Co-pyrolysis of oily sludge and algal biomass

Alternative fuels have attracted rising attention as sustainable energy options due to mounting pressures to lower greenhouse gas emissions and decrease dependence on fossil fuels. This study investigates the co-pyrolysis of oily sludge (OS), a petroleum refinery residue, and algal biomass (AB), a biological waste stream rich in organic content from refinery wastewater treatment units. The aim was to evaluate the potential of these residues to produce a solid biofuel with improved energy yield and char stability.The optimum blend composition of 75 % OS with 25 % AB (OS-AB) was used. Pre-drying of the feed with air at 105 °C for 24 h ensured the removal of moisture. Pyrolysis runs were performed at different temperatures of 350, 450, and 550 °C under constant nitrogen flow of 5 L/min with fixed residence time of 60 min. Optimum pyro-char yield was achieved at 450 °C.Test of residence time further at optimal 450 °C for 45, 60, and 75 min resulted in 75 min achieving best quality char. Holistic fuel characterization by higher heating value (HHV), proximate and ultimate analyses, energy recovery (ER), energy yield (EY), atomic ratios, and fuel ratio (FR) showed increased fixed carbon content and increased HHV, increased carbonization, and thermal stability of OS-AB chars. The resulting pyro-char HHV in this research was substantially increased by an approximate 63.92 %, i.e., from 4.85 MJ/kg (OS-AB control) to 7.95 MJ/kg under optimized co-pyrolysis (450 °C for 75 min). Interestingly, co-pyrolysis resulted in an increase in char quality compared to single feedstock systems. These results justify co-pyrolysis of OS and AB as an appropriate wastes valorization process for production of solid carbon fuel with added value of both environment cleanup and production of renewable energy in oil refineries petrochemical industries.