(Materials & methods
to ensure quality compost)
are many ways, such as bins, barrels, pits and windrows to compost
Open piles, windrows, or bins are the most widely used methods
for aerobic decomposition and maturing of organic refuse. Exact
arrangement of these systems depends on local requirements of materials,
labor, cost of systems, climatic conditions such as temperature,
rainfall, and wind.
To aerobically maintain the composting process by frequent turning
for aeration, windrows, piles and bins above the surface of the ground
are more efficient than pits. On the other hand, if the decomposition
is to be entirely anaerobic or aerobic only during a short initial
period, pits 3 to 4 feet deep and varying in length and width in
accordance with the daily quantity of raw material should be used.
WINDROWS, PILES AND BINS
Material in aerobic composting piles should be loosely stacked to
allow space for air in the interstices. Windrows or piles may be
of any length, but the height of the pile is critical. If piled too
high, material will be compressed by its own weight, thus reducing
pore space, which results in increased turning labor (costs) or longer
composting time as anaerobic conditions develop. In some instances,
the maximum practical height may be governed by the equipment used
for stacking the feedstocks, or by the tendency of the pile to become
excessively hot. Large piles in warm weather may reach temperatures
excessively high for bacterial life. Some have even caught fire.
Piles that are too low lose heat rapidly. They do not get hot enough
for destruction of pathogenic organisms and decomposition by thermophiles
Also, if the piles are too small, loss of moisture may be excessive,
especially near the edges, and decomposition slows.
Five to six feet is about the maximum height for any
pile, and 3 feet is the minimum for most shredded fresh organic matter.
The height can be greater in cold weather than in warm weather.
Thoroughly mixing compost materials in bins, windrows
or piles provides quickest and most complete decomposition. The pile
may normally be started directly on the ground. To ensure aeration
to the bottom of the pile and improve drainage, dig a trench across
the base of the area and cover with stiff wire mesh (hardware cloth)
before adding material.
may not have enough materials daily for windrows. In this case
circular or rectangular piles 4 – 6 feet in diameter
and 3 to 5 feet high works, with a rounded top for shedding rainwater.
For shallow pits, either the walls and bottom of the pit are lined
with brick or masonry or the natural earth is tamped and packed.
The material is stacked to a height of 1 foot or more above the ground,
making a total of 3 to 4 feet. The material can be turned in the
pit as often as necessary to provide the high temperatures and aerobic
conditions as required. When pits are used, a smaller stack surface
is exposed to the air, and the walls and bottom of the pit provide
some insulation against heat and moisture loss.
Any type of pit should be lined and is usually provided with a chimney
and trenches, or a porous bottom, for aeration and drainage of liquid
seepage from the pile. The same shape trenches without aeration and
drainage channels and without masonry lining may be used. But unless
pits are lined, the walls are apt to crumble and the shape of the
pit becomes irregular. When hand labor is used, turning the material
in a pit may be about the same as in a stack on the ground surface.
One effective method involves composting in pits approximately 3
feet deep by a system of providing aerobic conditions and high temperatures
for the first few days and then anaerobic conditions for 4 to 6 months.
Material is mixed in the pit. There is sufficient oxygen in the initial
stack for a high temperature to be produced by aerobic organisms
during the first few days. High temperatures are usually retained
for two weeks or so, owing to the insulating properties of the stack,
even though anaerobic conditions may exist after the first few days.
Leave the material to compost in the pit with no turning for about
or TRENCH COMPOST
To sheet compost, work a thin layer of material such as leaves into
the garden in the fall. By spring, the material should be broken
down. This would not be appropriate for materials such as wood chips
that would take a longer time to decompose, and might tie up soil
nitrogen in the spring, making it unavailable to other plants.
For trench compost,
dig a trench 8 – 15 inches deep, bury
the feedstocks, then cover back up with soil. It takes about a year