What is Used Oil?
Used oil is any oil that has been refined from crude oil or any synthetic oil that has been used and, as a result of such use, is contaminated by physical or chemical impurities. To be defined as used oil by EPA, a substance must meet three criteria.
The first criterion for identifying used oil is based on the origin of the oil. Used oil must be refined from crude oil or made from synthetic materials. Animal and vegetable oils are excluded from EPA's definition of used oil.
The second criterion is based on whether and how the oil is used. Oils used as lubricants, hydraulic fluids, heat-transfer fluids, buoyants and for other similar purposes are considered used oil. Unused oil, such as bottom clean-out waste from virgin fuel oil storage tanks or virgin fuel oil recovered from a spill, do not meet EPA's definition of used oil because these oils have never been used. EPA's definition also excludes products used as cleaning agents or solely for their solvent properties, as well as certain petroleum-derived products like antifreeze and kerosene.
The third criterion is based on whether or not the oil is contaminated with either physical or chemical impurities. In other words, to meet EPA's definition, used oil must become contaminated as a result of being used. This aspect of EPA's definition includes residues and contaminants generated from handling, storing and processing used oil. Physical contaminants could include metal shavings, sawdust and dirt. Chemical contaminants could include solvents, halogens and saltwater. If used oil is mixed with hazardous waste, it will have to be managed as a hazardous waste. To be safe, used oil should not be mixed with other wastes. Additionally, used oil should be analyzed routinely (at least annually) or whenever the oil stream changes to ensure proper waste profiling.
Recycling Used Oil
One of the more popular methods of used oil recycling, especially for machine lubricants and cooling/ quenching systems, is reconditioning the oil on site. This involves removing impurities from the used oil using a commercial oil filtration system. While this form of recycling might not restore the oil to its original condition, it does prolong its life.
A more sophisticated reuse method is re-refining. Used oil can be re-refined, which involves treating used oil to remove impurities so that it can be used as a base stock for new lubricating oil. Re-refining prolongs the life of the oil resource indefinitely. This form of recycling is the preferred option because it closes the recycling loop by reusing the oil to make the same product that it was when it started out and, therefore, uses less energy and less virgin oil. Re-refining used oil takes only about one-third the energy of refining crude oil to lubricant quality. It takes 42 gallons of crude oil, but only one gallon of used oil, to produce 2.5 quarts of new, high-quality lubricating oil.
Additionally, used oil can be processed and burned for energy recovery, which involves removing water and particulate so that used oil can be burned as fuel to generate heat. This form of recycling is not as preferable as methods that reuse the material because it only enables the oil to be reused once. Nonetheless, valuable energy is provided. Lastly, the used oil can be inserted into a petroleum refinery, which involves introducing used oil as a feedstock into either the front end of the process or the coker to produce gasoline and coke.
Know Your Transporter and Used-Oil Treatment Facility
It's not uncommon for used-oil transporter tankers to mix wastes from one company to the next. For example, a 2000-gallon used-oil tanker truck picks up 1,000 gallons of used oil from company X. When the truck arrives at your location to pick-up used oil to top-off the tanker, your used oil is mixed with Company X's material. This activity creates liability for both companies. Should the used oil be denied by the reclamation company or, worse yet, used for unintended processes, such as dust suppressant for roadways or as fuel in low efficiency systems like greenhouses, both companies incur the exposure risk. Therefore, it's good practice to not only know and document your used-oil management processes, but also hold your transporter and reclamation facilities to high standards. Ask for their standard operating procedures, audit their processes, and remember the cheapest alternative is not necessary the most cost effective in the long term.