Any of you hackers have a way to form recycled cardboard?

I'm not talking about folding, cutting, or taping. I'm talking about somewhere between pulping, molding, additives, papier-mâché, low strength composites, and IKEA furniture.

I'm wondering how cardboard egg cartons are formed or any number of other logistics packing materials. That process must be relatively cheap to do and might have a lower environmental impact compared to many other materials. I have a collection of various cardboard and discarded rough card stock I use for custom boxes, storage, and jigs, but it would be cool to make 3d printed molds filled with a pulp like slurry of old cardboard to make stuff for the cost of time and trash.