Can grass and straw be flame retarded?
In principle, sodium soufa polyborate works effectively.
I think that straw and rush can be fire-proofed, flame-proofed, flame-retardant, and non-combustible (unburnable).
The main raw material of straw and rush is cellulose, so it would be possible if a flame retardant effective for cellulose is prepared.
The prepared flame retardant compatible with cellulose is a boric acid flame retardant. Here it is.
Spray the tissue like this and dry it, then try to light it with a lighter.
Does not burn, just burn. I feel that straw and rush used for such tatami mats can be applied.
Regardless of whether there is demand, it seems that flames can be made even for rice bales.
Thatched or thatched roofs may be possible.