The two question are sort of related, because if the liner gets punctured the saw dust had better not rot. I've spent enough of my life dealing with issues from moldy houses.
Could hydrated lime powder be mixed into the wood chips or sawdust? I'd think there would be two advantages. First of all, it would make the wood chips inhospitable to rots, molds, and critters due to caustic action and a high pH. Secondly, any organic matter used will have at least some residual moisture. The lime would absorb that residual moisture and dry the material out.
But would the lime damage polyethylene or EPDM? Would borax work better?
I don't have any ideas on protecting the liners from mice, rats, gophers and rabbits. Has this been addressed?
I was thinking it could look something like this: wood chips pre-dried and dusted with lime. Then a layer of sand to smooth the layer out so there are no sharp bits poking up from the wood chips. Then two layers of cardboard that have been washed with lime and then dried. At this point I would suspend some plastic over the area with some branches or logs or something so that it turns the area into a greenhouse, drying the system out completely. Then, when you are satisfied that all the moisture is gone, remove the structure holding the plastic up, and lay it flat on the cardboard, and then protect it with a thick layer of newspaper or a double layer of cardboard, and then armored this with a few inches of sand. On top of this could be spread 1/2 inch wire mesh to keep rodents out. Then another layer of sand on top. Additional layers of plastic could be added for insurance, as long as they are under the layer of wire mesh so nothing could damage them. The armor of sand would protect the system from being punctured from above.
Actually you could have a final layer of plastic above the wire mesh, protected by cardboard and armored with sand, and it would help protect the wire mesh.
I've also been wondering about how insulative wet wood chips are. We've all heard that mulch insulates the soil, and it gets wet. What if a WOFATI type structure had the insulation layer on top of all the soil, as several feet of wood chips? Of course, they'd have to be replaced every few years.
Maybe with mulch on top and a layer of slate laid as shingles down below, we could build WOFATI type structures without any industrial products?
This could be quite functional, I think. A person could put a layer of drainage rock (round cobbles), so that the rain that hit the wood chips would have a place to run off and not saturate the chips. This would allow them to dry out more easily and the would last longer too.
What if a WOFATI type structure had the insulation layer on top of all the soil, as several feet of wood chips? Of course, they'd have to be replaced every few years.
I've manually processed enough branches into 1 inch chunks to fill a 32 gallon garbage can, it tool to long and aggravated my hand and wrist muscles.
Still, an underground building that works without plastic is worth pursuing.
I cannot find the R value for dry sand vs. dry wood chips,but if comparable why not go with all sand,and avoid much if the pest issue?
Of course, it might not be on site.
As usual, "it depends" is part of a sustainable solution.
Making wood into wood chips, on-site is probably more sustainable than shipping in sand.
Speaking of on-site solutions,what about other wood products,such as ash, charcoal or even wood vinigar, etc?
Making any of these for their own sake seems wasteful, but if you harvest the heat, maybe to make bricks or tiles?
It is a good point. However, woodchips are a biproduct or waste product from local industry, and making use of them makes sense to me, especially if they can be attained for free, and super especially if they can be delivered for free (as most arborist companies have to pay to dispose of them). In comparison, steel for wire mesh, or plastics usually made from petroleum products, are extremely resource intensive large environmental footprint industries.
I would count wood chips as am industrial product
Forest duff would be another option for use as an insulative material, but this is not necessarily sustainable either... but is it more sustainable than fiberglass pink, or styrofoam?
the R value for dry sand vs. dry wood chips
I would suspect that wood chips would be much better for insulation than dry sand.