Exploring the potential of peat-mineral-mix for sustainable clean energy: Process optimization of hydrothermal carbonization for biofuel production

The transition toward sustainable and clean energy sources is essential for addressing global energy challenges and attaining Sustainable Development Goal 7-(SDG 7). This study explores the potential of peat-mineral-mix-(PM) as a renewable bioenergy source through hydrothermal carbonization-(HC), a promising thermochemical conversion method. A central composite design was applied to investigate the combined effects of hydrothermal temperature-(HC-T) and residence time-(HC-RT) at 200 °C, 260 °C, and 320 °C for duration of 1 and 4 h on the physicochemical properties of PM-derived-hydrochars-(PM-HCs). The results demonstrated that HC-T and HC-RT significantly influenced the yield (69.51–57.01%), higher heating value-(HHV improvement: 43.11%–54.32%), and energy densification-(ED: 1.43–1.54) due to increased decomposition of organic matter at higher treatment severities. Comprehensive characterization techniques, including FTIR, XPS, ¹ ³C NMR, Raman spectroscopy, TEM, and XRD, revealed that increasing HC severity led to progressive aromatic condensation, enhanced carbonization, and formation of turbostratic graphitic domains, improving thermal stability and energy content of PM-HCs. SEM and BET analyses revealed morphological restructuring and increased particle dispersion at moderate HC-T and HC-RT, primarily due to the decomposition of organics and partial aromatization, whereas extreme conditions led to pore collapse or surface sealing. Additionally, ICP OES confirmed selective elemental transformations, highlighting potential for nutrient recovery and environmental applications. The findings highlight HC as a scalable and energy-efficient approach for converting PM into high-energy solid fuel, aligning with sustainable bioenergy production and resource recovery initiatives. These insights contribute to optimizing HC conditions for full-scale PM treatment systems, promoting clean, affordable, and sustainable energy solutions. • Fuel characteristics of PM-HCs were linearly associated with higher HC-T and HC-RT. • Reduced oxygenated groups and increased aliphatic and aromatic carbon were observed. • Graphitic ordering improved at moderate HC severity but declined at extreme levels.. • Significant changes in porosity, surface area, and particle dispersion were found at elevated HC-T and HC-RT. • HC-treated PM has potential to be used as a clean & sustainable energy source, supporting SDG-7.