(Materials & methods
to ensure quality compost)
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.
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
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 entrapped oxygen.
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.
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