If it doesn't rot, it will remain pretty much the same over time, just like the 800 year old stuff that I used on a roof. Those trees fell a century before my roofer split the shakes. If it rots, the R-value will drop.
To avoid the compaction problem, I'll use lots of thick chunks and fill the voids with sawdust. As stated in the original post, this is a durability test. If I can keep it dry enough to retain some usefulness as insulation, I'll lay it 4 ft thick against an earth sheltered structure. There's no end to the supply of scrap wood and sawdust. Call it carbon sequestration, or call it Penelope.
If anyone has ideas on how to make this work better, that might be interesting to look at.
There is no earthen wall. This is for a greenhouse with an earth floor.
It's something I expect to complete within a couple hours.
Now you are getting much warmer! (or better insulated )
And, I think I may have cracked it. Rather than covering the sawdust with the liner, I think the liner should have an open top that allows the wood and sawdust to poke above ground.