Pyrolysis of Scenedesmus obliquus Biomass Following the Treatment of Different Wastewaters

The potential of Scenedesmus obliquus biomass, after treating several wastewaters (WWs) (urban, dairy and brewery industries, cattle and poultry breeding), was evaluated for the production of bio-char, bio-oil and bio-gas, through a pyrolysis process. The experiments were carried out in a fixed bed reactor at a temperature of 748 K during 15 min. The thermochemical behaviour of each microalga was assessed by thermogravimetry analysis and infrared spectroscopy. The bio-oils obtained were also quantified and characterized. The results reveal that (i) all microalgae show a similar thermal degradation behaviour; (ii) microalga grown in urban WW shows a lower percentage of lipids; in dairy and cattle WWs, it shows a high percentage of both proteins and lipids, and in poultry and brewery WWs, it shows a higher carbohydrates content; (iii) the microalga grown in poultry WW shows the lowest protein content, whereas the urban grown microalga showed the highest protein content; (iv) the bio-oil obtained by pyrolysis process showed yields in the range 30–60% (w/w) and showed a high content of aromatic compounds.