I like alt building materials, I think I have an article filed from MEN about a hay bale house that really intrigued me. Then I actually saw a house in Flordia that all of the walls were from scrap 2x4's(18"-24" long) stacked like bricks, except they rounded some of the walls.
Where I live, the inspectors wouldn't know what to do with an earthship. They would probably just pass it and move on after talking about it for a couple hours and then their mandatory re-inspection for a small additional fee of course....