Which country are you talking about here?
I'll tell you a problem. Used oil collection companies, whilst charge nothing for the service, over here are really slack with meeting demand, even if they make 33c / Litre and charge us nothing. For instance, where I work has 7 deep fryers and a total of over 200 Litres between them all. They get changed weekly at the moment because of christmas, and my work is constantly having to call between two seperate companies trying to at least get one out to remove the oil from the used oil bin out the back when it gets full. They say "yeah yeah we'll be there soon" and never show up at the said time. We aren't the only store with this problem, and a lot of places solidify and then just bin the solid oil.