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

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.

​Duration of Composting and Changes in Temperature, pH and C/N Ratio during Composting: A Review

“…In the study done by Karanja et al (2019) initiation of the composting process led to a slight decline of pH upto 6.56 then, it rose gradually to alkaline conditions as high as 10.46 and then gradually decline to almost neutral at the end of composting period to 7.5 to 8.5. Long et al (2017) observed that the initial pH was low with 4.5 to 5.5 than it increased to 7-8.5. In an aerobic dumping of wheat straw treated with microorganisms the initial pH was 5 and as decomposition progressed pH increased upto 8 and the final value was 7 (Pan and Sen, 2013).…”

“…However in the control the rise in temperature was only upto 33.25C due to lesser variation of microbial activities. In different ratios of kitchen waste and vegetable waste composting in aerated reactor, the temperature during thermophilic phase reach upto 55C which gradually declined to 33C in the cooling phase (Long et al, 2017). In the aerated composting done by Guo et al (2012) the rise of temperature was upto 70C from an initial temperature of 25C and in the study done by Fan et al (2016) the initial temperature was 25C which reached upto 52C in the thermophilic stage.…”

“…Composting of rice straw was enhanced as the C:N ratio was least when it was treated with chicken manure compared to donkey manure. The C:N ratio decreased from 27.07 in vegetable waste to 8.7 and 50.7 to 27.88 in kitchen waste composting done by Long et al (2017). High C:N ratio of 128:1 was observed in initial stage which gradually decrease to an overall average of 17.1 with passage of substrate decomposition (Pan and Sen, 2013).…”