Now we get to another matter, that of two major classes of organisms that work to cause decomposition.

One group of creatures are called aerobic from the Greek work for air, that is they need air to live and do their work. These creatures work very well and efficiently. They generate a lot of heat while they convert the carbon and nitrogen inside the pile and reduce the volume of material. The high heat generated (about 160 degrees Fahrenheit) will kill many of the weed seeds and germs in compost. The heat also helps all the pile to break down faster and results in a nice clean fairly germ free product in just a few months. This system however is a lot more work. Since the organisms need a lot of air they will die off after a week or two as they use up the available air in the pile. When this happens you need to turn the pile and let it get more air into it, this will renew their ability to generate heat and reproduce. Ideally you will learn the timing of this and do it before their population has reduced in size. You can determine when this point is reached by the temperature inside the pile, when it cools down a bit it is time to turn it and re-wet it to keep the moisture nice and constant. When turning try to get the outside of the pile into the center of the new pile you created from the tear-down of the old one. This will let the materials on the outside that do not get much decomposition get into the center where all the action is going on. The high heat, the nice snug moist environment will ensure they get more quickly broken down.

Initially when putting the pile together you will mix the ingredients together, wet it all and cover it with a tarp if that is your want. Then after a couple days you will feel some heat inside the pile if you take a shovelfull of material out and feel inside or use a long soil thermometer. After a week as the organisms get to a large population level you will have the high heat of 160 degrees or so which is desirable to kill weed seeds and pathogens. It is at this time that they are using so much air that they are depleting it. After a few more days you may see a reduction in the temps. This is the time to turn it, and re-wet it. Then cover it again and let it start cooking. It will heat much faster this time as the organism populations are very high now. In fact the next day you might have the high temps. After a week or so it will be good to turn it again. Each time you turn it try to get the outside of the pile into the center if you can. I use a tractor to turn ours, and often just plow into it and roll it over, it will all mix in time anyway.

Hand turning it is hard if you are using the multiple bin methods described in so many books and publications. I prefer just a nice big space to make compost, I like to have lots of room to move and work efficiently. I would rather have a long area to move the compost over a few feet and then back if I did not use a tractor.

After a week of cooking again the pile will need to be turned again, this time it may not heat up so quickly as the major sources of nitrogen and carbon the organisms use are getting depleted by them, and converted into a form that the next stage of creatures would use. So the pile will still heat up, but not quite so much.

At the next turning the pile will heat even less, but you will notice that it is starting to look a bit more like compost and less like the material it was originally from. Each time you turn it not only are you adding air to the mix, you are also mixing the materials, and putting the materials near more of the hungry critters inside the pile.

When on the fifth turning or so the pile does not heat up all that much it can be left to sit and mature for a while. The aerobic bacteria have done their job of converting carbon to CO2 and nitrogen to nitrates and ammonia. When the pile sits for another month or two it will mellow and mature. Other creatures will get into it and do some more work on it, making it more of a product that the plants and soil can really use. A few more turnings here is OK. Any additions of air into the mix is beneficial, and be sure to keep the pile nicely and evenly moist. This is part of the reason I do much of my composting in the winter. Here in Central California we get most of our rain in the winter, and I do not need to worry about wetting the pile too much. Yet the high heat generated inside the pile will maintain itself in the mild winters we have here. It is really fun to dig the tractor into a big pile of hot compost in the winter cold. The steam that comes from the pile is amazing and impressive!

Let that pile sit for a month or more after the heat has stopped in it. It will then be OK for use. But it is best when it has been colonized by native worms. Yes, they are the true indicator of finished compost as they will not enter a pile while it still has a chance of developing heat. When you dig into a pile and there are masses of worms you have some really good compost that will make your soil very happy.

Anaerobic Compost is made with organisms that do not like air. These are the creatures that in nature do their work in the dank places we humans tend to avoid. Swamps, bogs, deep cold lakes etc. They will work on compost, but they work slowly. They tend to release noxious gases that are quite disagreeable. If you have ever left a bag of grass clippings and then tore it open a week later you have had a close encounter of the third kind with these creatures.

While anaerobic composting may be less labor intensive because you do not need to turn the pile, it is smellier, and takes a lot longer to finish out as the organisms do not have as high a metabolism. They do however tend to reduce the volume of the pile a lot less than the aerobic organisms. This means that more humus may be the result. To make an anaerobic pile gather the materials together and wet the pile. Cover it with the tarp and let it sit. The pile will initially be colonized by aerobic bacteria, but when they have used up the air and begin to die off, they will gradually be replaced by the anaerobic bacteria. All you have to do is monitor the moisture level of the pile. If the pile develops into a smelly mess it has too much nitrogen and you should add some carbon based material to it turning it as you do this. This will reduce the odors some and get it heating up again. But in a week or so it will again be an anaerobic pile.

Anaerobic piles will tend to have more likelihood to have an overabundance of nitrogen causing the dark slimy feel due to the fact that the organisms in such a pile have less of a need for nitrogen and high energy. They work slower, and the nitrogen will tend to convert to ammonia making a bit of a smelly mess. In the aerobic pile the bacteria use the nitrogen all the time, keeping such a condition from happening as much. In fact if the aerobic pile is getting smelly and slimy it is often enough to just turn it and renew the population of aerobic bacteria, they will quickly convert the nitrogen into nitrates and make the pile less offensive.

All in all I would rather have an aerobic pile, although I must confess that I do not always turn them weekly, and I often let my piles sit for five months or more before I use them. I may turn them in this time monthly or so. So in effect I guess I am using a bit of both systems.

This instruction is certainly not all-inclusive. Even though composting ahas been going on for centuries, and scores of books and thousands of articles have been written about it there are as many ways to build compost piles and manufacture it as there are materials that are suitable for it. And though this article is written mainly from the perspective of one who has always gone with the 'bigger is better' mentality and has never had a really tiny compost pile, many of the thinking in this article can be used to manufacture compost on a small scale in the common backyard compost barrel or worm bin.

At any rate I encourage you to try your hand at this, you will conserve resources, save yourself some bucks, and get some fresh air and exercise in the process.