This article is from the Food Preserving FAQ, by Eric Decker email@example.com with numerous contributions by others.
From: Mick Kunstelj
One thing I was after was how long such grains as wheat/rice etc., last for.
Rice is an interesting alternative, as it is cheap, can be used for a lot of
dishes (not least making bread), and would appear to be quite hardy. A
method that I use for storing is really suited to wheat and flour, but can
be applied to a number of other grains (rice) and foodstuffs.
I buy large drums (44 gallon drums or importers pickle container drums) but
any type of airtight drum will do. Naturally, make sure that the drum is
clean and dry. (I use a bleach solution, not the least to remove the smell of
pickles... :-) )
At the bottom of the container place a good layer of (rock?) salt, this will
over time remove any moisture from the container. Then, dry ice wrapped in
newspaper is placed into the container, followed by some more layers of news-
paper, then the rice. (I keep the rice in the bags I bought them in)
The drums are closed but not completely sealed (see important note). As the
dry ice (it's frozen carbon dioxide) melts, the gas expands to many times
its original size, forcing out the bulk of the original air. After some
time, the dry ice will completely melt, and the container can be sealed.
Important note: If the dry ice has not completely melted, the sealed con-
tainer will contain a lot of pressure, and may bulge, causing a possibly
dangerous condition. What a friend did in this situation was to punch a
small hole in the top of his metal 44 gallon drum, and the pressure abated.
He then arcwelded the small hole he'd created.
The carbon-dioxide atmosphere ensures that any little weavel/bug eggs that
may be in the grain will die once they hatch, instead of eating/multiplying
and giving you a nasty shock. Remnant moisture within the container is ab-
sorbed into the salt.
I have been advised that wheat (in the husks) last much longer than flour,
but I have no idea how long rice lasts for (treated in this way or not...).
Thus - if you have any idea, I'd love to know!