Here is a great question from Susan, and something I haven’t really talked about:
What’s the best way to store harvested compost that you
won’t be using for several months? Should it be kept in an airtight
Good compost is absolutely loaded with aerobic organisms (mostly microbes, but certainly also some invertebrates as well), so it is vitally important that you don’t completely seal it in a bag or container. If you do this the oxygen will be consumed very quickly and conditions will become anaerobic, potentially leading to the production of various compounds that can be harmful to plants (not to mention the death of your beneficial aerobic organisms).
It is best to store compost in a cool, dry place, providing air flow while not letting the material completely dry out. If it is really moist or wet, you should spread out the material and let it dry for awhile. It should be nice a crumbly and not feel damp when you hold it in your hands.
If you want to put it in plastic bags just make sure to add lots of holes in the plastic to allow for gas exchange. Any sort of bin/tub used to hold compost should also allow some air flow – generally, Rubbermaid type bins have loose fitting lids and some holes near the handles, so you won’t like need to actually drill any (as long as the moisture content is as described above).
Needless to say, compost should never be stored unprotected outside for any length of time. Rain will wash away a lot of the beneficial compounds (nutrients etc), and the sun can dry out the material too much as well. If properly prepared material is allowed to freeze this shouldn’t create too much of a problem – many microbes will die, but plenty of them will simply go dormant, ready to repopulate the material once it thaws out again.
Hope this helps!