Recycling Machines 0.13.20 and Omnibarrels 1.1.0 seem to conflict with each other. When loading sprites part of the game loading screen I get a error:

Error when opening
C:-blablabla-\Factorio\data\base\graphics\icons\heavy-oil-barrel.png for
reading: No such file or directory

Looks like this error may have more to do with Recycling Machines then Omnibarrels.

It's Recycling Machines making naive assumptions about icon names and paths. Nothing I can do about it on my end.

That's what I figured.
I posted this to both mods in case others run into the same issue.

I suggest using the Reverse Factory mod instead! Unless you're using one of the addons that reduces the amount of material you get back (for balance reasons) or trying to uncraft fluid recipes, it should do everything Recycling Machines does, and better, because it's a smelting machine that doesn't need to have a recipe set ;D