Environmental Impacts and Regulatory Compliance
Overview
ecomaine is a self-contained operation serving 27 municipalities and consisting of three integrated facilities: recycling, waste-to-energy and ashfill. The ecomaine waste-to-energy facility (WTE) processes up to 550 tons per day of municipal solid waste (MSW), which is converted into 100,000-110,000 megawatts of electricity per year - enough to power 15,000 homes.
Environmental impacts at the facility include air emissions from the combustion process, such as heavy metals, NOx, SO2, CO, particulates, HCl, ammonia, and some amounts of dioxin/furans. ecomaine has installed air pollution control systems on the WTE facility's combustors to minimize these emissions and comply with license limits. Systems at ecomaine include:
- Activated carbon absorption to eliminate 94% of mercury and dioxin emissions
- A dry scrubber to neutralize 80% of acid gases, such as sulfur dioxide, and 95% of hydrogen chloride
- A selective non-catalytic reduction (SNCR) system to reduce nitrogen oxide emissions by 35-40%
- A 5-field electrostatic precipitator to eliminate 99.9% of particulate emissions
Details on air quality impact are provided in the discussion below.
Although ash generation from the combustion process also produces a significant environmental impact, it has distinct advantages over traditional landfills. Ash occupies just one-tenth the space needed for burial and is the difference between filling a 300-acre site to a depth of 15 feet and filling a 30-acre site to a depth of 15 feet deep. In addition, weight is reduced by 30%.
Conversion of MSW into an inert ash, through the ecomaine waste-to-energy plant, eliminates the MSW decomposition process. If not processed through the WTE plant, that decomposition would generate acidic, heavy metal-bearing leachate that could contaminate ground and surface water. In ash form, however, the heavy metals are stabilized into compounds such as hydroxides and sulfates that remain in the ash and pose minimal risk of release into the environment. (See "Landfill/Ashfill" for more information.)
Surface Water Monitoring
Surface water runoff on the paved areas of the plant is collected in catch basins, which flow, to a stormwater detention basin. The water that is collected in this basin discharges to a small tributary of the Stroudwater River, which discharges into Casco Bay. ecomaine has developed a Stormwater Pollution Prevention Plan to help ensure that management practices are in place to limit the potential for surface water runoff carrying pollutants into the receiving water. Practices such as daily sweeping of the road and parking area, keeping materials covered or inside, and installation of a concrete pad and sump to collect liquids/drippage from roll-off trucks have been implemented as part of the daily routine.
In addition, three times per year, ecomaine collects and analyzes surface water samples for analysis of parameters specified in the Surface Water Sampling and Analysis Program and submits these results to the Maine Department of Environmental Protection. The sampling locations represent surface water conditions upstream of and downstream from the ecomaine site. The results show that the ecomaine Stormwater Pollution Prevention Plan has been successful and that its operations do not significantly impact surrounding surface waters.
Air Quality
Operation of the ecomaine waste-to-energy facility is governed by several air quality requirements. Because the WTE is defined as a major source of air pollutants, it operates under a Title V Operating Permit (also referred to as a Part 70 Operating Permit). This permit requires ecomaine to perform monitoring and testing for a number of pollutants, as described below. Using a system of two (redundant) continuous emission monitoring systems (CEMS) on each flue, ecomaine ensures that emissions are monitored at least 99% of the time. ecomaine also performs annual stack testing to measure pollutants such as heavy metals, hydrogen chloride, dioxin and particulates.
Continuous Emissions Monitoring
Sulfur Dioxides (SO2)
Sulfur dioxide (SO2) is formed from the combustion of sulfur found in the delivered waste and is problematic because it contributes to the formation of acid deposition. Removal of SO2 is accomplished with a dry scrubber into which lime slurry is injected. ecomaine monitors SO2 before the dry scrubber system and at the stack to demonstrate a removal efficiency rate of least 80%.
ecomaine has a limit of 29 ppm (parts per million) SO2 corrected to 7% oxygen over a 24-hour average or 80% removal of SO2. Average emissions from the ecomaine unit during 2005 were 6.4 ppm. Since 2000, ecomaine has never experienced a day in which it exceeded its emission limit of 29 ppm and/or removed less than 80% of the SO2.
Nitrogen Oxides (NOx)
Nitrogen oxides (NOx) are formed during the combustion process of either nitrogen-bearing material in the fuel itself or from the reaction of nitrogen in the combustion air with excess air in the boiler (thermal NOx). NOx contributes to acid deposition, but its primary environmental impact is as a precursor to the formation of photochemical smog, or ground level ozone.
A selective non-catalytic reduction (SNCR) system was installed in early 2000 to reduce NOx emissions by 30-40%. Testing in 2005 showed an annual average emission level of approximately 150 ppm, which is well under the NOx limit of 180 ppmdv @ 7% oxygen over a 24-hour average. There has been no exceedance of the NOx limit since the SNCR system was installed.
Carbon Monoxide (CO)
ecomaine monitors carbon monoxide (CO) both for environmental and process control reasons. CO is produced by the incomplete combustion of fuels containing carbon. The lower the CO emissions, the more complete the combustion process and the less likely that other products of incomplete combustion are being generated. Complete combustion requires a specified temperature and excess air in the boiler.
Although ecomaine has a carbon monoxide limit of 100 ppm over a four-hour block average, it averaged only 25 ppm of CO in 2005. ecomaine was in compliance with the CO limit for all but 66 hours during 2005, due primarily to startup and shutdown incidents.
Opacity
Opacity has a limit of 10% as measured over a 6- minute average. Opacity is monitored continuously as an indirect measure of the emission of particulate matter. ecomaine operates an electrostatic precipitator (ESP) to remove over 99% of the particulate matter generated by the combustion process and averages less than 2% opacity from the combustion process. Particulate matter is aesthetically unpleasing (smoke) and the small particles may result in respiratory problems to those that inhale them. ecomaine was in compliance with the opacity limit for all but just 42 minutes in 2005.
Stack Emissions Testing
ecomaine performs annual emissions tests on the flue gas from each of its two boilers, as required in its air emissions license and applicable regulations. The test results on various pollutant emissions, which include cadmium, lead, and mercury, are summarized in a report to the Maine Department of Environmental Protection (Maine DEP). ecomaine has always been in compliance with all limits - a perfect record (see Table 1).
Mercury
The mercury emission limit that came into effect on December 19, 2000, is 50 pounds (annually) and testing results for ecomaine have been well under that limit (21 pounds in 2005). Across the air pollution control system, ecomaine reduced 93% of its emissions.
Lead
The ecomaine lead emission limit is 440 ug/dscm, corrected to 7% oxygen. The most recent stack test data shows an average of 51ug/dscm for Boiler A and 45 ug/dscm for Boiler B.
Cadmium
The cadmium emission limit for ecomaine is 40 ug/dscm, corrected to 7% oxygen. The average of the cadmium test results for Boiler A was 5 ug/dscm and Boiler B was 6 ug/dscm - well below the emission limit of 40 ug/dscm.
Dioxins and Furans (PCDD and PCDF)
Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are two hazardous organic substance compounds that are formed during most combustion processes. The emission limit for polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) is 60 ng/dscm PCDD and PCDF at 7% oxygen (total of the two). The average PCDD/PCDF results show Boiler A at 6.18 ng/dscm and Boiler B at 1.43 ng/dscm. Both boilers are far below the emission limit of 60 ng/dscm.
Particulate Matter
The ecomaine emission limit for total particulate matter (total PM) is 24 mg/dscm. The most recent stack test results show the PM average for Boiler A was 11.8 mg/dscm and Boiler B was 3.7 mg/dscm, for a combined total PM of 15.5 mg/dscm. Well below the limit.
Hydrogen Chloride
The dry scrubber is designed to remove the 95% or more of hydrogen chloride (HCl) generated by the combustion process. The emission limit for HCl is 29 ppmdv at 7% oxygen, or 95% reduction by weight or volume. The October 2005 stack test results show the dry scrubber technology produced a 98.9% reduction of HCl emission in Boiler A and a 95.5% reduction of HCl emissions in Boiler B.
Ash Characterization
Bottom ash is the residue by-product of the combustion process. Fly ash is the finer, lighter residual material that is collected in the air pollution control systems (the cyclone, scrubber and ESP) that follow the waste combustion process. These two ash streams combine in a quench/extraction process, which is then conveyed to trucks that transport the ash to ecomaine's own disposal facility.
The ash characterization program is designed to comply with its site license and with Maine Solid Waste Regulations (Ch. 400 and Ch. 403). The primary purpose of the ash characterization program is to confirm the ash is not RCRA (Resource, Conservation & Recovery Act) hazardous as defined Maine DEP hazardous waste regulations (Ch. 850). ecomaine performs ash monitoring according to the "Ash Characterization Program, October 1995" prepared by Caswell, Eichler & Hill. The primary compliance parameter is TCLP (Toxicity Characteristic Leaching Procedure) metals and if the long-term average concentration exceeds the threshold, the ash could be classified as hazardous waste, requiring disposal at a licensed hazardous waste disposal facility. As indicated in Table 2 (below), the level of heavy metals at ecomaine is below the TCLP limits, which makes the ash non-hazardous and allows disposal in ecomaine's own special waste landfill.
Environmental Management System
- Environmental Policy
- Environmental Aspects
- Legal and Other Requirements
- Environmental Objectives and Targets
- Environmental Management Programs
- Training, Awareness and Competence
- Environmental Communications
- Document Control
- Operational Control
- Emergency Preparedness and Response
- Monitoring and Measurement
- Nonconformance & Corrective and Preventive Action
- Records
- Environmental Management System
- Audit Management Review
ecomaine has developed an Environmental Management System (EMS), which, since 2003, has been certified under the ISO 14001 EMS standard by an accredited third party auditor. The EMS was developed to ensure that RWS identified and evaluated ways of minimizing its environmental impact and implemented policies and procedures in a number of areas including:
As part of the EMS process, a working group, composed of ecomaine employees in each area of facility operations, identified and evaluated all the environmental aspects of ecomaine operations and determined which ones were the most significant. The emission of air pollutants and generation of ash from the municipal solid waste (MSW) combustion process were ranked at the top.
In order to address its air emissions impact, ecomaine developed a startup/shutdown/ malfunction plan to minimize the occurrence of elevated CO emissions during these phases of operation. ecomaine is also in the process of purchasing new controls for its gas burner to allow for more efficient startup and shutdown of the units.
To minimize ash disposal needs, ecomaine installed a magnet in 2003 to recover ferrous metals from the ash. This recovered metal reduces the amount of ash landfilled by about 5%.
Another project ecomaine has instituted as a result of the EMS, is to install new tanks in 2006 to collect clean water discharged from boilers during shutdown and prevent its discharge into the ash pit. A Geotube process will also be evaluated during the spring boiler outage to allow dewatering of the ash material generated during boiler outages and to minimize the volume of ash requiring disposal.
Programs implemented under the EMS in the past have included development of a stormwater pollution prevention plan, mercury product collections in member communities to reduce the amount of incoming mercury through the waste stream, and installation of a drippage collection system for trucks hauling roll-off containers.
The EMS also requires semi-annual audits by a third party to determine if it is in compliance with its own policies and procedures - and to determine if it will retain its ISO 14001 certification. This winter, Advanced Waste Management Systems, Inc. reported in its summary findings that: "ecomaine demonstrates the commitment and capability to fulfill its Environmental Policy through maintenance of its environmental management system, including the commitment to pollution prevention. It is the audit team's recommendation that AWM continue the registration of [ecomaine] to ISO 14001: 1996."
Other Waste Handling
ecomaine provides limited collection for residential mercury-containing items at the WTE facility. ecomaine inspects the waste stream and removes any detected hazardous or unacceptable materials, which are then disposed of by a qualified contractor.
ecomaine conducted household hazardous waste collections through six regional mercury-item collections in 2001.
The City of Portland, our host community, provides for collection of all universal waste and construction debris at its recycling facility for Portland and other area residents.
ecomaine surveyed its owner-communities in 2004 as to whether ecomaine should invest in a household hazardous waste collection center. The majority of the towns preferred collecting household hazardous waste and universal waste at the local level. ecomaine has, instead, written articles/issued news releases, participated in a news conference, and testified in favor of two bills before the legislature.
ecomaine provides information on its web site about household hazardous waste collection, including a detailed guide to locations where such materials can be taken.
In 2005, ecomaine initiated and hosted a meeting for communities to meet with a Maine DEP representative about a complicated, new e-waste law that would be effective in 2006. (Maine is one of the first states in the country to create a law holding manufacturers responsible for disposal costs.)
