Hydrogen-rich energy recovery from microalgae (lipid-extracted) via steam catalytic gasification

Identifying and tackling indispensable developments in microalgae-based bio-economy should be a priority to unravel the contentious water-food-energy-environment nexus that algae inhabit. This research investigated the catalytic and non-catalytic steam gasification of two types of lipid-extracted microalgae biomasses, Chlorella vulgaris and Spirulina platensis in a thermogravimetric analyzer coupled with online mass spectrometry. A hybrid-functional mixture consisting of CaO naturally derived from waste eggshell as catalyst and sorbent, Ni as catalyst and Y2O3 as support was employed during the gasification that mainly generated H2, CO and CO2. The varied CaO loading (10 to 50 wt%) showed an evident effect on the overall gasification of lipid-extracted microalgae biomass, indicating an optimal CaO loading of 40 wt% for Ni-CaO-Y2O3 mixed materials which enabled 400.81 and 324.93 mL g−1 of H2 yield, with maximum purity of up to 53.25 and 41.82 vol% in gaseous product for Chlorella vulgaris and Spirulina microalgae residues, respectively. The addition of Ni, Y2O3 in mixed form (Ni-CaO, Ni-CaO-Y2O3, CaO-Y2O3 and Ni-Y2O3) drastically enhanced H2 yield and its purity. Ni-CaO produced the maximum H2 yield and purity of 497.29 and 435 mL g−1, and 63.15 and 45.78 vol% for Chlorella vulgaris and Spirulina platensis, respectively.