Catalyst driven optimization of cogasification and economic evaluation for enriched hydrogen syngas production from lignocellulosic waste toward biorefinery applications

Abstract

Growing environmental concerns have driven the search for renewable energy sources, particularly H₂ production. This study evaluated conversion of coconut shells and wood blends in downdraft gasifier to maximize H₂ yield and minimize tar formation in syngas, using mineral catalysts of cement, dolomite, and limestone. Effects of key parameters temperature (700–900 °C), catalyst loading (0–30 wt%), and blending ratio (20–80 wt%) were investigated. Process optimization was performed in Design of Expert and economic analysis was carried out at optimal conditions. Results revealed that dolomite achieved highest H₂ yield, with significant increased from 4.49 to 23.31 vol% as temperature varied from 700 to 900 °C at 15 wt% catalyst loading. In case of cement, H₂ yield increased from 13.22 to 20.57 vol% followed by limestone. CO yield increased from 17.82 to 25.96 vol% at higher temperature. coconut shell proportion in blend marginally improved CO yield. However, higher catalyst loading reduced CO yield. Among all catalysts, limestone yielded highest CO (30.13 vol%) at 900 °C, 30 wt% catalyst loading, and CS50:W50 blend. Tar formation was reduced significantly from 8.02 to 1.17 g/Nm³ with increasing temperature and catalyst loading (dolomite case). Under optimal conditions (900 °C, 30 wt% catalyst loading, CS50:W50) process achieved maximum 23.31 vol% H₂ yield and minimum 1.17 g/Nm³ tar formation. Economic analysis indicated 3.09 MYR/kg syngas production cost that could be further reduced by process scale-up and adopting autothermal gasification. Overall, this study aids in selecting an effective catalyst for biomass gasification and provides an economic analysis to assess its commercial viability.