Renewable Bio-Oil from Pyrolysis of Synechocystis and Scenedesmus Wild-Type Microalgae Biomass

In this study, biomasses of microalgae Scenedesmus and Synechocystis species were thermochemically converted to biofuel in a fast pyrolysis process. The effect of pyrolysis temperature on the products yield was investigated. The optimal pyrolysis temperature for Scenedesmus and Synechocystis biomass was 500 °C and 600 °C, respectively, resulting in higher bio-oil yield of 35.3 wt% and 21.1 wt%. The produced bio-oil had higher high heating value (HHV) (35–40 MJ/kg) than that of beech wood source bio-oil (23–35 MJ/kg). The obtained biochar had low surface area but with considerable nitrogen, phosphorus, and other mineral content was suggested as fertilizer. It was concluded that the microalgae type and its cultivation and harvesting method affects the characteristics of the products and final energy efficiency as well. Energy efficiency assessment showed that the technology needs to be improved substantially to reduce the energy demand in cultivation, harvest, and pyrolysis step to be energy efficient.