EXPERIMENTAL INVESTIGATION ON CO-PYROLYSIS OF CORNCOB AND WATER HYACINTH: SYNERGETIC EFFECT ON BIOCHAR PROPERTIES AS SOIL AMENDMENT

Abstract

Pyrolysis of water hyacinth is the best alternative to control the infestation of this weed through producing biochar for soil amendments due to its contents of essential nutrients required for soil fertility. However, it has less lignin component which affects the yields of biochar. Co-pyrolysis has recently been promoted as the preferred technique for improving the quality and yield of pyrolysis products. The aim of this study is mainly to advance the understanding of thermal decomposition behavior, physiochemical properties, and synergetic effects of those biomasses' co pyrolysis. Accordingly, the co-pyrolysis of corncob (CC) and water hyacinth (WH) was studied using thermogravimetric analysis (TGA) in the temperature range of ambient to 800℃ at heating rates of 5 and 20℃/min and Fixed bed reactor at 350°C. A blend containing 30 wt.% WH and 70 wt.% CC (C7:W3) exhibits the greatest possible degree of synergism when compared with other blends. The kinetic variables (pre-exponential factor and activation energy) were determined using the model fitting method (Coats Redfern) and iso-conversional (model-free) methods, Kissinger-Akahira-Sunose (KAS), and Flynn–Wall–Ozawa (FWO). The average apparent activation energy for the blended samples decomposition (C7:W3, C3:W7, and C5:W5) was 111,116.1,131.1KJ/mol and 118, 120, and 138.3KJ/mol from KAS and FWO, respectively. Thermodynamics parameters (change in Gibbs free energy, enthalpy, and entropy) of the blends were also calculated. The mean enthalpy values from KAS approaches were noted as 107, 159.5, and 158KJ/mol for C7:W3, C3:W7, and C5:W5, respectively. Thus, co-pyrolysis reduces the activation energy and Gibbs free energy of the process. The sample biochar was produced from individual CC, WH, and their blends C5:W5 using a fixed bed pyrolyzer. Hence, the physical and chemical properties of biochar determine its potential for a specific application, it was characterized for soil amendments. It was determined that the yields of produced biochar were 46.67, 45.16, and 46% for CC, WH, and C5:W5, respectively. The biochars had a bulk density ranging from 0.26 to 0.39 g/cm3 . Bulk density was increased for blends. The pH values were ranging in basic (9.44 to 9.83), which could contribute to amending soil acidity. Higher nutrient content was noted for WH while blending improves the nutrient content. The highest cation exchange capacity (CEC) was obtained for C5:W5. Thus, the co-pyrolysis shows positive synergism on the most properties and those biomasses have been identified as being good options for enhancing acidic and nutrient-depleted soils.