Things You'll Need
Ice chest, cooler or large, heavy-duty trash bags
A keg is a small barrel containing around 30 gallons of liquid, primarily beer. Use a keg to store beverages for a few hours or a few days. Keeping the keg cold until needed is critical, and dry ice is an inexpensive solution. Dry ice is frozen carbon dioxide and often is used to preserve foods and beverages. There are safety precautions, however, when using dry ice.
Buy the dry ice as close to the time of the event as possible. Buy 1/4 pound of dry ice per 5 gallons of beverages you want to keep cold, suggests the Dry Ice Info website.
Place the keg in a very large ice chest or cooler. Make certain the ice chest or cooler is large enough to hold the keg. Another option is a trash bag that holds at least 40 to 50 gallons.
Place the dry ice around the keg in the chest, cooler or trash bag. Be sure to use insulated gloves when handling the dry ice.
Close the ice chest or cooler tightly or securely tie the trash bag. This keeps the dry ice from sublimation, or turning to carbon dioxide gas at a slower rate. (Most ice melts and becomes a liquid, which then evaporates, but when dry ice melts, it immediately turns to gas and skips the liquid phase. This process is called sublimation.)
Keep the container of dry ice in a well-ventilated area, and keep windows open in a room where a keg is stored with dry ice. Even in an airtight container, the dry ice melts, releasing a small amount of carbon dioxide.
Remove the keg from the ice chest, cooler or trash bag when it is needed.
Dispose of the dry ice by placing it in a well-ventilated room. The Dry Ice Info website states that the dry ice melts at room temperature and turns into gas.
If it is a keg party, keep an eye on the room with the melting dry ice so that an intoxicated person doesn't wander in and possibly succumb to the gas fumes.
Dry ice also can freeze beer, so don’t exceed the amount suggested in Step 1.