Notorious for their heavy weight--which results from their solid iron construction--cast-iron pans are perhaps one of the best-known cookware types available. Among the advantages of cast-iron cookware is that decomposing foodstuffs "season" the iron, which gives it a natural "nonstick" quality over time. If, for whatever reason, you decide you want to dispose of your cast-iron pans, you can utilise your choice of means to do so, each of which presents its own set of benefits.
Bring your cast-iron pans to your local recycling centre. Inform the attendant that you have "iron scrap" or "ferrous scrap" and would like to recycle it. Alternatively, you could throw the pans away as you would any other trash item, but you must keep in mind that cast iron is not biodegradable--it would not decompose if placed in a landfill.
Give your cast-iron pans away to a friend or family member, or donate them to a charity like Goodwill. As a result of their heavy weight, cast-iron pans tend to be more expensive that other types of cookware and might be appreciated all the more by the recipient. Additionally, used--or "seasoned"--cast iron pans afford more effortless cooking than newer ones.
Place your cast-iron pans beside your trash receptacle, but not inside it. In many cities, people peruse dumpsters and their vicinities for items they can use, a practice colloquially known as "Dumpster diving." If you don't personally know anybody who wants or needs a cast-iron pan, leaving it outside increases the likelihood that someone else will benefit from the pans.