It's an interesting topic. One of the reasons that a lot of fryer grease is 'retired' is that it fails (or decomposes) after a period of time at a high temperature and some of it's characteristics change. There is some concern about these burnt fats containing traces of potentially carcinogenic compounds (but I have not read anything on that, and it might be the burnt protein, so I'm just mentioning it in case someone wants to look it up). If there weren't any other issues, how would you 'clean it up'? Obviously, you'd strain it (coarse mesh, fine mesh, paper towel/Whatman), but after that? Some people baste a potato in it, others go for baking soda and other things. You could try activated charcoal, but you have to use a chunk-type that you could easily strain out after. Interesting.