur dioxide, they will likely continue to be a focus of concern with respect to asthma and other respiratory diseases.
The American Cancer Society (ACS) has a pamphlet that provides a brief review of environmental health risk assessment. This pamphlet states that the cancer hazard depends on dose and observes that many risks that concern the public are unproven or negligible. The document also reviews mortality rates from various cancers and notes which cancers are increasing or decreasing in frequency. The International Agency for Research on Cancer (IARC) also has a list of chemicals evaluated for evidence of carcinogenicity to humans and provides a classification of those chemicals. Neither ACS nor IARC mentions WTE or solid waste combustion as a cancer risk.
Dioxin
In 1994, public concern about adverse health effects escalated through preliminary findings in EPA’s draft, Health Assessment of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and Related Compounds. This document found that (1) humans are most likely vulnerable to the same spectrum of biological effects that are induced in other animals by TCDD, (2) the evidence is fairly strong that TCDD is a human carcinogen, and (3) current exposures to polychlorinated dibenzo-dioxins/polychlorinated dibenzo-furans (PCDD/PCDF) could be causing adverse health effects in some people. In related work by EPA, solid waste combustion was incriminated as the major source of PCDD/PCDF emissions to air. Members of the public are often vehemently opposed to construction of new WTE facilities because of the concern that even slight increases in dioxin exposure, on top of unavoidable background exposure, might trigger toxic injury. Hence, they might consider such facilities to be dioxin factories.
The preliminary findings by EPA, described above, are highly controversial in the scientific community. Many scientists argue that studies do not show harmful effects in humans at environmental levels of PCDD/PCDF (as opposed to, perhaps, industrial or poisonous exposure levels), that TCDD carcinogenic action in laboratory animals may proceed by a threshold mechanism not triggered at low exposure levels, that TCDD is not a human carcinogen, and that population exposures to PCDD/PCDF have been decreasing. Other scientists consider the evidence of toxicity strong on all counts.
The most recent assessment of the contribution of solid waste combustion to current releases of PCDD/PCDF is the Inventory of Sources of Dioxin in the US, a draft prepared and released by EPA in 1998. This reassessment is under continuing peer review and review by the Science Advisory Board. The inventory, however, is a significant update of the database on sources and emissions presented in EPA’s 1994 draft Estimating Exposure to Dioxin-Like Compounds, which incorporates additional data and research. Important findings of EPA’s research are the following: (1) Annual releases of PCDD/PCDF in the US from all quantified sources appear to have dropped significantly between 1987 and 1995 from an estimated 11,900 g of 2,3,7,8-TCDD toxic equivalents to an estimated 3,000 g, and (2) the decrease in emissions is largely the result of decreased emissions from solid waste and medical waste combustion. A third important conclusion of the inventory is that the relative importance of a particular source (such as solid waste combustion) to total emissions is not necessarily indicative of the relative importance of that source to the general populations exposure to PCDD/PCDF. Because most of our exposure to PCDD/PCDF comes from diet (more than 90%), only emission sources affecting what we eat will have a marked effect on our exposure to dioxins. Releases of dioxins into the air from local solid waste combustors generally have a very small incremental effect on exposure.Scientists have sought changes in environmental levels of PCDD/PCDF because of the activities of particular solid waste combustors. The findings can be broadly interpreted as worst-case, as the combustors are of older designs and used (or might have used) air pollution control devices that did not hinder PCDD/PCDF formation. While impacts have sometimes been noted in environmental media or cows’ milk, we know of no study finding increased levels of dioxins in the blood or fat of persons residing near (but not working at) solid waste combustors.
The main points, then, are as follows:
- Solid waste combustion technology has improved tremendously and emits far less PCDD/PCDF than in the past.
- New Source Performance Standards will reduce PCDD/PCDF emissions even further.
- Solid waste incinerators are rarely a significant source of PCDD/PCDF for the local population, as most exposure comes from food and not air, water, or soil.
- Much is suspected, but little is actually known, about the effects of PCDD/PCDF on people at the low doses received through environmental media.
Metals
Toxic metals in waste have been a potential concern to many critics of WTE technologies. Unlike organic compounds, metals are not destroyed by incineration but instead are distributed among ash and stack emissions. WTE ash is therefore more concentrated in metals than waste prior to combustion. As described below, however, the mobility of metals in ash is quite low and not believed by most analysts to be of environmental concern.
Emissions of metals via stack gases for municipal waste combustors are strictly regulated. Federal regulations, 40 CFR 60 Subpart Cb and 40 CFR 60 Subpart Eb, strictly limit allowable concentrations of Cd, Pb, and Hg and indirectly limit the stack gas concentrations of other metals by regulating particulate matter in air emissions. Among these metals, mercury has been of greatest concern for combustors. Not only is it a vapor at normal operating conditions, making its capture inefficient by particulate control devices, but it can also accumulate in fish in the form of methyl mercury, which is a potent neurotoxin.
About 19% of anthropogenic emissions were attributed to solid waste combustors. EPA expects mercury emissions from solid waste combustors to decline to approximately 4.4 tpy as Subpart Cb and Subpart Eb emission limits are implemented. According to EPA, the recent decreasing trend in the amount of mercury in solid waste, if it persists, will also reduce emissions from solid waste combustors.
Ash Residue
Issues surrounding ash have changed substantially over the past decade. Data accumulated since the late 1980s have demonstrated that leachate from ash landfills, though concentrated in simple salts, is not concentrated in heavy metals. These data suggest that metals in ash are of limited mobility, at least in the environment of a landfill. Laboratory testing of ash, which can be treated to bind metals, has also shown only limited mobility of metals or other potentially toxic constituents. These data, from both field and laboratory tests, have led to a gradual acceptance of WTE ash as a material that could be used as daily cover in sanitary landfills. This is far different from the traditional thinking that ash was a material so dangerous that it had to be separately disposed of in ash monofills. Florida allows such ash reuse without any special approvals. Reuse as daily cover is allowed in other states with specific approvals. Reuse of ash, rather than landfilling of ash, has a potential economic benefit to a WTE facility. A recent legal review of the liabilities of reusing ash, sponsored by the US Conference of Mayors and conducted by the law firm of DeCotiis, Fitzpatrick and Gluck, is available on the SWANA Web site (www.swana.org, click on Technical Divisions).
Environmental Justice
Opposition to WTE facilities may be founded on concern for environmental justice. Environmental justice is the belief that frequently poorer, minority communities are targeted for many pollutant-generating projects that confer benefits on many and risks on a few. Would-be developers of solid waste combustors should be mindful of the litigious aspects of this issue. While the authors of this report do not know of any successful lawsuits charging industrial facilities with miscarriage of environmental justice, a large amount of time, energy, and money has been spent in defense of these claims.
Other issues affecting the WTE business include economics, the Clean Air Act amendments, and flow control. The evaluation also included public health and monitoring studies and information on the operational responses to environmental issues. The findings have been that public outcry in some cases resulted in implementation of costly environmental monitoring programs such as soil and biota sampling that, contrary to public expectations, never found any contribution of contaminants from a single facility.
The historic public health issues of concern that have been used by opponents of WTE have not been confirmed through scientific study and environmental monitoring programs. Concern regarding these public health issues resulted in more stringent regulations, which ultimately result in more stringent emission controls and less emissions from WTE facilities.
In conclusion, WTE has made great strides by:
- reducing facility emissions such as NOx, acids gases, mercury, and dioxins;
- successfully adapting to changing regulations, such as the Clean Air Act Amendment of 1990;
- developing state-of-the-art facilities using either mass-burn or RDF technologies that can meet the current stringent air pollution control regulations, while producing a renewable energy that is cleaner than coal or oil power-generated energy;
- implementing recycling programs that enhance the technology in a synergistic process often referred to as integrated solid waste disposal;
- demonstrating a high level of reliability of mass-burn and RDF facilities to process waste and produce energy.
In addition, the US WTE industry needs to continue to work on the following areas:
- increasing public education to improve public opinion,
- increasing improvement or development of reliable alternate technologies that can improve WTE economics and still maintain a high level of environmental control,
- evaluating technology improvements achieved in other countries.
