What is an oil?
This might seem like a simple question, but there are many possible answers… and sometimes an oil is not always an oil.
Let’s begin with the dictionary definition (though this is always a bit venturesome when discussing environmental regulations). The Oxford English Dictionary defines the noun ‘oil’ as:
- A viscous liquid derived from petroleum, especially for use as a fuel or lubricant
1.1 Petroleum.
1.2 [with modifier] Any of various thick, viscous, typically flammable liquids that are insoluble in water but soluble in organic solvents and are obtained from animals or plants.
‘potatoes fried in vegetable oil’
1.3 A liquid preparation used on the hair or skin as a cosmetic.
‘suntan oil’
1.4 [Chemistry] Any of a group of natural esters of glycerol and various fatty acids that are liquid at room temperature.
Compare with fat
- Oil paint.
‘a portrait in oils’
Even in the OED, then, ‘oil’ has multiple meanings, but we need not concern ourselves with suntan oils or oil paints (unless, arguably, someone has more than 1,320 gallons of above-ground suntan oil storage, but we will leave that question for Florida or perhaps the Jersey Shore).

Now let’s look at some of the regulatory definitions of oil that apply in Massachusetts. The narrowest definition is found in the Resource Conservation and Recovery Act and its state-level analogues such as 310 CMR 30.00:
Oil means petroleum in any form including crude oil, fuel oil, petroleum derived synthetic oil and refined oil products, including petroleum distillates such as mineral spirits and petroleum naphtha composed primarily of aliphatic hydrocarbons. It does not mean petrochemicals or animal or vegetable oils. (310 CMR 30.010)
The same regulations subsequently also define a handful of subcategories of oil, such as “unused waste oil,” “used waste oil” and “used oil fuel”, and the ‘mixture’ rule applies, but basically we have 1) petroleum only (and thereby excluding olive oil, fish oil, lard, and rapeseed “canola” oil), and 2) not petrochemicals. Petrochemicals are separately defined in the same section as “an individual organic chemical compound for which petroleum or natural gas is the ultimate raw material, except that aliphatic hydrocarbon compounds, which maintain, after use, closed cup flashpoints equal to or greater than 140o F (and which are not otherwise a characteristic or listed hazardous waste) are oils.” This would therefore apply to compounds such as white spirits, low-aromatic solvent naphtha, or high-flash mineral spirits, referring back to the aliphatic ‘petroleum distillates’ inclusion in the oil definition.
Although RCRA distinguishes between hazardous waste and waste oil, and has separate and less stringent provisions for waste oil, Massachusetts (like many states) classifies waste oil as a state-listed hazardous waste, and applies most of the same requirements to both categories. When it comes to waste management, materials meeting this definition should be listed on a Uniform Hazardous Waste Manifest as MA-01 waste oil, or if being managed as a regulated recyclable material, as MA-97 specification or MA-98 non-specification used oil fuels. Non-petroleum oils, such as spent machining coolant mixtures containing only, say, vegetable oils or lard, would not be regulated as waste oils under these regulations, but these distinctions must generally be made based on information provided by the products’ manufacturers and knowledge of the process generating the waste. This definition would, for example, exclude waste biodiesel oil, but only if it did not contain a petroleum admixture or contaminant (pure biodiesel fuel is rarely used as a transportation or heating fuel, and most commercial grades of biodiesel are sold as biodiesel/petroleum blends). Significantly, oils that don’t contain petroleum mixtures, such as a cutting fluid that is free of ‘tramp oil,’ do not need to be counted against a hazardous waste or waste oil generator’s generation or accumulation limits.
The definition in MGL c. 21E and the Massachusetts Contingency Plan is broader, as it includes non-petroleum and animal or vegetable oils, for example fryer oils and vegetable-based hydraulic oils or synthetic cutting oils, with the mixture rule applying in some circumstances per 310 CMR 40.0352:
Oil means insoluble or partially soluble oils of any kind or origin or in any form, including, without limitation, crude or fuel oils, lube oil or sludge, asphalt, insoluble or partially soluble derivatives of mineral, animal or vegetable oils and white oil. The term shall not include waste oil, and shall not include those substances which are included in 42 U.S.C. §9601(14). (310 CMR 40.006)
The MCP also has differing Reportable Quantities for petroleum and non-petroleum oils, respectively 10 gallons and 55 gallons.
The MCP in turn separately defines ‘waste oil’ as:
[U]sed and/or reprocessed, but not subsequently re-refined, oil that has served its original intended purpose. Waste oil includes, but is not limited to, used and/or reprocessed fuel oil, engine oil, gear oil, cutting oil, and transmission fluid and dielectric fluid. (310 CMR 40.006)
The 42 USC 9601(14) citation referenced above by the MCP refers to the CERCLA list of hazardous substances (in effect reiterating that a material may either be an oil or a CERCLA substance, but not both at once), and from which petroleum oils are granted certain often-litigated exemptions originally intended to cover crude oil, but which were subsequently extended by litigation to cover refined petroleum products that were not otherwise listed under CERCLA or categorically included through CERCLA’s references to RCRA (e.g. having a flashpoint less than 140oF or failing TCLP for benzene).
This distinction is important in the legal aspects of assessment and remedial matters in Massachusetts (meaning the windy, desolate parts where lawyers predominate rather than LSPs). While the MCP applies essentially the same regulatory framework and remedial requirements for both “oil” and “hazardous material” sites, section 5(a) of the 21E statute limits liability for releases of oil falls only to current owners and operators and those who have “otherwise caused” such releases or threats of release, while liabilities for releases of hazardous materials are not so limited, and any prior owners and operators could potentially be dragged into the PRP box and dunned for cost recovery.
The definition of “oil’ used in the Clean Water Act and the Oil Pollution Act of 1990 is the broadest, since it includes a broad spectrum of non-petroleum oils, and also the most vague:
Oil means oil of any kind or in any form [and thus including mixtures], including, but not limited to: fats, oils, or greases of animal, fish, or marine mammal origin; vegetable oils, including oils from seeds, nuts, fruits, or kernels; and, other oils and greases, including petroleum, fuel oil, sludge, synthetic oils, mineral oils, oil refuse, or oil mixed with wastes other than dredged spoil. (40 CFR §112.2)
This definition even includes milk and other dairy products, since it contains fats of animal origin. Since a large spill of liquid milk products (or, for that matter, canola oil, coconut oil, or even tea tree oil if you amassed enough of it) can have a destructive effect on a river or lake easily on par with that from a similarly sized spill of fuel oil, e.g. by rapidly depleting the water’s dissolved oxygen content and thereby annihilating fish and other aquatic life in the spill area, this makes sense from a chemical and ecological perspective. In a rare spasm of regulatory praxis for farmers, however, these and other non-petroleum materials are exempted from certain requirements for containers but are still subject to requirements for contingency plans and notification of releases to water bodies. It also raises the tempting prospect of classifying deep-fat fryers as regulated “oil-filled operational equipment.”
The OPA definition is also sufficiently vague as to create confusion and some apparent contradictions, since it gives very little idea where ‘oil’ stops—if gasoline is considered an oil, what about solvent-grade toluene that is refined from oil? Under other statutes and regulations, toluene would be considered a non-oil petrochemical, but under the OPA it is arguably an oil. Or, consider an oil terminal where large quantities of oil are processed by adding dyes required by motor fuel tax regulations. The oils would be subject to SPCC and FRP requirements, but the status of the dyes themselves could be arguable.
Department of Transportation regulations (49 CFR §130.5) emulate the OPA definition but rather sensibly break it down into three separate components, for petroleum oils, non-petroleum oils, and animal or vegetable oils.
The first result of all these different definitions of a single three-letter word can be somewhat strange, semantically speaking. Hypothetically, a release of non-petroleum oil from an OPA-regulated facility (perhaps the vast strategic reserves of extra-virgin olive oil at Rachel Ray’s house) can be reported to MassDEP as a release of oil, but the recovered product and remediation waste doesn’t have to be identified as an oil on the manifest. A further hiccup is that some waste receiving facilities, such as asphalt batching plants accepting oily soil or oil product batchers and recyclers, are limited by their permits (and likely the material requirements of their end product) to petroleum products, and generally cannot accept materials contaminated by non-petroleum oils. A thermal desorption plant (where the oil is volatilized and combusted in an afterburner) would not necessarily be so limited.
The second result is, of course, that the environmental professional must remember which regulations apply when he uses the word, particul
arly if he primarily works on MCP projects and is occasionally called to assist in hazardous waste or OPA work.