Acacia mangium is a widely grown tree species across the forests in Brunei Darussalam, posing a threat to the existence of some native species in Brunei Darussalam. These species produce large quantities of lignocellulosic biomass from the tree parts comprising the phyllodes, trunk, bark, twigs, pods, and branches. This study examined the thermochemical characteristics and pyrolytic conversion behavior of these tree parts to assess the possibility of valorization to yield bioenergy. Proximate, ultimate, heating value, and Fourier Transform Infrared Spectroscopy (FTIR) analyses were performed to assess the thermochemical characterization, while thermogravimetric analysis was conducted to examine the pyrolytic degradation behavior. Proximate analysis revealed a moisture content, volatile, fixed carbon, and ash contents of 7.88–11.65 wt.%, 69.82–74.85 wt.%, 14.47–18.31 wt.%, and 1.41–2.69 wt.%, respectively. The heating values of the samples were reported in a range of 19.51–21.58 MJ/kg on a dry moisture basis, with a carbon content in the range of 45.50–50.65 wt.%. The FTIR analysis confirmed the heterogeneous nature of the biomass samples with the presence of multiple functional groups. The pyrolytic thermal degradation of the samples occurred in three major stages from the removal of moisture and light extractives, hemicellulose and cellulose decomposition, and lignin decomposition. The bio-oil yield potential from the biomass samples was reported in the range of 40 to 58 wt.%, highlighting the potential of Acacia mangium biomass for the pyrolysis process.

Continuously increasing energy requirements coupled with environmental pollution have established pressure to utilise lignocellulosic biomass for energy production. Acacia auriculiformis is a fast-growing species capable of accumulating large quantities of biomass without requiring major agricultural inputs. The aim of this research was to investigate the thermochemical properties of its tree parts including phyllodes (leaves), trunk, bark and branches to utilise them as solid fuel to produce bioenergy. Thermogravimetric and derivative thermogravimetric (TGA and DTG ) analyses were performed to study the biomass degradation behaviour, which showed the decomposition of biomass in three major stages corresponding to the decomposition of hemicellulose, cellulose and lignin components. Fourier transform infrared (FTIR) analysis was carried out to determine the functional groups. Proximate analysis showed the weight percentages of moisture contents, volatile matter, fixed carbon and ash contents as 7.25–9.27%, 61.79–73.28%, 16.50–27.92% and 2.13–3.72%, respectively. Ultimate analysis showed the ranges of carbon, hydrogen and oxygen as 44.27–49.41%, 5.3–6.10% and 41.93–49.44% respectively, while lower values of sulphur and nitrogen components were reported which are encouraging from an environmental perspective. Higher heating values (HHV) for the parts were reported to range between 17.85 and 20.93 MJ/kg on a dry basis.