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Biochar, a recalcitrant carbon, is known to enhance organic matter degradation and improve physical properties. The objective of the study is to examine the probable effect of biochar addition during composting of a fibrous aquatic waste, i.e., water hyacinth though degradation kinetics and spectroscopic (FTIR and PXRD) analysis. Four dosages of biochar (0, 2.5, 5, and 10% w/w) were mixed to a mixture of water hyacinth, cow-dung and saw-dust comprising a total weight of 150 kg and composted using rotary drum composter for 20 days in batch mode. The study outcomes indicated that the amendment of biochar prolonged the duration of the thermophilic temperatures, reduced salinity, and promoted nutritional quality of compost. Moreover, biochar amendment enhanced the organic matter degradation with a rate constant of 0.029 day -1 and increased the total Kjeldahl nitrogen content up to 1.75% from an initial value of 1.10% in the reactor with 2.5% biochar amendment. Concurrently, biochar amendment aided in reducing Cu and Cr in the final product inferring 2.5% biochar is best suited for composting of water hyacinth. However, future studies are encouraged to decipher the microbial shifts and bioavailability of metals due to biochar dosage during composting for mitigating and managing the menace of such fibrous waste like water hyacinth by converting it to a soil conditioner., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Invasive aquatic weed management is one of the biggest challenges in the field of solid waste management. Eichhornia crassipes, Pistia stratiotes and Hydrilla verticillata (L.f.) Royle pose some of the world's most noted aquatic weed problems. Previously reported studies on management of H. verticillata, a submersed aquatic plant, have shown that temporary removal, chemical treatment or biological control methods each have advantages and disadvantages. Removal programs that propose to compost harvested H. verticillata biomass may provide a novel technique to manage this issue. However, the properties of such compost as an agriculture resource are unclear. This study presents the different mix proportions of H. verticillata, cow dung and sawdust used for the composting of 550 L rotary drum composter. This work characterizes the biological, physicochemical, and respirometry properties of the various mixes over a 20-day composting period. The results suggest that the biomass of H. verticillata can be beneficially utilized to produce stable compost for potential use in agricultural systems., (Copyright © 2018 Elsevier Ltd. All rights reserved.)