Honestly looks pretty good to me. If something is burning that's producing that black smoke, it's going to be dense. Just maybe unrealistic to be burning something like that in a barrel, unless it's crude oil or something lol.
Reminded me instantly of a tire or tires on fire when I saw it.
While it's not a super common thing to see in a lot of places, a chunk of rubber on fire emits smoke very similar to that.
Black, fluffy, and quite opaque.