Thats a old school method of packing 5 gallon buckets.Your wheat is best kept in 5 gal. cans the kind they use for paint. When you fill the bucket up leave a little room on top for a cake of dry ice to sit there. Then close it up and as the dry ice breaks down it will kill all the bugs in the wheat and they won't be eating it while you are waiting for the SHTF before you open it again for consumption.
Better way is to use a mylar bag inside the bucket, fill bucket with product and a 1000cc oxygen absorber in bottom and one at top. Press out as much air as you can then seal bag, then put lid on bucket.
The oxygen absorbers will remove all oxygen leaving a mostly nitrogen atmosphere where no bug will live or hatch. Plus side to this method is your food will not oxidize. Ever see really old ice turn yellowish? Thats food oxidation.
Do a youtube search for "long term food storage". There are a couple really good videos there.