Investigating composting progress of kitchen wastes using rate of change and cross-correlation approaches

Kitchen wastes usually require addition of some bulking agent for proper composting. In this study, mixtures of kitchen and pruning of elm trees were composted under three treatments of natural, low and high aeration rates. Temperature, ammonia, carbon monoxide, pH and volatile organic matter were monitored and analysed. The results indicated with increase in aeration rate, temperature of the treatments increased. The pH values of the treatments decreased initially to a minimum of 5.0 and then increased continuously. The emitted ammonia and CO initially rose but then continually decreased. The rate of change graphs showed two distinct phases of: 1) active; 2) constant rate for all measured factors. A correlation analysis on the five considered factors indicated the reduction in volatile organic matter and emitted CO and ammonia were highly negatively correlated with pH of the pile (r = −0.72), but their correlations with temperature were low.