Composting is nature's way of recycling. Composting
biodegrades organic waste. i.e. food waste, manure, leaves,
grass trimmings, paper, wood, feathers, crop residue etc.,
and turns it into a valuable organic fertilizer.
is a natural biological process, carried out under
controlled aerobic conditions (requires oxygen). In this
process, various microorganisms, including bacteria and
fungi, break down organic matter into simpler substances.
The effectiveness of the composting process is dependent
upon the environmental conditions present within the
composting system i.e. oxygen, temperature, moisture,
material disturbance, organic matter and the size and
activity of microbial populations.
Composting is not a mysterious or
complicated process. Natural recycling (composting)
occurs on a continuous basis in the natural environment.
Organic matter is metabolized by microorganisms and
consumed by invertebrates. The resulting nutrients are
returned to the soil to support plant growth.
Composting is relatively simple to
manage and can be carried out on a wide range of scales in
almost any indoor or outdoor environment and in almost
any geographic location. It has the potential to manage
most of the organic material in the waste stream
including restaurant waste, leaves and yard wastes, farm
waste, animal manure, animal carcasses, paper products,
sewage sludge, wood etc. and can be easily incorporated
into any waste management plan.
Since approximately 45 - 55% of the
waste stream is organic matter, composting can play a
significant role in diverting waste from landfills
thereby conserving landfill space and reducing the
production of leachate and methane gas. In addition, an
effective composting program can produce a high quality
soil amendment with a variety of end uses.
The essential elements required by
the composting microorganisms are carbon, nitrogen,
oxygen and moisture. If any of these elements are
lacking, or if they are not provided in the proper
proportion, the microorganisms will not flourish and will
not provide adequate heat. A composting process that
operates at optimum performance will convert organic
matter into stable compost that is odor and pathogen
free, and a poor breeding substrate for flies and other
insects. In addition, it will significantly reduce the
volume and weight of organic waste as the composting
process converts much of the biodegradable component to
gaseous carbon dioxide.
The composting process is
carried out by three classes of microbes -
Psychrophiles - low temperature
• Mesophiles -medium temperature microbes
• Thermophiles - high temperature microbes
Generally, composting begins at
mesophilic temperatures and progresses into the
thermophilic range. In later stages other organisms
including Actinomycetes, Centipedes, Millipedes, Fungi,
Sowbugs, Spiders and Earthworms assist in the process.
Temperature is directly proportional to the biological
activity within the composting system. As the metabolic
rate of the microbes accelerates, the temperature within
the system increases. Conversely, as the metabolic rate
of the microbes decreases, the system temperature
decreases. Maintaining a temperature of 130°F or more
for 3 to 4 days favors the destruction of weed seeds, fly
larvae and plant pathogens.
At a temperature of 155 degrees F,
organic matter will decompose about twice as fast as at
130 degrees F. Temperatures above 155 degrees F may
result in the destruction of certain microbe populations.
In this case temperature may rapidly decline. Temperature
will slowly rise again as the microbe population
Moisture content, oxygen
availability, and microbial activity all influence
temperature. When the pile temperature is increasing, it
is operating at optimum performance and should be left
alone. As the temperature peaks, and begins to decrease,
the pile should be turned to incorporate oxygen into the
compost. Subsequently , the pile should respond to the
turning and incorporation of oxygen, and temperature
should again cycle upwards. The turning process should be
continued until the pile fails to re-heat. This indicates
that the compost material is biologically stable.
Composting microorganisms thrive in
moist conditions. For optimum performance, moisture
content within the composting environment should be
maintained at 45 percent. Too much water can cause the
compost pile to go anaerobic and emit obnoxious odors.
Too little will prevent the microorganisms from
The ideal particle size is around 2 to 3 inches. In some
cases, such as in the composting of grass clippings, the
raw material may be too dense to permit adequate air flow
or may be too moist. A common solution to this problem is
to add a bulking agent (straw, dry leaves, paper,
cardboard) to allow for proper air flow. Mixing
materials of different sizes and textures also helps
aerate the compost pile.
During the composting process oxygen is used up quickly
by the microbes as they metabolize the organic matter. As
the oxygen becomes depleted the composting process slows
and temperatures decline. Aerating the compost by turning
should ensure an adequate supply of oxygen to the
The composting period is governed by a number of factors
including, temperature, moisture, oxygen, particle size,
the carbon-to-nitrogen ratio and the degree of turning
involved. Generally, effective management of these
factors will accelerate the composting process.
Carbon to Nitrogen Ratio
The microbes in compost use carbon for energy and
nitrogen for protein synthesis. The proportion of these
two elements required by the microbes averages about 30
parts carbon to 1 part nitrogen. Accordingly, the ideal
ratio of Carbon to Nitrogen (C:N) is 30 to 1 (measured on
a dry weight basis). This ratio governs the speed at
which the microbes decompose organic waste.
Most organic materials do not have
this ratio and, to accelerate the composting process, it
may be necessary to balance the numbers.
The C:N ratio of materials can be
calculated by using table 1 below.
Example, if you have two bags of cow manure (C:N =
20:1) and one bag of corn stalks (C:N = 60:1) then
combined you have a C:N ration of (20:1 + 20:1 + 60:1)/3
= (100:1)/3 = 33:1
Table 1 lists the Carbon/Nitrogen
Ratios of Some Common Organic Materials
The C:N ratios listed above are for
Plastic bin (well ventilated)
Metal or plastic drum (base removed well
Rotating drum (in vessel)
Enclosure (made from 4 x 4 pallets lined with chicken
Open pile windrow (covered with plastic or tarp)
An in-vessel, aerobic mechanical composter can be
constructed from a steel drum, or tank designed to rotate
at three to five revolutions per hour. Rotation can be
carried out with a simple hand crank or a timed
electrical mechanical device. This type of composter can
produce a stabilized compost in three to four days and
can be an environmentally appropriate, low management
alternative to bin composting.
An aerated bin can be constructed using 4' × 4' pallets
fastened together to form a box and lined with wire mesh.
To limit the degree of turning and permit air to flow
through the pile the structure can be elevated or, in the
alternative, perforated pipes can be incorporated into
the structure. One side of the structure should be
detachable to facilitate loading, mixing and unloading.
The composter should be waterproof and located in and
area that is protected from the wind.
Static compost piles
and windrows should be large enough to retain heat and
small enough to facilitate air to its center. As a rule
of thumb, the minimum dimensions of a pile should be 3
feet by 3 feet by 3 feet.
Turning units are ideally suited for batch composting and
are extremely practical for building and turning active
compost. Turning units allow convenient mixing for
aeration and accelerated composting.
Hot composting is the most efficient method for producing
quality compost in a relatively short time. In addition,
it favors the destruction of weed seeds, fly larvae and
pathogens. While hot composting, using the windrow
or bin method, requires a high degree of management, hot
composting, using the in-vessel method, requires a lesser
degree of management.
This method is ideal for adding organic matter around
trees, in garden plots, in eroded areas etc. The time
required to decompose organic matter using this method is
governed, to a large extent, by environmental conditions
and could take two years or more.
Sheet composting is carried out by spreading organic
material on the surface of the soil or untilled ground
and allowing it to decompose naturally. Over time, the
material will decompose and filter into the soil. This
method is ideally suited for forage land, no-till
applications, erosion control, roadside landscaping etc.
The process does not favor the destruction of weed seeds,
fly larvae, pathogens etc. and composting materials
should be limited to plant residue and manure. Again,
decomposition time is governed by environmental
conditions and can be quite lengthy.
Trench composting is relatively simple. Simply dig a
trench 6 - 8 inches deep, fill with 3 - 4 inches of
organic material and cover with soil. Wait a few weeks
and plant directly above the trench. This method does not
favor the destruction of weed seeds, fly larvae and
pathogens and the composting process can be relatively
Bin / Windrow
Place the raw materials in layers using a balance of high
carbon (moist) and low carbon (dry) materials. Each layer
should be no more than four to six inches in depth. Spray
each layer with a light mist of CBCT Stock Solution (Mix
CBCT Concentrate and water at a rate of 1:200). This will initiate and accelerate the
composting process and eliminate odors).
Step 1. Start with a 4
to 6 inch layer of coarse material set on the bottom of
the composter or on top of the soil.
Step 2. Add a 3 to 4
inch layer of low carbon material.
Step 3. Add a 4 to 6
inch layer of high carbon material.
Step 4. Add a 1 inch
layer of garden soil or finished compost.
Step 5. Mix the layers
of high carbon material, low carbon material, and soil or
Repeat steps 2 through
5 until the composting bin is filled (maximum 4 feet in
height). Cap with dry material.
Vessel (in-vessel composting)
To accelerate the composting process, simply mix the high
carbon and low carbon materials together before placing
them in the composter. Add the mixture to the composter
in small batches, spraying each batch with a light mist
of water or CBCT stock solution.
material during the composting process
Ideally, new materials should be added to the composting
system during turning or mixing. Generally, the addition
of moist materials accelerates the composting process
while the addition of dry materials slows the process.
Finished compost can be classified as a 100% organic
fertilizer containing primary nutrients as well as trace
minerals, humus and humic acids, in a slow release form.
Compost improves soil porosity, drainage and aeration and
moisture holding capacity and reduces compaction. Compost
can retain up to ten times it's weight in water. In
addition, compost helps buffer soils against extreme
chemical imbalances; aids in unlocking soil minerals;
releases nutrients over a wide time window; acts as a
buffer against the absorption of chemicals and heavy
metals; promotes the development of healthy root zones;
suppresses diseases associated with certain fungi; and
helps plants tolerate drought conditions.
Compost can be used in a variety of applications. High
quality compost can be used in agriculture, horticulture,
landscaping and home gardening. Medium quality compost
can be used in applications such as erosion control and
roadside landscaping. Low quality compost can be used as
a landfill cover or in land reclamation projects.