The following chart, taken from the 2012 publication What a Waste, shows the global composition of solid wastes, the overwhelming majority of which are organic. Paper plays a large part as well, and taken together they compose 63% of all global solid waste.

More than 60% of solid waste is organic or paper, both of which can be directly used by consumers in a variety of ways

There are many sources of information available about how consumers can directly recycle organic and paper wastes — The Integral Urban House which I’ve mentioned already is one of them — so I merely want to make the point that there are an enormous amount of resources available to those willing to use them.

Used paper handtowels under the bathroom sink in my office

One of those sources is used paper handtowels — a common sight in every non-household bathroom one enters — whether in a five-star restaurant, a government building or an office. I’ve said that circular economies have been on my mind a lot over the past year and I’ve come across many new ideas from The Integral Urban House, The Permaculture City and this excellent episode of The Permaculture Podcast about waste farming — so when I started passing this box each day at work, I wondered how I could use this ‘waste’ as a resource.

Since I had some experience and a lot of interest in growing mushrooms on urban wastes, I decided to use the paper for growing oyster mushrooms (Pleurotus ostreatus). The general consensus among the home-growing community is that oysters are the easiest to grow and I had some prior experience with this species from the coffee grounds experiment.

Briefly, the steps I used are as follows:

Pasteurize the paper and achieve correct moisture content Combine grain spawn with paper Allow time to colonize Fruit, or use colonized paper as spawn (as in step number 2)

Step 1 was the most difficult. At first I tried steam pasteurizing — holding the paper in steam for a period of time, much like steaming vegetables. This was difficult to get right and uses a substantial amount of energy.

Next I tried submerging the paper in water, bringing that water to pasteurization temperature (~70° C) and allowing the paper to drain out after the process. This created large, glutinous clumps of paper with uneven moisture content which were difficult to work with.

I realized that simply introducing the ‘correct’ amount of water from the start would be the best approach. After some experiments with small amounts of paper, I hit upon the magic ratio of 1 part paper (in grams) to 1.34 parts water (in milliliters). The process looks like this:

Measure the paper. As an example, in the batch pictured below I used 1500 grams of paper waste. Boil 1.34 times the paper weight in milliliters. In this case, that is 2 Liters (1500 * 1.34 = 2010). Put the paper in a heat-resistent container with a lid. I used a 30L aluminum pot, but a 5 gallon plastic bucket would also work fine (as long as it is heat-resistent). Pour the boiling water over the paper, put the lid on and shake it around a bit so there are no dry spots. Put a blanket or something else over the container so the heat stays in and leave it until it’s cool to the touch. This takes anywhere from 2–4 hours.

At that point, the paper is pasteurized and ready to combine with spawn.

In the pictures below, I combine pasteurized paper with spawn I had from previous waste paper experiments, you could just as easily use grain spawn from a supplier. I used shiitake.de for my first few experiments.

Paper colonized by oyster mycelium now used as spawn

Layering pasteurized paper with spawn. Note the texture of the paper: it’s evenly moist but not dripping wet

A finished tub — the white bits are oyster spawn