Combustion Portal: Environmental Compliance for Combustion Processes

OSWIOther Solid Waste Incinerators (OSWI)

Other Solid Waste Incinerators (OSWI) are basically incinerators that due to their small size or other characteristics are not covered under other incinerator air emissions regulations, such as Municipal Solid Waste Combustors. OSWI units are most often used for burning municipal waste collected from the general public and from residential, commercial, institutional, and industrial sources. They may be found at municipalities, correctional institutions, primary and secondary schools, churches, camps and national parks.

Air Emissions Regulations

  • 40 CFR Part 60 Subpart EEEE - New Source Performance Standards (NSPS) for Other Solid Waste Incineration Units for Which Construction is Commenced After December 9, 2004, or for Which Modification or Reconstruction is Commenced on or After June 16, 2006.

  • 40 CFR Part 60 Subpart FFFF - Emission Guidelines (EG) and Compliance Times for Other Solid Waste Incineration Units That Commenced Construction on or Before December 9, 2004.

The U.S. Environmental Protection Agency (EPA), under section 129 of the Clean Air

Act (CAA), is required to regulate emissions from certain categories non-hazardous solid waste incinerators. Section 129 requires EPA to set numerical emissions limitations of nine pollutants from Other Solid Waste Incineration (OSWI) units. The nine pollutants are:

  • cadmium (Cd)
  • carbon monoxide (CO)
  • total mass basis dioxins/furans (TMB PCDD/PCDF) and toxic equivalency basis dioxin/furans (TEQ PCDD/PCDF)
  • hydrogen chloride (HCl)
  • lead (Pb)
  • mercury (Hg)
  • nitrogen oxides (NOx)
  • particulate matter (PM)
  • sulfur dioxide (SO2)

All standards established pursuant to CAA Section 129(a)(2) must reflect maximum achievable control technology (MACT). The MACT "floor," or minimum level of stringency set forth differing levels of minimum stringency that EPA’s standards must achieve, depending on whether they regulate new or existing sources.

The CAA allows EPA to subcategorize a source category based on differences in class, type, or size. The OSWI regulation is subcategorized by unit type:

  • Institutional Waste Incinerators (IWI)
  • Very Small Municipal Waste Combustors (less than 35 tons per day)

Institutional Waste Incineration (IWI) units are incinerators located at institutions (e.g., public or private school; college or university; church or civic organization; fire or police department; town, city, county, State or Federal government; etc.) that burn non-hazardous solid waste generated on site.

Very Small Municipal Waste Combustion (VSMWC) units are incinerators that burn less than 35 tons per day of municipal solid waste. Municipal solid waste is nonhazardous solid waste or refuse collected from residential, commercial, institutional, and industrial sources. Large municipal waste combustion units are already regulated under two other rules (see Municipal Solid Waste Combustors).

The enforcement authority is different for the NSPS and EG. The NSPS are directly enforceable federal regulations, and under CAA section 129 (f)(1), become effective 6 months after promulgation. The EG are not themselves directly enforceable. Rather, the EG are implemented and enforced through either an EPA-approved state plan or a promulgated federal plan. States are required to submit a plan to implement and enforce the EG to EPA for approval not later than 1 year after EPA promulgates the EG (CAA section 129 (b)(2)). The state plan must be "at least as protective as" the EG and must ensure compliance with all applicable requirements not later than 3 years after the state plan is approved by EPA, but not later than 5 years after the relevant EG are promulgated. If a state does not develop an approvable implementation plan, EPA will promulgate a federal plan that will apply to existing OSWI units located in that state.

Solid Waste

The burning of waste in incinerators creates residual ash (fly ash and bottom ash), which can contain any of the elements that were originally present in the waste. Incinerators reduce the need for landfill capacity because disposal of ash requires less land area than unprocessed waste. However, because ash and other residues from incinerators may contain toxic materials such as metals, the combustion residuals wastes must be tested regularly to assure that the wastes are safely contained to prevent toxic substances from migrating into groundwater supplies. Under RCRA and state regulations, incinerator ash must be sampled and analyzed regularly to determine whether it is hazardous or not. Hazardous ash must be managed and disposed of as hazardous waste. Non-hazardous ash may be disposed of in a municipal solid waste landfill, an ash monofill or recycled.

More resources for solid waste:

Water Resources Protection

Incinerators generate wastewater associated with processes such as cooling tower blowdown, flue gas treatment, and washdowns. Discharges of wastewater are regulated under the Clean Water Act (CWA). Facilities which discharge indirectly through a publically owned treatment works (POTW) are regulated under the Pretreatment Program, which insures that facilities pretreat wastewater to remove pollutants which would affect the pollutant removal ability of the POTW. Facilities that discharge process or non-process wastewater directly streams, rivers, etc. are regulated under the National Permit Discharge Elimination System (NPDES) and must obtain coverage under a General Permit or an Individual Permit.

In addition to compliance with rules covering wastewater generated by incinerators, applicable facilities must be concerned with stormwater runoff.

Each of these topics is summarized below with links to related web pages and documents.

Indirect Discharge

Facilities with SSI incinerators that discharge wastewater into a sewer system that leads to a municipal treatment plant, also known as Publicly Owned Treatment Works (POTW) are indirect dischargers. The POTW typically is owned by the local municipality or a regional board or sewer authority.

In response to potential problems caused by industrial wastewater being discharged into POTW's, federal pretreatment regulations were developed. These regulations apply to all municipal, industrial and commercial facilities. Local POTW's with approved pretreatment programs have responsibility for enforcing pretreatment requirements. Otherwise, the rules are enforced by the state or EPA regional authority.

All indirect dischargers must meet national General Pretreatment Regulations (40 CFR 403). Additionally, certain types of facilities must also meet applicable categorical pretreatment standards. When a pollutant, discharged by an indirect discharging industry is not specifically limited by pretreatment standards, it is up to the state or local regulatory agency to develop local limits or to determine other appropriate means to control its discharge.

More information on indirect discharges to POTW's:

Direct Discharge

Facilities with OSWI units that discharge process wastewater or cooling water to surface waters are direct dischargers. Direct dischargers must obtain a permit under EPA's National Pollutant Discharge Elimination System (NPDES) program. A NPDES permit sets limits on the amount of specific pollutants that can be discharged to surface waters.

Some states offer general permits for non-contact process water (e.g., cooling water). The purpose of the general permit is to provide a streamlined NPDES permitting process for certain classes or categories of industrial point source discharges. Coverage under a NPDES general permit is unique in that a facility operates and discharges under the requirements of the applicable general permit rule rather than the requirements of an individual permit. Check with your state environmental agency to determine if a general permit is applicable to your facility.

More information on direct discharge NPDES permits:


Leachate from waste unloading and storage operations caused by exposure to precipitation and from residual liquids in the waste itself may contain organic matter, nutrients, metals, pathogens, and hazardous chemicals. Stormwater regulations promulgated under the Clean Water Act help prevent these materials from polluting nearby streams and other water courses. Operations such as OSWI units must develop a Stormwater Pollution Prevention Plan (SWPPP), obtain coverage under a NPDES stormwater permit, and implement methods of controlling stormwater pollution, including best management practices. For more information about the Stormwater Program, visit the Stormwater Basic Information page.

Throughout most of the nation, U.S. EPA has delegated the stormwater program to the states to administer as they see fit, so long as minimum federal requirements are met. For more information on state stormwater rules see the Industrial Stormwater State Resource Locator. The locator will help you find state-specific information on permitting, technical resources and points of contact.

More information on stormwater:

Spill Prevention, Control and Counter Measures

EPA promulgated the Spill Prevention, Control and Counter Measures (SPCC) rule to reduce the risk of damaging our waterways from oil spills. These rules are applicable to a very wide rage of facilities and operations, including fuel oil storage tanks for incinerators. The rule requires specific facilities to prepare, amend, and implement SPCC Plans. The SPCC rule is part of the Oil Pollution Prevention regulation, which also includes the Facility Response Plan (FRP) rule.

An SPCC Plan is required for facilities which due to their location, could reasonably be expected to discharge oil to surface water or adjoining shorelines and have:

  • Total aboveground storage capacity of 1,320 gallons or more of oil (however, only containers or oil-containing equipment with a capacity equal to or greater than 55 gallons count toward the threshold); or

  • A total oil underground storage capacity of 42,000 gallons or more (however, underground storage tanks subject to regulation under RCRA [40 CFR 280 or 281] are not included); or

  • Been required by the EPA to prepare and implement an SPCC Plan.

The SPCC regulations require the facility owner/operator to prepare and implement an SPCC plan for their facility. This plan must be well thought out and prepared in accordance with good engineering practices. It must document the location of storage vessels, types of containment, dangers associated with a major release of material from the tanks, types of emergency equipment available at each site, and procedures for notifying the appropriate regulatory and emergency agencies.

To assist facility owners and operators with SPCC compliance, EPA has published a useful document: Spill Prevention, Control, and Countermeasure (SPCC) Regulation.

More resources on SPCC:

Applicable rules: 40 CFR 112.

Pollution Prevention

EPA encourages practices that reduce the amount of waste needing to incinerated, such as waste prevention, recycling, and composting.

  • Source reduction, or waste prevention, is designing products to reduce the amount of waste that will later need to be thrown away and also to make the resulting waste less toxic.
  • Recycling is the recovery of useful materials, such as paper, glass, plastic, and metals, from the trash to use to make new products, reducing the amount of new raw materials needed.
  • Composting involves collecting organic waste, such as food scraps and yard trimmings, and storing it under conditions designed to help it break down naturally. This resulting compost can then be used as a natural fertilizer.

Currently, in the United States, 33.8 percent is recovered and recycled or composted, 11.9 percent is burned at combustion facilities, and the remaining 54.3 percent is disposed of in landfills.

More OSWI Resources

National Solid Waste Management Association. NSWMA is a trade association representing for-profit companies in North America that provide solid, hazardous and medical waste collection, recycling and disposal services, and companies that provide professional and consulting services to the waste services industry.

Association of State and Territorial Solid Waste Management Officials (ASTSWMO). An organization supporting the environmental agencies of the States and trust territories. ASTSWMO focuses on the needs of State hazardous waste programs; non-hazardous municipal solid waste and industrial waste programs; sustainability, recycling, waste minimization, and reduction programs; Superfund and State cleanup programs; waste management and cleanup activities at federal facilities; and underground storage tank and leaking underground storage tank programs.

National Overview: Facts and Figures on Materials, Wastes and Recycling. EPA began collecting and reporting data on the generation and disposition of waste in the United States more than 35 years ago. The Agency uses this information to measure the success of materials management programs across the country and to characterize the national waste stream. These Facts and Figures are current through calendar year 2018.