How about a row of 50 gallon plastic oil drums with screw on lids?
A lot of American pepper’s bury then all over their land with everything in. You could bury them with just the top few inches shown and build your shed base on top. The barrels are perfectly sealed and the ground with keep long life food stable. Hell of a lot cheaper and easier then concrete plus you also don’t need to tank it.
Homes and Retreats