Houses rise and fall, crumble, are extended,
Are removed, destroyed, restored, or in their place
Is an open field, or a factory, or a by-pass.
Old stone to new building, old timber to new fires,
Old fires to ashes, and ashes to the earth
Which is already flesh, fur and feces,
Bone of man and beast, cornstalk and leaf.
--T.S. Eliot, Four Quartets: East Coker
The wind tells me we're in the heart of Autumn. Heaps and piles of leaves swept and blown from the sidewalks remind me of the ephemeral. Skeletons of plants from the late summer harvest now crumble in the compost pile. It was only early this past year that I discovered the joys of composting. Over the course of about ten months, my housemates and I have developed a fairly extensive composting system for our home and garden. Quite by surprise, I have found particular delight in watching the green flesh of life return to the flesh of the earth. To preface this discussion, by formal training I am a physical scientist. By the scientific method, I observe and I experiment. These skills have found particular worth in high throughput composting while providing an interesting perspective for gardening. Here I introduce you to my composting philosophy and outline the variety of composting methods we employ.
Our passive compost pile at work. It consists only of a trellis wire wrapped into a cylinder. This is the lazy dude's compost pile. Without turning, this pile will take upwards of two years to mature. I am not a particular fan of this method, but it has provided a place for some of the hard to break down materials, include many thick root systems and crazy weeds.
Composting science boils down to the prolific growth of thousands of billions of aerobic bacteria. Decomposition is an inevitability, but a good compost pile is so much more than just a degradation process. It is a seething universe of bacteria, fungi, nematodes, protozoa and countless other forms of life. In the fall of one, comes the rise of another. A mold entwined between straw, pockets of ant colonies, a bulbous writhing mass of grubs, spindling outgrowths of mycelium--one feeds on top of the other to contribute to a growing network of life feverishly relishing in diversity. From egg shells to tomato vines, from coffee grounds to laundry lint, to watch a myriad of organic forms transform into a fluffy humus rich in nutrients is a marvelous thing!
A view behind our garage at the composting station: home to two conventional compost bins, a compost tumbler and the passive compost pile. The two large compost bins were built out of scrap lumber we scored from "
In the prime of compost decomposition, a tremendous amount of heat is generated; because of this, it is not uncommon to see steam rising from a pile. This past year I monitored the internal temperature of our large compost piles each day over the course of a month. Within 24-48 hours of layering a pile, the temperature reaches upwards of 160-170 degrees Fahrenheit (~75 degrees Celsius). A peak in temperature is quickly reached with a gradual drop to a steady 110-130 degrees over the course of a week. At that rate of heating, the vast majority of weed seeds are killed (one of the many positive benefits of a well manage pile).
I recall with great joy the first time I felt that incredible amount of heat. At first, with care, I measured the internal temperature using a long thermometer. One hundred sixty seven degrees Fahrenheit! Excited by this observation, I drove my hand into this ripening mass of multitudes--it was as if to touch a foundation of life emerging and thriving out of the death of another--boundaries between individuals blurred with biochemical thermodynamics playing out on a stage before me--half decomposed, nearly unrecognizable fragments steamed with vapor. A feeling swept over me as if I were the first human to have lit a fire with a purpose and intention. And still, there was a strong tone of humility in that touch of warmth. With each turn of the compost pile I took pause to reflect on the earth, its creatures and my grandly tiny niche in the scheme of all this cacophonous harmony. And then a sort of awkward realization came over me. I had told my housemates it was totally cool to urinate all over the compost piles--as a sort of activator, you know? They gladly obliged… Fortunately, I don't much give a shit about piss and I love my housemates.
Another view of the composting stationing, including one of the primary bins and the compost tumbler. Right now I use the compost tumbler mostly as a backup bin. The internal temperatures in the tumbler have a tendency to be much lower (100-120 degrees Fahrenheit), although it is significantly easier to aerate and turn the material. I ascribe this difference to the relative sizes of these two systems. The larger bins (around
But what is the source of such thermal energy? ‘Tis but the breath of billions of bacteria! Almost in an act of meditation, I humble myself before this fact. The same progression from order to disorder, from complexity to simplicity, occurs with each breath of our being as in the compost pile. It is the second law of thermodynamics at work: a system tends toward great disorder with respects to time. In a downhill spiral from complex biological molecules and oxygen to carbon dioxide and water, you and I, as well as trillions of bacteria, burgeon with new growth in the combustion of old life. Indeed, if you dissect the process of decomposition to the molecular level, you can view it fundamentally as a combustion sequence. That is to say, the process of aerobic bacteria growth can be paralleled to the metabolic action on the part of animal equally as well as the exothermic bloom of flames from timber. A fire is alight both in my gut and the compost pile! Solid matter goes into the compost pile largely in the form of rigid, complex biological molecules, and a substantial portion of that matter makes its exit as a gas.
The home made mobile compost tumbler: made entirely out of recycled materials from “
The chemistry of compost is an obvious complexity, but the fundamentals behind the process are well understood. The goal is to bring together solid feedstocks of nitrogen rich and carbon rich materials with ample oxygen. The carbon rich portion of the pile serves primarily as an energy source for the burgeoning bacteria while also providing the scaffolding necessary for cell protoplasm construction. The microbial respiration of this carbon content is an exothermic process and thereby evolves a tremendous amount of heat. A product of this respiration is a substantial volume of carbon dioxide gas. As we humans breathe in oxygen and expel carbon dioxide, so too do our relatives the bacteria. This fact is most evident in the gradual volumetric loss of the compost pile--over the life of compost, about 2/3 of the volume entering the system is released from the atmosphere in the form of carbon dioxide! The nitrogen rich material provides the other critical building block for cell develop: to access amino acids, proteins, and nucleic acids necessary for growth and reproduction.
What is more, multitudes of life rise and fall in overlapping successions with continuous recycling of organic material. As if from the dusk of one civilization to the dawn of another, the bacteria steadily grow and die with distinct forms prospering in different temperature regimes. For rapid composting, temperatures above 130 degrees Fahrenheit should be reached and sustained. At these heightened temperatures the thermophilic bacteria dominate and yield the quickest decomposition. Thus, from the beginning of my compost enterprise, I made it a priority to actively turn the compost piles to support a rich aerobic environment. It is only with the appropriate initial ratio of carbon to nitrogen-rich material and ample aeration that a compost pile will reach sustained temperatures above 130 degrees Fahrenheit. That is what we want—an eruption of life and energy!
With the aid of the compost tumbler, active turning of our main piles combined with a chipper/shredder used to increase the surface area of the solid feedstocks, we have aged about a cubic yard of mature compost and integrated it into the garden as a mulch. For the past 4 months, we have been composting all of our kitchen waste in the composting piles. I look forward to the spring when this investment in decay will pay dividends to our soil. In future posts, I will take care to discuss the details of each composting pile and the techniques we employ when preparing and maintaining the piles.
Returning me to common clay
All that I am will feed the trees,
Animals, and fishes in the seas.
When radishes and corn you munch,
You may be having me for lunch
And then excrete me with a grin,
Chortling, "There he goes again!"
--Lee Hays, 1979
