Hi Jeremy, Scott beat me to the suggestion to use wool--an excellent and light-weight alternative! I have seen it used for ceiling insulation on two projects and know the homeowners are very satisfied with it. I imagine it would perform well as floor insulation so long as it was under a floor above a well-ventilated crawl space. On the horizon (I hope) in N. America is blown-in straw, with a weight and R-value similar to blown-in cellulose...which is also plant based, although processed in that it is recycled paper waste that has been treated with borate or some similar substance that is both a fire retardant and has repels insects. This is already available in Europe (
https://www.iso-stroh.ch/en/) and in my view, the technology couldn't arrive in North America soon enough! Apparently there have been pandemic related supply chain disruptions for cellulose, which may also be related to the significant decline in newspaper publications. My local paper, the Medford Mail Tribune just ceased print publication and is now available only on-line. I understand that newspaper is a huge part of the waste stream that goes into blown-in cellulose as we have known it. And although drought in grain-growing regions of N. America can influence crop yield and thus straw (a "waste product" of grain production) availability, it doesn't seem that grain production will suffer the same fate as newspapers.
Still, new materials and sources come along, and may prove useful. For example, every autumn I shred dried cornstalks and the flowering spikes of kniphofias, commonly known as Torch Lilies or Red-Hot Pokers. Both produce a light-weight mulch almost like foam peanuts. As I mulch trees with this material I sometimes wonder how it might perform as a wall or ceiling insulation? Who knows what some enterprising individual might one day stumble upon?
Jim
Many Hands Builders