Continuous thermochemical conversion for sesame stalks into eco-friendly biochar using auger reactor torrefaction

Torrefaction is an essential technique for improving the energy density of biomass and maximizing its potential. This research maps the thermal decomposition of sesame stalks (SS) in a torrefaction auger reactor at 200°C, 250°C, and 300°C for 30 and 60 min. The research included proximal and ultimate analyses, bulk density evaluations, solid, liquid, and gas yields, and energy density. The study assessed several key parameters, including enhancement factor (EF), torrefaction severity index (TSI), and fuel ratio (FR). Additionally, it evaluated the thermal behavior characteristic index (D_i), volatile ignitability (VI), combustibility index (CI), energy return on investment (EROI), and crystallinity index under varying torrefaction settings. The results indicated that higher torrefaction temperature and residence time increased the fixed carbon, ash percentage, and fuel ratio. Conversely, volatile matter, combustibility index, energy return on investment, O/C, H/C, and crystallinity index decreased. The energy content of SS biochar was 91.3%, with a solid output of 96.87%. Carbon content increased to 55.23%, and the higher heating value (HHV) rose to 21.886 MJ/kg. Producing biochar from SS at 250°C for 60 min is both energy-efficient and essential for achieving excellent and continuous torrefaction in the bioenergy sector.