Wednesday, November 30, 2011

Composting 101

Over the course of several postings I’ll tell you all I know about composting.  I won’t claim to know everything but I have been actively composting for at least forty years so I do know quite a bit. Much of what I have learned through experience and experimenting does not agree 100% with what many other “experts” will say.  So, as in all things, you’ll have to read what I write and do some research on your own, and then decide what works best for you.

As most of you know I am a Soldier and have been on active duty since February 1983 and was in the PA National Guard for five years before that.  So I move quite often; on average about every 34 months.  Even so, with a few exceptions, I have continued to have at least a small garden and to make and use compost in my gardens.

So what exactly is compost?  Very simply it is organic material (anything that was once living) that has been allowed to biodegrade through microbial action. In other words, it has rotted. During the composting process, various other life forms (worms, insects, bacteria, fungi) eat and digest the organic material (leaves, grass, sawdust, food scraps, etc.) and then excrete their own waste products.  As well, most of those life forms go through their own accelerated life cycle and the compost contains their decomposing bodies. It is mostly the digestive process of the micro-animals and the colonization of various fungi and bacteria that produce the nutrients contained in the compost.

Think of it this way.  What is the difference between the grass, hay, and grain that a cow eats and its manure?  Mostly - the inclusion of the stomach acids and the intestinal bacteria (which also adds nitrogen).  Otherwise it is the same stuff coming out as went in.  There is no transmutation of elements (alchemy) involved here.

There are several different methods of composting but only two major processes; aerobic composting and anaerobic composting.

Aerobic means “with oxygen” and anaerobic means “without oxygen”. For our purposes we will only talk about aerobic composting but I’ll briefly explain anaerobic composting here.

Anaerobic composting is also sometimes called “digestion” because that is what happens in the stomach and intestines of animals.  A completely different class of bacteria is involved in anaerobic digestion; they can only live in a low or no-oxygen environment.  By-products of anaerobic digestion are such things as methane gas and sulfur-dioxide; the two principle parts of flatulence. In a controlled environment, organic materials can be turned into energy by use of a “methane digester”, a large anaerobic composter that produces large amounts of flammable methane gas, which can be used to run an electric generator for instance. Suitable for large dairy farms perhaps, but not so much for the back-yard gardener.

Aerobic composting is what we are interested in. All organic material will break down, decompose, over time.  But what we want to do is speed up the process and retain the resultant nutrients.  This requires intentional composting.

Efficient composting requires five things: 1. Carbon-rich material (the food); 2. Nitrogen-rich material (the energy); 3. Moisture (all living things need water); 4. Oxygen (the life forms we are interested in must breath oxygen); 5. Heat (life processes slow down when cold).

Let’s look at each of these:

Carbon-rich material. These are often referred to as the “brown” components of compost.  Carbon-rich materials are such things as dead leaves in the fall, straw, wood chips and sawdust, shredded paper and cardboard, and other dead, dried out plant material. This material will be the bulk of your compost pile; in fact it should be at a 30 to 1 ratio with the Nitrogen-rich material. The carbon-rich material provides the food and shelter to the various life forms in the compost pile. They also create the air spaces needed to maintain a suitable level of oxygen in the pile. Fungi and bacteria will immediately colonize the “brown” material and start to break it down into its chemical component parts.  It is this fungi and bacteria smorgasbord that attracts slightly higher life forms such as insects, worms, and other microbes

Nitrogen-rich material. These are often referred to as the “green” components of compost. Nitrogen-rich materials are such things as animal manure and urine, green grass clippings, green plants and leaves, and kitchen scraps.  This green material provides the energy the various life forms in the compost pile need to maintain there digestive activity.  Too much green material in a compost pile, such as a huge pile of green grass clippings, and bacteria immediately use up the oxygen and die off.  The pile is then colonized by anaerobic digesters and you end up with a slimy, smelly pile of goo. Green material should be at a 1 to 30 ratio with the brown material. 
Moisture. All living things need water to survive but too much water is no good.  Too much water in a compost pile fills in the tiny air spaces and suffocates the living organisms. Likewise, if the compost material is too dry the composting process will slow down or halt. Your compost material should be about as moist as a wrung out sponge.  If you can squeeze water out of the composting material, it is too wet. If it is too wet you can do a couple things. One is to turn the pile to mix the drier outer layers with the wetter inner layers.  Hopefully this will balance it out. Or, you can add more dry materials to soak up some of the moisture. If the compost pile is too dry, you can spray it with water while you turn the pile to moisten the material evenly. REMEMBER-chlorinated water will kill microbial organisms.  You don’t want to do that.  So if you are on chlorinated water you will need to fill up buckets or a kiddy pool with water and let it sit out in the sun for a couple days to de-chlorinate.

Oxygen. Not all living things thrive on oxygen but the ones we are interested in do.  Therefore the more oxygen you can get into the pile the better.  This is most often accomplished by “turning” the pile.  I have a four bin compost set-up so turning the pile is as easy as forking it out of one bin and into another.  As I do this I shake and “fluff” up the material so there is lots of air space in between. DO NOT pack down your compost pile.  It will settle on its own but what you really want is lots of open space in the material.  The more often you turn your pile the faster it will compost (all other things being equal).  That is the purpose and success of the rotating compost barrel systems you can buy.  Each day you go out and turn the crank a couple times and the compost is aerated. 
Heat. Most living organisms prefer to be warm as opposed to being cold.  The micro-organisms in your compost pile are no different.  The heat given off by the billions (trillions?) of micro-organisms in your compost pile will heat the material up to over 120 degrees and depending on the materials and oxygen content even up to 150 degrees. This is desired because it helps to kill weed seeds and other undesired pathogens. In the summer it is not too hard to keep the pile warm, although normal evaporation of the moisture from the pile will tend to cool it down quite a bit.  In the winter, especially if you live in the north, it is difficult to maintain any warmth at all and the composting process crawls to a stop.  Deep inside the pile there is probably still some activity though. You can increase the heat by ensuring there is a proper Brown to Green ratio, by frequently turning the pile to add oxygen, by placing the pile in a sunny location, and by wrapping the pile in clear plastic in the cooler months.

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