Hemp hurd × Ganoderma lucidum.
21-day colonization · low-temperature finish · packaging-grade composite
Reference recipe for the simplest production-grade mycelium composite. Industrial hemp hurd substrate, Ganoderma lucidum grain spawn, 21-day colonization in passive growth chambers, finished at 80 °C × 4 h. Target density 180–280 kg/m³, compressive 200–500 kPa. Reproduces against Atlas cell hemp × G. lucidum.
Bill of materials · 10 kg finished output
| Component | Quantity | Source / notes |
|---|---|---|
| Hemp hurd, 1–8 mm particle | 25 kg dry | Industrial-hemp byproduct. Decortication mill or licensed agricultural supplier. ≤ 12 % moisture as-received. |
| Grain spawn, G. lucidum, 8-week culture | 1.5 kg | Commercial sterilized rye, oat, or millet spawn. Phasal reference strain (open lineage) or any non-proprietary G. lucidum strain. |
| Reverse-osmosis water | 37 L | Sterilization and substrate hydration. Tap water acceptable if chlorinated < 1 ppm. |
| Calcium sulfate (gypsum) | 250 g | pH buffer + Ca source. Food-grade. |
| Wheat-bran nitrogen supplement | 1.25 kg | 5 % w/w of dry substrate. Boosts colonization rate; omit for ultra-low-input variant. |
Total dry-substrate input ≈ 27.75 kg → ≈ 10 kg finished composite (≈ 36 % yield, density-dependent).
Substrate prep
Mix hemp hurd, wheat bran, and gypsum dry. Add water to bring substrate to 62–65 % w/w moisture — squeezing a fistful releases 2–3 drops; not a stream. Rest 30 min covered to let moisture equilibrate.
| Parameter | Target | Tolerance |
|---|---|---|
| Moisture content (substrate) | 63 % | ± 3 % |
| Particle size distribution | 1–8 mm | d50 ≈ 3 mm preferred |
| Bulk density (loose, dry) | 110–130 kg/m³ | Lower → faster colonization, lower final density |
| pH (after gypsum) | 6.5–7.5 | ± 0.3 |
Sterilization
Pack the moistened substrate into autoclavable polypropylene bags with 0.2 µm filter patch. 12 kg substrate per bag maximum. Sterilize at 121 °C × 90 min in a steam autoclave. For container-cell builds, a pressure-cooker stack at 15 psi achieves the same target. Cool to ambient inside the closed bag — minimum 8 h, ideally overnight.
Alternative paths (covered in PCB-004):
- Pasteurization at 65 °C × 6 h — lower energy, ≈ 18 % contamination rate. Production-acceptable.
- Cold lime bath (Ca(OH)₂ slurry, 12 h) — no thermal input, ≈ 25 % contamination rate. Off-grid acceptable.
Inoculation
Work in front of a HEPA flow hood. Open the cooled sterile bag, add 5 % w/w grain spawn (1.5 kg spawn per 30 kg sterile substrate), mix by hand or with a sterilized paddle to even distribution. Reseal with the filter patch facing up. Time-in-hood under 4 minutes per bag.
Spawn-to-substrate ratio is the single biggest knob for colonization time. 5 % hits the 21-day target reliably. 3 % still colonizes but adds 4–6 days. 8 % trims 2–3 days off but adds spawn cost.
Colonization (days 0–21)
Move sealed bags to the growth chamber. Reference geometry: Phasal modular bioreactor, 1 m³ chamber, passive ventilation through 0.2 µm filters.
| Phase | Days | Temp | Humidity | Light |
|---|---|---|---|---|
| Primary colonization | 0–14 | 22–26 °C | 75–85 % | Dark or low ambient |
| Consolidation | 15–21 | 22–24 °C | 70–80 % | Dark · no fruiting trigger |
Visual checkpoint by day 7: mycelium has bridged 30–40 % of visible surface. By day 14: 90 %+ surface coverage, white mat consolidating. By day 21: fully colonized to substrate edges, slight white "skin" on bag surface. Bags showing green, blue-black, or pink contamination at any point are pulled and composted.
Forming (day 21–22)
Open bags in clean room or low-flow space. Break the colonized substrate into 5–10 cm pieces — mycelium re-bonds at break surfaces, which is the entire mechanism of the second-grow. Press into the target mold geometry at 110–130 kg/m³ packed density.
Return molded pieces to the growth chamber for 3–4 days second-grow at 24 °C, 80 % humidity. A new white skin forms over the surface — this is the load-bearing layer of the finished part.
Mold release: PE liner, demoldable silicone, or oiled wood. Avoid metal contact during second-grow — local cool zones cause uneven skin formation.
Finishing (heat treatment)
Demold. Dry in a convection oven at 80 °C × 4 h, target final moisture ≤ 6 % w/w. The heat treatment kills the mycelium (no further growth, no fruiting in storage) and stabilizes mechanical properties.
For ultra-low-energy variant: solar-dehydrator at 50–60 °C × 14 h achieves the same final moisture with about 60 % less energy. Mechanical properties are within band but on the lower end of the Atlas range.
Quality check
| Test | Method (ASTM-equivalent) | Acceptance band |
|---|---|---|
| Density | Gravimetric, conditioned to 23 °C / 50 % RH | 180–280 kg/m³ |
| Compressive (10 % strain) | D695-equiv. on cubic coupon | 200–500 kPa |
| Visual | White-to-cream surface, no blue/green/black | Reject any colored spotting |
| Moisture | Oven-dry mass loss | ≤ 6 % w/w |
| Dimensional | Caliper, three axes | ± 2 % of mold dimensions |
Energy accounting · joules per kg finished
Cradle-to-gate, per kg of finished composite. Substrate-supply embodied energy from published agricultural-byproduct LCA; on-site energy measured per batch. Numbers reproducible from BOM and step durations above.
| Stage | Energy | Note |
|---|---|---|
| Hemp hurd supply (embodied) | 1.4 MJ | Cultivation share allocated to hurd byproduct |
| Substrate prep + mixing | 0.2 MJ | Paddle mixer, 2.5 kWh/batch ÷ 10 kg |
| Sterilization (autoclave 121 °C × 90 min) | 4.8 MJ | Steam autoclave or pressure-cooker stack |
| Spawn production (allocated) | 0.6 MJ | 5 % w/w spawn; embodied energy of grain culture |
| Colonization (chamber + humidifier) | 2.1 MJ | 21 days × 70 W average chamber draw |
| Finishing (oven 80 °C × 4 h) | 1.5 MJ | Convection oven; solar-dehydrator variant ≈ 0.6 MJ |
| Packaging + transport (regional) | 0.6 MJ | 200 km radius assumed |
| Total · cradle-to-gate | 11.2 MJ/kg | ≈ 3.1 kWh/kg · solar-dehydrator variant 9.4 MJ/kg |
For comparison · expanded polystyrene packaging cradle-to-gate ≈ 88 MJ/kg. This recipe is ≈ 13 % of EPS energy intensity.
Reproducibility checklist
- BOM quantities scaled linearly with target output
- Sterilization temp + time logged per batch (datasheet attached at [email protected] on completion)
- Colonization chamber temp + humidity dataloggers (5-min cadence minimum)
- QC results (density, compressive, moisture) reported with raw fixture data
- Energy meter readings per stage
- Contamination rate logged per cohort
- Variations noted: substrate batch ID, spawn batch ID, ambient conditions
License · lineage
Published under CC BY-SA 4.0. Anyone may reproduce, modify, or commercialize this recipe with attribution. Improvements that produce a different property profile should be published as PCB-001.x or as a new cookbook entry, citing this baseline.
Lineage · v0.1 draft · Phasal Bioharvest · 2026-05-14
References · published mycelium-composite literature (Yang 2017, Jiang 2017, Joshi 2018, Bruscato 2019, Yang 2022), cross-referenced against Phasal Atlas cell hemp × G. lucidum.