Non-wood fibres and grown packaging

Sheet formation is the same everywhere: a dilute fibre slurry drains through a screen, water menisci pull the fibres together, and hydrogen bonds set the strength. What changes between feedstocks is the fibre itself — its length, wall, cleanliness — and the logistics of getting it to the machine. Wood pulp occupies a sweet spot: millimetre-scale fibres, no silica, a supply chain that stores for years. Non-wood materials enter with different geometry and different economics, and their markets are the exact shape of those differences.

Fibre geometry sets the ceiling

Grass, straw and crop residues bring fibres of roughly a millimetre against the three or four of softwood tracheids, a large fraction of short non-fibrous cells, and silica with ash that interferes with pulping, drainage and chemical recovery. Harvest is seasonal and low in bulk density, so collecting a mill’s worth of residue is a logistics problem wood never poses. The consequence is mechanical: shorter fibres share less bonded area, so residue papers cannot reach the tear and tensile of wood grades, and they live where that does not matter — stationery, printing specialties, packaging accessories. Algae is a step further out: lagoon biomass is largely not cellulose fibre at all, and algae paper works as a fraction blended into a wood-pulp sheet, contributing colour and texture rather than strength. What algae genuinely supplies is on the input side: the harvest is an environmental service — nutrient removal from an over-fertilised lagoon — so the feedstock is collected regardless, and paper is what the collected nuisance becomes.

Mycelium: growing instead of forming

Mycelium packaging abandons sheet formation entirely and with it the whole paper machine. Fungal hyphae colonise a lignocellulosic substrate — husks, sawdust — inside a mould, binding the particles into a low-density composite over days; heat then kills the organism and dries the part. The physics is a grown foam: cushioning where expanded polystyrene is used, heavier per unit volume, but formed to shape with almost no pressing energy and compostable at end of life. Its limits mirror the mechanism. A foam cannot be a web: there is no tensile sheet, no print surface, no reel to convert. The material is hygroscopic and needs coating against moisture. And production runs at a biological rate — days per batch where a paper machine produces tonnes per hour — so it fits shaped protective parts, not commodity tonnage.

Where the niche is honest

The honest cases are the ones where the alternative was never good. Lagoon algae would be dredged anyway; field residues are burned in the open where collection is absent; expanded polystyrene is unrecycled in most of the world. In those places the new material is not outcompeting a champion but absorbing a waste stream — the strongest version of the story, and the one the long-lived producers in this space actually tell. What keeps the tonnage small is equally honest: dispersed seasonal feedstock, low bulk density, and fibre geometry that caps mechanical grades. The paper physics does not bend for any of them — grass paper wicks, sizes and weakens exactly as the sizing and strength rules predict. The limiting quantities are fibre dimensions for the papers, and for the mycelium the trade between density, moisture and biological throughput.