The Effect of Initial Carbon to Nitrogen Ratio on Kitchen Waste Composting Maturity

Abstract

A home electrical composter has arisen as a popular tool to expedite the lengthy composting process. It has been conveniently selected as a compost producer in kitchen households and is especially favoured in urbanized settings. The generated composts from the electrical composter, however, are still found to be immature and would require additional curing. The quality of the compost can be improved by investigating the initial carbon-to-nitrogen ratio (C/N ratio) of kitchen waste. It is, therefore, the aim of this paper to determine the optimum initial C/N ratio by preparing two primary samples: with and without soil. Samples of 10:1, 15:1, 20:1, 25:1, 30:1, and 35:1 C/N ratios were fed into the electrical composter and allowed to cure for 4 weeks. The six main samples were further divided into sub-samples for replications. The phytotoxicity levels and maturity of the produced compost were assessed in terms of the germination index (GI), using a seed germination test. In addition, statistical analyses using box plots and T-distributed Stochastic Neighbour Embedding (T-SNE) were carried out to observe the root growths’ variability and to deduce any significant clusters amongst the samples. The results have shown that samples with and without soil performed better with C/N ratios of 10:1 and 25:1 and with GI values of 16.2 and 31.8, respectively. The results also indicate the presence of a substantial level of phytotoxins within the samples, even after four weeks of curing.