They eat the part people don't want---the hull, which is the soft case that protects the nut while it grows. California currently has 1.7 million dairy cows. The herd doubled between 1980 and 2009, reaching a peak of 1.84 million before declining somewhat in the ensuing years. In most years, milk generates more revenue than any other California farm product, just ahead of grapes and almonds. California produces more milk than any other state.
Minor typo—each *pound* of shelled almonds results in 1.46 pounds of almond hulls.