I'm only half kidding. I'm a bit of a prepper and I have lots of powerbanks and devices that charge from USB but besides idling my truck I really had no other way to charge any of them in case of a long-term power outage which seemed a bit of an oversight on my part.
Not like this solves the issue. 30 watts (under ideal conditions) isn't much but it's a start.
Wood is a potentially scarce resource, access to it is situational, it requires significant storage space, wood smoke is bad for you, fire is dangerous and requires skill to manage that can take a long time to learn, same goes for the process of preparing the wood.