What can I do with vegetable oil after it’s been used once?
I’ve deep skillet fried chicken with a substantial amount of oil for frying. I’ve now strained it and kept it in a metal bowl. It seems a shame to dispose of this oil immediately, without using it again.
Can this oil be used more than once?
If so, how do I “keep it” until further use?
If not (or even after it’s second use) how can I dispose of it properly?
Yes, you can keep using frying oil until it smokes. Let it cool and put in an old oil bottle. Disposal: do the same, and throw it in the trash.
My mommies rule is twice then toss. Especially if you cook more than one batch. Even then, add new oil. 
I hate the smell of used oil, yet loves me the fried foods. I dump it the minitue I am done with it.
I wish there was a place that (remnicient of WWII) wanted our oil to blast the Japs. or something. I wouldn’t care if they didn’t blast anyone. I do plumbing and I know what kind of crap my dumped oil causes.
So what is the dope? I know we have a few chemical engineers onboard here. Is it too expensive to collect this potential fuel than it is worth? I imagine used fryer oil would be MUCH cheaper to refine than say, drink boxes, or even bottles.
Lightly used, properly stored oils can be re-used many times. Restaurants (which hardly qualify as light use) often only change it once or twice a week --dozens or hundres of uses. Oxidation, water contamination and “burned bits” all contribute to oil degradation. I find that allowing it to cool, then filtering it into a jar through filter paper is enough. The instructions for many deep fryers say it can be stored in the fryer for a 3-4 weeks in cooler climes, and you know that they are going to be conservative – they have nothing but liability to motivate them. The type of oil and deep fryer is also very important. many deep fryers and a cool trap under the heating coil which can greatly extend oil life by trapping burned bits and moisture.
This isn’t medical advice. It’s barely even English.
Cheaper indeed. At its simplest you can do this:
The car program Top Gear did this a few years ago with a Volvo, after first emptying it of real diesel fuel. It worked fine. I would not recommend going down this route, however. In the long run it will likely foul up your engine. It is quite possible, however, to be a bit more sophisticated and you will be able to run a diesel vehicle just fine on used cooking oil. It makes most sense if you have access to a business that produces a lot of the stuff. Collecting domestic used oil would probably be uneconomic.