The characterization and composting of the municipal solid waste of Riyadh city, Saudi Arabia

摘要

The rapid increase in population and change in life style in Riyadh city, Saudi Arabia have resulted in a dramatic increase in municipal solid waste (MSW) which has recently reached 12,000 tons per day. Most of it (about 85%) is disposed as land fill. The present study was initiated to address the problems of MSW disposal and assess the feasibility of the composting of separated organic matter of MSW generated in low, middle and high income districts of Riyadh city. A complete characterization of MSW compost was conducted. Results showed that the average recyclable materials in the three districts were more or less similar. The average organic fraction in the three districts was about 52%. The organic fraction had a number of coli form cells at the starting time of composting which completely disappeared after 21 days from starting the composting process. The composting of MSW resulted in a significant reduction in the volume of municipal solid waste and finally produced earthy smelling soillike material compost. The obtained mature compost contained high levels of the different major elements; N (2.0%), P (0.5%) and K. (0.25%). On the other hand, levels of Cd, Cr and Pb were below the standard values suitable for compositing. The pH and organic matter content of the mature compost were typically 7.70 and 33%, respectively. The C/N ratio showed high rates of change during the first 60 days after composting, and then stabilized. In general, the obtained results demonstrated the good quality of the produced compost, which can safely be used for enhancing physical, chemical and biological soil properties.