MOROCOMP (LIFE TCY05/MA000141) - Unit of Environmental ...

equire longer composting periods while the excess carbon is used by the microorganisms.
The rate at which carbon compounds decompose must also be considered. If the
carbon is in a form that is difficult to decompose, the composting rate may be slower
(e.g. wood waste). Since decomposition occurs on particle surfaces, degradability can
be improved by reducing the particle size as long as porosity is not a problem (see
above). If required, the C:N ratio can be adjusted to increase the proportion of carbon
to compensate for the presence of poorly degradable sources of carbon. This may,
however, results in a longer composting time period.
2.4. pH
The composting process is relatively insensitive to pH within the range commonly
found in mixtures of organic materials. The composting process can work over a wide
spectrum of pH values, but a range of between 6.0 and 8.5 is preferred [2, 3, 4, 5, 6].
Although the composting process will be less effective at the extreme ranges of 5.5
and 9.0 it will still work. A pH above 8.5 encourages the conversion of nitrogen
compounds to ammonia, which further adds to the alkalinity. Adjustment of the pH
downward below 8.0 to reduce the ammonia loss is possible by using additives. As
decomposition occurs the composition of the raw materials and the associated pH
change. However, irrespective of the pH of the starting raw materials, the composting
process yields a final composted organic material with a stable pH that is close to
neutral (7.0).
2.5. Moisture
Moisture supports the metabolic processes of the micro-organisms. Water is the
medium for chemical reactions, transportation of nutrients and allows the
microorganisms to move about. Biological activity ceases below 15% moisture
content and in theory activity is optimal when materials are saturated. Generally
moisture content of between 40% and 65% should be maintained. At moisture content
of below 40%, micro-organism activity will continue but at a slower rate and above
65% water will displace much of the air in the pore spaces of the composting material.
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