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

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pH
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Days
Figure 5: Changes in pH values during the 1 st composting trial
The pH of the extracts increased during the first 8 days of the 1 st composting trial.
This is more probably related to the degradation of the organic matter, which releases
ammonia [17]. At the onset of composting, compounds such as amino acids, proteins
etc. were mineralized through the activity of proteolytic bacteria to give ammonia and
thus the pH value increased reaching a maximum of 8.86 on the 8 th day. Thereafter,
through ammonia volatilization and its oxidation to nitrates by the action of
nitrobacteria, the ammonia content decreased and thus the pH value drops from 8.86
to 7.31 on the 30 th and final day of the process [12, 18].
5.1.6.2. Total Carbon
During composting, controlled microbial transformation of the organic matter that is
present in the compostable material takes place. Part of the organic matter is
mineralized to carbon dioxide, ammonia and water. The carbon loss occurs through
bio-oxidation of organic carbon to CO 2 during composting. The CO 2 can escape as a
gas or dissolve in the liquid, forming carbonic acid (H 2 CO 3 ) bicarbonate (HCO - 3 ) and
carbonate (CO 2- 3 ). The other part of the organic carbon is transformed into humic
substances which are structurally very similar to those present in soils. Figure 6
presents the total carbon evolution during the 1 st composting trial.
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