The following instructions list the steps to build a backyard compost pile, and related information about each step. Those steps which are optional are noted -- remember that following these optional steps will decrease the decomposition time from 1 - 2 years to as little as 6 weeks.
Read the document from beginning to end, or use the links below to jump to any point in the document.
We urge you to utilize all links within the text to discover the maximum amount of information. Refer to the "Alternatives" link to get a list of different ways you can perform the step ranging from the least effort alternative to the greatest effort alternative.
Find a Location for the Pile
Your pile can be built anywhere except up against a structure such as a house or fence. Macroorganisms, i.e., bugs, etc., will assist you in the composting process. You want them in the pile, not in the house. Also, I've read that compost can rot some types of wood, although I would imagine that the moisture and organisms in a pile have a greater effect than the compost itself.
The following list will give you a number of points to consider in locating your pile. The more of them you meet, the better off you are. Remember that your pile can be moved at any time, so you don't have to get it right the first time.
- At least 2 feet away from a structure such as a fence or house
- Easy access for you
- Close to source of materials, i.e., leaves, grass clippings
- Easy access to a source of water for wetting down the pile
- Level surface
- Well-drained surface
- Pavement or earth underneath are OK (on pavement, the nutrients can't leach out into the ground; on ground, earthworms will come to help decompost your pile)
- Near, but at least 2 feet away from, a wall or tree to break the wind (which could dry out your pile)
- Not so near a pine tree that it would catch a lot of needles (pine needles are high in carbon and will slow down the composting process)
- Shade if you live in a very dry, hot climate (to keep pile from drying out in intense sun)
- Away from vegetable gardens (slugs and other critters may like your compost pile)
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A bin is unnecessary. You can just build your pile on the ground. However, bins are useful for keeping your pile looking neat, retaining heat and moisture, and avoiding the negative effects of wind and weather. If you live in a rural area where food wastes are composted in your pile, a bin can help deter pests. If space is a problem, a bin can be helpful in containing your pile within a confined area.
If you want to use a bin, you may build one or buy one. If saving time is your highest priority, buy one. If saving money is your highest priority, build one -- it is not difficult. Refer to the following links to assist you:
- Instructions for Building a Compost Bin. Materials which can be used to build a compost bin are almost limitless. Some are hogwire, cinder blocks, bales of hay, wooden pallets, and lumber.
- Types of Compost Bins Available from Vendors. The thing I like the best about ready-made bins is that if you are already dragging your feet in your efforts to start composting, you can take a "giant step" by getting a ready-made bin. The bin I use came in two parts. The first piece was the four sides of the bin already connected, but folded. The second part was an aeration tube for the middle of the pile with a plastic cap on it. I just unfolded the bin (2 seconds) and put the plastic cap on the aeration tube (18 seconds). In just 20 seconds I went from thinking about starting a home compost bin to having one in operation.
The best thing to do when choosing your bin is to walk through the Step-by-Step Instructions, imagining how you would do each step with the bin you are considering. Whether you are buying or building, you should consider the following factors:
- Size. The pile should be at least 1 cubic yard (3 feet wide x 3 feet deep x 3 feet high). This is large enough to retain heat and moisture, but small enough to remain aerated in the center as long as the pile is frequently turned. Do not build a bin larger than 5 feet wide x 5 feet high x any length. This size would be too large to remain aerated in a home compost operation.
- Easy access to add materials. You need to make sure that the method for adding materials is appropriate for the composting you will do. For instance, if there is a plastic lid that is difficult to remove and/or attach, that might be OK for someone who was going to compost infrequently in batches because they wouldn't have to deal with it very often. However, if you are using the "add as you go" method, it could be quite frustrating and may discourage composting.
Larry Wilhelm of the Earthworks organization has an interesting setup. He places some of his compost bins under a group of rabbit hutches. This allows the rabbits to add manure to his pile on a regular basis without additional effort from him. To move the manure throughout the pile, he keeps chickens in the compost bin who distribute the manure by scratching (and also provide manure of their own). Of course, the chickens also eat some of the pile's decomposers -- no system is perfect, but this one is close!
- Easy access to remove finished compost. I once saw a commercial bin that required that you turn the bin onto its side and remove the bottom to access the finished compost. If you are composting in batches, but don't intend to turn your pile, this might not be a problem. At the end of the composting process, the compost would take up only 25 - 40% of the original weight of the pile. However, if you "add as you go", you would have to turn over a sizable container loaded with material and, therefore, quite heavy. Also, when you opened the bottom, partially decomposed materials may fall out along with the finished compost.
I heard of one woman who built a compost bin out of a discarded rabbit hutch. She set it up on cinder blocks at each corner and placed a metal tray underneath the bin and between the blocks. As compost was created at the bottom of the pile (there wasn't a lot of turning going on here), the compost fell through the 1/2" wire mesh to the tray below. She just slid the tray out to access her compost, then returned the tray to its location. Great idea!
- Ability to turn pile. Some commercial bins have a handle to turn the entire bin without having to handle the product. Ask if the vendor has a demo bin FULL of materials you can test. Make sure the full bin is not too heavy for you to turn.
If there is no handle, think about how you would turn the pile by (1) stirring with a pitchfork or (2) restacking the pile. The side of the bin will be 3 to 4 feet tall, so it is best if there is a way to remove one side so you can get at it easily.
- Appearance. If you are going to place the bin where you or your neighbors will see it, you need to make sure its appearance is not objectionable.
- Creature access. If you live in an area where composting food scraps is acceptable (does not include most suburban or urban areas), make sure that your pile cannot be accessed by whatever local wildlife is present -- from rodents to bears!
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Compost can be made without materials preparation. However, preparing the proper materials for a "batch" will provide for faster composting. Preparing materials includes two things: gathering enough materials for a batch and chopping up woody (carbon) materials.
Where do I look?
Materials can be located almost everywhere and are available at any time of the year. Assuming that the finished compost is going to be used on your property, the best place to find the raw materials is on your property. If there are not enough materials generated on your property, look nearby. If animal waste is available (not dog or cat feces), mix that with vegetative materials. However, you can build a pile with only vegetative materials such as grass and leaves.
Carbon vs. Nitrogen
Alias: Browns vs. Greens, Burnable Things vs. Stinking Things, etc.
All living organisms need a large amount of carbon and a smaller amount of nitrogen in order to sustain themselves. This applies to the bacteria that will decompose your pile. These bacteria need a ratio of 30 parts carbon to 1 part nitrogen to create an OPTIMAL environment for growth and reproduction. Note that the 30:1 ratio is by weight, not volume. All this growth, reproduction, and decomposing generates heat. The hotter your pile becomes, the faster it decomposes. (If this is news to you, see our discussion on the mesophilic, psychophillic, and thermophilic bacteria.) The closer to 30:1 the ratio gets, the warmer your pile will become. TNRCC reports that one study showed that at 30:1, the pile reached 160 degrees; at 40:1 it reached 140 degrees; but only 118 degrees at 60:1.
Because 30:1 is the optimal C:N ratio, we refer to materials greater than 30:1 (e.g., 40:1) as "carbons". Materials less than 30:1 (e.g., 15:1) are referred to as "nitrogens".
Calculating an exact 30:1 carbon to nitrogen ratio (C:N) would require a knowledge of the C:N ratio of each element, weight of each element, and math skills. In other words, no one would ever compost. So, we have "rules of thumb" that allow you to get it close to right.
If you are composting leaves and grass, gather about 60% leaves and 40% fresh grass. If you have some fresh materials and some dry materials, gather equal amounts of each. If you have both vegetative and animal matter, gather 20% vegetative and 80% animal. Refer to our lists of organic materials so you can see which of these are located in your area. As you go through the process with materials native to your own environment, you will develop your own "rules of thumb" that guide you. Check our list of carbon and nitrogen materials or reference books from your library to find the C:N ratio of the materials you are using. Adjust the percentages based on whether your materials contain more or less nitrogen or carbon. Once again, if you want to figure it out mathematically, be my guest.
Gather enough carbons and nitrogens to fill a cubic yard of space. Gather the materials that you feel will balance the carbons and nitrogens in your pile. You can tell by monitoring the pile if you are off by very much and then make easy adjustments. You don't have to get it right the first time. See our FAQ page for troubleshooting.
Chop Carbon Material
Chip, chop, shred, or grind carbons that are more than 1-2" in size. You don't need to shred nitrogens because they will compost quickly anyway. Chopping the size of the particles increases the surface area which bacteria may attack, therefore speeding the decomposition of the materials. A study reported in the TNRCC Master Composter Training Manual showed that piles built with particles around 1" in diameter reached 160 degrees F, those with 2" particles reached 140 degrees F, and those with particles 6" in diameter reached only 100 degrees.
The second benefit of chopping is that it produces pieces which are not uniform in size. A compost pile that has particles of only one size will not compost well because the particles tend to mat together. Matting will decrease the flow of oxygen and moisture through the pile. Oxygen and moisture are two key ingredients to creating compost rapidly. Including different textures as well as sizes helps the aeration of the pile.
You can use any tool that makes sense to you -- pruners, machete, hatchet, spade, shredders, chippers, or a lawn mower. I know people who pile leaves on their driveway and run over them with the car. A weed eater also makes a fine mulcher for leaves. The only way you can do this step incorrectly is to hurt yourself. Be careful.
One expert, Howard Garrett, says you can add organic fertilizer at the rate of 3 to 4 lbs/cu yd of compost -- the additional nitrogen will help the pile to compost faster. Another source suggested adding blood meal or cottonseed meal for the same purpose. Note that other experts say not to add any commercial starters. I don't add any. You will decide for yourself.
Some experts say don't add soil, there are already microorganisms on all the raw materials. Some say add a shovelful of soil per layer to introduce microorganisms to the pile. Some experts say that if your pile is located on pavement, add the soil, otherwise you don't have to. You decide. Personally, I don't add dirt, but I build my pile on the ground.
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Actually putting organic materials into the pile is the part of this step that is not optional. You may just throw in organic materials as they become available. This will result in a very slow decomposition process, but may be appropriate if you are not in need of the finished compost.
Awareness of the five critical factors of decomposition will help you to better understand the steps to follow. By "critical factors", we are not saying that you must have all elements for any decomposition to occur. We are saying that these are the factors you can manipulate in order to speed up or slow down the decomposition process.
The critical factors are:
- Carbon and Nitrogen Materials
It is easier to manage these variables in a batch process. In a batch process, an entire cubic-yard pile is built at the same time. The pile completes decomposition and becomes stable as a unit. This is the opposite of the "add as you go" method.
The steps listed here are useful in the batch process. Once you understand what is happening in the decomposition process, many of the steps are common sense. Review our page entitled What is Composting? for better understanding.
Now it is time to build the pile:
Wet the Ground Under the Pile (OPTIONAL)
Before you build a batch of compost, wet the ground under the pile. This will help prevent the ground from soaking up the moisture from the pile. It will also encourage earthworms to visit your pile.
Lay Twigs in the Bottom of the Bin for Aeration
Lay a 4-6" layer of twigs or other coarse carbons on the bottom of the pile to allow air to circulate at the base.
Add Nitrogen and Carbon Materials in Alternating Layers while Adding Moisture
Layer the rest of your organic materials, alternating carbon and nitrogen layers. Add water as you go, remembering that 45 - 50% of the pile by weight should be water.
Actually, it would be better for the materials to be completely mixed, rather than in layers. However, mixing them from the start makes it difficult to estimate the proportions. Just make sure that your layers are no more than 4-6 inches thick, thinner for fresh grass. This will allow most of the materials to come into contact with one of the adjacent layers. Bacteria will be able to access carbon and nitrogen at the same time. Once you turn the pile the first time, the carbons and nitrogens will be mixed.
End with a Carbon Layer
When the bin is almost full, make a final layer of carbon materials. Add water.
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Experts disagree on whether a cover is necessary, so don't feel obligated to use one. If you live in a region that is excessively dry or excessively wet, cover the pile with a black plastic garbage bag to retain moisture or guard against rain.
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You don't have to check your pile. You can just forget about it until you want to add something else if you're not in a hurry for compost.
Check for Heat -- That Means It's Working
Check to see that your pile becomes hot within a few days. You can use a compost thermometer, although some people just thrust their arm in the pile. A word of caution: Properly built, a pile will reach over 140 degrees F. Be careful that your arm doesn't get burned. The morning after I built my first pile, I set my hand down on it and literally jumped because I was so startled by the heat. Yes -- it gets HOT. If you don't have a compost thermometer, you may want to use a candy-making thermometer.
It is difficult for me to tell you what to expect in the way of temperature and time because the experts vary so widely in their experiences. Some say the heat should peak the next day, some say within 4-7 days. My experience has been that it peaks the next day.
Temperatures of 150 degrees F are good because they will kill pathogens and weed seeds, although I have heard experts quote lower figures of 140 degrees F and 131 degrees F. If your pile does not reach 120 degrees to 160 degrees F, you probably do not have enough nitrogen in your pile. Add more nitrogen materials, mix, and monitor again. The minimum temperature should be 115 degrees F unless you did not try to build the pile according to hot pile instructions.
Also monitor the moisture content of your pile. It should be 50% water by weight. To check, pick up a handful of material. It should feel like a wrung-out sponge. There should be enough water that it almost, but not quite, drips when you hold up a handful.
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Turning the pile means stirring it up by some method. Whether you are monitoring temperature or not, turn the pile to decrease composting time. Turning the pile allows all the material to be exposed to the hot center and increases aeration.
Turn the pile every time its temperature starts to decrease. If you add moisture as needed when you turn it, it should heat up again. This method allows for the quickest time to finished compost. In a study reported in TNRCC's Master Composter Manual, a pile turned every 3 days heated to 160 degrees F, turned every 10 days heated to 140 degrees, turned every 30 days, reached 122 degrees F. Clearly this is a factor in increasing the decomposition rate.
People often ask if they should turn the pile more often in winter or in summer. Season has nothing to do with it. Generally, the heat is from bacterial activity, not from the weather.
The proper way to turn a pile is to bring all the outside material to the inside of the pile, and the inside of the material to the outside. My bin is set up so I can do this rather easily. It is a 4-sided wire mesh square. I lift it up from around the pile. The moisture in the pile holds the shape of the pile. I set up the bin to one side of the pile. Then I shovel the ingredients into the bin, taking shovelfuls from the outside first and dropping them in the middle, then take from the middle and deposit on the outer edges.
If you don't have a bin that is easily moved, you may want to consider other alternatives: Just stirring the pile (not as effective but better than not turning), removing all the materials and putting them back in (a lot of work), or having more than one bin. With more than one bin, you can take out of bin #1 and put into bin #2 similar to my process, then start a new pile in bin #1 or leave it empty so you can use it to turn the same pile next time.
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