Pyrolysis and Gasification Characteristics of Galdieria sulphuraria Microalgae

Low-lipid microalgae such as Galdieria sulphuraria can survive extreme conditions suggesting low cultivation costs and potential industrial uses. However, so far, its energy potential for syngas and bio-oil production by pyrolysis and gasification is not fully explored. Herein, pyrolysis/gasification of Galdieria sulphuraria was studied by thermogravimetry and fixed bed reactor in a nitrogen atmosphere with/without downstream Co-Mo-based sour shift catalyst. The yield and higher heating value (HHV) of the product for each experimental run are determined and evaluated in terms of bio-char and bio-oil elemental analysis and syngas composition. Temperature greatly affects the product yield, conversion rate, and gas composition for pyrolysis experiments. However, even at high temperatures, the hydrogen content of the produced syngas is low. Low-temperature catalytic gasification experiments of Galdieria sulphuraria (500 °C) lead to the production of hydrogen-enriched syngas (41.7 vol% H₂) and high HHV (~ 30 MJ/kg) bio-oil with lower oxygen and nitrogen content. The results found in this work show the potential of Galdieria sulphuraria as a renewable energy resource for high-quality oil and syngas production.