Effect of C/N on Water State during Composting of Kitchen Waste and Vegetable Waste Mixture

Yuyang Long,Yuqiang Yang,Weijia Liu,Dongsheng Shen

doi:10.1155/2017/9409145

Abstract

The objective of this study was to evaluate the effects of the C/N ratio on the water state changes during the composting of kitchen waste (KW) and vegetable waste (VW) mixtures. The C/N ratios in KW and VW were 50.70 and 27.07, respectively, and the VW was added to the KW to amend the C/N ratio. Five composting treatments were used, R1 with 0% KW, R2 with 25% KW, R3 with 50% KW, R4 with 75% KW, and R5 with 100% KW, and the initial C/N ratios increased in the order R1 < R2 < R3 < R4 < R5. As the composting process progressed, the capillary water (CW) and multi-molecular-layer water (MMLW) were changed into entrapped water (EW), and a high C/N ratio could delay the changes in the water state. The percentage of EW and CW significantly positively correlated with the C/N ratio during the composting of KW. The composting process performed better in treatments R2 and R3 than in the other treatments, and it was found that treatments R2 and R3 each had a lag phase of around 4 d until the water states started to change.

Highlights

Composting has been used to dispose of kitchen waste (KW), which is the residue from meals and is a typical type of organic waste [1]
Free water can be divided into entrapped water (EW) and capillary water (CW), and bound water consists of multi-molecular-layer water (MMLW) and monolayer water
In our previous studies [15, 16], we found that the C/N ratio decreases as the percentage of EW increases and the percentage of CW decreases, because a large amount of biodegradable organic matter is degraded and the nitrogen that is present becomes concentrated

Summary

Introduction

Composting has been used to dispose of kitchen waste (KW), which is the residue from meals and is a typical type of organic waste [1]. A low MC is unfavorable for microbial growth in composting, and a high MC can suppress the mass transfer of air. A balanced MC should be maintained to achieve the most mature composting possible. The composting of KW system is a typical mixed organic matter system, and the water is present as two fractions: free water and bound water [5]. The EW, CW, and MMLW are the focus of the MC balance during the composting of KW

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Conclusion