Parametric study on mechanical-press torrefaction of palm oil empty fruit bunch for production of biochar

Abstract

This study investigated the impact of varying temperatures and pressures during torrefaction under mechanical compression on the mass yield and chemical properties of torrefied empty fruit bunch (MTEFB). It also examined how these factors influenced the biochar derived from MTEFB. Experiments were conducted at temperatures ranging from 240 °C to 300 °C and mechanical pressures of 25, 50, and 75 MPa. The results indicated that at all temperatures above 280 °C, mass yields were significantly reduced, and higher mechanical pressures further accelerated thermal degradation. FTIR analysis revealed structural modifications, including dehydration, decarboxylation, and demethylation, particularly at elevated pressures. Elemental analysis showed an increase in carbon content to 55.68 % when MTEFB was prepared at 300 °C and 75 MPa. The HHV reached 23.11 MJ/kg, indicating improved energy yield. The proximate analysis demonstrated an increase in fixed carbon to 26.32 %, highlighting the influence of temperature and pressure on biochar characteristics. Further carbonization at 600 °C of MTEFB, which was prepared under mechanical-press torrefaction conditions at 300 °C with 75 MPa, produced biochar with enhanced yield and a more graphitic structure. The combination of mechanical-press torrefaction and subsequent carbonization presented a promising pathway for producing high-quality biochar and other solid carbon materials.