Any idea what this stuff in the bottom of my kerosene can is?

[OM617YOTA]

This was a one gallon jug of standard off-the-shelf kerosene. When I used it all, I refilled the jug with jet-A for easier dispensing into appliances. Few months later, it stunk strongly of vinegar and wouldn't burn well at all in a kero lantern. The 5 gallon can of jet-A I poured it out of also smelled of vinegar, though not as strongly, and it had no residue on the bottom. The residue appears solid and does not flow at all. No cloudiness to the fuel was detected.

Any ideas?

[compress ignite]

Vinegar is acetic acid

https://pubchem.ncbi.nlm.nih.gov/compound/acetic_acid#section=Top

That looks like what a "Stay Fresh" tab would look like ...
(If such a thing even existed for Kerosene)

'Not in ANY way to be considered a Chemist...

But, given what acetic is and it's compounds what I "Think" you're smelling
is the decomposition of either the Kero or the JP
(Or mayhaps The Entrails of Both entrapped in the Tab)

[Boy , I sure can produce the Horse Manure if Facts are lacking !]

[OM617YOTA]

Hah, that does sound impressive!

Based on this:

What

The scent is definitely more "roadkill" like, meaning bacteria. Lovely.