Gasification of lipid-extracted microalgae biomass promoted by waste eggshell as CaO catalyst

Abstract

Significant amounts of lipid-extracted microalgae biomass (LMB) could be generated as a by-product from biodiesel production, therefore its ability to be processed into and converted into a more valuable product needs to be explored to determine its true potential market value. In this study, the catalytic gasification of two LMB's, Spirulina platensis and Chlorella vulgaris, were performed in a thermogravimetric analyzer with mass spectrometry. The CaO based catalyst, naturally derived from waste eggshell, was varied to determine influence of catalyst loading (10, 30 and 50 wt%). The reactions were conducted over a 30–800 °C temperature range, in 5% O2/Ar at a 500 mL min−1 flow rate. Scanning electron microscopy and X-ray diffraction methods were utilized to characterize and observe physicochemical changes among the standard, fresh and calcined catalysts. For Spirulina platensis, H2 yield was improved with an increased catalyst loading from 53.6 to 110.0%, whereas CO and CO2 yields decreased by 58 and 52%, respectively, compared with the absence of the catalyst. For Chlorella vulgaris, H2 yields were increased as a result of increasing catalyst loading from 21.2 to 114.4%, whereas CO and CO2 decreased by 50.0 and 55.0%, respectively, compared with the absence of the catalyst. The CaO catalyst promoted the catalytic activity and captured CO2 via CaO absorption property which encouraged the water gas shift reaction to occur to a greater extent, which in turn increased the H2 production.