Stella McCartney, who has debuted a prototype of her Falabella bag made entirely from mycelium leather [29]. So the big question is, how hard can this be? The answer is not at all. In this section, we will be diving into the fabrication process for myco-leather and exploring the versatility of this material that has the same kind of luxury as a McCartney bag.

​

The recipe for this speculation draws upon the techniques described by PhD Researcher Elise Elsacker at the Vrije Universiteit Brussel via the BioFab forum [24] as well as in combination with our own experimentation. The mycelium we’ll be using comes from the mushroom species Pleurotus ostreatus, otherwise known as your friendly neighborhood oyster mushroom. A single petri-dish size of viable mycelium should be sufficient, and this can be easily extracted from a kit ordered online. Alternatively, use oyster mushroom stems from the grocery store. 

Sawdust pellets are a wise choice for the substrate. They are relatively affordable, and the pasteurization process they undergo means that there is no need to sterilize the substrate, saving time and money -- a double win. To make the cells grow big and strong in record time, it would be beneficial to hydrate the pellets in a sterilized medium of malt extract, yeast extract, peptone, glucose, and distilled water. These ingredients provide the building blocks for the mycelium proteins themselves, as well as with the energy it needs. No autoclave is needed for the liquid growth medium sterilization -- a home kitchen pressure cooker will do perfectly. Pack the substrate in a thin layer in a shallow container of the desired size (preferably also transparent, so you can watch it grow and maniacally laugh, “it’s alive!”). 

After an ideal period of incubation at slightly above room temperature and in high moisture, the myco-leather will grow at its maximum rate. Oyster mushrooms like to bask in warm and humid environments, so this will ensure that the hyphae grow all the way through the substrate as fast as possible. Once this happens, the sheet can be harvested. While the sheet is still alive and somewhat humid, preserve the flexibility by soaking it in an equal parts choline chloride and ethylene glycol plasticizer. This optional step will emphasize the characteristics of actual leather: flexible, durable, and versatile. After this, allow it to fully dry, ideally at a high temperature (i.e. dehydrator or low temperature oven), to stop the growth of the mycelium. Since the substrate layer was thin, it will be easy to cut it into your desired shape, including the silhouette of a real-life cowhide.  

​

With this speculative recipe, a myco-leather rug should be able to grow to the size of a standard cowhide within a couple of weeks, compared to the years it takes to raise a cow for slaughter [25]. Affordable, accessible materials and clear, comprehensible instructions make this speculation less of a shot-in-the-dark concept and, instead, a highly feasible grow-it-yourself project. Imagine that: a myco-leather cowhide for a fraction of the time and cost for the real, unsustainable thing. The combination of its raw style and the environmentally-friendly morality boost will very soon have you asking “does IKEA have this in stock, yet?”. Unfortunately, they don’t, so it’s a good thing you can now make this conversation starter yourself to adorn your hardwood floor in no time.