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The service station next to my office saves the used oil from oil changes to burn in a special heater in the colder months.

It is my understanding that used motor oil can be recycled in a number of ways:

  1. refined to create new lubricants
  2. used to make asphalt
  3. burned to generate electricity
  4. refined to create heating oil

Burning on site avoids all the transportation impacts associated with recycling and redistributing recycled material as well as the energy inputs required for the recycling itself. But burning in so many potentially poorly maintained heaters could cause much greater carbon and other emissions than processing in a regulated facility.

Do the benefits of recycling outweigh those costs in terms of environmental impact or sustainability. Should this used motor oil be collected and managed in a single facility rather than burned on site in many facilities?

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There are two issues with used motor oil. One is that PCAH forms Thats Poly cyclic aromatic hydrocarbons. Benzene like rings with odds and ends attached. Many are biologically active, some are carcinogenic. If burned at high temp, with sufficient oxygen, they aren't a problem. Incompletely burned they are serious problems.

The second issue are the very fine metal particles -- stuff fine enough to go through a normal oil filter. Depending on the engine, this can include babbit metal (used for bearings which has some lead in it) or elements other than iron that were alloyed with the steel. (Can include vanadium, chromium, manganese...)

If you use a centrifugal separator you can get these out of the oil.

My opinion:

Transport kills. As far as possible deal with the mess locally. Designing a good used oil burner is not rocket science. And I would rather that it be burned, than used as asphalt where the PCAH and metal is out there for the rain to leach.

Recycling into new oil is viable, but if you have to ship it significant distances, the damage of the shipping outweighs the gain from re-using it.

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