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In the United States, hazardous wastes are subject to regulations mandated by the Resource Conservation and Recovery Act (RCRA). Every month, we provide clear, in-depth guidance on a different aspect of the RCRA regulations. The information presented here is an excerpt from McCoy’s RCRA Unraveled, 2023 Edition.

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Introduction to Solid Wastes

When Congress passed the RCRA statute in 1976, they included a definition of “solid waste”:

“[A]ny garbage, refuse, sludge from a waste treatment plant, water supply treatment plant, or air pollution control facility, and other discarded material, including solid, liquid, semisolid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations, and from community activities….” [Emphasis added.] [RCRA Section 1004(27)]

From this definition, it appeared to EPA that Congress intended solid wastes to be discarded materials. Therefore, when determining what constituted a solid waste, the agency first had to consider the universe of “discarded materials.” As EPA put it when it first issued the RCRA regulations:

“A review of both RCRA and its legislative history indicate that Congress intended to regulate four broad categories of materials as solid wastes under RCRA, and particularly Subtitle C, irrespective of their ultimate disposition. The common thread linking all these materials is that they are ‘sometimes discarded.’ Because they are ‘sometimes discarded,’ they not only fall within the general rubric ‘waste,’ but also may become part of the ‘discarded materials disposal problem’…which Congress sought to remedy under RCRA.” [May 19, 1980; 45 FR 33093]

Discarded materials

The four categories of “discarded materials” identified by the agency are [45 FR 33093]:

  1. Garbage, refuse, and sludge—Congress apparently regarded these materials as waste, regardless of their disposition.
  2. Materials that are thrown away, abandoned, or destroyed—This category includes those materials that are intended to be thrown away, abandoned, or destroyed as well as those that actually are so managed.
  3. Spent materials—EPA referred to these materials as “wastes which have served their intended purpose…. While acknowledging that some of these post-consumer wastes might be recycled…, Congress also recognized that they were sometimes discarded and therefore were wastes.” Included in this category are waste solvents, waste acids, used drums, and waste oil.
  4. Tars, residues, slags, and other materials that are incidentally generated as part of a manufacturing or mining process—These incidental residues, as we call them, consist of the “waste by-products [from] the nation’s manufacturing processes.”

To illustrate EPA’s concepts of what constitutes a discarded material, look at the hypothetical manufacturing plant in Figure 1. This facility produces products; they could be automobiles, chemicals, pharmaceuticals, fuels, electricity, airplanes, computers, nuclear weapons, etc. It also produces a number of waste streams. We will classify all of the materials that come out of the plant with respect to the four categories of discarded materials.

Figure 1


The RCRA regulations do not apply to products that are used for their intended purpose. Raw materials are purchased and stored in warehouses, and the plant then uses these materials in its manufacturing processes to make products that it sells. Both the raw materials and products are being used for their intended purpose, and RCRA has no say in the transportation, storage, use, or other management of those materials. [RO 11398, 11501]

As an example, suppose the plant buys a pesticide for pest control. Although the pesticide is used in accordance with the directions on the label, some pesticide residue remains in the soil of the plant yard. As long as the product was used for its intended purpose, RCRA doesn’t regulate that activity or resulting contamination. [January 4, 1985; 50 FR 628, RO 11291, 12357] Some other environmental statute might apply to the pesticide’s use (such as the Federal Insecticide, Fungicide, and Rodenticide Act—FIFRA), but not RCRA.

One potential concern regarding products under RCRA is when they aren’t used for their intended purpose. For example, no matter how careful plant personnel are, some raw materials and products are bound to be spilled from time to time. Raw materials and/or products are also discarded occasionally if they get too old, are no longer needed, etc. If a product is spilled (and cannot be reclaimed) or discarded, it is considered to be discarded material, and RCRA Subtitle C potentially applies.

The RCRA statute actually consists of two parts that are of interest here: Subtitle C and Subtitle D. In Subtitle C, Congress specified the requirements for managing hazardous waste. Spills and discarded product are potentially regulated under the Subtitle C hazardous waste provisions. If hazardous, they will have to be managed in Subtitle C units (e.g., a hazardous waste incinerator or hazardous waste landfill). All of the materials exiting the plant that are potentially subject to RCRA Subtitle C are indicated by solid lines in Figure 1.

RCRA Subtitle D governs nonhazardous waste. For example, trash will also be generated in the manufacturing plant. These office, packaging, and cafeteria wastes (e.g., waste plastic, cardboard, paper, orange peels) are regulated under RCRA, but it is the Subtitle D, nonhazardous provisions that apply. Typically, these wastes will be placed in a dumpster or other container and will eventually be recycled or managed in a Subtitle D, nonhazardous waste combustor or landfill. Materials not subject to RCRA or subject only to the Subtitle D provisions are indicated by dashed lines in Figure 1.

Garbage, refuse, and sludge

Garbage and refuse make up the facility’s trash stream that we mentioned previously; these discarded materials will be disposed of in a Subtitle D facility.

A “sludge” is actually a defined term in the RCRA regulations (that’s why it’s in quotation marks in Figure 1). In essence, “sludges” are residues from either water or air pollution control devices. [RO 11879]

In the manufacturing plant, scrubbers may be installed on the stacks from the boilers, process heaters, and furnaces that are used in manufacturing operations. Air emissions from manufacturing operations are generally subject to the Clean Air Act (CAA)—not RCRA. RCRA is limited to regulating gaseous emissions from waste management activities. However, residues from the scrubbers (e.g., fly ash, slurries, scrubber water) are usually disposed of and are discarded materials. The residues from the scrubber, which is an air pollution control device, are considered “sludges” and are potentially subject to RCRA Subtitle C.

Sludges are also typically generated during onsite treatment of process wastewater. Tanks and ponds used to treat this wastewater are water pollution control devices, since their purpose is to treat the water to make it amenable for discharge. Thus, residues from these devices also meet the definition of “sludges,” as noted in Figure 1. Sludges often contain toxic substances, so EPA wants to regulate their management under RCRA (when discarded or recycled).

Materials that are thrown away, abandoned, or destroyed

A number of the waste streams generated in the manufacturing plant fall into this category of discarded materials. If spilled or discarded product is hazardous and cannot be reclaimed, it will be thrown away or abandoned in a hazardous waste landfill or possibly destroyed in a hazardous waste incinerator.


Most manufacturing facilities produce wastewater. As shown in Figure 1, process wastewater, often after onsite treatment, can be managed in a number of different ways. But no matter how it is managed, the plant is trying to get rid of it; it is being thrown away or abandoned. Several possible wastewater management scenarios are as follows:

  • Wastewater can be discharged to surface water of the United States (e.g., a lake or river). The discharge is regulated under a Clean Water Act (CWA) program called the National Pollutant Discharge Elimination System (NPDES) program. It is the NPDES permit that limits or controls what is discharged from the facility into the waters of the United States. RCRA Subtitle C potentially applies to the management of the wastewater from its point of generation (where it comes out of the manufacturing process) to the point where it is actually discharged. At the point of discharge, however, the wastewater is subject to the CWA. Thus, an interface or handoff exists between RCRA and the CWA at the discharge point.
  • Wastewater is sometimes abandoned or thrown away by being discharged into a domestic sewer line that leads to a publicly owned treatment works (POTW). In this case, the wastewater is simply mixed with domestic sewage for subsequent treatment in a public sewage treatment plant. Again, RCRA Subtitle C potentially applies to the wastewater from its point of generation until it is discharged into the sewer line. At that point, RCRA stops, and the CWA regulates the wastewater flowing to the POTW. Standards established under the CWA pretreatment program limit or control what can be put into the sewer line. So, another RCRA/CWA interface is associated with this wastewater management option.
  • A third management option for wastewater generated at the plant is to get rid of it by simply injecting it into an underground well. This practice is common in certain parts of the United States, such as Texas, Louisiana, Indiana, and Ohio. Underground injection wells are not regulated under RCRA, but under the Safe Drinking Water Act (SDWA). In this situation, management of the wastewater is potentially subject to RCRA Subtitle C from its point of generation until it is injected. At that point, the SDWA takes over, delineating another interface between RCRA and a separate environmental program. Even after injection, however, the wastewater may continue to be a hazardous waste.
  • Finally, wastewater can be managed in onsite evaporation ponds. In this option, which isn’t used very often for hazardous wastes, no discharge of wastewater actually occurs—it’s just evaporated. One of the reasons this management practice is utilized infrequently for hazardous wastewater is that the evaporation ponds would be hazardous waste surface impoundments (which are regulatory nightmares). The wastewater remains potentially subject to RCRA Subtitle C from its point of generation through and including its storage/treatment in the evaporation ponds. Additionally, CAA regs may apply to this scenario, since evaporation of contaminants into the air may be occurring.

Process wastes

Process wastes are frequently generated at manufacturing facilities. These could be liquid, semisolid, or solid waste streams. At this hypothetical plant, some high-organic process waste is treated onsite. The process waste is potentially subject to Subtitle C regulation from the point it exits the manufacturing unit all the way through the treatment process. If the process waste meets the definition of a hazardous waste, the facility is conducting hazardous waste treatment, which usually requires a RCRA permit. The treatment selected at this plant is onsite incineration, due to the waste’s high organic concentration. Incinerating the waste constitutes destroying it, making it a discarded material.

Gaseous emissions from the incinerator stack are subject to regulation under RCRA as well as the CAA (creating another interface between environmental statutes/regulations). These emissions will be treated to meet certain contaminant concentrations and then will be discharged to atmosphere; that is, the gaseous emissions will be thrown away (abandoned).

Gaseous emissions from manufacturing operations

We mentioned previously that gaseous emissions will be generated from manufacturing operations. Like those from the waste incinerator, these emissions will be discarded by being thrown away or abandoned. In general, the only regulations that apply to these gaseous emissions are those promulgated under the CAA.

Obsolete chemicals

The last waste stream that fits under this category of discarded materials is obsolete chemicals. There may be some old or unwanted raw materials or products sitting in plant warehouses. Because the facility knows it’ll never use or sell them, they are wastes the plant hasn’t yet sent for disposal. These obsolete chemicals are being abandoned or they are intended to be thrown away. In either case, they are considered discarded materials.

Spent materials

A maintenance shop at the facility may generate spent solvents, used oil, paint-related wastes, and more. These wastes fit into the spent materials category of discarded materials and are thus very likely to be subject to Subtitle C regulation, even if the facility usually recycles them. Residues from maintenance activities are common RCRA hazardous wastes.

Incidental residues

Finally, a slag is generated at the facility. These wastes are common at steel plants or metal refineries. Such incidental residues are simply stored in a slag pile that extends for many acres across the plant site. These slags often contain leachable heavy metals, and EPA is concerned about their management. Incidental residues like these are discarded materials because they are being abandoned.

“Discarded materials” is a very broad net

By looking at all of the materials generated at a hypothetical manufacturing plant (Figure 1), we have determined, from a practical standpoint, “discarded materials” are potentially anything that comes out of a facility other than products used for their intended purpose. EPA is concerned about discarded materials that have the potential to enter or contaminate the environment. This includes materials intended for discard but are being stored instead (potentially to avoid disposal costs). As we noted, this might include raw materials or products that are no longer usable and cannot be reclaimed or recycled.

From EPA’s perspective, a discarded material can also be something that will be sent for recycling, not disposal. For example, the spent solvents and used oil coming out of a maintenance shop will more than likely be recycled; but, they are still considered discarded materials, because these materials are “sometimes discarded.” [45 FR 33093]


Topic: Hazardous Waste Lamps

©2023 McCoy and Associates, Inc. All rights reserved.

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Considerable care has been exercised in preparing this document; however, McCoy and Associates, Inc. makes no representation, warranty, or guarantee in connection with the publication of this information. McCoy and Associates, Inc. expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal law or regulation with which this information may conflict. McCoy and Associates, Inc. does not undertake any duty to ensure the continued accuracy of this information.

This document addresses issues of a general nature related to the federal RCRA regulations. Persons evaluating specific circumstances dealing with the RCRA regulations should review state and local laws and regulations, which may be more stringent than federal requirements. In addition, the assistance of a qualified professional should be enlisted to address any site-specific circumstances.