Strategic Use of Extremophilic Microalgae as a Carbon Source in the Thermo-Chemical Process

Abstract

Microalgal biomass has a high CO2 fixation and growth rate when using CO2 as a carbon source. Moreover, biomass can also be employed as a carbon resource to produce biofuels and chemicals. As the growth rate of extremophilic microalgae remains unaffected by harsh conditions, the present study proposes that these microalgae (such as Galdieria sulphuraria) are a rapidly growing carbon resource for syngas production. Hence, two different experiments were performed as part of this study: (1) cultivation of G. sulphuraria under outdoor conditions and (2) conversion of G. sulphuraria into syngas. The productivity of G. sulphuraria under mixotrophic condition (0.82 g L–1 d–1) was about 1.6 faster than a widely cultivated Chlorella sp. HS2. Moreover, G. sulphuraria was converted into syngas using CO2 as a co-feedstock. The simultaneous reduction of CO2 and the oxidation of volatile matter (VM) from the thermolysis of G. sulphuraria promoted syngas formation. The chemical reaction was influenced by the molecular size of the VMs. In the presence of the Ni catalyst, low-molecular-weight VMs were formed owing to chemical bond scissions. Syngas formation under CO2 doubled compared with that under inert conditions. The findings suggest that G. sulphuraria is a feasible carbon source for CO2 fixation and chemical production.