Carbonisation and Characterization of Senna obtusifolia, Flueggea virosa, and Ficus aurea for Sustainable Production of Charcoals

Invasive plant species (IPS) like Senna obtusifolia (SO), Flueggea virosa (FV), and Ficus aurea (FA) pose environmental and economic problems in Nigeria. Notably, IPS have adverse impacts on native flora, biodiversity, and ecosystems, whilst weakening agricultural productivity and land use effectiveness. However, such plants are characterised by high lignocellulosic content, woody stems, and rapid growth rates, which make them abundant, accessible feedstock candidates for bioenergy recovery and utilisation. Therefore, this study explores the charcoal production potential of SO, FV, and FA through carbonisation. The process was accomplished by heating the samples at a temperature of 600 °C and 30 minutes residence time, followed by cooling and characterisation of the charcoal mass yield (MY), mass loss (ML), higher heating value (HHV), and energy yield (EY). The results showed that the MY and ML ranged from 21.55% to 29.81%, and 70.19% to 78.45%, respectively, whereas the HHV and EY ranged from 26.41 MJ/kg to 27.18 MJ/kg, and 5.86 MJ to 7.87 MJ, respectively, which indicate adequate results for the sustainable production of charcoals from SO, FV, and FA. The highest HHV and ML were observed in FA, whereas the highest ML and EY were observed in FV. The SO sample revealed intermediate values for most parameters examined in the study. The results demonstrated that carbonisation of such plentiful, yet underutilised plant species is a practical management approach and route for sustainable solid fuels production. Lastly, this strategy helps to ensure environmentally sustainable ecosystem protection and promotes the sustainable livelihoods of locals who can tap into such initiatives.