Monitoring the changes of some physical, chemical, microbial and enzymatic parameters during composting of three garden wastes

Abstract EN

The present study aimed to evaluate the composting (during 25 days) of three garden wastes through the changes in its physical, chemical, microbial and enzymatic parameters by using the bioreactor method.

The used wastes were grass clippings and fallen leaves of Jambul trees, Eucalyptus trees and Ficus trees.

The obtained results revealed that the physical changes such as temperature reached the maximum value after 10 days and then gradually decreased by the end of composting, while that of ouder and colour showed exhibited clear changes.

The values of the chemical parameters including: ash content, total nitrogen (TN), and cation exchange capacity (CEC) were increased by the end of composting, while organic matter (OM), organic carbon (OC) and carbon: nitrogen ratio (C/N ratio) were decreased.

The decrease in pH was recorded after 10 days and then gradually increased and reached the maximum value (from 5.63, 5.00 and 5.89 to 6.72, 6.76 and 7.07 for Jambul, Eucalyptus and Ficus, respectively) by the end of composting.

Electrical conductivity (EC) increased during the first ten days and then gradually decreased by proceeding the composting.

Both mesophilic bacteria and fungi gradually decreased with time, whereas the thermophilic ones gradually increased and reached the maximum after 10 days and then gradually decreased with time and disappeared by the end of composting.

The activity of α-amylase increased and reached the maximum value (0.02, 0.02 and 0.03 µmol/ml/min for the three garden wastes, respectively)after 5 days and then decreased gradually by the end of composting, while the activity of Carboxymethyl cellulase (CMC ase) increased and reached the maximum value (0.04 µmol/ml/min) for the three garden wastes from starting composting process after 5 days and then decreased gradually by the end of composting.

Finally, the activity of xylanase increased and reached the maximum value (0.23, 0.23 and 0.24 µmol/ml/min) for Jambul, Eucalyptus and Ficus garden wastes, respectively, after 10 days and then decreased gradually by the end of composting.