A novel oxidative microwave torrefaction approach for producing empty fruit bunch-starch binder briquettes as a potential biomass-based energy

This study introduced a novel microwave torrefaction (MWT) strategy combining optimal briquetting conditions and oxidative MWT (OMWT) to create briquettes using empty fruit bunch (EFB)-starch binder for enhanced physical and fuel properties. An analysis was conducted to evaluate the impacts of compaction pressure (20–80 MPa), EFB-to-starch binder mixing ratios (90:10, 80:20, and 70:30 by wt%), and drying duration (50–150 min) on the final moisture content, unit density, and physical properties of the EFB-starch binder briquettes. This study also investigated the influences of heating duration (5–15 min), microwave (MW) power levels (200–400 W), and oxygen (O2) concentration (0–6 vol%) on the physical and fuel properties of oxidative MW-torrefied EFB-starch binder briquettes. The optimal briquetting parameters were determined using a compaction pressure of 80 MPa, mixing ratio of 80:20 (wt%), and drying duration of 120 min. Meanwhile, the optimal conditions for the OMWT process to produce satisfactory physical appearance and competitive compressive strength with higher heating value were a heating duration of 10 min, MW power level of 300 W, and O2 concentration of 6 vol%. Consequently, this process demonstrated an enhanced MWT method using minimal charcoal-activated carbon (C-AC) in an oxidative environment.