Evaluation of Two Drying Systems in Municipal Organic Solid Waste Composting

Abstract

An experimental study design with laboratory analysis was used to evaluate effects of natural and artificial drying on the quality of organic fertilizers. Organic waste was subjected to windrow composting and the matured compost was dried using two different methods: Sun Drying (SD) and an Electric Rotary Dryer (ERD). Part of the fertilizer was spiked with chemical fortifiers (phosphate and urea). Organic and organo-mineral fertilizers were analysed for nutrient and heavy metal contents. The nutrient levels: %N (1.88±0.02; 1.37±0.01), %P (2.86±0.01; 2.05±0.01), %K (8.62±.01; 5.47±.01), %O.C (4.57±.01; 6.48±.01) and heavy metal contents: Pb (2.49±0.01mg/kg; 1.57±0.01mg/kg), Cd (1.97±0.01 mg/kg; 1.24±0.01 mg/kg), Zn (96.86±0.01 mg/kg; 89.47±.01mg/kg), Cr (0.68±0.00; 0.62±0.01mg/kg) were significant higher in SD than ERD samples respectively. Hence, both methods were effective as the guidelines were maintained in both samples. It is recommended that the use of electric dryer should be complemented with chemical fortification to boost the fertilizer nutrient levels.