Catalytic Pyrolysis of Torrefied Municipal Solid Waste Using Local Iron for Improved Bio‐Oil Yield and Energy Efficiency

ABSTRACT

South Africa faces growing municipal solid waste (MSW) accumulation and energy insecurity due to fossil fuel dependence. Torrefaction improves MSW for waste‐to‐energy use, while conventional pyrolysis produces low‐quality oxygen‐rich bio‐oil. Catalytic pyrolysis with locally available iron‐based catalysts offers a cost‐effective method to upgrade bio‐oil and support sustainable energy production. This study investigates the catalytic pyrolysis of the torrefied organic fraction of municipal solid waste at 550°C–700°C and atmospheric pressure (1 atm) using a locally synthesized Fe ₂ O ₃ catalyst at a 1:10 catalyst‐to‐biomass ratio. Feedstock and catalyst characteristics were evaluated using thermogravimetric analysis, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller surface analysis, while bio‐oil composition was analyzed using gas chromatography–mass spectrometry (GC–MS) and elemental analysis. The torrefied feedstock, with 48.6 wt.% volatile matter and 57.8 wt.% carbon, produced 38.6 wt.% bio‐oil non‐catalytically. Using an Fe ₂ O ₃ catalyst increased the yield to 47.5 wt.% at 600°C, reduced oxygenates, and improved fuel quality, achieving a higher heating value of 33.8 MJ kg ⁻¹ . GC–MS analysis identified phenolic and heterocyclic compounds, indicating effective catalytic cracking, deoxygenation, and hydrocarbon enrichment during vapor upgrading. These results demonstrate that locally sourced iron‐based catalysts effectively upgrade torrefied MSW pyrolysis vapors, producing higher‐quality bio‐oil and improving overall conversion efficiency. The proposed catalytic waste‐to‐energy approach provides a scalable and economically viable strategy for converting municipal waste into renewable fuels, strengthening energy security and sustainable waste valorization in South Africa, and supporting SDG 7, SDG 12, and SDG 13.