Sustainable carbon conversion from agro-biomass: Factorial optimization of pyrolysis parameters for enhanced product yield

• Pyrolysis of cashew shell and cashew husk was carried out. • Thermal degradation indicated that shell was more temperature sensitive than husk. • Higher activation energy for shell confirmed the temperature sensitivity. • Optimized temperature was 450 °C and 600 °C for husk and shell at 25°C.min -1 . • High NPV and IRR, and low payback periods indicated high profitability. Cashew nut shell and husks are the major sources of agro-industrial wastes from cashew cultivation. This study aims to compare and contrast the process and product production from cashew shell and husk. The thermal degradation of cashew shell is higher than that of the cashew husk at active and passive pyrolysis stages. A full-factorial design of experiments indicated an optimum operating temperature of 600 °C for the shell and 450 °C for the husk. The optimum heating rate was found to be 25 °C.min -1 for both the biomasses. An average activation energy of 159.05 kJ.mol -1 and 92.13 kJ.mol -1 was observed for shell and husk, respectively. The lesser activation energy for cashew husk matches significantly with the lower operating temperature obtained from the factorial model. The difference in activation energy indicates that the cashew shell is more temperature sensitive than the husk. Positive net present values were observed for both these processes and internal return rates were 15% and 350% for cashew shell and husks conversion respectively, indicating that the technology is profitable. The payback period was calculated as 9.23 months and 4.41 months for the conversion of cashew shells and husks, respectively.