Waste is increasingly recognized as misplaced biomass, underscoring its potential for reintegration into sustainable environmental management strategies. Biomass pyrolysis has emerged as a promising value-adding process capable of enhancing material properties for diverse applications. In this study, discarded Pili (Canarium ovatum Engl.) nutshells (PS) were utilized as a pyrolysis feedstock to upgrade their fuel characteristics. Pyrolysis conditions were optimized using response surface methodology (RSM) based on a central composite design (CCD) to maximize fixed-carbon content and higher heating value (HHV). The optimized biochar achieved a maximum fixed-carbon content of 86.15% and an HHV of 32.10 MJ/kg at a pyrolysis temperature of 600 °C and a residence time of 60 min, values comparable to those of conventional coal. Under these optimized conditions, the fixed-carbon content and HHV of the precursor biomass were enhanced by up to 254.7% and 58.4%, respectively. Statistical analysis indicated that pyrolysis temperature was the most significant factor influencing both fixed-carbon content and HHV (p < 0.05). The optimized biochar exhibited low volatile matter (8.88%), low ash content (4.97%), and low atomic ratios (H:C = 0.291; O:C = 0.077), indicating a high degree of carbonization and thermal stability. Energy-dispersive X-ray (EDX) analysis identified alkali and alkaline earth metals (Ca, Mg, Na), which contributed to the ash fraction, with minor heavy metals present, predominantly Pb. Hence, these findings enhance understanding of how pyrolysis conditions affect PS–biochar properties, improving fuel quality indicators.

The growing demand for sustainable energy has intensified interest in converting abundant agricultural residues into renewable fuels. Among these feedstocks, corn stover represents a promising biomass for thermochemical conversion due to its high volatile matter content and widespread availability. This study investigates syngas production and product distribution from corn stover via pyrolysis and steam gasification in an atmospheric fixed-bed tubular furnace at temperatures of 650–850 °C. Furthermore, the effects of steam-to-carbon (S/C) ratio and nickel aluminate (NiAl₂O₄) catalyst loading at 650 °C were also investigated to determine their influence on product distribution and syngas composition. Increasing temperature significantly enhanced gas production in both processes, while steam gasification consistently produced higher gas yields than pyrolysis. At an S/C ratio of 3, the gas yield increased from 37% to 58.6%, with a 55.1% increase in H₂ production after 60 min compared with the pyrolysis baseline. Furthermore, incorporation of NiAl₂O₄ improved the H₂ yield and H₂/CO molar ratio while suppressing CO₂ and CH₄ formation, indicating enhanced catalytic reforming and secondary cracking of pyrolysis vapors. These findings demonstrate that optimizing steam addition and nickel aluminate catalyst loading effectively promotes hydrogen-rich syngas from corn stover and provides valuable insight for the development of efficient biomass-to-fuel conversion technologies.