Switchable solvent for lipid extraction from microalgae

In the work described in the thesis a novel effective switchable solvent system for direct lipid extraction from (unbroken) microalgae in (concentrated) aqueous solutions was investigated and evaluated. The secondary amine N-ethylbutylamine (EBA) which uses CO2 as stimulus for switching was selected for it switchable hydrophilicity and outstanding extraction performance. the lipid extraction yield from non-broken Neochloris oleoabundans slurries (~5% dry weight) using EBA was maximized for both single stage extractions, and for multistage extractions. For FW-stressed Neochloris oleoabundans, in one stage extraction the lipid extraction yield was 47.0 wt.% (all based on algae dry weight) of which 52.9 wt.% total fatty acids. A maximum yield of 61.3 wt.% was reached after four stages of extraction. A model was developed that described the equilibrium stage of lipid extraction from fresh water stressed Neochloris Oleoabundans sp.. With the hypothesis that after extraction, the algae cells were completely filled with the organic solvent phase, having the same composition as the organic phase outside the cells, the model was successfully fitted to the experimental crude lipid yields of the four stage extractions at various solvent to feed ratios. Moreover, an alternative solvent switching method (using the lower critical solution temperature behavior of EBA-water mixtures) for lipid separation and solvent recovery was found and investigated. Besides the lipid extraction, attention has been paid to the EBA recovery from both the raffinate and from the residual microalgae cells after extraction. At last, the energy flows of the two process options studied in this thesis for wet lipid extraction from microalgae with EBA were compared and evaluated.