Characterization and comparison of pyrolysis products from fast pyrolysis of commercial Chlorella vulgaris and cultivated microalgae

Chlorella vulgaris algae is comprised of a complex mixture of compounds such as carbohydrates, lipids, and proteins and is a suitable feedstock for biofuels. The aim of this study was to convert commercial and a low cost field cultivated algae, via pyrolysis, to produce bio-oil, synthesis gas, and biochar products. The thermal degradation behaviour of algae was investigated by thermogravimetric analysis. Proximate, ultimate, fatty acid methyl ester and carbohydrates analyses, and pyrolysis-GCMS were further employed to characterize the chemical components of algae. Commercial and field cultured C. vulgaris algae was pyrolyzed (450, 500, and 550 degrees C) and their pyrolysis products were collected and characterized. The highest biochar yield was 42% at 450 degrees C and the highest bio-oil yield was 47.7% at 550 degrees C. The biochar physical and chemical properties were assessed using proximate and ultimate analysis, calorific value, specific surface area, butane absorption activity, Raman spectroscopy, and electron microscopy. Algae biochar was found to be mostly composed of condensed phenolic compounds and majorly disordered amorphous carbon. The bio-oils were characterized by the combination of GC-MS, high-pressure liquid chromatography, and electrospray ionization mass spectrometry. Fatty acids, carbohydrates, nitrogen-containing compounds, and aromatic hydrocarbons were abundantly found in the algae bio-oil.