Simultaneous productions of biodiesel and biochar from krill

The Antarctic krill, referring to Euphausia superba, feeds phytoplankton, grown up with photosynthesis for CO₂ fixation. Therefore, the use of krill as a raw feedstock for energy production is a highly carbon negative approach, not disturbing the food supply chain of human. Although the krill has high lipid content (up to 40 wt%, dry basis), its use as a raw feedstock for biodiesel production has not been considered. In this study, the feasibility of Euphausia superba to be used as a biodiesel feedstock was scrutinized. Prior to biodiesel production, an annual biodiesel production potential from the krill without disruption of ecosystems was estimated (129% larger than current biodiesel production in Korea). Because krill oil contains high fraction impurities, (trans)esterification with acid catalyst resulted in low yield of biodiesel (6.5 wt%), while non-catalytic transesterification achieved 94.7 wt% of biodiesel yield. To maximize the utilization of krill, solid residue obtained after biodiesel production was synthesized to krill biochars, and they were used as sorptive materials for adsorption of toxic chemicals. Among different model pollutants (Cd(II), Cr(VI), and methylene blue), krill biochar had the best adsorption capacity for Cd(II) (13.7 mg g⁻¹), which is comparable value with other studies.