Here's an economical and ecological way to throw a backyard party this summer: Rent a keg. Liquor and grocery stores are good places to inquire about renting one. Typically, a keg holds about 31 gallons of beer, but you can also rent half kegs if you're having a smaller bash. Renting a keg eliminates endless cans and bottles, and the store will reuse it after you return it. You can green up your party even more by using glasses or compostable cups made from plant resin.