Municipal Waste Combustors

Households, businesses, and institutions across Massachusetts dispose of about 6 million tons of solid waste per year. This waste is:

• Burned in waste-to-energy facilities (municipal waste combustors),
• Buried in modern lined landfills, or
• Transported to out-of-state disposal facilities.

There are five solid waste combustion facilities in Massachusetts. Learn about how these facilities fit into the state's solid waste management system, what they burn, how they work, the wastes they generate, and how their emissions are controlled. 

There are more than 100 municipal waste combustion facilities in operation across the United States. Five of these are located in Massachusetts.

Municipal waste combustors burn a wide range of household and commercial solid wastes, including empty packaging and containers, consumer goods, office supplies, and numerous other items not specifically banned from disposal. Facility operators may turn away loads that contain significant quantities of banned materials, hazardous products, or wastes that are bulky or difficult to manage.

Also known as incinerators or waste-to-energy plants, these facilities burn trash at a very high temperature (approximately 2,500°F). The combustion process:

• Shrinks waste 90 percent by volume and 75 percent by weight, so significantly less needs to be buried in landfills;
• Converts water to steam, which then passes through turbine generators to produce renewable electricity; and
• Reduces greenhouse gases by offsetting carbon emissions from fossil fuels and methane generation from landfills.

Combustion facilities also generate several forms of waste:

Ash Residue: Must be buried in landfills that are specifically approved to accept ash. 

Wastewater: From cooling and ash dewatering operations.

Air Emissions: The primary focus of this guide.

Air emissions from a well operated and maintained combustion facility are generally much lower than the limits established by law. Pollution controls, monitoring, and government inspections ensure that facilities are operating as cleanly as possible. At the same time, their emissions may still contain:

Acid Gases: Contribute to acid rain and can cause or aggravate breathing problems.

Dioxins, Furans & Other Chlorine-Containing Organics: Known or suspected to cause cancer and birth defects.

Fly Ash & Soot: Seen as smoke; reduce visibility and can make it harder to breathe.

Mercury, Lead & Other Heavy Metals: Can affect the human brain, kidneys, liver, and nervous system, as well as child development.

Nitrogen Oxides (NOx): Primary ingredient of ground-level ozone (smog) that can cause or aggravate breathing problems.

MassDEP regulates municipal waste combustors to ensure that their emissions do not pose significant risks to public health or the environment.

The five largest combustion facilities are required to submit periodic plans to MassDEP, summarizing how they will prevent discarded items that contain mercury from entering their facilities.

These Material Separation Plans (MSPs) must be submitted to MassDEP at intervals the agency designates. Each facility develops its own plan in consultation with commercial, industrial, and municipal customers.

Draft plans are submitted to MassDEP for review. The agency solicits public comment on these documents before approving them, attaching additional conditions, if necessary. Facilities then must implement their MSPs and submit annual progress reports to MassDEP.

See the individual Facility Profiles for Reworld Haverhill, Reworld of SEMASS, WIN Waste Innovations Millbury, WIN Waste Innovations North Andover, and WIN Waste Innovations Saugus for their respective Material Separation Plans.

The owner/operators of the five largest combustion facilities in Massachusetts are required by MassDEP to submit:

• One-time Emission Control Plans, demonstrating how and when they will use pollution control technologies to reduce air emissions, and
• Periodic emissions reports to MassDEP, including notification of when facilities have exceeded specific emission limits. 

While specific pollution controls vary from plant to plant, all facilities are equipped with systems for reducing smog-causing emissions, neutralizing acid gases, trapping fly ash and other particles, and lowering concentrations of mercury and organic chemicals.

It is important to note, however, that no combination of technologies available today can completely eliminate emissions from combustion.

See Key Actions below to access to the emissions data these facilities have reported to MassDEP and Additional Resources for the forms they use in this reporting.

See the individual Facility Profiles for Reworld Haverhill, Reworld of SEMASS, WIN Waste Innovations Millbury, WIN Waste Innovations North Andover, and WIN Waste Innovations Saugus for their respective Emission Control Plan approvals from MassDEP.

Massachusetts combustion facilities typically operate within the limits established by their state environmental permits. On occasion, however, they may exceed the specified limits.

MassDEP regulations allow higher emissions for limited durations and under specific circumstances: during start-up, shutdown, certain malfunctions, or isolated operating "spikes."

The agency may take enforcement action when a facility releases excess emissions that are not covered by these exceptions and continuous monitoring or stack testing reveal that they:

• Pose actual harm or a significant threat to public health or the environment, or
• Indicate that facility operations and/or maintenance are deficient, or
• Suggest that air pollution control equipment is inadequate.

Depending on the circumstances, MassDEP may:

• Require the facility operator to test again or implement operational changes, or
• Issue a Notice of Noncompliance (NON) requiring corrective action by a specific date, or
• Order the facility to correct specific problems and possibly pay a financial penalty.

When emissions exceed allowable limits only barely or for a very brief period of time, MassDEP may elect to take no further action.

If a facility demonstrates a chronic pattern of noncompliance or is found to be willfully violating the law, MassDEP has the option of referring the case to the Massachusetts Attorney General or the U.S. Environmental Protection Agency (EPA). 

See Additional Resources below for additional information.