Intermediate pyrolysis of Acacia cincinnata and Acacia holosericea species for bio-oil and biochar production

•Intermediate pyrolysis A. cincinnata &A. holosericea species was studied at 500 °C.•Bio-oils and biochars produced were characterised using standard analysis methods.•Highest yield of bio-oil was 52.95% from the trunk of A. cincinnata species.•Highest biochar yield was 38.78% from the phyllodes of A. holosericea species.•CVs of bio-oils and biochars were in the range of 23.46–30.65 and 25.57–27.53 MJ/kg. Ever-increasing energy requirements coupled with the desire to cope with global warming have motivated researchers to look for alternative energy resources. Lignocellulosic biomass is an abundant renewable energy resource which can be exploited to reduce the dependency on fossil fuel resources. Acacia cincinnata and Acacia holosericea are fast-growing tree species which produce large quantities of biomass within short span of time and does not require major agricultural inputs to grow. This study is aimed at the intermediate pyrolysis process of Acacia cincinnata and Acacia holosericea species to produce biofuels such as bio-oil, biochar and gaseous product. Mass balance was done to calculate the yields of different products along with the characterisation of bio-oil and biochar produced. Experiments were carried out in a fixed-bed reactor at the pyrolysis temperature of 500 °C, heating rate of 25 °C/min and nitrogen gas flowrate of 100 cm3/min for the biomass feedstock having particle size between 0.5 and 1 mm. Comprehensive thermochemical characterisation of biomass samples was carried out prior to pyrolysis experiments. The chemical composition of bio-oil samples produced was determined using Gas Chromatography-Mass Spectroscopy (GC–MS) technique. Ultimate analysis, calorific values, pH values and the ash contents in the bio-oil samples were also determined. Bio-oil produced were reported to be complex mixtures of heterocyclic and phenolic compounds resulting from the thermal degradation of basic components of biomass with the calorific values obtained in the range of 23.46–30.65 MJ/kg. Biochar samples produced in the study were characterised with the help of ultimate analysis, FTIR analysis, calorific values, pH values and SEM and EDX analysis. Properties of biochars indicated suitability for energy as well as other applications such as soil remediation and adsorption purposes. Study revealed a decent potential of Acacia cincinnata and Acacia holosericea species as biofuels resources.