Why does kerosene go bad after sitting in the sun?

Factual Questions
1

I live in Japan and for some unknown reason a great majority of people still use kerosene to heat their homes in the winter. It is cheaper than electric heat, but still, c’mon Japan.

Anyway, last year I had about 20L of kerosene left over so I just sealed it up and set it on the balcony for storage. When I started to need it again in November, I opened it up and filled the heater but the stuff wouldn’t burn. The heater just gave me errors until I bought some new stuff, cleaned out the old, and tried again. No problem.

The old stuff doesn’t even smell very much like kerosene anymore (smells very weak) and is basically useless. What happened to it? A lot of sunlight was hitting it over the summer, so I’m guessing the light broke down the hydrocarbons and whatnot (I don’t know much about fuels, so general knowledge would help here as well).

Why is the old stuff not working? Can I recycle all this old stuff? Does anyone want it (I’m not going to dump it down the drain, but I don’t want it taking up space either)?

2

You distilled off the lighter fractions of hydrocarbons.

Kero is a mix of lighter, more flammable stuff and heavier less flammable stuff. The heavy stuff will burn but only when it is kept alight by the lighter, flammable fractions.

The heavier fractions are said to be ‘combustibe’. The lighter fractions ‘flammable’. All depends on the flash point of the individual components.

Anyway you basicallly got rid of the smaller, more volatile*, lower flash point components that get the stuff burning.

*volatile means how easy it evaporates

3

Soo… It’s garbage, right? Did the sun do this? …or just the warmth from the summer heat? How enviro-evil would I be to dump it in a field?

4

Yup garbage. You could blend it back, but I would not recommend.

The heat is what did it. Store fuels in cool places. The heat drove the lighter constituents of the mixture off into the atmosphere.

Very enviro-evil if you dump it. Take it to a council waste collection point - assuming they exist in Japan.