Grain silos are everywhere so when they go unused, there's no much you can do with them other than tear them down or leave them sitting around -or convert them into houses, which is a great way to reuse the materials and end up with a unique house.
Alternatively, out of commission airplanes can be sold off for scrap and melted down, or they can be used for housing parts like this incredible house in Malibu that features airplane wings for the roof.
And these are only a few of the non-conventional building materials featured on this great Homes and Hues article: 8 Homes Made From Non-Traditional Materials