TECHNICAL PAPER #7
UNDERSTANDING COMPOSTING
By
J. Walter Fitts & Jerry B. Fitts
Technical Reviewers
Ellen M. Craft & David
J. Graham
VITA
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel: 703/276-1800 . Fax 703/243-1865
Internet: pr-info@vita.org
Understanding Composting
ISBN: 0-86619-207-7
[C]
1984, Volunteers in Technical Assistance
PREFACE
This paper is one of a series published by Volunteers in
Technical
Assistance to provide an introduction to specific
state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their
situations.
They are not intended to provide construction or
implementation
details. People are urged to contact VITA or a similar
organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and
illustrated
almost entirely by VITA Volunteer technical experts on a
purely
voluntary basis. Some 500 volunteers were involved in the
production
of the first 100 titles issued, contributing approximately
5,000 hours of their time. VITA staff included Leslie
Gottschalk
and Maria Giannuzzi as editors, Julie Berman handling
typesetting
and layout, and Margaret Crouch as project manager.
VITA Volunteers Dr. J. Walter Fitts and Jerry B. Fitts, the
authors of this paper, are agronomists with Agro Services
International,
Inc., an agricultural consulting firm. They have both
published widely in the fields of agronomy and soil science.
Dr.
J. Walter Fitts was formerly the head of the Soil Department
at
North Carolina State University, and was director of the
International
Soil Fertility Evaluation Program at North Carolina
State University for several years. Jerry B. Fitts was
formerly
with the Soil Science Departments at North Dakota State
University
and the University of Minnesota. VITA Volunteer Ellen M.
Craft, a reviewer of this paper, is a research associate
with the
Department of Agronomy, Iowa State University. She has
taught
upper level courses in agronomy there. VITA Volunteer David
J.
Graham, also a reviewer of this paper, is Special Assistant
to
the Director, Office of Environmental Engineering and
Technology,
Office of Research & Development, Environmental
Protection Agency
in Washington, D.C. The laboratories at EPA where Mr. Graham
works have been involved in composting research for over 10
years.
VITA is a private, nonprofit organization that supports
people
working on technical problems in developing countries. VITA
offers
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to
their
situations. VITA maintains an international Inquiry Service,
a
specialized documentation center, and a computerized roster
of
volunteer technical consultants; manages long-term field
projects;
and publishes a variety of technical manuals and papers.
UNDERSTANDING COMPOSTING
By VITA
Volunteers J. Walter Fitts and Jerry B. Fitts
I. INTRODUCTION
Composting is the process of bringing together plant or
animal
wastes to hasten their decomposition. The result of this
process
is a nutrient-rich organic fertilzier called compost or
humus.
Farmers have practiced composting for thousands of years.
They
knew that the use of plant and animal wastes would return
nutrients
to their soil and enrich their farmlands. This in turn
promoted the growth of their crops. In sum, they took
advantage
of all the plant and animal wastes that were so abundant and
made
rich compost from them, instead of burning them or throwing
them
away.
Composting, however, is not to be regarded as a basis of
permanent soil fertility. This concept is inapplicable
because
the application of decomposed waste will not neutralize
excessive
soil acidity (i.e., increase soil pH) nor will it supply
corrective applications of nutrients such as phosphorus on a
phosphorus deficient soil.
The most attractive and feasible concept is the use of
composting
in a gardern plot. The advantage is: the ease with which the
plant residues from the garden may be supplemented with
those
grown elsewhere.
Adding compost to soils high in clay loosens and improves
compacted soil. This increases both the infiltration and
water
holding capacity of the soil. In sandy soils, the addition
of
composts increases the organic matter content of the soil,
which
in turn increases the soil's ability to store water. By
increasing the infiltration of water into the soil, compost
can
also help to reduce soil erosion. Compost contributes
nutrients
from organic materials that would otherwise have been
wasted.
This more favorable soil environment can increase the depth
and
density of root growth. Composting also favors plant growth
by
destroying many harmful weed seeds, insect eggs, and disease
organisms during a stage where a lot of heat is generated.
Due to
the positive influence on chemical and physical properties
of a
soil, compost can increase the productivity of your land.
Fine finished compost serves as an excellent soil basis to
transplant seedlings into. When mixed into the seed bed,
compost
provides nutrients and an extra source of moisture for the
germinating seeds. Compost can be applied throughout the
growing
season to crops as a sidedressing mixed in a depth of an inch
or
so just before a rain. Mulching with compost nourishes the
crop
while controlling weeds. In locations where plots of land
are
not available, compost can serve as the soil base of potting
soil
for indoor or container gardening. Composting is also an
excellent way to utilize fast growing plants such as water
hyacinths, which otherwise would create disposal problems.
II. COMPOSTING PRINCIPLES
Decomposition is part of nature's life cycle. Grasses,
trees,
weeds, shrubs, and other succulent plants obtain carbon,
hydrogen,
and oxygen from air and water and the dissolved nutrient
elements nitrogen, phosphorus, potassium, calcium,
magnesium,
sulfur, boron, copper, iron, manganese, zinc, and molybdenum
from
the soil. Then, through the green chlorophyll of their
leaves
and with energy from the sun, they manufacture food products
that
nourish other forms of life, including human beings.
At the conclusion of the growing season, leaves and other
plant
parts wither, die, and become plant residue. However, the plant
residue (or animal residue) does not accumulate for long
because
it is soon attacked by lower forms of plant and animal life.
The
process of higher plant growth cannot go on indefinitely
unless
nutrients such as nitrogen, phosphorus, potassium, sulfur,
and
other elements are returned to the soil. Plant or animal
wastes
contain compounds that must be broken down (decomposed) so
the
nutrient elements contained in the waste can replenish the
soil
and be reused for crop growth.
The replenishing process is carried out mostly by
microorganisms,
including fungi, bacteria, algae, protozoa, nematodes, and
worms.
Fungi and bacteria, of which there are several thousand
species,
are responsible for most of the decomposing process. Some
species
grow and decompose waste material under a fairly wide range
of
environmental conditions, whereas others can perform only
under
very specific conditions. As long as the environmental
conditions
are favorable, microorganisms will quickly multiply to
decompose the waste material, no matter how much waste
material
is available.
Good composting depends on a number of factors that
influence the
activity of the microorganisms that cause decomposition.
These
include: (1) the type of raw waste material to be
decomposed;
(2) nutrient availability, especially nitrogen; (3)
moisture;
(4) temperature; and (5) acidity (pH). Other factors to
consider
in maintaining a composting pile are: nutrient losses during
composting, aeration, pests and diseases that may be
transmitted,
the ratio of carbon to nitrogen, the presence of toxic
substances
in the waste, etc. All of these factors are discussed in
more
detail below.
FACTORS INFLUENCING DECOMPOSITION
Type of Raw Waste Material
Almost any plant or animal waste will decompose if
preservative
measures have not been taken. And some wastes are more
resistant
to decay than others and are not considered good compost
material. Food scraps, including meat scraps, can be used
with
plant wastes. For rapid decomposition to form a good
compost,
the waste must be high in carbohydrate, low in lignin
compounds,
and have a nitrogen content about 1.5 percent or more.
Choose materials according to what is available to you.
Here's a
list of good things to include (not in order of priority):
*
rice husks
*
coconut trash
*
sugarcane waste
*
leaves
*
water hyacinth
*
corn stalks and husks
*
bean plants
*
kitchen wastes
*
spoiled food
*
sawdust or wood shavings
*
banana skins and leaves
*
crushed animal bones
*
seaweed
*
garden trash (e.g., weeds, stalks, leaves,
pads)
*
manure from cattle, chicken, pigs, etc.
Many materials for composting can be obtained free from
manufacturers such as:
*
dried blood, bones, and hair from animal slaughter
houses;
*
hulls from graineries (rice, corn, cocoa,
beans,
peanuts)
*
coal ashes
*
fish scraps from fisheries
*
hair from barber shops
*
molasses residue from sugar factories
*
sawdust and woodchips from sawmills
*
leather dust
Items that should not be composted include:
*
plastic
* glass
bottles
*
tin cans
* wax coated
cardboard
*
stones
* newspaper
with colored ink
*
human waste
* waste from
domestic cats
and dogs
You should never use human waste in a compost which is to be
applied to an area where food crops are to be raised for
either
humans or animals which will be used for meat. Depending on
a
person's diet, living location, and health, the human waste
can
contain metal and chemical compounds which could be
hazardous.
By composting these compounds can accumulate to high levels
within soils. Some plants selectively take up thse
compounds.
When eaten by humans they can pose a health risk. Thus, it
is
best not to compost human waste unless a complete chemical
analysis can be performed to assure its safety.
Remember, animal waste products such as meat and fish scraps
are
good too, but may attract hungry dogs, flies, and other
insect
pests to your pile. One word of caution: manure piles are
notorious for attracting flies and other insect pests and the
same can happen in compost piles. For steps that can be
taken to
prevent this from happening, see "Pests, Toxins, and
Other Undesirables,"
page 10.
To speed up the decomposition process, you will want to
break up,
chop, or grind large chunks (e.g., corn stalks, banana
leaves) of
raw waste material into small, degradable pieces. Remember,
the
finer the waste is shredded, ground, or pulped, the easier
and
faster the decomposition will be.
Nutrient Availability and the Carbon-to-Nitrogen Ratio
Be sure the plant or animal waste to be decomposed contains
a
sufficient amount of nitrogen. Waste that is deficient
particularly in nitrogen, or in other elements such as
phosphorus, potassium, calcium, magnesium, sulfur, boron,
copper,
iron, manganese, zinc, and molybdenum, will slow the growth
of
bacteria, making decomposition difficult.
Generally, plant wastes should contain about 1.5 percent or
more
nitrogen for bacteria to function properly during the
decomposition process. For wastes high in carbohydrate and
low
in protein, you may need to apply about 10 kg of nitrogen
(25 kg
urea or 40 kg ammonium sulfate) per ton of waste.
Carbon-to-Nitrogen Ratio. Generally, the ideal
carbon-to-nitrogen
ratio of a good compost pile is about 30:1. If the ratio is
either much higher or much lower than 30:1, the
decomposition
process might slow down. Table 1 shows the
carbon-to-nitrogen
ratios for a variety of raw waste materials. Of the material
listed in that table, those whose carbon-to-nitrogen ratios
fall
in the mid range can be combined or used individually for
composting without upsetting the ratio. However, those
materials
whose carbon-to-nitrogen ratios fall to either extreme of
the mid
range will cause the ratio to be either too high or too low.
So,
if you use a material that has a low carbon-to-nitrogen
ratio,
you will also need to use a material whose
carbon-to-nitrogen
ratio falls in the high range, enabling the two materials to
balance each other out.
Table
1. Carbon-to-Nitrogen Ratio and Nitrogen
Content of Compost Materials
Percentage of
Percentage of
Raw Waste
Nitrogen
Carbon-to-Nitrogen Moisture
Material
(Dry Basis) Ratio
(Fresh Basis)
Fish scraps
6.5-10 4:1
80
Poultry manure
6.3 4:1
75
Meat scraps
5.1 6:1
65
Fresh grass
clippings
4.0
12:1
95
Sun-dried grass
clippings
2.4 19:1
40
Raw garbage
2.15 25:1
90
Mixed fresh
garden debris
2.0 20:1
80
Cow manure
1.7 27:1
80
Seaweed
1.9 19:1
90
Fresh leaves
1.5 30:1
80
Oat straw
1.05 48:1
25
Dry leaves
1.0 45:1
40
Raw sawdust
0.25 208:1
5
Determining the Carbon-to-Nitrogen Ratio of Your Compost.
List
the various ingredients in your compost and the approximate
weight for each. Using the data from Table 2, list for each
ingredient the fresh weight, the percentage of moisture, the
percentage of nitrogen, and the carbon-to-nitrogen ratio. If
the
specific material you are using does not appear on the
table,
estimate the characteristics by comparing it to similar
material.
Table
2. Determining the Carbon-to-Nitrogen
Ratio of Your Compost
Fresh
Percentage of Carbon-to-
Characteristic
Weight Moisture
Nitrogen
Nitrogen
Ingredient
(Pounds) (Percent)
(Dry Basis)
Ratio
Chicken manure
50 50
6.00
4:1
Sawdust
50 5
0.11
511:1
Food garbage
50 80
2.15
25:1
Dry leaves
75 25
1.00
45:1
Grass clippings
50 95
4.00
12:1
Total
275
Determine from the assembled data the following quantities
for
each ingredient:
*
the pounds dry weight by subtracting from
the fresh
weight the
percentage of moisture;
*
the pounds nitrogen by multiplying the dry
weight by
the percentage of nitrogen contained on a
dry-weight
basis; and
*
the pounds of carbon by multiplying the
pounds of
nitrogen by
the carbon-to-nitrogen ratio.
Compute for the total compost the cumulative moisture
content by
dividing the total dry weight by the total fresh weight.
Example:
144.5
----- =
53 percent
275.0
Compute for the total compost the cumulative
carbon-to-nitrogen
ratio by dividing the total pounds of carbon by the total
pounds
of nitrogen.
Example:
62.80
----- =
27 percent
2.33
Balancing the Carbon-to-Nitrogen Ratio. Spreading a thin
layer
of well-rotted manure within layers of fresh plant waste
provides
a good source of nitrogen. Table 1 shows the percentage of
nitrogen and phosphate for several types of animal manure.
Table
3. Average Nutrient Content of Animal
Manure
Type of
Amount of Nitrogen Amount of
Phosphate
Animal
(Percent)
(Percent)
Rabbit
2.4 1.5
Chicken
1.1 0.8
Sheep
0.7 0.3
Horse
0.7 0.3
Duck
0.6 1.4
Cow
0.6 0.2
Pig
0.5 0.3
Any mixed fertilizer containing nitrogen will be helpful if
applied at the rate of about 10 kg per ton of waste. The
other
elements, including phosphorus and potassium, which might be
in
the mixed fertilizers, will promote decomposition also,
especially
if the waste being decomposed is low in these elements.
Moisture
To increase the rate of decomposition, a compost pile should
always be moist but never too wet. Bacteria will grow under
a
wide range of moisture conditions--from almost dry to
saturation.
However, the best moisture for aerobic decomposition will be
less
than saturation but about that of green plants. In soils, it
will be slightly above the field capacity or the amount of
water
a soil retains against gravity. There will be a marked
reduction
in the number of bacteria and fungus with drying and a great
reduction in the rate of decomposition. So the residue
should be
kept moist but not saturated.
In tropical areas it may be necessary to cover the compost
pile
with removable mats or temporary shelter to keep rains from
saturating the pile.
Temperature
Bacteria grow and decompose wastes at a rather wide range of
temperatures, but for composts the optimum temperature is
around
30[degrees] to 37[degrees] C, especially during the initial
stages of the
decomposition process. Turning the pile to permit air to get
in
will cool the mass. The temperature can also be moderated by
wetting the compost pile. If the temperature is kept low,
say
below 20[degrees]C, the rate of decomposition will slow
down.
One note of caution: the process of decomposition generates
heat, and if fresh plant wastes are packed tightly in a pile
with
adequate moisture, the pile may become quite hot. Many barns
have burned down because uncured hay stored in them began to
decompose and generated enough heat to start a fire. This is
known as spontaneous combustion. The appearance of ash spots
in
the compost indicates that temperatures are too high and
steps
should be taken to cool the pile.
Acidity (pH)
Like other conditions, acidity greatly influences the type
and
number of microorganisms required for decomposition. Some
different species of microorganisms will grow at various
acidity
levels--from very acid (pH 1.0) to strongly alkaline (pH
11.0).
Plant wastes decompose best in the pH range of 6.0 to 7.5.
You may need to add some finely ground limestone (preferably
dolomitic lime) to keep your compost pile from becoming too
acid.
Usually 25 kg to 50 kg of limestone per ton of waste
sprinkled
through the pile is enough to do the job.
MAINTAINING THE COMPOST PILE
Nutrient Losses
Some valuable nutrients, particularly nitrogen, can escape
during
the decomposition process. For example, one of the end
products
of decomposition is ammonia, which can convert to a gas and
evaporate into the atmosphere, unless you mix fine-soil clay
or
ground phosphate into your compost pile. In addition,
nitrate,
ammonia, and potassium ions can seep through the soil, enter
the
ground water, and dissolve if too much water is applied. And
in
poorly aerated pockets of the waste undergoing
decomposition,
valuable nitrogen gas can evaporate into the atmosphere.
You can avoid the loss of nutrients by:
*
placing a fence (woven wire) or wooden
slats on all
four sides
to maintain the shape of your pile and to
keep animals out;
*
not overwatering your pile; and
*
mixing fine soil clay or ground phosphate
into your
pile.
A thin layer of soil on the surface of your pile is good.
This
absorbs ammonium ions and prevents the loss of nitrogen. The
soil
layer also discourages insect pests from breeding in your
compost
pile.
Aeration
If your compost pile (or soil) is well aerated, the
microorganisms can obtain oxygen from the atmosphere, and
decomposition will be aerobic, with aerobic bacteria and
fungi
predominating. If your compost pile is compacted, saturated
with
water, and poorly aerated, the anaerobic bacteria will take
over.
Turning the contents of your compost pile at least once a
week
will: (1) prevent the pile from getting waterlogged; (2)
aerate
the contents, which promotes rapid decomposition of the raw
waste
material; (3) mix and spread the nutrients uniformly
throughout
the pile; and (4) keep the pile from smelling bad.
You can test whether your pile needs to be turned by
inserting a
stick into the center, and removing the stick after a few
minutes. If the stick smells bad, turn the pile. If the pile
is
dry, add enough water to moisten it.
Clearly, if you turn the contents of your compost pile more
frequently, you will produce compost in a shorter period of
time,
given that all other factors are present. In temperate
regions,
if you do not stir the pile at all, it will take about four
to
six months to produce compost. If you turn the pile once or
twice every other month, it will take about two to three
months
to produce compost. If you turn it once every other day
(i.e.?
four or five times in two weeks), your compost will be ready
in
about two weeks. In tropical regions these time periods will
likely decrease.
Pests, Toxins, and Other Undesirables
A major problem in using composts is the possibility of
spreading
disease organisms (fungi and virus) and insects. Spores from
disease pathogens may carry over in the compost pile and
then be
spread over a field to a new crop. Though heat produced in
the
compost pile during decomposition may destroy weed seeds and
most
insects, the spores of many fungi, including the fungi
causing
some plant diseases, may not be destroyed. For this reason,
tobacco, potato, and tomato crop wastes are not recommended
for
use in compost piles as they may carry serious plant
diseases.
To protect a compost pile against insect pests, spread a
thin
layer of soil over the top of the pile. This soil layer also
prevents the loss of nitrogen.
Do not add any raw waste materials to your compost pile that
have
been treated with herbicides, insecticides, feed additives,
or
medications (e.g., antibiotics used in animal feeds or
injected
into animals). Such materials risk (1) slowing down the
decomposition
process; (2) retaining nondegradable amounts of toxins
in your compost; (3) killing your food crops caused by
toxins in
your compost.
Correcting Problems During Composting
If your compost pile does not heat up:
*
You may not have used enough nitrogenous
material.
This means
you may have used too much sawdust, paper,
or straw,
all of which have very high carbon-to-nitrogen
ratios due
to their high cellulose and lignin
content. To
correct this problem, simply add more of a
good
nitrogen source to your compost pile.
*
Or you may have added too much water to
your compost
pile. Too
much water suffocates the aerobic organisms
(i.e., they
need oxygen to function) to the point where
the
anaerobic organisms (i.e., they work in an oxygen-free
environment) take over, producing ammonia and bad
smells. To
correct this problem, turn your compost
pile
frequently or layer the raw waste material into a
long-term
compost pile.
If your compost pile gives off a strong smell of ammonia:
*
You may have added too much of a high
nitrogen source
to your
compost pile. To correct this problem, simply
add old
leaves, straw, or shredded paper in small
amounts.
*
Or you may have added too much limestone
or other
element
high in calcium carbonate to your compost pile.
This is
difficult to remedy, but adding acid leaf
litter and wet garbage may help. Next
time, add the
calcium to
the soil rather than to the compost pile.
Recognizing Finished and Semi-Finished Compost
The following are signs of finished compost:
*
ammonia smell is gone;
*
the temperature of the compost pile has cooled down
completely;
*
the compost is crumbly, dark, and sweet
smelling; and
*
at least three species of arthropods are
present (e.g.,
the sow and
pill bug, ground beetle, and centipede).
Indications of semi-finished compost that can best finish
composting in soil are:
*
the compost pile smells slightly of
ammonia;
*
the temperature has started to decline but
steam still
comes off;
and
*
possibly one or two species of arthropods
are present.
When and How to Apply the Finished Compost
It is best to use the compost when it is still fresh. Remove
the
compost in sections from top to bottom of the pile rather
than
from the top only. If time and labor permits screen the
compost
through a 0.6 cm mesh screen and return the larger materials
to
the compost pile. To avoid losing the compost to wind or
water
erosion it is best to incorporate it into the soil,
particularly
when it is used in large or sloping land areas.
III. DESIGNING THE SYSTEM RIGHT FOR YOU
COMPOSTING METHODS
A wide range of composting methods is available. These
extend
from simply adding raw waste material to soils and allowing
it to
decompose under natural conditions, to sophisticated
containers
with special chemical fertilizers that help raw waste
material to
rot quickly. Because chemical fertilizers are costly and not
always readily available to people in developing countries,
we
have focused only on those composting methods that do not
require commercial fertilizers.
As you familiarize yourself with the various composting
methods
outlined in this section, keep in mind that you may have to
adapt
specific methods to local conditions and available
resources.
You can modify a particular method a little to fit your
resources
without decreasing its overall effectiveness.
The size of a compost pile depends upon the amount of raw
waste
material available and how it is to be used. The biggest
factor
is to have a manageable pile large enough to take care of
available waste materials but small enough to be tended
easily.
If great quantities of material are available, such as from
a
slaughter house or sugar factory, several smaller piles will
probably be more manageable than a single large one.
Composting in Pits or Heaps
Although natural composting (i.e., decomposing raw waste
material
directly in the soil) retains just as many nutrients as does
controlled composting (composting in a pile), the latter
method
nevertheless offers more:
*
raw waste material decomposes much faster
in a pile;
*
the temperature within a compost pile is
much higher
than that
found in soil;
*
controlled composting kills many weed seed
and reduces
potential pathogens;
*
decomposed compost applied to soil loosens
hard,
compacted
soil immediately, allowing the soil to take
up oxygen and
to absorb water in a much shorter period
of time; and
*
adding decomposed manure to soil promotes
the growth of
food crops,
whereas adding fresh, undecomposed manure
can damage
the crops (i.e., the crops burn due to the
high amount
of nitrogen in fresh manure).
Choose a protected area, well drained and close to a water
source. The site should also be conveniently located since
it
should be checked regularly. In temperate climates it may be
best to avoid shaded areas since this will lower the
temperature
during cool seasons. In tropical or arid regions, shade may
be
more beneficial in decreasing moisture lost by evaporation.
Chop or crunch under a roller all hard materials such as
sugarcane
stubbles and dry stalks. Split up and cut all the soft but
bigger-sized materials like banana stumps. Dig a pit approximately
1.5m x 1.5m x .5m deep. Heap all the available refuse
around the pit. To make the material decompose easily, use a
"starter." The starter can be dung or urine. If
these are not
available, well-decomposed manure, tank silt, or surface
scraping
from forests can be used. To make a good compost, you also
need
some ash and dry earth.
As shown in Figure 1, organic materials are layered in
categories
uc1x14.gif (437x437)
in the compost pile and kept moist. To prepare the compost
pile,
put the refuse in the pit in a layer about a foot high.
Sprinkle
16 gallons (four or five buckets) of water and a thick paste
made
with 60 pounds (two buckets) of dung in 16 gallons of water.
Spread half a basket of ash and one basket of the starter on
the
layer. Put the second layer of trash over this. Five such
layers will bring the heap two feet above the ground level.
Cover this with a three-inch layer of soil on the top. See
to it
that you fill the pit completely in a day or two.
Speed Composting
Speed composting requires that all materials either be
chopped
into small particles (large kitchen scraps, weeds, straw) or
already come in small sizes (grass, leaves) and that the
slower
decaying materials such as wood, twigs, eggshells and bones
not
be used.
The volume of the compost pile should be no less than one
cubic
meter to allow the generation and retention of heat.
Ingredients
must be layered by categories (dry, green and manure) so
that the
pile builder can estimate the ratio of the different
materials.
Essential to the speed composting method are:
*
frequent turning,
*
proper moisture levels, and
*
sufficient amounts of nitrogen to promote
decomposition.
Here is a simple formula for speed composting:
*
Loosen the soil in the area where the pile
is to be
built.
*
Build a bin no smaller than 1m x 1m x 1m.
*
Layer compost ingredients as follows:
- Bottom
layer--approximately 6 inches of absorbent
material
(straw or sawdust).
- 4 inches of
green garden and kitchen wastes.
- 2 inches of
manure, possibly mixed with soil.
- 3 to 6
inches dry roughage (dry grass, leaves, or
sawdust).
*
Repeat this layering until the bin is full,
sprinkling
the layers
with water as you go.
*
Every second or third day, turn the pile
with a
pitchfork or
shovel. Turn the outer layers inward,
mixing
thoroughly from top to bottom. Turning the
pile every
day speeds up the decomposition process.
*
Keep the pile moist but not waterlogged.
*
Compost should be ready to spread over your
farmland in
about one
month.
RESOURCES, MATERIALS, AND EQUIPMENT REQUIRED
The resources, materials, and equipment necessary for
composting
depend on what composting method you employ. Nevertheless,
for
basic composting you need:
*
plant residues and/or animal wastes;
*
something with which to turn the compost
material
(e.g., a
shovel, pitchfork);
*
a sufficient supply of water to keep the
compost
moist;
*
a cutting tool, (e.g., a machete) to break
up large
chunks of raw
waste material;
*
a fence of woven wire, wooden slats, or
bamboo, or a
simple pit to
maintain the shape of the compost pile;
*
a supply of urea or ammonium sulfate in
case you use
raw waste
material that is low in nitrogen;
*
a supply of finely ground limestone to
maintain the
acidity level
of the compost pile;
*
a supply of clay loam, fine soil clay, or
ground
phosphate to
prevent the compost material from losing
valuable
nutrients during and after the decomposition
process; and
*
some woven mats, a thick layer of straw, or
a straw
root to protect
the compost pile when it rains.
ENERGY USE/EFFICIENCY
There are essentially four steps in the controlled
composting
process that require energy use: collecting the raw waste
material, preparing the compost pile, maintaining the pile,
and
adding the finished compost to the soil. The quantity of
energy
used in each of these steps depends primarily on the amount
of
compost being produced. Compared to natural composting,
which is
simply adding raw material to the soil and letting it
decompose
naturally, controlled composting in a pit or heap clearly
requires
more energy. However, because controlled composting
speeds up the decomposition process, it can produce compost
in a
shorter period of time given the right conditions.
COST/ECONOMICS
The cost of composting depends on the amount of raw material
available, and whether people and equipment must be hired to
collect and process it and return the compost to the soil.
Costs
must be balanced against the benefits of increased soil
fertility, crop production, etc.
The amount of labor needed depends on the method used, size
of
compost pile, and availability of materials. For a household
compost pile, one person may spend on average between one
and
three hours a week maintaining a pile. This time commitment
will
vary each week depending on the stage of decomposition of
the
pile.
Composting is typically done on a small-scale basis within
households or on small farms. However, where there is an
abundance of raw materials and potential for marketing
exists,
composting has been an economically feasible business.
Depending on the quantity and type of materials used,
composting
has the potential to be sold as a soil conditioner or as an
organic fertilizer. This market tends to increase near urban
areas where small-scale gardening requires a source of soil.
If
raw materials are readily available and labor or low cost
equipment are available, composting has the potential to be
maintained as a business.
SPECIAL PROBLEMS
Due to the potential health problems there may be laws in
more
populated urban areas which prohibit the use of certain
materials
for composting. These restrictions should be explored.
IV. COMPARING ALTERNATIVES
The main disadvantage of composting is that it can be time
consuming and the pile must be checked regularly. Beyond
this the
disadvantages of composting only become apparent when proper
care
for the compost pile is not followed. Insects and animals
can be
attracted to the pile if the raw materials are not selected
or
covered carefully. Disease and weed problems can increase if
the
compost pile did not heat up sufficiently (to kill them
while
composting). The pile can be a potential fire hazard if
moisture, temperature, and aeration are not watched
regularly.
Composting is relatively inexpensive and simple. Thus, if
you
want to convert waste organic materials to fertilizer,
composting
would be a good choice.
On the other hand, if large quantities of raw materials are
available and you want to produce more than just fertilizer,
you
might consider biogasification as an alternative. With
biogasification,
raw waste materials can be digested under specific
anaerobic conditions, and returned to the environment in the
form
of fertilizer and fuel, without degrading the environment.
Biogasification
requires a considerably larger investment in capital,
materials, and labor. For example, the equipment (i.e., a
biogas digester, systems, pumps) necessary for
biogasification is
generally more expensive than the equipment necessary for
composting.
BIBLIOGRAPHY
Bartholomew, W.V. Soil Nitrogen--Supply Processes and Crop
Requirements.
Technical Bulletin 6. Raleigh, North Carolina:
North Carolina
State University, 1972.
Bartholomew, W.V., and Kirkham, D. Mathematical Descriptions
and
Interpretations
of Culture Induced Soil Nitrogen Changes.
Madison,
Wisconsin: American Society of Agronomy, 1960.
Clark, F.E. "Bacteria in Soil." Soil Biology. New
York: Academic
Press, 1967.
Corven, James. Basic Soil Improvement for Everyone.
Arlington,
Virginia:
Volunteers in Technical Assistance, 1983.
Fitts, J.W. "A Nitrification Procedure for Predicting
the Availability
of Nitrogen in
Iowa Soils." Ph.D. dissertation,
Iowa State
University, 1952.
Reddy, K.R.; Khaleel, R.; and Overcash, M.R. "Behavior
and
Transport of
Microbial Pathogens and Indicator Organisms in
Soils Treated
with Organic Wastes." Journal of Environmental
Quality.
Madison, Wisconsin: American Society of Agronomy,
1981.
Rodale, J., ed. The Complete Book of Composting. Emmaus,
Pennsylvania:
Rodale Press,
Inc., 1969.
Russell, E. Walter. Soil Conditions and Plant Growth.
London,
England:
Longmans Press, 1961.
Warcup, J.H. "Fungi in Soil." Soil Biology. New
York: Academic
Press, 1967.
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