(Materials & methods to ensure quality
Shredding or grinding raw materials is beneficial,
particularly when composting fibrous materials
such as leaves, woody plants or corn stalks.
Shredding exposes a greater surface area,
which makes it more susceptible to bacterial
invasion. Large pieces of wood or leaves
packed together do not decompose quickly
in a compost pile. Insufficient oxygen in
the center of a wood chunk or a wad of leaves
does not permit more rapid aerobic decomposition.
Shredding material makes it more uniform
in size, aerates it, and makes it easier
to handle and keep moist. Smaller particles
enable the compost to heat more evenly, and
to withstand excessive drying at the surface.
The compost pile is then is insulated against
heat loss, and also better resists moisture
penetration from rain. Fly control is also
better when material is pulverized or shredded.
Uniform compost made from shredded material
can be more easily applied to the land.
The best sized particles for composting are
less than 2 inches in the largest dimension,
but larger particles can be composted satisfactorily.
The particle size of material being composted
is determined by the finished product requirements
and by economics. If the material is to be
used on lawns or flower gardens, compost
should be screened through a one-inch screen
so it looks better and is easier to apply
and work into the soil.
Sometimes it may not be worth added cost
and labor to shred the material. Particles
too large can be forked or screened out or
broken up when necessary. Some people are
not particular about uniformity of compost
structure when preparing compost. For example,
uniformity is not as important for agricultural
fields as for the home gardener.
Initial shredding of all material is not
absolutely necessary. Often, the best practice
is to shred only large pieces of organic
materials. Using some larger irregular pieces
creates greater air spaces and hence more
Large, tough feedstocks may require grinding
to speed decompostition. Vegetative and herbaceous
matter should not be ground up because it
becomes soggy. The high moisture content
of these materials makes them more difficult
to manage in aerobic composting. The type
of raw materials for composting determines
when to shred.
Regrinding can be done either after the compost
is mature, or near the end of the maturing
process. Regrinding near the end of the period
of active decomposition can serve as the
last turning for aeration, and the pile can
be left to stabilize.
Whether to grind or shred depends upon the
nature of the raw material, the desired features
of the final product--such as the appearance,
size, and quality--and the economic requirements
of the operation. Shredding and grinding
the materials will shorten the decomposition