Experimental investigation on thermal behavior and thermo-kinetic study on pyrolysis of de-oiled microalgae

The evaluation of microalgal wastes has gained importance both economically and environmentally since microalgae have a wide range of use and their use in industry has increased rapidly in recent years. In this context, one of the most effective and efficient processes for the evaluation of waste microalgal pulp is pyrolysis. This study aims to determine the thermal behavior and pyrolysis kinetics under different parameters of various types of freshwater and marine microalgae wastes using the thermogravimetric method. Concordantly, pyrolysis processes of freshwater microalgae Chlorella minutissima and Botryococcus braunii wastes and marine microalgae Tetraselmis suecica and Nannochloropsis oculata wastes were investigated. As a result of the thermogravimetric analysis, mass loss of about 75% for freshwater types and 55% for marine types was observed. Pyrolysis activation energy values determined by the Coats-Redfern method using different models were also calculated between 14.223 and 54.687 kJ/mol with a regression coefficient of more than 0.90. According to these results, it is seen that the most suitable models for pyrolysis of waste microalgal pulp were D3, R2 and R1 for all microalgae species. When all the results obtained as a result of this study are analyzed, it can be said that the pyrolysis process is an appropriate way to evaluate microalgal waste pulp and the obtained products have a stable structure and are more energy-efficient.