I'm all about a little recycling and re-purposing of waste, but I feel like there is a line that needs to be drawn. One of those crazy prepper people used some rabbit crap to power his flame thrower. Check out the vid and I'll commence with the snark:
I really hope that blender wasn't used for making margaritas the following evening... Sure using rabbit poo to power a flamethrower is creative, but a flamethrower as a defensive weapon seems questionable. It is bulky and fragile, and I don't think it is very effective against any bad guy who has a projectile hurling device like a bow and arrow, sling shot, or atlatl. I also don't think it would be too easy to mount that shop vac, fuel tank, and a rabbit to that old ALICE pack frame...
I would highly advise against any DIY type flamethrowers and I feel like a little bit of safety gear would go a long ways... I'm not sure how effective sweaty cotton shirts are against a fireball of weaponized rabbit dung, but maybe some safety glasses or gloves might be a good starting point.