I know you can make fish oil but can you sun render any fat or fatty meat? What about eggs for instance. Once I forgot a dozen of night crawlers in my car and 3 days later of it sitting in the hot sun it was so strong. It was like a stink bomb, what if you did the same process of making fish oil but you used worms instead of fish?

I don't know about worms, but you can do beaver tail oil. And most fats will render down in the sun.

Organic materials that do not contain much or any fat will tend to rot and decompose that is a given. The stink odor will then draw in all those that depend upon such decomposing material to reproduce and feed upon for survival. Insects and animals a like.

Many materials that die or are exposed to conditions not well suited to their benefit will break down and decompose. Eggs are no different. Once exposed long enough to temperatures they will break down and begin a transformation as well. How long they are left in the heat will determine the outcome of their final condition. Eggs can be cultured and broken down to a real stinky material as well.

Fat from skunks, I start with sun.
Than finish just like rendering lard.
I keep them separately, each has a use with different lures.

I've rendered down lots of skunk fat in a kettle on the stove. take your time and don't scorch it. Just like the essence the oil separates and you'll get pure clear oil and like the mustard in the gland you'll get some murky oil that hardens like bacon fat in the cold. both have there attributes. The clear oil is what papa used to rub on our chest when we had a cold. And No it doesn't smell like skunk.

Sun Rendering some drained beaver oil sacs this week. Got walleye fat and beaver tail going also

How would I go about rendering beaver tail oil? And can I use the oil to make bait?

I Cut up my beaver tail into 1 1/2 inch square pieces. Pack in a mason jar 3/4 full and set out in the sun. Every few days I pour of the liquid into another jar. At some point in time it will have rendered itself out and no more liquid will come out of it. Now you will see the separation of fluids in your other jar.I pour the oil off the top and discard the rest. The left over pieces of beaver tail make excellent bait. Yes you can use the oil in bait making