WITHDRAWN: Assessment of the effect of particle size and selected physico-chemical and biological parameters on the efficiency and quality of composting of garden waste

Abstract

<h2>Abstract</h2> For composting of garden waste, particle size is an important factor for efficient degradation of lignocellulose compounds. The present study is aimed at investigating how particle size effects selected physicochemical and biological parameters such as temperature, moisture, total volatile solids lignin degradation, coliform reduction, germination index, and carbon dioxide evolution during the composting of garden waste. The garden waste was shredded using a shredder into different particle size namely R₁ (0.5-1.5cm), R₂ (1.5-3.0cm), R₃ (3.0-4.5cm) and R₄ (4.5-7.5 cm). The feedstock was fed into rotary drums for 45 days composting period. The temperature rose to the thermophilic phase within 48 hours in all the drums and continued for R₁ (7 days), R₂ (8 days), R₃ (4 days), and R₄ (3 days). Moisture content reduction observed was R_{1 (}23.4%), R₂ (22.7%), R₃ (21.7%) and R₄ (20.8%). Total volatile solids reduction was 29.10, 31.20, 24.23, and 17.12 %, CO₂ evolution rate was 4.92, 4.14, 6.18 and 8.16 mg/gVS/d, C/N ratio was 16.91, 15.05, 18.13 and 20.99, germination index was 92.00, 94.12, 85.21, and 81.20 in R₁, R₂, R_3, and R₄ reactor respectively after end of the composting period. The reduction of hemicellulose, cellulose, and lignin was highest in the R₂ drum and lowest in R4. The percentage reduction of coliforms was also found to be highest in R₂. As per the analytical hierarchy process, the performance of reactors was observed in the following trend, R₂>R₁>R₃>R₄. Particle size range 1.5-3.0 cm diameter showed optimum size for efficient composting of garden waste.