Effects of initial C/N ratio on organic matter degradation of composting of rose oil processing solid wastes

Abstract

This research study was aimed to investigate the degradability of organic substances of rose oil processing solid wastes mixed with separated dairy manure and straw. The experiment was conducted in 2014. Compost mixtures were prepared at five different C/N ratios of 16.52, 23.27, 27.48, 31.39, and 32.35 by keeping the moisture content (on a wet basis, %) between 67.76 and 74.87. Each mixture was replicated twice in composting reactors. To assess degradation rates changing with the initial C/N ratio, a first-order kinetic equation based on mass balance was utilized. Results showed that the highest decomposition rate was calculated as 0.03 kg kg−1 day−1. For each mixture, the compost mass ratio was also determined. The relationship between loss on dry matter and organic matter content and the initial C/N ratio were ascertained by using regression analysis applying Gaussian equation. According to the results, the maximum loss on dry matter and organic matter content was found to be 14.53 and 24.34%, while the corresponding initial C/N ratio was 29.50 and 24.25, respectively. It was concluded that the initial C/N ratio of the mixture could be greater than 30 in order to reduce nitrogen loss. Carbon loss was also expressed as a function of the initial C/N ratio by using regression analysis. An initial C/N ratio > 21.77 was suggested to reduce carbon loss for composting of rose oil processing solid wastes mixed with separated dairy manure and straw.