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How to Build Two and Three Bin Composting Systems

Adding good rich compost to your gardens is one of the smartest things you can do as a gardener. Compost is pure organic matter and when added to the soil it helps to reactivate micro-organisms which help to maintain a healthy balance in the soil.

A 3 bin composting system.

Composting is not complicated, but there are certain things you can do to make your composting pile or bin more effective, thus creating good rich, usable compost in less time.

Proper Dimensions and What to Add to a Compost Pile

Leaves, twigs, grass clippings, straw, rotted livestock manure, fruits and vegetables can be added to a compost pile. The size of your compost pile will determine how well it works. A compost pile should be larger than one cubic yard, and smaller than 5 cubic yards. A cubic yard is 3′ wide by 3′ wide, by 3′ high. A small pile will not heat up enough to make the process work effectively, while a pile that is too large will not allow for enough air circulation or water penetration.

The amount of surface area of your pile is also important to it working effectively. The more surface area there is, the more it allows water penetration from rain plus it also increases & improves air circulation. Making a pile with a large surface area that is not adequately deep will result in a compost pile that does not generate enough heat. Moisture, heat, and air circulation are the keys that make a compost pile work.

The finer the material you put into your compost pile, the sooner it will break down into good rich compost. If you don’t have a shredder, at least cut the materials up with a spade before adding it to the pile.


Your compost pile should be made up of different layers. The bottom layer should be coarse material such as twigs to allow for air circulation around the base of the pile. The second layer should be a mixture of leaves, grass, or other leaf matter. Mixing dry leaves with fresh green material also helps to keep this layer in good balance. The third layer should be soil to add micro-organisms to the pile. A fourth layer can be rotted cow or horse manure if it is available. If you do not have access to manure just start over with a layer of more coarse material and repeat the steps above.

Keep building your pile until it is 36 to 40 inches high. Once you have the pile you want, don’t add anymore to it. You don’t want to keep mixing fresh materials with the batch you have cooking. After 5 or 6 weeks you can turn the pile with a fork and let it cook a little longer and turn it again in 5 or 6 weeks. Keep repeating this process until you have good rich, dark brown compost that crumbles through your fingers.

That’s the recommended way to create compost. However, I have a weak back and find that turning compost with a fork aggravates my back. Not only that it’s a lot of work! So this is what I do…

I build two compost bins side by side. More accurately, I build one large bin that is 10′ long with just two sides 5′ long and put a 5′ divider in the middle. This gives me two, three sided bins that are 5′ by 5’. Filled to the height of 42″ each bin holds almost 3 cubic yards of raw compost material. I construct these bins by digging postholes and setting 3″ by 5″ garden timbers in the holes vertically. The slides are made by nailing pressure treated 2 by 4’s to the timbers, making sure to leave a 2″ gap between each board for air circulation.

I fill one of the bins as described above, until it reaches the desired level. Once the first bin is full, I start filling the second bin as I get more organic material. Instead of turning the pile with a fork, I use my front tine rototiller to dig into the front of the pile, chewing up the materials and turning it into mulch. I then shovel this mulch like material up onto the top of the pile and rototill it some more.

I just continue this process until I can’t put any more on top. This procedure makes my pile higher and narrower and admittedly the material in the back of the pile does not get turned until I remove some of the material from the pile. By turning the material with a rototiller and then putting it back on the pile, it breaks down quicker. When I have some good rich material in the front of the pile, I remove it for use in my gardening efforts.

This allows me to till deeper into the pile and turn more of the compost material. Why this is all taking place my second pile is already on its way to becoming compost. When I have completely emptied the first bin, I start filling it again, and start the roto-tilling process on the second bin.

Mike McGroarty is the owner of McGroarty Enterprises and the author of several books. You can visit his website at  and read his blog at

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