Composting
Gardeners have used compost for centuries. When materials such as leaves and 
grass clippings are composted, a microbial process converts plant wastes to a 
more usable organic amendment. Many homeowners may find it convenient and 
economical to compost these materials in their own backyards. In either case, 
the finished compost can be used as a soil amendment or mulch to improve most 
soils for gardens, landscape beds, lawn preparation or even as 15% of a potting 
medium. 

Decomposition of organic material in the compost pile is dependent on 
maintaining microbial activity. Any factor which slows or halts microbial growth 
will also impede the composting process. Efficient decomposition will occur if 
the following factors are used to their fullest advantage. 

AERATION: Oxygen is required for microbes to efficiently decompose the organic 
wastes. Some decomposition will occur in the absence of oxygen (anaerobic 
conditions); however, the process is slow and foul odors may develop. Because of 
the odor problem, composting without oxygen is not recommended in a residential 
setting unless the process is conducted in a fully closed system. Turning the 
pile once or twice a month will provide the necessary oxygen and significantly 
hasten the composting process. A pile that is not mixed may take three to four 
times longer before it can be used. A well mixed compost pile will also reach 
higher temperatures which will help destroy weed seeds and pathogens. 

MOISTURE: Adequate moisture is essential for microbial activity. A dry compost 
pile will not decompose efficiently. If rainfall is limited, it will be 
necessary to water the pile periodically to maintain a steady decomposition 
rate. Enough water should be added to completely moisten the pile, but 
overwatering should be avoided. Excess water can lead to anaerobic conditions. 
Water the pile so that it is damp, but does not remain soggy. The compost will 
be within the right moisture range if a few drops of water can be squeezed from 
a handful of material. If no water can be squeezed out, the material is too dry. 
If water gushes from your hand, it is too wet. 

PARTICLE SIZE: The smaller the size of organic wastes, the faster the compost 
will be ready for use. Smaller particles have much more surface area that can be 
attacked by microbes. A shredder can be used before putting material in the 
pile, and is essential if brush or sticks are to be composted. A low cost method 
of reducing the size of fallen tree leaves is to mow the lawn before raking or 
run the lawn mower over leaf piles after raking. Raked piles should be checked 
to insure that they do not contain sticks or rocks which could cause injury 
during operation of the mower. If the mower has an appropriate bag attachment, 
the shredded leaves can be collected directly. In addition to speeding up the 
composting process, shredding will initially reduce the volume of the compost 
pile. 

FERTILIZER AND LIME: Microbial activity is affected by the carbon to nitrogen 
ratio of the organic waste. Because microbes require a certain amount of 
nitrogen for their own metabolism and growth, a shortage of nitrogen will slow 
down the composting process considerably. Materials high in carbon relative to 
nitrogen such as straw or sawdust will decompose very slowly unless nitrogen 
fertilizer is added. Tree leaves are higher in nitrogen than straw or sawdust 
but decomposition of leaves would still benefit from an addition of nitrogen 
fertilizer or components high in nitrogen. Grass clippings are generally high in 
nitrogen and when mixed properly with leaves will enhance decomposition. Poultry 
litter, manure or blood meal can be used as organic sources of nitrogen. 
Otherwise, a fertilizer with a high nitrogen analysis (10-30%) should be used. 
Other nutrients such as phosphorus and potassium are usually present in adequate 
amounts for decomposition. 

During the initial states of decomposition organic acids are produced, 
decreasing the pH. In the past, small amounts of lime have been suggested for 
maintaining and enhancing microbial activity at this time. However, high rates 
of lime will convert ammonium nitrogen to ammonia gas which will lead to the 
loss of nitrogen from the pile. Research indicated that lime additions may 
hasten decomposition; however, the loss of nitrogen from the pile often offsets 
the benefits of lime. In general, lime is not necessary for degradation of most 
yard wastes. The pH of finished compost is usually alkaline (pH = 7.1-7.5) 
without the addition of lime. If large quantities of pine needles, pine bark, or 
vegetable and fruit wastes are composted, additional lime may be necessary. 

Many organic materials are suitable for composting. Yard wastes, such as leaves, 
grass clippings, straw, and non woody plant trimmings can be composted. Leaves 
are the dominant organic waste in most backyard compost piles. Grass clippings 
can be composted; however, with proper lawn management, clippings do not need to 
be removed from the lawn. If clippings are used, it is advisable to mix hem with 
other yard wastes, otherwise the grass clippings may compact and restrict 
airflow. Branches and twigs greater than 1/4 inch in diameter should be put 
through a shredder/chipper. Kitchen wastes such as vegetable scraps, coffee 
grounds, and eggshells may also be added. 

Sawdust may be added in moderate amounts if additional nitrogen is applied. 
Approximately 1 lb. of actual nitrogen (6 cups of ammonium nitrate) is required 
for 100 lbs. of dry sawdust. Wood ashes act as a lime source and if used should 
only be added in small amounts (no more than 1 cup per bushel or 10 pounds per 
ton of compost). Ordinary black and white newspaper can be composted; however, 
the nitrogen content is low and will consequently slow down the rate of 
decomposition. If paper is composted, it should not be more than 10% of the 
total weight of the material in the compost pile. 

Examples of other organic materials that can be used to add nutrients to the 
pile include: blood meal, bone meal, livestock manure, non-woody clippings, 
vegetable and flower garden refuse, hay, straw and lake plants. Livestock manure 
and poultry litter are nitrogen sources for composting. Approximately 100 pounds 
of poultry litter will provide 1.8 pounds of nitrogen. 

Some materials may pose a health hazard or create a nuisance and therefore 
should not be used to make compost. Adding human or pet feces cannot be 
recommended because they may transmit diseases. Meat, bones, grease, whole eggs, 
and dairy products should not be added because they can attract rodents to the 
site. Most plant disease organisms and weed seeds are destroyed during the 
composting process when temperatures in the center of the pile reach 150-160 F. 

Although plants that have been treated with herbicides or pesticides should be 
avoided for composting, small amounts of herbicide-treated plants (e.g., grass 
clippings) may be mixed in the pile as long as one is careful to allow thorough 
decomposition. Ideally, clippings from lawns recently treated with herbicides 
should be left on the lawn to decompose. 

Use of plastic garbage bags is perhaps the simplest way to make compost. The 
bags are easy to handle, and require minimal maintenance. To make compost using 
this method, 30-40 gallon plastic bags should be alternatively filled with plant 
wastes, fertilizer and lime. About one tablespoon of a garden fertilizer with a 
high nitrogen content should be used per bag. Lime (one cup per bag) helps 
counteract the extra acidity caused by anaerobic composting. After filling, add 
about a quart of water. Close tightly. Set aside for six months to a year. Bags 
can be set in a basement or heated garage for better decomposition during winter 
months. Using garbage bags requires no turning or additional water after 
closing. The main advantage of composting in garbage bags is that it requires 
little maintenance; however, because oxygen is limited, the process is slow. 

The barrel or drum composter generates compost is a relatively short period of 
time and provides an easy mechanism for turning. This method requires a barrel 
of at least 55 gallons with a secure lid. Be sure that the barrel was not used 
to store toxic chemicals. Drill 6-9 rows of 1/2 inch holes over the length of 
the barrel to allow for air circulation and drainage of excess moisture. Place 
the barrel upright on blocks to allow bottom air circulation. Fill the barrel 
3/4 full with organic waste material and add about 1/4 cup of high 
(approximately 30%N) nitrogen containing fertilizer. Apply water until compost 
is moist but not soggy. 

Every few days, turn the drum on its side and roll it around the yard to mix and 
aerate the compost. The lid can be removed after turning to allow for air 
penetration. Ideally, the compost should be ready in two to four months. The 
barrel composter is an excellent choice for the city dweller with a relatively 
small yard. 

For larger quantities of organic waste, bin type structures are the most 
practical. As an example, a circular bin can be made by using a length of small 
spaced woven wire fencing and holding it together with chain snaps. The bin 
should be about three to five feet in diameter and at least four feet high. A 
stake may be driven in the middle of the bin before adding material to help 
maintain the shape of the pile and to facilitate adding water. With this design, 
it is easiest to turn the composting material by simply unsnapping the wire, 
moving the wire cylinder a few feet, and turning the compost back into it. 

A very efficient and durable structure for fast composting is a three-chambered 
bin. It holds a considerable amount of compost, and allows good air circulation. 
The three chambered bin works on an assembly line idea, having three batches of 
compost in varying stages of decomposition. The compost material is started in 
the first bin and allowed to heat up for three to five days. Next, it is turned 
into the middle bin for another 4-7 days, while a new batch of material is 
started in the first bin. Finally, the material in the middle bin is turned into 
the last bin as finished or nearly finished compost. 

To make a three-chambered bin, it is best to use rot resistant wood such as 
redwood, salt treated wood or wood treated with an environmentally safe 
preservative or a combination of treated wood and metal posts. Unless the wood 
is treated or rot resistant, it will decompose within a few years. Each bin 
should be at least three to five feet in each dimension to contain enough volume 
to compost properly. Using removable slats in the front offers complete access 
to the contents for turning. 

The compost pile should be located close to where it will be used and where it 
will not interfere with activities in the yard or offend neighbors. From the 
aesthetic point of view, it is best to compost in a location screened from view 
of both your property and neighbor's property. Examples of good locations for 
the pile include: near the garden or between the garage and house. Do not locate 
the compost pile near a well or on a slope that drains to surface water such as 
a stream or a pond. The pile will do best where it is protected from drying 
winds and in partial sunlight to help heat the pile. The more wind and sun the 
pile is exposed to, the more water it will need. Locating the pile too close to 
trees may also create problems as roots may grow into the bottom of the pile and 
make turning and handling the compost difficult. 

Organic wastes, such as leaves, grass, and plant trimmings are put down in a 
layer eight to ten inches deep. Coarser materials will decompose faster if 
placed in the bottom layer. This layer should be watered until moist, but not 
soggy. A nitrogen source should be placed on top of this layer. Use one to two 
inches of livestock manure, or a nitrogen fertilizer such as ammonium nitrate or 
ammonium sulfate at a rate of one third of a cup for every twenty five square 
feet of surface area. If these nitrogen sources are not available, one cup of 
10-10-10 fertilizer per 25 square feet of surface area will also suffice. Do not 
use fertilizer that contains herbicide or pesticide. 

About a one inch layer of soil or completed compost can be applied on top of the 
fertilizer layer. One purpose of adding soil is to ensure that the pile is 
inoculated with decomposing microbes. The use of soil in a compost pile should 
be considered optional. In most cases, organic yards wastes such as grass 
clippings or leaves contain enough microorganisms on the surface to effect 
decomposition. Studies have shown that there is no advantage in purchasing a 
compost starter or inoculum. One way to insure that activator microbes are 
present in the new compost is to mix in some old compost as the pile is 
prepared. 

Most compost piles should initially be prepared in layers. This will facilitate 
decomposition by insuring proper mixing. Each pile ideally should be about 5 
feet high. If only tree leaves are to be composted, layering may not be 
necessary. Fallen leaves can be added as they are collected. Leaves should be 
moistened if they are dry and since dead leaves lack adequate nitrogen for rapid 
decomposition, addition of a high-nitrogen fertilizer (10- 30% analysis) should 
be added to speed up breakdown. Approximately 5 ounces (about 1/2 cup) of 10% 
nitrogen fertilizer should be added for each 20 gallons of hand compressed 
leaves. 

To prevent odors and hasten decomposition, the pile must be turned occasionally. 
Turning also exposes seeds, insect larvae, and pathogens to lethal temperatures 
inside the pile. Odors may arise either from the addition of excessive amounts 
of wet plant materials like fruits or grass clippings, or from overwatering. A 
properly mixed and adequately turned compost heap will not have objectionable 
odors. An actively decomposing pile will reach temperatures of 130-160 F in the 
middle. 

Reasons for the pile not heating up may be due to: too small a pile, not enough 
nitrogen, lack of oxygen, too much or not enough moisture. The pile should be 
turned when the temperature in the center begins to cool. This will introduce 
oxygen and undecomposed material into the center and subsequently regenerate 
heating. The composting process is essentially complete when mixing no longer 
produces heat in the pile. 

Generally, a well managed compost pile with shredded material under warm 
conditions will be ready in about 2-4 months. A pile left unattended and 
material not shredded may take over a year to decompose. Piles prepared in the 
late fall will not be ready for use the following spring. When the compost is 
finished, the pile will be about half its original size and have an earthy smell 
to it. 
http://www.maasnursery.com/composting.htm 
