Several companies specialize in buying surplus or used steel kegs to refurbish and resell to breweries. These are the most professional outlets for selling in bulk.
If you have a standard commercial keg and simply want your money back, the original seller is your best bet. Sell Your Kegs To Us who buys empty kegs
: Buys used steel kegs you no longer need and refurbishes them for major brands like Carlsberg. Several companies specialize in buying surplus or used
: Purchases used kegs that are no longer in use to give them a "new life" through refurbishment. who buys empty kegs