Characterisation of Oil Palm Trunks for Potential Bioenergy Recovery and Utilization

Abstract

The cultivation of oil palm (Elaeis guineensis Jaq.) and its production generate large quantities of solid wastes annually. Current strategies adopted for tackling oil palm trunks (OPTs), which account for a significant proportion of oil palm waste (OPW), are considered expensive, inefficient, and unsustainable. Analysts posit this scenario could exacerbate efforts to not only effectively dispose and manage OPT but also lower the carbon footprint of the Oleo industry. Hence, immediate and urgent attention is needed to address the challenges posed by current strategies. Biomass torrefaction has recently gained traction as a practical approach for OPW valorisation into biochar. Therefore, this study seeks to (i) characterise the physicochemical characteristics of OPT through ultimate, proximate, and calorific analyses and (ii) examine the thermochemical, degradation, and temperature profile characteristics of OPT as potential torrefaction feedstock using thermal gravimetric analysis (TGA). TGA was performed at torrefaction temperatures; Tt = 200–300 °C (Δ25 °C stepwise increase) under isothermal/non-isothermal conditions of nitrogen (N2) flowrate 100 mL/min), heating rate 20 °C/min, and 30-min residence time. The results showed that OPT contains high carbon (>45 wt.%), hydrogen (>6 wt.%), volatile matter (>80 wt.%) but low ash (2 wt.%), fixed carbon (5 wt.%), and moisture (10 wt.%) contents. OPT experienced 14.55–60.82 wt.% weight loss during TGA degradation from 200 to 300 °C. The increase in temperature resulted in a corresponding rise in OPT biochar yields ranging from 85.45 to 39.18 wt.% and higher heating values of 20–23 MJ/kg. The DTG plots showed that the TGA torrefaction process occurred in two stages, (i) 100 °C and (ii) >100 to the selected Tt, which could be ascribed to the drying and devolatilization/depolymerisation of OPT, respectively. Overall, this study demonstrated that OPT is a potentially practical feedstock for torrefaction into biochar.