The world wouldn’t be where it is now without machine shops.  Manufacturing operations such as tool and die plants, aerospace parts manufacturers, surgical fitting fabricators, firearms manufacturing, and other metalworking industries (particularly precision work) have had a long history in Massachusetts, from the founding of the Springfield Armory in 1777 through the present day.

As any good machinist knows, though, if you want to work with metal you have to know a fair amount about oil, which is used in many forms in metalworking operations.

The two kinds of oil most commonly used are:

  • Way oil, also known as lube oil, slide oil, or brown oil, is a high-grade hydraulic oil formulated with a tackifier, an additive that improves the oil’s adhesion to metal surfaces such as the hydraulic pistons or sliding surfaces found in CNC machines, lathes and other heavy machine tools, to prolong the useful life of the oil and prevent it from oozing into the working process.
  • Modern cutting fluids, sometimes called metalworking fluids, cutting lube, or cutting oils, are sprayed, misted or flowed onto machining surfaces in manufacturing for several purposes—they lubricate the cutting process and allow machines to go faster, they cool the process and prevent tip welding, where the drill bit or other machine tool overheats to the point where it welds itself onto the workpiece. These products are typically an emulsified mixture of oils and water (either water outside oil or oil outside water),  by means of an oil engineered to be water soluble, or a surfactant or detergent additive. Most cutting fluids range from 1% to 5% oil by volume, and the emulsions can remain stable for weeks. Cutting oils used in these mixtures may be petroleum based or derived from plant or animal materials (lard and fish oil are surprisingly common, especially for manufacturing food grade equipment components), or based on synthetic oils (often used in milling and grinding). High-flash kerosene is sometimes used for working with aluminum.
CNC head
Close-up view of a CNC machine and cutting fluid

In addition, some facilities use quantities of other kinds of oil, such as lubricants, rust preventatives (especially in firearms manufacturing), quench oils, and other products.

It makes economic sense to reuse cutting fluids as much as possible, but cutting fluids deteriorate and almost inevitably become contaminated with way oil and other oils, such as oil films used to protect bar stock, etc., which form separate phase liquids called “tramp oils” that float in blobs on top of a container of cutting fluid, and that would foul the process if allowed to recirculate through the system. If you let a drum of well-used waste cutting fluid sit for a few hours, more often than not a layer of tramp oil will partition out on top. Many modern CNC machines have onboard sumps in which the cutting fluid accumulates before it is recirculated, fitted with skimmers or other devices to remove separated tramp oils. Some larger facilities have central cutting fluid management systems with sophisticated tramp oil separators.

Eventually any machine shop or metalworking facility generates waste oil. In the late 1980s, EPA developed a regulatory framework for waste oils that didn’t meet the RCRA criteria for hazardous wastes (40 CFR 279), and which has been implemented by most states, in many cases along with the states’ identification of waste oil (variously defined) as a state-listed waste.

These regulations ultimately had two goals. The first was regulatory, in order to prevent the inappropriate disposal of hazardous wastes. The second reason was to provide for the beneficial reuse of oils that would otherwise have to be disposed.

Cutting fluids can also accumulate concentrations of RCRA metals (chromium, cadmium, lead, etc.) or chlorinated solvents such as perchloroethylene (PCE), trichloroethylene (TCE), or 1,1,1-trichloroethane (TCA), which were historically widely used for degreasing and cleaning metal parts before and after working on them. The older generation of consultants and manufacturing veterans remember the ‘old days’ when jet engines or other machines were dipped whole into vats of solvents for degreasing, like deep-frying a Thanksgiving turkey, and “waste oil” was historically a sort of catch-all waste stream that could contain many other things, including solvents, PCBs from transformer and hydraulic oils, pesticides and caustics. The use of waste oil containing highly toxic dioxins for oiling dirt roads is what turned Times Beach, Missouri into a ghost town. The use of solvents like PCE, TCE and TCA  has decreased greatly over the last couple decades (down by about 90% since 1991, based on data provided by the Massachusetts Toxics Use Reduction Program) but they are still used in reduced quantities and remain of concern.

Uncontaminated way oils are readily recyclable, useful for fuel blending or lube base production, and can typically be recycled as heating fuel in standard waste oil burners if no other option is economical. It’s therefore a good idea to keep spent hydraulic and way oils and tramp oils separate from cutting fluids.

Cutting fluids, by contrast, can pose a number of problems:

  • Although the percentage of oil in a cutting fluid is small, environmental regulations in many states require that the whole volume of the material be managed as a waste oil or hazardous waste, because of the RCRA “mixture rule” requirement that goes with being a listed waste. This can result in relatively small facilities generating enough oil/water mixtures to trigger Large Quantity Generator status, which comes with higher annual regulatory fees, planning and training requirements, etc.
  • On their own, dewatered non-petroleum cutting oils typically have little fuel value, limiting their reuse options, although they can be blended with other oils with higher fuel values to produce a marketable fuel product.
  • Breaking the emulsions and separating the oil from water is advantageous, but this can involve some fairly complicated chemical treatment, such as heating, acidification to a pH of roughly 2 and subsequent neutralization, or the addition of a salt or acetate. Even then the separated decant water will still likely contain some oil and may need to be evaporated, recycled into the process with new oil additives, or treated as an industrial wastewater.
  • Residual cutting fluids will also often cling to metal turnings, and well-managed shops will typically clean their turnings with a centrifuge, wringer, bath, or other means to remove most of these residues before shipping them for recycling.
  • Potentially most seriously, waste cutting fluids or their sludges can contain chemical impurities picked up during use, including metals and solvents. These contaminants can greatly increase the cost of managing the oil, ranging from “off-spec” costs for water, solids or halogens, to needing to manage the oil as a hazardous waste. Addressing these complications after they come up can cost time and money.

One common problem with waste oil is based in simple chemistry. Much of the waste oil generated by commerce and industry is reused for fuel, whether burned in the ubiquitous waste oil fired space heaters, or sent to a plant for batching, re-refining and resale. When oil containing chlorine-containing compounds is burned, the chlorinated compounds break down and the result is hydrochloric acid (HCL). This poses health hazards to workers and the public, and can also corrode and damage the oil-burning equipment. The more chlorine there is in the oil means the more acid there is in the off-gas.

EPA’s policy therefore centered on a “rebuttable presumption” that oils containing less than 1,000 parts per million (0.1%) total halogenated compounds were unlikely to have been mixed, intentionally or not, with a listed hazardous waste, while oil containing more than this threshold were considered to be hazardous unless shown not to be by further testing or generator knowledge. Most waste oil handlers will accept oil with high halogens, but will typically assess a surcharge on a sliding scale according to the halogen concentration.

Halogens are a family of chemicals including chlorine, fluorine, bromine and iodine, so called because they readily form salts (halides) with alkaline metals such as sodium (e.g. sodium chloride, calcium chloride, or potassium bromide). They also readily bond with hydrocarbons to form ‘organochlorine’ compounds, and many of the “better living through chemistry” era’s hazardous legacy products were based on organochlorine technology, whether old standbys such as DDT, perchloroethylene, pentachlorophenol, polychlorinated biphenyls, trichloroethylene, their lesser-known cousins such as Halowax or polybrominated fire retardants, or the increasingly notorious perfluorinated compounds such as the PFAS and PFOS families.

One of the problems with this approach, of course, is that oil technology has changed a great deal since the late 1980s, and in some respects the regulations and analytical methods haven’t kept pace. Many modern waste oils contain concentrations of chlorine greater than EPA’s 1,000 ppm threshold even though they aren’t contaminated with RCRA-listed solvents, or weren’t even generated at facilities where these old solvents are used at all (not even the old and sparingly-used-just-for-repair-emergencies bottle of old-formulation 3-in-1 oil (the kind loaded with trichloroethylene) that so many maintenance men kept in their toolboxes)!

Many modern synthetic or vegetable-based machine cutting oils, as used in machine shops, contain engineered chlorinated compounds in the form of biocides such as CMIT (to keep bacteria from degrading the oil) or as “EP” temperature and pressure additives (typically chlorinated paraffins, although there has been considerable regulatory whiplash over the now-aborted phase-out of shorter-chain hydrocarbons  in favor of less toxic long and very-long-chain paraffins). Let’s just emphasize that these compounds are NOT currently listed by EPA as hazardous wastes, and for the most part didn’t even exist in trade when EPA’s waste oil policy was developed in the late 1980s. It’s also worth noting that, as we discussed in a prior blog post, cutting oils that don’t contain petroleum and that aren’t otherwise a hazardous waste often do not need to be managed as a hazardous waste or state-listed waste oil.

The sticking point is that the common ‘total halogens’ analyses (SW-846 laboratory methods 9253, 9056, 9075, 9076 and the Method 9077 field test kits such as Chlor-N-Oil) report only a total concentration of all the chlorinated, brominated or fluorinated compounds in the sample, which doesn’t tell you if your oil was formulated with a non-regulated chloroparaffin or brominated ingredient, or if it somehow became contaminated with a regulated degreaser such as trichloroethylene or a nonregulated product like a chlorinated brake cleaner. “Failing” a total halogens screening test does not automatically mean your oil is a hazardous waste. Most environmental laboratories can run chemical tests for solvents or other regulated chlorinated compounds in waste oil, and this may be necessary, but the cost can be several hundred dollars per sample to cover EPA’s entire list of potentially regulated compounds.

The first step in a solution to this conundrum is, of course, plain old good recordkeeping. Safety Data Sheets, product formulation spec sheets, and other documentation that provide information on the chemical makeup of the parent product, any additives, and most particularly, what your facility doesn’t use (e.g. solvent products containing more than the 10% chlorinated hydrocarbons threshold in EPA’s listing descriptions for solvent wastes), go a long, long way towards demonstrated that the oil doesn’t contain a listed solvent, and reducing the effort and cost of testing, handling and disposing of these materials.


Some of the OTO crew participated in the Joseph Freedman Company’s seventh annual charitable Bowl-A-Thon on November 10, 2018. This is a fun annual benefit for Camphill Village, held at AMF Lanes in Chicopee, Massachusetts.
Bowling is a great sport for engineers, since it’s a community activity (that gets us away from our labs, offices and job sites), while still letting us try to solve problems (how to knock down more pins than our teammates) using our knowledge of natural science principles such as force, friction, inertia, gravity and centrifugal force.
Some of the things we learned this time around:

  1. Lighter balls are better because they don’t lose momentum and go off-course as quickly as heavier balls.
  2. Aim for the gap right after the lead pin in the triangle for best resultsrightpocket
  3. Centrifugal force (spin) matters but is much easier said than done.index
  4. Nice and easy does it.
  5. Don’t bowl better than the boss….unless you’re bowling for the boss.

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:

  1. 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

  1. 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).

Unfortunately that’s crude oil from the Exxon Valdez, not tanning oil.

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.