Optimization, techno-economic, and environmental assessment of co-pyrolysis of oil palm EFB and rubber wood sawdust

This study optimized the co-pyrolysis of oil palm empty fruit bunch (EFB) and rubber wood sawdust (RWS) to enhance biochar and liquid oil yields, with non-condensable gas (NCG) as a by-product. Experiments were conducted in a fixed-bed reactor, varying key process parameters, including pyrolysis temperature (750–850 °C), biomass particle size (0.3–5 mm), and EFB: RWS ratio (0:100–100:0). Response surface methodology (RSM) with a Box-Behnken design (BBD) was employed to analyze parameter interactions and optimize product distribution systematically. Statistical validation confirmed the model's reliability, with prediction errors below 10 %. The optimal biochar yield (33.73 wt%) was achieved at 782.25 °C, a particle size of 2.94 mm, and an EFB: RWS ratio of 6:94. In comparison, the highest liquid oil yield (28.46 wt%) was obtained at 850 °C, with a biomass size of 3.00 mm and an EFB: RWS ratio of 100:0. Co-pyrolysis offers flexibility to adjust product yields based on energy needs. Simulations proved the scalable design and economic analysis confirmed its financial viability with a payback period of just 5.8 years. The environmental evaluation was also conducted through the Life Cycle Assessment (LCA). The LCA revealed that the pyrolysis process had the highest impact on global warming potential (GWP), contributing 61.15 %, followed by product utilization (estimated at 20 %), feedstock production (11.67 %), transportation (2.18 %), and end-of-life processes. This study shows the potential of using local biomass in Southern Thailand for sustainable energy. These findings pave the way for scaling up industrial pyrolysis, enhancing energy security, and waste valorization.