Investigating synergistic effects in Co-prolysis of groundnut shell and waste tyres on product distribution under different blend ratios

Amid the projected depletion of petroleum products and the severe environmental challenges, this study addresses the urgent need for sustainable alternatives to fossil fuels by investigating co-pyrolysis as a means to valorize two different wastes. Groundnut shell and scrap tyres were individually pyrolyzed at 350–600 °C, while co-pyrolysis was conducted at an optimal temperature of 500 °C using tyre blend ratios of 20%, 40%, 50%, 60%, and 80%. Product yields, synergistic effects and properties of bio-oil, char, and gas were systematically evaluated. Individual groundnut shell pyrolysis favored high CO2 and oxygenated liquids with moderate heating value, whereas tyre pyrolysis produced hydrogen- and hydrocarbon-rich gases, carbon-dense char, and high-calorific oil. Co-pyrolysis demonstrated clear synergistic interactions, particularly at 40% tyre blending, yielding improved liquid fuel with higher calorific value, reduced oxygen content, and intermediate density and viscosity compared to the individual feedstocks. Co-pyrolysis char exhibited enhanced fixed carbon and reduced sulphur relative to tyre char alone, while gas fractions showed increased H2 and CH4 with lower CO2 than biomass pyrolysis. These improvements arise from complementary radical interactions and synergistic behavior of volatiles between the feedstocks. The results demonstrate that co-pyrolysis effectively optimizes product quality and energy potential, providing a sustainable pathway for simultaneous waste valorization, reduced greenhouse gas emissions, and renewable biofuel production in a circular economy framework.