Check out Babington burners ... thinking of making one eventually. They allow you to burn waste oil in a jet but without the need to filter (and all the problems that go along with that) ... basically, you don't even have to fish the french fries out of the oil, because they just bounce off the burner...
i just learned something new... thanks to
@HansFranz and the other posters here. it turns out, I have a bootleg version of a Babington burner already installed in my hot tub. it normally burns kerosene, but a few mods and it could burn waste oil. (i was looking into this already).
The idea i had was to offer a contract to the local military base to get rid of their waste motor oil, on a cheaper than other local entities and use it to heat a 12 Kl (4k gal) tank of water to heat my cabin through the winter. (think outdoor water boiler without the wood.) don't get me wrong i love my wood burner, that's what brought me to this forum originally.
If i can build a larger version of the Babington burner that (edit: currently heats my) heats my outdoor bath, IE size it up to the 4K gal tank then i could conceivably only cut wood and burn wood for aesthetics.. relying upon the 4k gal tank of hot water to heat the house through the winter... originally i had thought of solar power into a hot water diversion scheme, but this seems to be more advantageous.
I can charge the local base say 70% of the going rate, and make money while receiving free fuel. if I get too much, i can stockpile for next winter and after a winter or two i can see what actual usage is. Then, if i have to much I can pay a seperate entity to dispose of the excess balancing cost per contract against any recycling fees (if needed).
if the unit is running 24/7 in the winter and I have too much excess, then expand and heat shop as well... that will really use some oil there.
and if all else fails, filter the best out, use it as bar oil and fuel for my 7.3 and then pay for removal of sludge.
brains a burning right now...