A little speculation on the Zelfo material.
Lignin based glue/binder?
"...by continuously grinding the raw material... into a microfiber pulp having an increased internal fiber surface and an increased degree of interlinking..."
"...compares lignin to the concrete used in buildings, with cellulose as the steel frame. Without lignin, a tree could only grow to be about 6 feet tall...Brown kraft paper, the dark brown paper used in grocery store bags, and cardboard are stiff and sturdy because they have more lignin in them...
"Lignin was isolated from sawdust and used as a substitute in phenol formaldehyde resins."
"...Some pulping processes are designed to remove as much lignin as possible, while others are designed merely to separate the fibers so as to allow banding. The more lignin is removed, up to a certain point, the more bonding can take place, and the stronger the paper. (The amount of lignin in a sheet, by the way, cannot be estimated by how brown it is: high-yield bleached chemi-thermomechanical pulp is white, but kraft grocery bags, which contain only 3 1/2 %to 8% lignin, are brown.)"
"Milled wood lignin is produced by milling of wood in a rotatory ball mill."
"Zelfo is made using a mechanical process involving pressure and heat...sprayed fibres are adhered in specific direction that adds to the tensile strength. While still wet Zelfo can be textured, patterned, stamped or coloured...Unbleached fibres have a better water resistance due to their higher lignin content."