Contributed by Elizabeth Smith, Director of Waste Services, PPM Consultants
Trick Question: What is a solid… waste?
When I was in middle school, we were first introduced to the three phases of matter – solid, liquid, and gas. Simple enough, right? Fast forward to when I began my environmental science career and was first exposed to the regulations governing the proper disposal of hazardous waste, and things got a little more, let’s just say, complicated. Hazardous waste identification begins with a straightforward principle: for any material to be classified as hazardous waste, it must first meet the criteria of solid waste as defined in the Resource Conservation and Recovery Act (RCRA). Under RCRA regulations, the term “solid waste” encompasses discarded materials in solid, semisolid, liquid, or contained gaseous forms. Wait, what?
So, abandoning the “solid” teachings of my 6th grade science class, I delved into the complex (and sometimes confusing) world of hazardous waste consulting. Waste management in industrial and chemical manufacturing is crucial for compliance and environmental responsibility. It’s not always clear when a material moves from useable to discarded. Navigating the complexities of waste determination requires an understanding of what constitutes waste, when materials transition into waste (point of generation), and how to manage them responsibly.
What Is Considered Waste?
The U.S. Environmental Protection Agency (EPA) defines waste as any material that is discarded or deemed no longer usable for its intended purpose and does not qualify for exemptions or exclusions outlined in the Federal Registry at 40 CFR 261.4.
Waste may appear in many forms, including spent chemicals, industrial wastewater, wastewater treatment plant sludge, or unusable off-spec materials. A material is considered discarded when it is abandoned, recycled improperly, or inherently waste-like.
- Abandoned Materials: Items that are disposed of, incinerated, or accumulated without a clear purpose fall into this category. For instance, leftover solvents or expired reagents that are no longer needed.
- Improperly Recycled Materials: Materials that are processed in a way that violates regulatory standards—such as unauthorized handling or incomplete recycling—are considered discarded.
- Inherently Waste-Like Materials: Certain materials, like dioxin-containing residues, are deemed waste regardless of their intended use due to their extreme risk profiles.
Determining the Point of Generation
The Point of Generation is when a material officially becomes a waste, typically when it is removed from the process. Once classified as waste, the next step is determining whether it is hazardous. This classification directly influences how the material must be handled, stored, and disposed.
Hazardous Waste Categories
The EPA categorizes hazardous waste into two groups: Characteristic and Listed.
Characteristic hazardous waste (“D” code) exhibits one or more of the following traits:
- Ignitability: Materials that catch fire easily (flashpoint of less than 140 degrees Fahrenheit.)
- Corrosivity: Substances capable of corroding metals or causing severe tissue damage (e.g., acids and bases). Non-corrosive waste has a pH between 2 and 12.5.
- Reactivity: Materials prone to violent reactions or explosions (e.g., peroxides).
- Toxicity: Substances harmful to human health or the environment (e.g., lead or mercury-containing compounds). Analytical testing is required to determine toxicity.
The Toxicity Characteristic Leaching Procedure (TCLP) is used to determine toxicity. Certified laboratories perform this analysis on samples obtained from the point of generation. The TCLP simulates landfill conditions by leaching a liquid through the waste. The resulting liquid is analyzed, and results are compared against the EPA regulatory thresholds listed in 40 CFR 261.24. If any of the contaminants are above these thresholds, it carries the corresponding hazardous waste characteristic code.
Table 1
Maximum Concentration of Contaminants for the Toxicity Characteristic
| EPA HW Code | Substance | TCLP Regulatory Level (mg/L) |
| D004 | Arsenic | 5.0 |
| D005 | Barium | 100.0 |
| D018 | Benzene | 0.5 |
| D006 | Cadmium | 1.0 |
| D019 | Carbon tetrachloride | 0.5 |
| D020 | Chlordane | 0.03 |
| D021 | Chlorobenzene | 100.0 |
| D022 | Chloroform | 6.0 |
| D007 | Chromium | 5.0 |
| D023 | o-Cresol | 200.0 |
| D024 | m-Cresol | 200.0 |
| D025 | p-Cresol | 200.0 |
| D026 | Cresol | 200.0 |
| D016 | 2,4-D | 10.0 |
| D027 | 1,4-Dichlorobenzene | 7.5 |
| D028 | 1,2-Dichloroethane | 0.5 |
| D029 | 1,1-Dichloroethylene | 0.7 |
| D030 | 2,4-Dinitrotoluene | 0.13 |
| D012 | Endrin | 0.020 |
| D031 | Heptachlor (and its epoxide) | 0.008 |
| D032 | Hexachlorobenzene | 0.13 |
| D033 | Hexachlorobutadiene | 0.5 |
| D034 | Hexachloroethane | 3.0 |
| D008 | Lead | 5.0 |
| D013 | Lindane | 0.4 |
| D009 | Mercury | 0.2 |
| D014 | Methoxychlor | 10.0 |
| D035 | Methyl ethyl ketone | 200.0 |
| D036 | Nitrobenzene | 2.0 |
| D037 | Pentachlorophenol | 100.0 |
| D038 | Pyridine | 5.0 |
| D010 | Selenium | 1.0 |
| D011 | Silver | 5.0 |
| D039 | Tetrachloroethylene | 0.7 |
| D015 | Toxaphene | 0.5 |
| D040 | Trichloroethylene | 0.5 |
| D041 | 2,4,5-Trichlorophenol | 400.0 |
| D042 | 2,4,6-Trichlorophenol | 2.0 |
| D017 | 2,4,5-TP (Silvex) | 1.0 |
| D043 | Vinyl chloride | 0.2 |
It’s important to note that characteristic hazardous waste can also be considered a listed hazardous waste.
Listed hazardous wastes are identified based on where they came from (industry and/or process) and are included in EPA’s “F”, “K”, “P”, or “U” lists. Each list has a different focus and can be found in 40 CFR § 261.31 through 261.33, as described below:
- F-List: Wastes from common industrial processes, such as solvents, degreasers, or spent cleaning solutions.
- K-List: Industry-specific wastes, like wastes from petroleum refining or pesticide manufacturing.
- P-List and U-List: These contain unused chemicals that are acutely toxic (P-List) or commercial-grade (U-List).
Understanding the processes that generate waste is essential for determining if any apply to the waste.
Generator Status and Regulatory Requirements
Waste determination also plays a critical role in determining your hazardous waste generator status. Only hazardous waste determines your generator status; non-hazardous waste does not count toward generator status. It is critical to have an expert, either on your staff or through the experts at PPM Consultants, Inc. (PPM) to help you identify and quantify your hazardous waste. The amount of hazardous waste generated at a facility will determine the generator status using one of the following categories:
- Very Small Quantity Generators (VSQGs): Facilities generating less than 100 kg of hazardous waste per month.
- Small Quantity Generators (SQGs): Facilities generating between 100 and 1,000 kg of hazardous waste per month.
- Large Quantity Generators (LQGs): Facilities generating more than 1,000 kg of hazardous waste per month.
Each category carries specific requirements for recordkeeping, storage/shipping time limits, reporting, and contingency planning.
Waste determination is not just a regulatory obligation; it is an integral part of regulatory compliance, operational efficiency and environmental stewardship. Understanding when a material becomes waste, how it is classified, and the implications of that classification are essential. With careful planning, proactive strategies, assistance and support from qualified environmental consultants, like PPM, facilities can meet the challenges of waste management head-on even when the regulations seem to redefine what we understand to be “solid” fundamentals of science.