Surfactant-assisted direct biodiesel production from wet Nannochloropsis occulata by in situ transesterification/reactive extraction

Abstract

This article reports an <em>in situ</em> transesterification/reactive extraction of <em>Nannochloropsis occulata</em> for fatty acid methyl ester (FAME) production using H₂SO₄, sodium dodecyl sulphate (SDS) plus H₂SO₄ and zirconium dodecyl sulphate (ZDS). A maximum 67 % FAME yield was produced by ZDS. Effect of inclusion of sodium dodecyl sulphate (SDS) in H₂SO₄ for FAME enhancement and water tolerance was also studied by hydrating the algae with 10 % - 30 % distilled water (w/w) dry algae. Treatment with SDS in H₂SO₄ increases the FAME production rate and water tolerance of the process. Inclusion of SDS in H₂SO₄ produced a maximum 98.3 % FAME yield at 20 % moisture in the algae. The FAME concentration began to diminish only at 30 % moisture in the algae. Furthermore, the presence of a small amount of water in the biomass or methanol increased the lipid extraction efficiency, improving the FAME yield, rather than inhibiting the reaction.