Sustainable production of cashew nutshell briquettes: experimental assessment and optimization of factors affecting the physical and fuel characteristics

Physical, mechanical, and energy characteristics of the briquettes produced with cashew nutshell waste under different process conditions are reported in the present study. The cashew nutshell briquettes are produced with a lower compression force of ≤ 7.75 kN. The main objective of the study is to examine the effects of binder (starch), binder water addition, and drying duration on the different characteristics of the cashew nutshell briquettes. The influence of these parameters on the various properties was examined with the help of ANOVA and regression analysis. From the experimental results and mathematical models, it is evident that the most influencing parameter was found to be starch content and drying duration. Binder water content addition did not significantly affect the quality of the briquettes. The optimal values achieved for the analyzed briquetting process parameters are starch content of 12.917%, water content of 50%, and a drying duration of 7 days. According to the mathematical model achieved, these optimal parameters gave a maximum compressive strength of 1249.17 kPa, optimal density of 1047.681 kg/m 3 , shatter resistance of 99.9%, durability of 99.547%, water-resistance of 97.342%, the calorific value of 18.681 MJ/kg, and moisture content of 11.789%. Furthermore, it was found in the study, the volumetric energy density of the biomass increased from 9.497 to 19.57 GJ/m 3 . The results of the tests and optimization study indicate that cashew nutshell briquettes have good mechanical and energy properties that make them eligible for use in different thermal applications.