Conversion of palm oil mill wastes into high-value biochar and syngas using wet torrefaction and gasification with palm oil mill effluent as a liquid stream

The palm oil industry generates significant waste, particularly oil palm empty fruit bunch (EFB) and palm oil mill effluent (POME). This study successfully converted these wastes into high-heating-value (HHV) biochar, bio-oil, and syngas through a combination of wet torrefaction and gasification processes, addressing a research gap in bioenergy co-production. EFB and POME underwent wet torrefaction at 200 °C for 30 min, producing biochar with an HHV of 22.6 MJ/kg, a 31% increase from that of raw EFB. Subsequent gasification of the biochar at 700–900 °C further enhanced the HHV to 23.8 MJ/kg, a 38% increase from raw EFB. Gasification yielded biochar, bio-oil, and syngas in proportions of 39–55%, 12–20%, and 27–44%, respectively. Gas chromatography analysis of the syngas identified CO₂ (0.003 mmol/mL), H₂ (0.002 mmol/mL), CH₄ (0.002 mmol/mL), and CO (0.005 mmol/mL). The novelty of this paper lies in integrating wet torrefaction and gasification processes for the co-production of high-quality biochar and syngas from palm oil mill waste, particularly EFB and POME, offering a sustainable energy solution and addressing gaps in biomass conversion technologies.