I think I've written about this before, but I thought of an extension of it again.
What if you took the used malts and hops from a brewer, ground them up, dried them, and then compressed them and impregnated it with some sorta resin?
With the right composition I think it would make for a fairly reasonable material akin to the wood and metal filled filaments for 3D printers. The resin could also be introduced in a mold so the final cleanup would be minimized, just like fiberglass or whatever. Would also be like +5 hipster points for drinking beer out of a recycled hop cup.