Valorisation of Mesosphaerum suaveolens, Calotropis procera, and Chromolaena odorata Invasive Species for Charcoal Production

Globally, the spread of invasive plant species (IPS) poses substantial ecological and economic problems. Although considered weeds by farmers, such plants are woody-stemmed and lignocellulosic in nature, which, in addition to their abundance and underutilisation, makes them suitable for bioenergy recovery and utilisation. Therefore, the current study seeks to examine the bioenergy potentials of three abundant, problematic, and underutilised IPS, Mesosphaerum suaveolens (MS), Calotropis procera (CP), and Chromolaena odorata (CO), as sustainable raw materials for charcoal production through carbonisation. Additionally, the physico-chemical and energy characteristics of the IPS charcoals are critically examined to present a comprehensive strategy for effective biomass resource management and renewable material/energy production in Nigeria. The carbonisation process was conducted in a muffle furnace at a temperature of 600°C and with a residence time of 30 minutes. On completion, the biochars were characterised to examine the impact of the process and plant structure on the biochar mass yield (MY), mass loss (ML), higher heating value (HHV), and energy yield (EY). The results revealed that the IPS charcoals display favourable characteristics. Notably, the MY for MS, CP, and CO ranged from 23.33% to 39.20%, whereas the ML ranged from 60.80% to76.67%. In contrast, the HHV and EY ranged from 25.53 MJ/kg to 27.01 MJ/kg and 6.30 MJ to 10.01 MJ, respectively. The highest ML and HHV were observed from MS, whereas the highest MY and EY were observed for CP. The high values of HHV and EY highlight not only the solid biofuel potential of these abundant, underutilised, and woody IPS but also present a sustainable approach to their ecological management and sustainable energy production. Future studies could critically explore the optimisation of the carbonisation parameters and wider applications of the IPS charcoals.