Pyrolysis of Chlorella vulgaris: Kinetic analysis, advanced characterization, and bio-oil optimization


POLAT S., Kılıç Ö. F.

Journal of Environmental Chemical Engineering, cilt.13, sa.6, 2025 (SCI-Expanded, Scopus) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 13 Sayı: 6
  • Basım Tarihi: 2025
  • Doi Numarası: 10.1016/j.jece.2025.120374
  • Dergi Adı: Journal of Environmental Chemical Engineering
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Compendex, INSPEC
  • Anahtar Kelimeler: Box–Behnken design, Chlorella vulgaris, Model-free kinetics, Pyrolysis, TGA-FTIR-MS
  • Marmara Üniversitesi Adresli: Evet

Özet

Pyrolysis of Chlorella vulgaris was investigated to evaluate its thermal degradation behavior, kinetic parameters, and potential for producing biochar and bio-oil as sustainable energy sources. Thermogravimetric analysis revealed that the main active pyrolysis occurred between 200 and 500 °C, corresponding to a significant release of volatiles. The resulting biochar exhibited improved carbon content (80.8 wt%), a surface area of 161.3 m2/g, and a higher heating value (HHV) of 31.6 MJ/kg. Kinetic modeling using model-free methods (Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Starink, and Tang) estimated activation energies within the range of 138.7–141.5 kJ/mol, while thermodynamic analysis indicated an endothermic and non-spontaneous process. Gaseous products such as CO2, H2O, and CH4 were identified via TGA-FTIR/MS. Py-GC/MS analysis of the bio-oil showed a complex composition, including 42.6 wt% oxygenated compounds, 25.4 wt% nitrogenous species, and light hydrocarbons. Process optimization using the Box–Behnken design identified the heating rate as the most influential factor for maximizing bio-oil yield. The optimum conditions were determined to be a pyrolysis temperature of 500 °C, a heating rate of 100 °C/min, and a nitrogen flow rate of 50 mL/min, under which the maximum bio-oil yield of 32.08 wt% was achieved. The upgraded bio-oil exhibited enhanced fuel properties (H/C = 1.18, O/C = 0.28, HHV = 30.4 MJ/kg). In conclusion, the present study suggested that C. vulgaris appeared to be a promising renewable biomass for biofuel production using pyrolysis technology.