I recently cleaned up after brewing one day and realized that I threw away a couple of four gallon water jugs. Could these be used for storing grain for long term? Would the air in the container affect my grain over time? If these can be used for storage I can save the money I wanted to spend on feed containers.
Most maltsters ship their grains in bags that are not air-tight, but they don't recommend storing them for long periods of time (12 months, max). A plastic jug isn't as air-tight as it seems because it is gas permeable. Even if it was air-tight, it wouldn't matter unless you used nitrogen or CO2 to flush-out all oxygen from the container. Nobody really does that kind of thing with grains.
The main idea for your containers is to keep pests out of your grain (bugs, mice). They should work just fine for that purpose.
I would recommend using wine must buckets, you can normally find them for a few bucks and some of them are compatible with Gamma Seal Lids.
These will help with storage, but you should aim to go through your supplies within 12 months of manufacture.
I use 5 gallon buckets and large mylar bags to store grain. Place mylar bag in bucket and leave open. Pour grain into bag. Compress or push as much air out of bag as possible (could use a vacuum sealer if you want) and seal. Place bucket lid on top.
The hard plastic bucket keeps animals, rodents, neighbor kids, etc out. The mylar keeps air out. Unless you vacuum seal, never get all air out, but this is the best method I have come up with. I am not storing grain for much more than a few to maybe 12 months. If storing longer (like for apocalypse survival), probably vacuum seal.
Try these options for the mylar bags. Works great: