Life cycle assessment of carbon-based adsorbent preparation from algal biomass

Abstract

The adsorbent prepared by algae was found to be very feasible and effective for removing tetracycline from water. Therefore, this manuscript investigated the capacity of adsorbents through co-pyrolysis of Enteromorpha (EN) and Chlorella vulgaris (CV). Through the experiment, it was determined that the pyrolysis of Enteromorpha and Chlorella vulgaris was carried out at 500 °C at the mixing ratio of 2∶8. The obtained biochar was mixed with NaOH at 1∶0.5 and activated at 800 °C. The mixed algae-based adsorbent had the highest removal rate of tetracycline (97.56%). To further evaluates the environmental impact of the adsorbent preparation process, OpenLCA was applied to the three adsorbent preparation processes using Enteromorpha (EN), Chlorella vulgaris (CV) and mixed algae (MIX). The results show that EN-based adsorbent preparation has the least environmental impact. This is because CV requires much freshwater during cultivation, while EN is cultured in ocean. The culture of CV-based and MIX-based adsorbents account for the majority of all environmental impact indicators. For example, the CO2 emissions of CV and MIX culture account for 75.05% and 69.21% in preparation process, respectively. The sensitivity analysis showed that the environmental impact indicators of CV-based and MIX-based adsorbents preparation was extremely sensitive to aquaculture water. If 80% of the aquaculture water is replaced with aquaculture wastewater, the environmental impact of the MIX-based adsorbent preparation will be the least of the three schemes. The LCA of algae-based adsorbent preparation was carried out in this study, which provided guidance for the optimization of adsorbent preparation engineering.