The Adjustment of Medium-High Range of the C/N for Commercial Composting

Abstract

This study aimed to evaluate effectiveness of composting performance and cost of raw materialunder the adjustment of medium-high initial C/N ratio. The methodology was divided into three phases.Phase 1 was to investigate the effect of initial C/N ratio on composting by varying the C/N ratios of 30, 40,50, and 60 and using batch reactors (working volume 4.61 l). Phase 2 was to scale up the appropriatecondition which obtained from the Phase 1 to the pilot scale in the factory. Phase 3 was to examine theoptimum compost to soil ratio by testing the plant growth (Chinese mustard) at the ratios of 0:100, 5:95,10:90, and 15:85 respectively. Throughout the study, physical and chemical changes of compost weremonitored and the parameters of plant growth were also measured. Results show that the composting canbe efficiently managed at the initial C/N ratio up to 40, where the process had achieved thermophiliccomposting (>55°C) for 2 weeks which satisfied the regulatory requirement for a process to further reducepathogens (USEPA 40CFR503). Dry mass loss and organic matter degradation rate constant which followedfirst-order model (r2=0.8) were 33% and 0.004 day-1. The study was found that composting performedby turning significantly promoted the N loss during the first 2 weeks, especially the composting atlower C/N40 afterwards. The production cost (chicken dunk, cow manure, waste from mushroom cultivation,and coconut coir) was 0.40 Baht/kg and the quality of compost obtained was qualified the recommendedcriteria set by Department of Agriculture of Thailand (2548 B.E.). The significant differences(P<0.05) indicated the compost to soil ratio of 10:90 was the optimum condition for the plant growth.

Keywords : C/N ratio / Composing / Chicken Dunk / Cow Manure / Waste from MushroomCultivation / Coconut Coir