It is good for that. I've had a dryer fire.
It can also be felted and used for clothing/blankets/etc...
Didn't believe it until I saw it done.
/johnny
I am a professional felter. That has been one of my businesses for 27 years.
Most dryer lint is cotton/poly and assorted hair. To properly wet felt it, you need to add wool and if the wool is not carded into the other fibers, it will not adhere. It _can_ be needle felted, which requires the barbed felting needles (available anywhere, just do a search), but the fibers are so small, it needs to be needle felted onto some substrate.
Wool felts because it has little barbs running lengthwise along the fiber strand. Those barbs interlock w/pressure and heat. The wool fiber itself shrinks into a ball, one end curling around to the other. Time increases this shrinkage and it is one of the controlling elements for ultimate density. If the original wool mass is not somehow contained, ideally with some compression, the result is a tangled mess of hardened wool, with no shape. The necessary conditions for wet felt are compression, heat, agitation or pressure and time.
I would be interested to have your observations of how the dryer lint was felted. I have even had problems with card fly, which is the lint that accumulates under a wool carder. I originally tried to manufacture my main product with waste wool from commercial carders, but finally, about 25 years ago, I switched, first to mill ends and then to carded batts. The mill ends were of varying quality, not all of which, even when 100% wool, would felt reliably enough for production. Today, I only use carded batts.
Anyway, could you describe the process you witnessed?