Combustion Portal: Environmental Compliance for Combustion Processes

CISWIIndustrial and Commercial Solid Waste Incinerators (CISWI)

A CISWI unit is any device used to burn solid waste at a commercial or industrial facility. This does not include municipal solid waste combustors, which are covered under separate rules (see MWC rules). Also, a combustion device that is otherwise subject to CISWI, but combusts material solely for the purpose of energy recovery, i.e., the process of recovering thermal energy from combustion for useful purposes such as steam generation or process heating, is not currently subject to CISWI.

Examples of CISWI units include:

  • Units designed to discard solid waste
  • Energy recovery units designed to recover heat that combust solid waste
  • Waste burning kiln that combust solid waste in the manufacture of a product

Air Emissions Regulations

Section 129 of the Clean Air Act directs the Administrator to develop regulations under section 111 of the Act limiting emissions of nine air pollutants (i.e., particulate matter, carbon monoxide, dioxins/furans, sulfur dioxide, nitrogen oxides, hydrogen chloride, lead, mercury, and cadmium) from four categories of solid waste incineration units: municipal solid waste; hospital, medical and infectious solid waste; commercial and industrial solid waste; and other solid waste.

EPA promulgated the new source performance standards (NSPS) and emission guidelines (EG) to reduce air pollution from commercial and industrial solid waste incineration (CISWI) units, for Subparts CCCC and DDDD on December 1, 2000. Those standards and guidelines applied to incinerators used by commercial and industrial facilities to burn non-hazardous solid waste. The NSPS and EG were designed to substantially reduce emissions of a number of harmful air pollutants such as lead, cadmium, mercury, and dioxins/furans, which are known or suspected to cause adverse health and environmental effects.

On March 21, 2011, EPA promulgated the revised NSPS and EG to address voluntary remand that was granted in 2001 and the vacatur of the CISWI definition rule in 2007. In addition, the revised standards accounted for the 5-year technology review of the new source performance standards and emission guidelines required under Section 129. Following promulgation of the 2011 CISWI rule, EPA received petitions for reconsideration requesting to reconsider numerous provisions in the 2011 CISWI rule. EPA granted reconsiderations on specific issues and promulgated CISWI reconsideration rule on February 7, 2013. Subsequently, EPA received petitions to further reconsider certain provisions of the 2013 NSPS and EG for CISWI units. On January 21, 2015, EPA granted reconsideration on four specific issues and finalized the reconsideration of the CISWI NSPS and EG on June 2, 2016. In September 2024, EPA issued the final federal plan to implement the emission guidelines in states without their own state plans.

The current applicable rules include:

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 CISWI regulation is subcategorized by unit type:

  • Incinerators
  • Energy Recovery Units (Solid)
  • Energy Recovery Units (Liquid)
  • Waste Kilns
  • Small Remote

CISWI units are distinct operating units of any commercial or industrial facility that combusts, or has combusted in the preceding six months, any solid waste as defined in 40 CFR Part 241. If the operating unit burns materials other than traditional fuels as defined in 40 CFR 241.2 that have been discarded, and there are no associated records as required by 40 CFR 60.2175(v), the material is solid waste, and the operating unit is a CISWI unit. CISWI does not include Municipal Waste Combustors, which are covered under separate rules. A combustion device that is otherwise subject to CISWI but combust material solely for the purpose of energy recovery (the process of recovering thermal energy from combustion for useful purposes such as steam generation or process heating), is not currently subject to CISWI.

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 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 is promulgated. If a state does not develop an approvable implementation plan, EPA will promulgate a federal plan that will apply to existing CISWI 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, 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 CISWI 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 CISWI incinerators 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:

Stormwater

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, salts, 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 CISWI incinerators 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.

General Resources for CISWI Incinerators

None located.