Life cycle and energy implications of tubular vs chamber furnace pyrolysis for activated carbon production

Pyrolysis is one of the most energy-intensive stages in activated carbon (AC) production and often dominates its environmental impacts. However, the influence of pyrolysis furnace configuration on the environmental performance of biomass-derived AC remains poorly understood. This study presents a comparative life-cycle assessment (LCA) of olive stone (OS)-derived AC, evaluating chamber (muffle) furnace (CF) and tubular furnace (TF) pyrolysis under comparable operating conditions. The results indicated that CF pyrolysis exhibited lower environmental burdens, with climate change (CC) impacts as low as 2.1 kg CO₂-eq kg⁻¹ AC and net energy demand (EN) of 48 MJ kg⁻¹ AC, compared with 2.9 kg CO₂-eq kg⁻¹ AC and 66 MJ kg⁻¹ AC, respectively, for TF pyrolysis. This improvement was primarily attributed to greater material throughput per heating cycle, resulting in lower normalized electricity demand per unit mass of AC produced. In addition, pyrolysis by-products provided a combined recoverable energy potential of 17.98 MJ kg⁻¹ AC, while estimated direct pyrolysis emissions included 0.540 kg biogenic CO₂ kg⁻¹ AC and methane emissions corresponding to 1.94 kg CO₂-eq kg⁻¹ AC. These findings provide laboratory-scale comparative insight into the influence of pyrolysis furnace configuration on AC production and may help guide future process development, energy-recovery integration, and scale-up studies.