Renewable fuels from pyrolysis of Dunaliella tertiolecta: An alternative approach to biochemical conversions of microalgae

Abstract

The cultivation of microalgae as a feedstock for renewable fuels is widely touted as a way to sequester CO2 while negating food versus fuel competition for land. However, the widespread industrial use of microalgae for biofuels has yet to reach a critical stage based on lipid extraction alone. One alternative to the transesterification of microalgae for liquid fuel production is to use thermochemical conversion techniques. In the present work, we demonstrate that Dunaliella tertiolecta can be converted to biofuels via pyrolysis at temperatures significantly lower than terrestrial biomasses. The primary gaseous pyrolysis products were CO2, H2O, CH4, alcohols, aldehydes, organic acids and phenols. The iso-conversional distributed activation energy model was used to calculate the kinetic parameters, showing average activation energy of 243.3 kJ/mol, with a peak in activation energy at mass fraction conversions between 0.45 and 0.65. However, the substantial amount of pyrolysis gases evolved at low temperatures (between 280 and 320 °C), suggests that pyrolysis at higher temperatures, and especially to completion, might not be necessary to optimize pyrolytic production of biofuels from microalgae.