can you compost onions?
Yes — onions and their trimmings compost without trouble in any outdoor pile; just keep big batches out of the worm bin.
breaks down in 1–2 months chopped; sprouters take longer
C:N ≈ 15:1
which bins can take it?
- hot pile yes
- cold pile yes
- worm bin caution
- bokashi yes
- tumbler yes
- curbside yes
- worm bin: Alliums repel red wigglers in quantity — a few scraps are fine, a whole bag of onion ends is not.
why?
The sulfur compounds that make onions sting your eyes — mainly syn-propanethial-S-oxide — are no obstacle to compost bacteria, which dismantle them along with everything else. Those same compounds do repel red wiggler worms, which retreat from a bin overloaded with alliums. And a sprouting onion in a cool pile can root and regrow rather than rot.
how to prep it
- Halve whole or sprouting onions so they can't regrow
- Bury pungent scraps to keep odors down
often confused with
- Onion Skins — The papery outer wrappers act more like a brown and take longer than the juicy layers — they get their own page.
quick answers
Why does my compost smell like rotting onions?
That's usually anaerobic decomposition, not the onions themselves — the pile is too wet or too compacted. Turn it and fork in dry browns; the sulfur smell fades within days.
Can I compost cooked onions?
Yes — cooking softens them so they vanish even faster. If they're coated in butter or oil, send them to a hot pile or bokashi bucket rather than an open cold bin.