Composting of common organic wastes using microbial inoculants

It is important to use renewable resources to maximize crop yields and minimize the environmental hazards associated with chemical residues. Composting is an age old practice for the biological conversion of organic waste to a humus-like substance which can enhance physical, chemical and biological soil properties. To explore the effect of microorganisms in the composting process, three potent bacterial isolates were selected. Their morphological, cultural and biochemical characteristics were identified, and 16S rDNA studies identified isolates B1U/1 and D3L/1 as Bacillus subtilis and isolate RAT/5 as Pseudomonas sp. Common organic wastes were composted using the selected isolates individually and as a consortium. The C/N ratio of each substrate reduced gradually to 25-30:1 within 120 days and remained constant thereafter. The reduction in NH4+ and NO3- ion concentrations also indicated compost maturity after 120 days. The pH of the mature compost was typically 7.0 +/- 0.2, and the PO4-3 ion concentration was high throughout the decomposition process. This study describes the optimization of the composting process using a consortium of isolates from composted soil.