Acacia Melanoxylon: A pathway from an invasive species to renewable bio-oil via thermochemical conversion

Abstract

This article presents a comprehensive modelling approach for the liquefaction of mixed Acacia Melanoxylon biomass. The proposed model combines a statistical method that uses quantitative data from appropriate experimental designs to determine and simultaneously solve multivariate equations, simulating the complex thermochemical processes that occur during the liquefaction process, to predict the yield of the process. It considers crucial factors such as reaction temperatures (100, 135, 170 °C) and residence time (30, 115, and 200 min), as well as catalyst concentrations ranging from 0.5 % to 10 % (w/w). The optimal conditions for bio-oil yield were 86.42 %, with a higher heating value (HHV) of 32.93 MJ/kg, while the HHV of fresh biomass was 14.07 MJ/kg. A response surface methodology (RSM), Box-Behnken design, was used to optimize the liquefaction process. The independent variables were selected as the reaction temperature, reaction time, and catalyst concentration. The obtained model presented a high adjusted R-squared (0.944) and a good p-value (less than 0.002). Fourier Transformed Infrared (FTIR), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR) were used to characterize the products. Additionally, scanning electron microscopy (SEM) was used to assess the impact of the morphological changes on the solid samples' surface area. By harnessing biomass thermochemical liquefaction, this study not only unlocks the valorization potential of invasive species but also offers an opportunity to validate a sustainable and clean process for upcycling such woody matrix.