Microbial Life of a Compost Pile

If you are expecting my science project here forget it. I have decided that if you want the down and dirty  on the microbial life of a compost pile you can check out this link for The Cornell Waste Management Institute at Cornell University. If you want to know the very specific science of the composting process from the shapes and habits of the bacteria and fungi to how to observe them I recommend you check it out. That site is the bomb.

I am putting together what I hope will be an overview to aid in the general understanding of what goes on in a compost pile at a microscopic level.

Your compost pile is a metropolis of life. Remember the Invertebrates of The Compost Pile article?
Those are just the big fish. The compost pile just teams with life beyond our ability to see without magnification. The life there, the microbial characters, their vast numbers and the work they do makes compost not just possible but an amazing, nutrient packed plant medium without equal. Your compost pile is the most efficient super producing factory ever, and this all happens in your back yard, and with only a small work contribution by you, so go on, lie in the hammock, sip lemonade and watch your compost at work. (Yeah, I know, I don’t actually use the hammock in the yard either.)

Bacteria are the smallest living organisms and the most numerous in compost; they make up 80 to 90% of the billions of microorganisms typically found in a gram of compost. (Nancy Trautmann) 

 As they begin working to break down your compost they contribute a huge variety of enzymes to your compost.  Enzymes are proteins and they do the breakdown work of the the single cell organisms that made them.  I would call enzymes digesters.  The work done by bacteria and their enzymes is the primary source of heat in your compost pile.  As the pile heats up past 104 f. new bacteria, thermophilic bacilli come to life from dormant spores. They are called Thermophilic because they thrive in high temperatures, and there are multiple varieties of them that carry on work in temperatures up to 140 degrees f.  These types of bacilli are also present in hot springs, steaming hot piles of manure, and under sea thermal vents, and in mats and clumps of rotting vegetation on the ground.  

During the thermophilic stage the breakdown of plant matter is accelerated. Proteins, fats and complex carbohydrates are used up in this phase. This is also the time when weed seeds are broken down and destroyed (remember; seeds are made of protein, fats and complex carbohydrates), and bacteria from manure (more protein) is consumed. When the high energy plant matter is mostly exhausted the pile cools, and other bacteria take over the curing of the pile and the final plant matter break down. In addition to consuming plant matter the organisms of the compost also consume each other, their own wastes, and the corpses of invertebrates. The longer your pile cures the more diverse it’s bacterial life becomes, and that is desirable.  

Lucky I didn’t get too technical right?  WAIT  There’s more.

The earthy smell of your compost pile comes from a group of bacteria called Actinomycetes they are present during the end of the heat phase, and predominantly during the curing phase. Their enzymes break down specific complex organics such as cellulose, lignin, chitin, and proteins. Their enzymes enable them to chemically break down tough debris such as woody stems, bark, or newspaper. They grow long branchy filaments. So if you see what looks like grey spider webs going through your compost pile. That might be the Actinomycetes…  or actual spider webs. 😀

There are also fungi which includes molds and yeasts in your compost. They are present in all phases hot and cool of the composting process. They break down cellulose and bark and particles too acidic, dry or lacking in nitrogen for bacteria to handle. They break those tougher particles down to a composition that bacteria can then finish. Like Actinomycetes they make what looks like strands or webs in your compost.  

Protozoa are one-celled microscopic animals found in water drops in compost. Protozoa can consume organic matter like bacteria do but they also chow on bacteria and fungi.  

Rotifers are multicellular organisms also found in water drops in compost. They consume organic matter, bacteria, and fungi like the Protozoa do.  

Curing Compost is the ending of compost and the beginning of soil. The longer it cures the more populated and diverse the life of the soil becomes. As soil it will have become a living universe of bio organisms ready to team up with plants to make the ecosystem that will be your super healthy super productive vegetable garden.

Hopefully if you get through this overview you see that there is a lot of repetitive break down of plant components like cellulose happening in your compost pile, and not just there either. It happens nearly anywhere stuff falls and lays on the ground in your yard. However without invertebrates and billions of microbes to break down our wastes we would soon be overrun with undigested garbage. In landfills microbes do not have a favorable environment in which to thrive and break down vegetative wastes. Wastes stand undigested in landfills for ages. It should be a moral imperative of every gardener to keep the wastes of gardening out of landfills and recirculating through the garden environment where it breaks down very quickly and is ever needed as mulch, compost and finally soil.  

Now go turn that pile.  😀

One Response to Microbial Life of a Compost Pile

  1. Danny says:

    Interesting article to the laymen. Very detailed. I had to read it twice. Well worth it.

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