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

This will limit the movement of air and lead to anaerobic conditions. Moisture content
should be above 40% at the starting point, as it will generally decrease as composting
proceeds. Therefore if the moisture content falls below 40%, water should be added to
maintain optimum conditions.
During composting the moisture levels change as water evaporates and usually there
is a need for water addition. In many composting cases more water evaporates than is
added so the moisture tends to decrease as the composting proceeds. Moisture levels
should be maintained so that materials are thoroughly wetted but without being
waterlogged.
The moisture content range of 40-65% works well for most materials. The upper limit
for moisture content is dependent on the absorbency and porosity of the raw materials.
A mixture with highly absorbent materials (e.g. dry grass) may need to be maintained
well above 40% moisture in order to support rapid decomposition. Materials should
not be allowed to dry out below 40% moisture content, as this will increase the chance
of damaging high temperatures or even spontaneous combustion.
2.6. Temperature
Composting takes place within two temperature ranges known as mesophilic (≈35 o C -
40 o C) and thermophilic (>40 o C). It is generally accepted that maintaining
temperatures between 43 o C and 65 o C allows for effective composting. The
thermophilic temperatures are favoured in the composting materials, because they
destroy more pathogens, weed seeds and fly larvae. A temperature of 55 o C should kill
human pathogens and most plant pathogens as well. Micro-organism activity during
composting releases large amounts of energy in the form of heat. This heat
accumulates due to the self-insulating qualities of the compost material and causes the
temperature to rise. At the same time water evaporates and water vapour and warm
gases are vented. Turning and aeration accelerate the heat loss and is used to maintain
temperatures within the desired range.
When temperatures rise above 60 o C the micro-organisms suffer the effects of high
temperatures and the process slows down. Temperatures can continue to rise up to
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