Table 1 Comparison of various algal lipid extraction methods

Botryococcus braunii

Switchable hydrophilicity solvent, N,N-dimethylcyclohexylamine

The solvent extracted up to 22 wt% of crude lipid from the algal biomass

Drawbacks include toxicity, poor selectivity, contaminants separation

[56]

Scenedesmus obliquus

Chlorella protothecoides

Nannochloropsis salina

Supercritical fluid method using CO₂

The maximum extraction yield 18.15 wt% was obtained at 60 °C and 30 MPa with 0.4 kg.h⁻¹ of CO₂ and 5 % of co-solvent (ethanol). Scenedesmus obliquus oil was found to be rich in ω-3 fatty acids

Environmental and safety issues in large scale extraction.

[57]

Botryococcus sp.

Chlorella vulgaris

Scenedesmus sp.

Autoclaving at 125 °C with 1.5 MPa for 5 min

The lipid content of the three species was in the range of 5.4–11.9 wt%

Poor extraction efficiency

[58]

Botryococcus sp.

Chlorella vulgaris

Scenedesmus sp.

Bead-beating

The lipid content of three species was in the range of 7.9–8.1 wt%

Difficult to scale up

[58]

Botryococcus sp.

Chlorella vulgaris

Scenedesmus sp.

Microwave

The lipid content of three species was in the range of 10.0–28.6 wt%

Easy scale-up high energy demand for cooling maintenance cost at scale.

[58]

Botryococcus sp.

Chlorella vulgaris

Scenedesmus sp.

Osmotic shock by 10 % NaCl solution

The lipid content of three species was in the range of 6.8–10.9 wt%

Requires longer treatment time.

[58]

Mixed algal culture of Scenedesmus sp., Chlorococcum sp.

Sonication

The ultrasound application enhanced the lipid extraction yield by about 96 % (26.8 wt% lipids extracted from 57.6 % of total biomass)

Reduced extraction time and increased lipid extraction efficiency

[59]