The two methods of generating compost can range from passive – allowing the materials to sit and rot on their own – to slightly to highly managed. Managing the compost means that you intervene in the process. If your goal is to produce as much compost as possible to use regularly in your garden, you will chose a more hands-on method of composting. If your goal is to dispose of yard waste, a passive method is your answer.
Passive composting will involve the least amount of time and energy on your part. Simply collect organic materials and place in a freestanding pile. It will take a long time (a year or two), but eventually organic materials in any type of a pile will break down into finished compost. Rather than an unattractive big pile of materials sitting in your yard, use a 3-sided enclosure made of fencing, wire, or concrete blocks, which keeps the pile neater and less unsightly. Just continue to add grass clippings, leaves, and kitchen scraps (always cover these with 8″ of other material). The pile will shrink quickly as the materials compress and decompose. After a year or two before check the bottom of the bin for finished compost. When it’s ready, shovel the bottom section into a wheelbarrow and add it to your garden beds. Keep adding greens and browns to the top of the pile to have a good supply of finished compost at the ready. Most simple piles will produce a few cubic feet of finished compost yearly, after the initial first or second year.
Managed composting involves active participation, ranging from turning the pile occasionally to a major commitment of time and energy. If you employ all of the techniques of managing the pile, you can make finished compost in 3-4 weeks. The number of techniques you employ reflect how much you want to intervene in the decomposition process and is determining factor in how fast you want to produce compost.
The cycle of producing finished compost will be determined by how you collect materials, whether you chop them up, how you mix them together, and so on. Achieving a good balance of carbon and nitrogen is easier if you build the pile all at once. Layering is traditional, but mixing the materials works as well.
Shredded organic materials will heat up rapidly, decompose quickly, and produce a uniform compost. The decomposition process time increases with the size of the composting materials. If you want the pile to decay faster, chop up large fibrous materials.
Add new materials on an ongoing basis to an already established pile. Most single-bin gardeners build an initial pile and add more ingredients on top as they become available.
Compost Gets Hot
Heat is a by-product of intense microbial activity. It indicates that the microorganisms are munching on organic matter and converting it into finished compost. The temperature of your compost pile does not in itself affect the speed or efficiency of the decomposition process. But temperature does determine what types of microbes are active.
There are primarily three types of microbes that work to digest the materials in a compost pile. They each work best in a particular temperature range:
The psychrophiles work in cool temperatures—even as low as 28 degrees F. As they begin to digest some of the carbon-rich materials, they give off heat, which causes the temperature in the pile to rise. When the pile warms to 60 to 70 degrees F, mesophilic bacteria take over. They are responsible for the majority of the decomposition work. If the mesophiles have enough carbon, nitrogen, air, and water, they work so hard that they raise the temperature in the pile to about 100 degrees F. At this point, thermophilic bacteria kick in. It is these bacteria that can raise the temperature high enough to sterilize the compost and kill disease-causing organisms and weed seeds. Three to five days of 155 degrees F. is enough for the thermophiles to do their best work.
Getting your compost pile “hot” (140 to 160 degrees F.) is not critical, but it does mean that your compost will be finished and usable within a month or so. These high temperatures also kill most weed seeds, as well as harmful pathogens that can cause disease problems. Most people don’t bother charting the temperature curve in their compost pile. They just try to get a good ratio of carbon to nitrogen, keep the pile moist and well aerated, and wait until everything looks pretty well broken down.
Use a compost thermometer to easily see how well your compost is doing. They are inexpensive, and quite convenient to have.
Commercial activators can help raise the temperature in your compost pile by providing a concentrated dose of microorganisms and protein. Other effective activators that can help to get your pile cooking include humus-rich soil, rotted manure, finished compost, dried blood, and alfalfa meal.
If the pile becomes too dry, the decay process will slow down. Organic waste needs water to decompose. The rule of thumb is to keep the pile as moist as a wrung-out sponge.
If you’re building your pile with very wet materials, mix them with dry materials as you build. If all the material is very dry, soak it with a hose as you build. Whenever you turn the pile, check it for moisture and add water as necessary.
Too much water is just as detrimental as the lack of water. In an overly wet pile, water replaces the air, creating an anaerobic environment, slowing decomposition.
To Turn or Not to Turn
Unless speed is a priority, frequent turning is not necessary. Many people never turn their compost piles. The purpose of turning is to increase oxygen flow for the microorganisms, and to blend undecomposed materials into the center of the pile. If you are managing a hot pile, you’ll probably want to turn your compost every 3 to 5 days, or when the interior temperature dips below about 110 degrees F.
After turning, the pile should heat up again, as long as there is still undecomposed material to be broken down. When the temperature stays pretty constant no matter how much you turn the pile, your compost is probably ready. Though turning can speed the composting process, it also releases heat into the air, so you should turn your pile less frequently in cold weather.
There are several ways to help keep your pile well aerated, without the hassle of turning:
- Build your pile on a raised wood platform or on a pile of branches.
- Make sure there are air vents in the sides of your compost bin.
- Put one or two perforated 4-inch plastic pipes in the center of your pile.
A more labor-intensive way to re-oxygenate the pile is to turn the pile by hand, using a large garden fork. The simplest way is to move the material from the pile and restack it alongside. A multiple-bin system makes this efficient, in that you only handle the material once. Otherwise, you can put the material back into the same pile. The object is to end up with the material that was on the outside of the original pile, resting in the middle of the restacked pile. This procedure aerates the pile and will promote uniform decomposition.
This is an excellent tool for aerating and mixing compost.