Reading Paul Stamets’ Growing Gourmet and Medicinal Mushrooms: Third Edition, I learned that many fungal species can be cultivated using sterilized paper as a substrate.
Since my main PhD task remains cutting down the length of my printed chapter drafts, I have begun setting aside used paper for this purpose rather than recycling. That sets up an entertaining dynamic between me and prospective thesis sections: either they make the grade, or I will feed them to my (eventual) mushrooms.