February 14, 2019

Used Oil Mixtures Enjoy Reduced Regulations

During standard operations, you may find your used oil mixed with, or contaminating, other materials such as fuels, refrigerants, absorbent pads, compressed air, and numerous other materials in use at your facility. The status of these oily mixtures doesn’t always follow the hazardous waste mixture rules found in §261.3(a), (b), and (g). We look at a few examples and provide EPA guidance to illuminate these issues.

Used Oil Mixed With Fuels

Assuming the mixture will be recycled (i.e., burned for energy recovery), EPA allows mixtures of used oil and fuels (or fuel products) to continue to be managed under Part 279. [§279.10(d)(1)] Easy. But, there could be a practical issue with purposely mixing these materials. When a used oil recycler visits your facility to pump out your containers and tanks filled with used oil, are they interested in the oil or the gasoline it is mixed with? For this reason, we caution facilities about mixing other materials, even fuels, into their used oil as your used oil recycler may not want the mixture. Check with your used oil recycler first.

There is an exception to the “used oil/fuel mixture managed as used oil” rule. A generator may mix used oil and diesel fuel onsite for use in the generator’s own vehicles and manage the mixture as a fuel. The mixture would no longer be subject to Part 279. [§279.10(d)(2)] While the used oil/diesel mixture is not subject to RCRA regulations after mixing, other applicable regulations (e.g., Clean Air Act standards) concerning the management or burning of such mixtures apply. Before mixing, the standards for used oil generators (Part 279, Subpart C) apply to the used oil. A few years after the used oil regulations were promulgated, EPA expanded this exception at §279.10(d)(2) to include mixtures of used oil and JP-8, a specific type of jet fuel. [RO 14305]

Used Oil-Contaminated Materials

What do you do when used oil is spilled? Clean it up immediately, of course. [§279.22(d)] Now you need to manage the used oil-contaminated absorbent wipes or kitty litter you threw down to soak up the spill. There are two categories this mixture may fall into, depending on whether or not the mixture contains visible signs of free-flowing oil. [§279.10(c)]

  1. Materials that contain visible signs of free-flowing oil and will be recycled are regulated as used oil until the oil is removed (i.e., until the material no longer contains visible signs of free-flowing oil). But again, there is a practical issue that must be considered. A used oil recycler that visits your site probably does not want contaminated absorbent media, rags, etc. inside your used oil storage containers/tanks. For this reason, we recommend that the used oil be separated from dripping used oil-contaminated materials: the used oil can then be managed under Part 279 and the de-oiled material under the applicable solid and hazardous waste regulations.
  2. Materials that do not contain visible signs of free-flowing oil are not used oil subject to Part 279. Rather, the materials are subject to the applicable solid and hazardous waste regulations.

These two provisions hold true whether the used oil-contaminated material is an absorbent used for cleanup, rags, tank bottoms, oil filters, or anything else. As with used oil/fuel mixtures discussed above, however, there is an exception to these two provisions. Materials that contain, or are contaminated with, used oil continue to be regulated as used oil under Part 279 if they will be burned for energy recovery. [§279.10(c)(2)] This exception applies regardless of whether or not the materials contain visible signs of free-flowing oil. Let’s look at some examples:

Steel turnings generated during machine shop operations are coated with cutting oil (used cutting oil is considered used oil). What is the regulatory status of the used oil-coated turnings?

The steel turnings coated with used oil would be regulated as used oil if they were visibly dripping with used oil. Once the used oil has been removed so that they no longer contain visible signs of free-flowing oil, they may be managed as scrap metal if recycled. [RO 11184, 11783, 13639]

Solids are building up in the bottom of an aboveground used oil storage tank. These bottoms exhibit the toxicity characteristic for benzene and chromium. What is their regulatory status if they will be removed and burned for energy recovery? Is there any time frame triggering their removal?

Materials containing or otherwise contaminated with used oil are considered used oil when they are recycled by burning for energy recovery. [§279.10(c)(2), 57 FR 41585] This applies regardless of whether the materials contain visible signs of free-flowing oil. As is the case with all used oils sent for recycling, the fact that the tank bottoms exhibit one or more characteristics of hazardous waste does not alter their status as used oil per §279.10(a). [RO 11808, 13697] Because these tank bottoms from the used oil storage tank qualify as used oil, no accumulation time limit applies. [57 FR 41587]


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This document addresses issues of a general nature related to the federal environmental regulations. Persons evaluating specific circumstances dealing with the environmental 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.