Drum composting of nitrogen-rich Hydrilla Verticillata with carbon-rich agents: Effects on composting physics and kinetics

Abstract

Composting of the Hydrilla verticillata, an invasive aquatic weed, signifies aquatic waste management as a safe and hygienic method that produces a nutrient-rich end product, i.e., compost. However, its higher moisture content, higher N-losses, and lower degradation rate have shown negative impacts on the composting process. Therefore the primary objective of this study was to assess the composting physics and the degradation kinetics after addition of three different carbon-rich agents with Hydrilla verticillata. To pursue this objective, three carbon-rich agents (viz. dry leaves in Run A, grass clippings in Run B and wood chips in Run C) each were mixed (10% w/w) to the optimized control mixture of Hydrilla verticillata, cow dung and sawdust (8:1:1) as reported in the earlier study. The composting experiments were performed in 550L rotary drum composter for 20 days to evaluate variation in physical, chemical, nutritional properties as well as degradation kinetics. The Run A and Run B were the only two mixtures that attained the temperature (55–70 °C) that indicates standard sterilization capacity in both with maximum moisture reduction (17%) and total Kjeldahl N increment (48%) in the latter. Organic matter losses throughout the process followed a first-order kinetic equation in all the Run (A-C) and control with the higher loss in Run B whereas least in control. Nevertheless, the addition of all carbon-rich agents is found to be beneficial to improve composting physics. Amongst all Runs (A-C), Run B achieved maximum reduction in the initial value of bulk density (64%) and increment in the initial value of free air space (20%). The study also concluded that all the carbon-rich agents have produced compost with the nutritional concentration suitable for agricultural proposes.