Advancing cleaner production and circular economy pathways: An experimental and simulation-based techno-economic assessment of peanut shell biochar-catalyzed pyrolysis of mixed plastic waste for liquid fuel and biochar production in Malawi

Abstract

Plastic waste accumulation and fossil fuel dependence present major environmental and energy challenges in Malawi, where inadequate waste management infrastructure and reliance on imported fuels contribute to pollution and energy insecurity. This study evaluates the experimental and simulation-based techno-economic performance of a decentralized catalytic pyrolysis system converting mixed municipal plastic waste into liquid fuel and biochar using locally derived peanut shell biochar as a catalyst and Aspen Plus-based process simulation. Experimental results showed that a catalyst dosage of 0.17 kg/kg plastic, which exhibited the most favourable performance among the investigated catalyst loadings, increased oil yields by 7–28%, reduced residence time by up to 17%, and improved calorific value to 43,974–45,384 kJ/kg, indicating enhanced process efficiency and fuel quality. Catalyzed natural mixed-plastic waste streams performed comparably to engineered polymer blends, eliminating the need for extensive feedstock sorting and reducing processing costs and energy requirements. Techno-economic assessment of five feedstock scenarios demonstrated strong economic viability, with catalyzed systems achieving net present values above $1.78 million, annual profits exceeding $309,000, and internal rates of return greater than 73%. By valorizing both plastic waste and agricultural residues, the system supports circular resource utilization while contributing to reduced open burning and partial fossil fuel displacement. The findings demonstrate the potential of decentralized catalytic pyrolysis as a scalable waste-to-energy pathway for sustainable waste management and alternative fuel production in Malawi and similar developing regions.