Sunday, August 04, 2013

Talking Shit


Why do we consider it rude to discuss the natural nutrient cycle?

Why are most gardeners afraid to do what is best for their vegetables?

Why is the topic of excrement taboo?


Humans, like every other animal on the planet, pass most of what they eat through their digestive tract. Fungus and bacteria, many resident in the lower intestines, convert this waste into soil that is optimal for growth of the plants, which produce the food upon which humans depend.

Modern life seriously disrupts this fundamental cycle.

First, a word about the taboo… Babies are curious about everything, including their own poop. They test with their primary sensory organ, their mouth. Baby shit, being digested mother’s milk, is pretty benign stuff, and little damage is done. But mothers have a natural drive to defend their babies, so they teach them, in no uncertain terms, that once that stuff leaves your ass you leave it alone. Thus, each of us has learned a primal lesson. “No shit!”

For most of human history, that primary lesson was enough. If you drop it on the ground and leave it alone, animal excrement becomes soil that encourages healthy plants. Organic farmers know this.

The problem apparently started with urban accumulation. When people started living in denser packs, the process of soil construction was often shortened, leading to people inadvertently ingesting feces from each other and domestic animals. Many fecal bacteria, such as E. Coli, are disruptive in tissues outside of the colon. We don’t want them breaking down our skin or our upper GI tract they way they do food waste.

The concept of waste management was born from a rudimentary understanding of the infectious potential of soil creating organisms. With limited availability of sufficient land to process growing amounts of shit, people developed a process unprecedented among land animals. We began to defecate in the water.

This bought some time before we finally realized that when the people downstream drink what the people upstream crapped in, and we again had contamination issues. Being creatures of habit, rather than questioning the assumptions that lead to flush toilets, we developed industrial processes to clean the water. These have never been perfected, but the problem seemed more manageable.

Scientists have long recognized fundamental differences between aerobic and anaerobic decomposition. Virtually every human pathogen is anaerobic. When air circulation is present through the decomposing mass, processes tend to be dominated by thermophiles, microbes that create and flourish in heat. In the same manner as a patient’s fever can kill a disease, thermophiles eliminate pathogens in fecal compost.

Unfortunately, decomposition under water is always anaerobic. It is virtually impossible to reconcile flush toilets with the natural process of soil building. Although elaborate systems have been developed to biodegrade urban waste aquatically, they fail to take advantage of the natural processes through which we evolved.

Composting toilets have been in use for generations. They are perfectly healthful. Furthermore, composting our waste completes the natural nutrient cycle and eliminates the need for commercial fertilizers, most of which are derived from fossil fuels.

As the industrial era crumbles around us, how can we best use this knowledge to create a healthy future? It makes sense for us to build and use simple composting toilets, which will safely process our natural waste for eventual use in our gardens.  Having built and used several composters, I’ll give you my favorite design.

The compost should be in direct contact with the soil, even though some state laws prohibit this. This makes it easier to maintain the right moisture levels, invites earthworms & microbes into the process, and does not increase the likelihood of contamination. Living soil is beneficial. That’s the whole point.

Containment should be substantial and rot resistant. Concrete blocks, poured walls, or rock are ideal for the first three feet off of the ground. Build two areas, each able to hold about a cubic yard of compost. There is no need for a separation wall between them. You will be using one while the other processes. Plywood flooring works fine for the top.

Besides the hole above from which to deposit the compost, each tank will need an access through which you can turn or remove the soil.  Use mesh and screen to keep flies and other pests out, but to allow air to flow through. Seal the toilet seat & lid with gaskets to prevent bugs and odors.

Start the pile with small sticks and reeds. Cover and nest each deposit with straw or wood chips. This will improve the carbon nitrogen balance and provide channels for airflow. It’s okay to put any household or garden compost into the system. Many find that green plant material, such as leaves or grass, is better than toilet paper, but either will decompose quickly.

By the time the second tank fills, the first should be substantially decomposed and pretty much free of odor. If it doesn’t seem completely broken down, you can turn it onto a new batch of sticks to continue the process before introducing it to your garden. Simply cover the pile with plant material and wait until it is nothing but clean soil.

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