Grown materials: mycelium, shaped trees, printed waste

Furniture is normally made by subtraction: a log or sheet loses material until a shape remains, and every cut fibre end becomes a future joint. The three approaches grouped here abandon subtraction itself. They differ chemically — fungal walls, living cambium, pectin-rich waste — but share one structural decision: the forming step moves inside a biological process, and human tooling only finishes what growth has started.

A binder that grows itself

Mycelium composites begin as particles of low-value agricultural matter inoculated with fungal spawn. Hyphae radiate outward, physically threading through the loose mass while secreting the polymers of their own cell walls — chitin and glucans — which cement particle to particle. Days later the cavity is full, and heat treatment ends growth, leaving a dry, rigid body nobody pressed: the binding energy came from metabolism rather than from hot platens. Two properties follow directly. First, the growth pattern leaves an open, interconnected pore architecture on every length scale, and interconnected pores are precisely where airborne sound loses energy to viscous drag — hence their industrial use as acoustic panels rather than structural ones. Second, because a colony is a population, not an injection moulding, batch-to-batch density varies more than in a pressed product, and the finished board reabsorbs water in humid service like other fungally grown bodies: the same grown-composite logic that fills insulation boards sets both the promise and the ceiling here.

Strength without joints

Wood owes its directional strength to cellulose microfibrils wound helically inside each tracheid wall, all aligned along the stem — lignin holds the assembly compressed. Conventional furniture saws this continuous reinforcement into pieces and rejoins it with fasteners and adhesive, creating regions where load must jump across cut fibres and glue lines: chair legs fail at the joint, not mid-shaft. Training a live tree bends the growing stem while the cambium still adds new wood, and the tree deposits subsequent rings through the curve; the fibres sweep continuously around the elbow exactly as nature already builds them around branches. No discontinuity ever forms, so none can propagate a crack. What replaces the weakness removed is time — the cycle runs in years of standing outside — plus respect for wood’s anisotropy rather than victory over it.

Turning heterogeneous waste into printable feedstock

Citrus peel, spent coffee grounds and bran are dominated by cellulose, hemicellulose and pectin — polysaccharides with usable film-forming and matrix behaviour but awkward processing character. Compounding them into a printable material means pairing those biopolymers with suitable binders, drying to controlled residual moisture, and accepting that particle size distribution shifts with each agricultural season: filler content raises stiffness while shortening melt-viscous flow, the classical filled-polymer trade-off, played out on input that was yesterday’s disposal problem. Print geometry then supplies stiffness cheaply — ribbed shells gain rigidity from shape instead of thickness, the same trick as the flutes of corrugated cardboard.

The unifying consequence: these products’ environmental argument rests less on what they are made of than on which steps never happened — no press, no joinery, no binder bought off the shelf. Biology performed the forming; everything after is finishing.