Characterization of South African Woody and Non-Woody IAPs for Energy-Efficient Bio-Oil Production: Enhancing Sustainability in Agricultural Production

Bio-oil plays a vital role in bioheating, biopowering, and fuel for agricultural machinery, yet its potential in South Africa is limited by a lack of suitable energy substrates. This study investigated the properties of six invasive alien plant species (IAPs), three woody species (Acacia mearnsii, Eucalyptus grandis, and Pinus patula), and three nonwoody species (Lantana camara, Chromolaena odorata, and Solanum mauritianum) to assess their suitability for bio-oil production. Key analyses included structural, elemental, proximate, atomic ratio, higher heating value (HHV), and thermogravimetric analysis (TGA) analyses. Results showed that woody IAPs had significantly higher structural composition (p < 0.05), improving bio-oil yield. The bio-oil can be blended with diesel for agricultural use, while lignin-derived biochar serves as a soil amendment. Higher carbon and hydrogen contents enhanced HHV and combustion, while lower nitrogen and sulfur levels reduced emissions. Despite oxygen hindering pyrolysis, its bioactive properties support crop protection. Compared to South African coal, IAP derived bio-oil shares similarities with peat coal and could be used for greenhouse heating. This study promotes energy efficiency in agriculture, reduces fossil fuel dependence, and supports environmental sustainability by repurposing IAPs. Future research should focus on lignin pretreatment, and bio-oil upgrading to reduce oxygenated compounds.