The log cabin I lived in for 5 years in Funter Bay, AK had moss insulation in the floor and ceiling. It was still there 50 years later (behind shiplap to keep out critters). I've started a few fires with dried moss, and I don't think I'd like to use it now. Look on the AHFC site for "log", they have a 199 page manual, and they talk about it. They pretty much dismiss it as old-school and not worth doing.
Wool is an accepted material; look for it on the web. Fire-resistant materials and construction are there to slow a fire from spreading to other parts of the house; not many materials, except brick, steel, and rock are fire proof. Which leads me to think that fiberglass is made of sand.
I found this on the Owens Corning site. If I had a heat tape (a major cause in AK) or some wiring go south, I'd want fiberglass (or anything non-organic) surrounding it..
Just my humble opinion...
REAL "alternative' insulation - as in cost???? Has anyone tried something different for your floor or roof? - sawdust, wool, cardboard, straw?? This is not about the "government's" codes, but rather really doing it different. Insurance? Fire? Dimensional lumber homes with all their fire rated insulation and sheetrock seem to pile up the same when burned to the ground - seems the same for a log home though they seem to burn down less than conventional houses. So uninformed/unsubstantiated fears set aside. This this inquiry is for Alaska not New Mexico. Is there anyone who has really done it different.