Microwave-assisted co-pyrolysis of sewage sludge and banana peel: Optimization of bio-oil production and characterization

Harnessing energy from biomass has led to an integrated approach toward enhancing resource efficiency while simultaneously reducing environmental burden. The present work focuses on microwave (MW) assisted co-pyrolysis of SS with banana peel (BP) for bio-oil production. The process parameters, MW power, residence time (T), sewage sludge (SS), and catalyst dosage were optimized in this work using response surface methodology (RSM). The maximum bio-oil yield of 41.1 ± 0.34 % (w/w) was obtained at an optimum power of 590 W, time of 6.4 min, SS of 60 % (w/w), and catalyst dosage of 37.4 % (w/w). An increase in the yield of bio-oil was observed upon adding activated carbon as a catalyst, and the bio-oil obtained was characterized using GC-MS to identify the volatile compounds in it. The GC-MS chromatogram of the bio-oil obtained at optimal pyrolysis conditions revealed that approximately 42.57 % of the components were C₆-C₁₄ hydrocarbons, representing the gasoline fraction, while the remaining C₁₆-C₁₉ hydrocarbons corresponded to the diesel range. These fractions of the bio-oil resemble conventional fuel oil in terms of the carbon chain. The elemental composition of bio-oil showed the presence of 77.434 % carbon, 11.204 % hydrogen, 3.775 % nitrogen, and 7.587 % oxygen in the bio-oil. Hence upgradation of bio-oil may replace the conventional fuel. The bio-oil’s HHV of 40.82 MJ/kg, determined through elemental analysis, makes it a viable candidate for upgrading and blending with diesel as a fuel alternative.