remember hi-fi speakers which used to have it stuffed inside?
Yes, mainly TL (Transmission Line) speakers used it (cost, upper end of the Hi-Fi markey)
The idea is to alter the speed of sound in air, and also add standing wave damping, thus reducing the length of the transmission line, which in a Cambridge R50 of the early 70's would be 7 to 10 feet physically. In an IB (infinite baffle) sealed box type, it also effectively increases the (acoustic) size of the enclosure.
NB. Over-packing is counter-productive, it has to be 'teased-out' to the correct optimum density.
Could be good, fireproof I should think (and toxic smoke proof too I hope)... but would it retain moisture, maybe not if not had natural oils washed off in processing (or had sizing added)