What to do with used fry oil?

Mostly lard.  I usually just dump it in the woods.  If we have a pig, I’ll mix it with its feed.  Is there anything else useful to do with it?

Great firestarter if melted into sawdust/shavings, used shop rags or cardboard strips. These act as a wick. Will attract animals though.

Rub on old tools as a preventative.

Rub on wood handles.

This article suggests that 100% vegetable oils such as soy, corn, coconut, olive, or sunflower oil can be composted:

https://www.bhg.com/recipes/how-to/cooking-basics/how-to-dispose-of-used-cooking/

We cook with it. Eggs fry up nicely in bacon grease, for example. We also give it to our dog over her food (only as an occasional treat.) It is good for their fur, like coconut oil, although articles say that it can be dangerous to give out too often because of the high salt content. Here's an article about that:

https://www.fabiandrosi.com/does-bacon-grease-make-dogs-coats-shiny/

Here's an article by Pioneer Woman who gives twenty ideas: https://www.thepioneerwoman.com/food-cooking/cooking-tips-tutorials/a101372/20-ways-to-use-bacon-grease/

This article gave some more ideas, some of which are pretty cool. Use it as a candle, shine your boots with it, and even make soap and moisturizer.

https://urbansurvivalsite.com/uses-for-bacon-grease/

Bird feeder, biofuel, candle, soap, cutting fluid in machining, anti-foaming agent (brewing, etc), anti-rust coating, lube for chainsaw.
https://permies.com/t/131086/experience-Bar-Chain-oil-alternatives#like

One of the challenges with used fryer oil is the salt content. That's more from the commercial restaurant side though. Lard/oil from home cooking is probably a lot better.

I wonder if reheating and refining the lard/oil would be worthwhile. The light, quality stuff gets used on tool handles, waterproofs shed walls and old boots. The sludge becomes firestarter. Hm.

Might be possible to wash the salt out.  Mix with water, salt should dissolve in the water, wait for the layers to separate, decant the layers (or use a chemist’s separatory funnel).

we make soap with it, using liquid lye, cold process. just filter the solids out (coffee filter works great), 5 liters of oil, 1 liter of liquid lye solution for soapmaking, a liter of cold water, stir it til it heats up and thickens and pour into molds, let it age.
It's almost impossible to get any scents into it, but it makes a soap that's great for washing dishes and getting grease out of clothes. We stopped frying and the only thing I miss is the soap!

Gray, how many times are you frying with it? If you strain out the food bits ( use fine mesh or coffee filter) you can reuse the fryer oil for cooking. Keeps longer if you refrigerate it.