I've read some stuff about these things being used for metal casting (http://tinyurl.com/5993tx) and for economical shop heaters (http://tinyurl.com/v0zg) and I think it's a pretty sweet concept. However i'm unsure about a few things...

do fast food places still allow you to haul this stuff away for free? there's quite a bit of noise about using it for biodiesel production... are they under contracts or any weird shit to hand it over for that, or can you still come by and fill your own container up for things like this?

melting point:
what is it on average? I hear for oils its more of a "melting range". i worked at T-bell in high school and the unused oil in back was a soft solid at [indoor] room temperature, but the drums of waste out back were a moderately viscous liquid. Is this cause it was outside? I only worked there in the summer so it was probly atleast 80-85 F when I saw it.
the reason melting temp is a concern is we're toying with the idea of building a water heater that runs on the stuff that would heat a redneck hot tub (made from a round cow tank), and most of the time itd be in use it would be cold... like 30 degrees. If the oil is solid at this temp, is there anything easy and cheap you can mix in to thin it?

i would sure like to hear from anyone who has built one of these burners before and knows the ins and outs.

thanks
-Jon

For your first question, I think that highly depends on where you go. It's hard to find anyone at a FF restaurant that knows what the hell is going on. That, and they generally have to follow more procedures, being a corporate franchise.

However, if you go to your local El Greaso Pendejo Panderia, they would probably be more than happy to let you take old grease off their hands.

Depending on your rig, you might be able to get by on used motor oil. I know a guy with a welding shop who has a furnace which runs on used motor oil. I've personally brought him some old 5w-30. Im not sure if he even refines the stuff. As for acquiring used oil, try automotive service shops. Maybe even Craigslist.


As far as viscosity-altering additives, I have no idea.

All you need to do to keep the oil flowing is have some sort of heated tubing coil through the tank. Of course, you'd need a thinner fuel to get the furnace going, heating up the main tank until the oil flows easily. A lot of biodiesel or veggie oil conversions use some sort of tank heater that starts on petrodiesel and switches over to bio/veg oil once the tank is up to temp.