Hydrothermal liquefaction for biochar production from finger millet waste: its valorisation, process optimization, and characterization

• Published in: RSC advances Vol. 14; no. 34; pp. 24492 - 24502
• Main Authors: Hussain, Afzal, Kandari, Ayush, Kotiyal, Sushant, Kumar, Vinod, Upadhyay, Shuchi, Ahmad, Waseem, Singh, Ajay, Kumar, Sanjay
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 05.08.2024; The Royal Society of Chemistry
• Subjects: Bulk density; Calorific value; Chemical analysis; Chemistry; Design optimization; Functional groups; Inorganic compounds; Liquefaction; Millet; Process variables; Solid fuels; Thermal stability
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d4ra03945a

In this study, the potential of finger millet waste biomass (FMWB) as a source of biochar production through hydrothermal liquefaction (HTL) was investigated. The HTL process was designed using Box-Behnken design (BBD) and carried out with process variables, , temperature (250 °C, 350 °C, and 450 °C), time (30 min, 45 min, and 60 min), and solid-to-water ratio (1 : 6, 1 : 8, and 1 : 10). The responses, , biochar yield (%), bulk density (g cm ), pH, and high heating value (HHV), were analysed. Optimisation was done using design expert software (version 13.0.1). The optimized finger millet waste biochar (O-F W ) was produced at optimum values (450 °C, 1 : 10, and 33.5 min). The results of proximate and elemental analysis revealed that moisture, ash, and volatile content, H, and O of O-F W decreased while fixed carbon, thermal stability, and C content increased compared to FMWB. FT-IR, SEM-EDX, and XRD analyses were performed for O-F W . The results of FT-IR showed the presence of O-H, C-H, C[double bond, length as m-dash]O, and C[double bond, length as m-dash]C functional groups. The SEM image revealed the rough surface of O-F W , and XRD confirmed the production of a broad range of inorganic compounds and minerals. This study provides the full exploitation of F W as a source of solid fuel.