I’ve borrowed most of this from Walton Feed and the USA Emergency Supply websites.  If sealing buckets is too much trouble and you can afford it, order food from emergency supply stores, but watch out — unless you live nearby or order a lot of food, the shipping charges can easily be more than the food itself is worth.

You’ve got to do this within 5 hours because the dry ice will slowly escape from the plastic container you’ve put it in.  The outside will become frosty, which is fine, but if water gets inside the dry ice container because it wasn’t pure, that’s bad because moisture can cause food decay.  It’s highly unlikely you’ve bought bad dry ice, but you’ll know you did if there’s water in the plastic container after the dry ice has boiled off.

Dry ice (frozen carbon dioxide) because:

1)    Acts as a fumigant to kill bugs

2)    Cheaper and far more effective than oxygen absorbers, freezing, or folk remedies like Diatomaceous earth, bay leaves, etc

3)    Less expensive than Nitrogen Sealing

Equipment needed

1)    Measuring scale.  You need to weigh 2 oz of dry ice per bucket.

2)    1/3 cup measuring cup – that’s about 2 oz of dry ice.  Technically 1 oz would work, so don’t be overly generous and overload the 1/3 cup measure.

3)    Dry Ice, available at welding supply ships, chemical supply houses, etc.

4)    Paper towels to put on top of dry ice before you pour food in

5)    Plastic container with sealable lid to put dry ice inside of when you buy it.  The lid shouldn’t seal too tightly because the gas needs to escape.  The outside will get frosty, but don’t worry about that.

6)    Hot pads or oven mitts to handle container with dry ice. At -110 F it can burn your skin – don’t touch it.

7)    5, 6, or 7 gallon buckets with lids that can form an airtight seal and a bucket lid remover.

8)    Leaf Bags.  Bucket goes inside in case it explodes because you put the lid on too early.

9)    Wheat, grain, powdered milk, etc – whatever it is you plan to store.

The process

1)    Put empty bucket into leaf bag in case it explodes

2)    Measure 1/3 cup of dry ice to get 2 oz worth

3)    Pour dry ice into bottom of bucket

4)    Put a paper towel on top

5)    Pour grain to within ½ inch of the top

6)    Set the lid lightly on top, but don’t seal it!  Or you can seal the lid all the way around except on one side.

7)    Feel the bottom – it should be “icy cold”.  When it’s not so cold, you can seal the bucket.  Check every 10 minutes.  The initial frost that formed will have melted off.

8)    After you’ve sealed the lid, you’ve got to make sure the lid doesn’t bulge (a sign you sealed it too soon).  Check every 10 minutes for an hour, and open and reseal if you put the lid on too early.

More tips

Don’t want to seal the lid completely as the carbon dioxide and air must have a place to escape. If the lid makes an airtight seal, the expanding carbon dioxide inside the bucket will continue to increase in pressure until something gives – either the lid will pop off or the bucket will split. Either way you are going to have food all over the place. How do you know when all the dry ice is gone and it’s safe to seal the lid? Simply pick up the bucket and feel the bottom. If it is still icy cold there’s still dry ice in the bottom. You may need to be a little patient here. My experience has been that it takes 1 to 2 hours for all the dry ice to change into a gas. I’ve had others E-mail me saying they had to wait around for 5-6 hours! So you may wish to plan in a certain amount of time for this in case it takes a while. You want to seal the lid just as soon as this has happened, however, because if you don’t, air will start circulating back into the container.

After 15 or 20 minutes, I start checking my buckets, and then recheck them every ten minutes or so. After you seal your buckets, it’s always a good idea to keep an eye on the lids for the next hour or so. The lids will start bulging up if you sealed them a bit prematurely. If this happens, use a bucket lid remover to crack open the lid on one side to let the excess gas escape, then seal the lid back down. I’m not sure why, as my logical brain tells me it should be otherwise, but over the next several days there will usually be a small vacuum created inside the bucket and the side will pop in a little bit. Don’t concern yourself with this. Your bucket will store just fine.

Why dry ice is better than oxygen absorbers and other methods

Unless you’re sure there are no infestations you should freeze grain to -10 F for 2 to 4 hours or for 2 to 4 hours with dry ice (carbon dioxide).  Dry ice has been shown to kill every insect at all stages of development.  It’s much easier to get enough CO2 into a bucket of grain than to remove 100% of the oxygen.

The problem with oxygen absorbers is that unless all of the oxygen has been removed, hatching bugs will be able to survive and thrive.  Also, oxygen doesn’t kill bugs, just keeps them from doing as much harm after they hatch.

Studies have shown that nothing is as good at killing insects as carbon dioxide.  Diatomaceous earth, bay leaves, and folk remedies simply won’t be as surefire.  If you don’t want to use dry ice, the next best bets are freezing and oxygen absorbers.

If you’re going to freeze your grain, do so for at least 3 days.  Some studies have shown that not all insect eggs are killed so if you freeze your grain, keep an eye on it so that if insects show up you can deal with it as soon as possible.

Even #10 cans with plastic lids on top can be penetrated by insects in infested areas, unlike buckets with secure, well-sealed lids.