It came as a bit of a shock when someone pointed out to me that nature wastes nothing. Nature throws nothing away, nor does it create any garbage whatsoever. This is in noticeable contrast to humans, especially those of us living in the United States, where each individual creates an average of five pounds of garbage per day. Our cumulative total is 250 million tons annually.
The problem that nature has is that it lives on a finite planet, where all of the resources necessary for life were delivered when the earth was formed. If these resources were actually thrown away, then there would be less potential for life to flourish with each passing day. Instead, nature not only recycles resources, but in fact the elements that make life possible are flowing constantly from the air and soil into plants, from plants to animals and back into the air and the earth.
About 25 of the 94 naturally occurring elements on earth (surely you remember the Periodic Table of Elements on the inside cover of your chemistry book?) are necessary building blocks in both plants and animals. For plants, three rise to the top of the list as being crucial for plant health—nitrogen, phosphorus and potassium. These are the common constituents of our plant fertilizers, often referred to by their chemical symbols, N (nitrogen), P (phosphorus) and K (potassium).
Nitrogen, phosphorus and potassium are limiting factors in agriculture; if one of them isn’t present in adequate abundance, plant productivity will be reduced. That’s why we fertilize. If we continually take crops off of land, we are taking these three elements (and many others) out of the soil. They will either have to be replaced or the soil will become depleted.
In our current agricultural system we depend on the fossilized solar energy in petroleum to replace these critical components of the soil. In modern agriculture, nitrogen fertilizer is produced using natural gas, and phosphorus and potassium are mined, crushed, and transported utilizing the energy in gasoline and diesel. The journey for the food and fiber that comes out of the soil is a one-way trip, from the field, to the human consumer, and then thrown away into the garbage or flushed away in the toilet.
These two methods of sustaining life—nature’s relentless cycling of nutrients and human society’s one-way transport from soil to garbage dump—have markedly different life expectancies. Nature has been cycling the earth’s critical elements for nearly 4 billion years now, with no end in sight. Our society’s linear transport of nutrients will roughly coincide with the Age of Oil, which started in 1859, and is predicted to last about 200 years, to 2059.
If we want our culture to be sustained beyond 2059, we will have to learn to emulate nature and cycle the elements and nutrients necessary to life back into the soil. Because we happen to live on a finite planet, that will of necessity have to include the byproduct of our own metabolism, which we call excrement or humanure.
Humanure is rich in the vital elements of life; it is composed of 6% nitrogen, 4% phosphorus and 2% potassium. And, it is available in great abundance. Every human being produces about 1000 pounds of humanure per year. Multiply that by the 6.5 billion people on the planet and see how much annual fertilizer you come up with. Imagine throwing away that quantity of vital life elements.
Our aversion to using humanure as fertilizer has two sources. One is that the material can harbor human pathogens if not composted properly. The second source is that humans have somehow forgotten that they are actually a product of the earth—we are literally made of soil and air. Unless you were dropped off here by a spaceship, there are no other options. We arise from the earth and when we die we go back to the earth. It’s a rather spiritual phenomenon.
But having forgotten this simple truth, we have developed a shyness or a fear of the natural cycles that make life possible. And that includes cycling the byproducts of our own lives back into the ecosystem.
Humanure can be easily and safely composted and made completely safe to use as fertilizer. For the full details, consult The Humanure Handbook: A Guide to Composting Human Manure by Joseph Jenkins, available at your favorite bookseller or as a loan from the PSM office.
Briefly, the three critical elements to composting humanure are
1) Creating a compost pile that has the necessary carbon: nitrogen (C/N) ratio for aerobic bacteria to break the manure down into humus. The ideal C/N ratio for bacterial decomposition is 30:1. Humanure has a C/N ratio of about 10/1 (it is high in nitrogen), so it is necessary to add high carbon material like straw to the compost pile. When properly built, a humanure compost pile does not give off any offending odor.
2) Adequate oxygen. The bacteria that break down the manure are aerobic—they require oxygen to function properly. Oxygen is easily made available by using bulky, hollow material such as straw in the compost pile.
3) Heat. Aerobic bacterial action produces heat; compost piles can warm to 140 degree or higher. Complete pathogen destruction in the humanure is guaranteed by arriving at a temperature of 143 degrees F for one hour, 122 degrees for one day, or 115 degrees for a week.
4) Time. Letting the compost pile “cure” for a year after it has finished the aerobic decomposition will offer a guarantee that all potential pathogens are destroyed.
The end product of this decomposition process is humus—organic matter rich in critical nutrients, like the composted steer or chicken manure we purchase at the feed store. These nutrients give life to plants, which give life to us, and then they go back into the living soil in an endless cycle.
The Latin root for humus, humility, and humanure are all the same, and translates as “earth.” Re-integrating our lives with the endless cycling of nutrients and elements is an act of humility in that it brings us out of the imaginary world we create inside our heads and back down to earth, which is a good place to be.
Dana Visalli is a biologist living in Twisp, WA. He is the president of The Partnership for a Sustainable Methow (www.sustainablemethow.net) and the editor of The Methow Naturalist (www.methownaturalist.com)