(Materials & methods
to ensure quality compost)
Just like people,
compost organisms need water to live. Some microorganisms use the
film of water to move—slipping and sliding to another
section of the pile. Biological activity stops when the pile dries
If adequately aerated, composting material with moisture content
between 30% and 100% will be aerobic. In practical aerobic composting,
however, high moisture content must be avoided because water displaces
air from the interstices between the particles causing anaerobic
conditions. However, too low moisture content deprives organisms
of water needed for their metabolism, and inhibits their activity.
Maximum moisture content for satisfactory aerobic composting varies
with materials used. If straw and strong fibrous materials are used,
the maximum moisture content can be much larger without destroying
structural qualities or causing material to become soggy, compact
and unable to contain enough air in the interstices. But if it contains
lots of paper or grass clippings, which have little structural strength
when wet, or if granular, like ash and soil, less water is better.
home compost piles whould contain 40 - 60% moisture.
It should feel as moist as a wrung out sponge. Dry carbon layers
can be watered as the pile is built, then with each turning, add
more water as necessary.
In University of California studies, fibrous materials containing
an abundance of straw were composted aerobically with moisture contents
of 85% to 90%, but other composts containing much paper became anaerobic
in one day when the moisture content was about 70%.
If anaerobic composting is practiced, the maximum moisture content
is not as important, since oxygen maintenance is not a factor. The
upper limit of moisture, which may be from 80% to over 90%, is the
amount of which excessive drainage from the compost will be produced.
If the composting procedure has initial aerobic conditions to produce
high temperatures lasting a few days for the destruction of pathogenic
organisms, followed by anaerobic composting, the maximum initial
moisture content may be as high as 65% to 85%, depending on the character
of the composting materials.