Non-plastic umbrella for thermal mass

We are looking for alternatives to the petroleum based options, to have 20' of dry and warm earth around our house, without polluting the soil with nanoplastics.

Around the thermal mass, an open trench, for easier maintenance and microclimate creation, versus a french drain.

Between the trench and the house, sloped insulation and waterproofing, both buried a bit, so that the area is walkable and some plants grow.

Buried waterproofing options:
A) Curved arabic clay roofing tiles: due to gaps below them, and weight above them, they may crack. The soil above may cause overflooding of the tiles?
B) Flat clay roofing tiles: the soil above may cause overflooding of the tiles? Less than in the curved arabic tiles?
C) Roman opus signinum: crushed ceramic + lime in a continuous layer. Difficult to renew the insulation below.
D) Galvanized steel sheet: not durable enough?

Buried insulation options:
A) Sheep wool, unprocessed: free, insulates better when compress, manages well some humidity. Can last +8000 years if the conditions are perfect, but 1 year if wet. Better if the waterproofing above makes easy changing the wool every ¿5-20? years.
B) Arlite: durable. Does it have any polluting additive?
C) Mineral wool: it has petroleum based additives.

Thank you for your ideas and experiences.

Are you considering doing a variation of john Hait's annualized geothermal?  I'm just trying to make sure I am answering the question you are asking.

Could you bury a layer of expansive clay (e.g. bentonite) as the waterproof layer, then back fill with topsoil, or gravel or whatever, depending on your intended use, lay paving stones where needed, etc?  Roots could penetrate the clay layer, especially if trees are grown on it, but even deep rooted grasses, alfalfa, etc. might.  So, I think you'd want to be cognizant of that likelihood when planting.  But, the clay should be somewhat self-healing of minor penetrations, also.  Seasonal dryness of the subsoil at the waterproofing depth might lead to cracking, though.

Clay may not be the solution...

Thank you Kevin for your reply.

Yes, we want something similar to annualized geosolar, combined with a solar hypocaust (air radiant floor, see Living Energy Farm), to have more flexibility and avoid overheating the house in summer to store heat for the winter. A high water table and adjacent buildings also encourage this decision, because we can't create the umbrella all around.

Yes, the raw clay here is expansive and cracks. It cracks in the summer, so it's not a problem for the heating part, but may be a problem for the dryness and conservation of the insulation.

The idea is to plant shallow rooted plants above the umbrella.

Another option is to use Opus signinum in flat clay tile shape pieces, but it could be a lot of work to create them. ¿Maybe not so much work thinking in the long term? Maybe in bigger sizes...