@Ashanna Hensley (Ren) In FMA they created water from air (moisture) and fire from air (only needed an igniter). Also in this manga the laws are much looser, like the size of the house he made from the amount of wood doesn't make sense if you try to infer equal equivalence, also the main gates used a smaller gate and turned into a bigger one with more compressed material to be stronger, that would be impossible using FMA logic.