1. Bring corn cobs and 8 cups water to a light boil in a Dutch oven over medium-high heat. Reduce heat to low, and simmer 30 minutes.
2. Stir in salt. Pour broth through a fine wire-mesh strainer into a large glass bowl, discarding cobs and pulp. Cover and let cool 1 hour or to room temperature. Store in an airtight container in refrigerator up to 1 week, or freeze up to 2 months.