One of the comments reads : Actually, we will probably never figure out, was it man or woman. but I thought this comment of the professor was an interesting eye opener. https://mastodonapp.uk/@MarkHoltom/112070436760917344
More than likely steam. Don’t need fuel to burn when when you can just make fire with magic. And we know people get employed for their bending ability since Mako got a job lightning-bending at the power plant.