(2026) Process Safety and Environmental Protection_Oxygen-rich torrefaction of bamboo: Multivariate process optimization and environmental assessment

Chen W.-H.; Lin Y.-T.; Biswas P.P.; Kwon E.E.; Tung T.-C.; Lee C.-E.; Ryšavý J.; Čespiva J.

(Institution of Chemical Engineers) Process Safety and Environmental Protection ISSN: 9575820 Vol.208 Issue. Article No.108473 DOI: 10.1016/j.psep.2026.108473

Torrefaction is a promising pretreatment method to enhance the fuel properties of lignocellulosic biomass; however, conventional studies are typically restricted to inert, air-limited, or air or flue gas atmospheres. In addition to inert and air torrefaction, this study also investigates the oxygen-rich torrefaction of bamboo (Phyllostachys makinoi Hay) under O₂ concentrations up to 30 % to analyze both process performance and environmental implications. A three-level full factorial design combined with analysis of variance (ANOVA) is employed to optimize torrefaction operations in terms of energy yield, higher heating value, and solid product quality. Oxygen enrichment accelerates the devolatilization of bamboo and enhances carbonization efficiency, resulting in significantly higher energy densification. However, these benefits are accompanied by increased mass loss as oxygen levels rise, highlighting a clear trade-off between biochar quality and solid yield. Statistical modeling reveals a strong predictive capability (R²> 0.95) for key responses, enabling the accurate determination of optimal conditions. For 1 kg of bamboo-derived biochar at a lab scale, the global warming potential (GWP) was found to range from 12 to 13 kg CO₂-eq. Higher O₂ levels improve fuel quality but increase indirect CO₂ emissions from oxygen supply in the life cycle assessment (LCA). This highlights the critical need to strike a balance between process efficiency and overall sustainability goals. Overall, this work provides novel insights into the mechanisms, optimization, and environmental trade-offs of oxygen-rich bamboo torrefaction, offering guidance for designing low-carbon bioenergy systems and expanding the applicability of torrefaction in sustainable energy transitions. © 2026 The Institution of Chemical Engineers

The authors acknowledge the financial support of the National Science and Technology Council, Taiwan, R.O.C., under contracts NSTC 114–2218-E-006–013 - and NSTC 114–2218-E-002–020 - for this research. The authors gratefully acknowledge the use of XRD005100 and ESCA003700 of NSTC 114–2740-M-006–001 belonging to the Core Facility Center of National Cheng Kung University. This research is also partly supported by Higher Education Sprout Project, Ministry of Education, to the Headquarters of University Advancement at National Cheng Kung University (NCKU). This publication is supported by the Technology Agency of the Czech Republic through the project "Recyclable Waste-derived Sorbents for Sustainable Process GHG Emissions Control", grant number: TQ16000072.