Life cycle greenhouse gas emissions of microalgal fuel from thin-layer cascades

Thin-layer cascades (TLCs) enable algae cultivation at high cell densities, thus increasing biomass yields and facilitating the harvest process. This makes them a promising technology for industrial-scale algal fuel production. Using Life Cycle Assessment (LCA), we calculate the greenhouse gas (GHG) emissions of aviation fuel produced using algal biomass from TLCs. We find that the impact (81 g CO2e per MJ) is lower than that of fuel from algal biomass cultivated in open race way ponds (94 g CO2e). However, neither of the two cultivation systems achieve sufficient GHG savings for compliance with the Renewable Energy Directive II. Seawater desalination in particular dominates the TLC impact, indicating a trade-off between carbon and water footprint. In both cultivation systems, the mixing power and fertilizer consumption present further significant impacts. There is uncertainty in the correlation between mixing power and algal oil yield, which should be investigated by future experimental studies.