The environmental sustainability of microalgae as feed for aquaculture: A life cycle perspective

The environmental sustainability of microalgae production for aquaculture purposes was analyzed using exergy analysis (EA) and life cycle assessment (LCA). A production process (pilot 2012, 240 m2) was assessed and compared with two upscaling scenarios (pilot 2013, 1320 m2 and first production scale 2015, 2.5 ha). The EA at process level revealed that drying and cultivation had the lowest efficiencies. The LCA showed an improvement in resource efficiency after upscaling: 55.5 MJex,CEENE/MJex DW biomass was extracted from nature in 2012, which was reduced to 21.6 and 2.46 MJex,CEENE/MJex DW in the hypothetical 2013 and 2015 scenarios, respectively. Upscaling caused the carbon footprint to decline by factor 20 (0.09 kg CO2,eq/MJex DW in 2015). In the upscaling scenarios, microalgae production for aquaculture purposes appeared to be more sustainable in resource use than a reference fish feed (7.70 MJex,CEENE and 0.05 kg CO2,eq per MJex DW).