Lipid Extraction

Lipid extraction involves removing compounds, such as terpenes, esters and triglycerides, from the other constituents of an organic feedstock in a non-destructive manner. Lipid extraction is typically conducted using solvents such as alcohol. The desired compounds are dissolved in the solvent for later separation. The process can be complicated since the solvent must saturate the feedstock through its natural pores and pathways to reach the lipids, and then carry the dissolved compounds out the same way. The rate at which the compounds are removed from the biomass is the major process bottleneck, and so processes are designed to maximize diffusivity, including heating and pressurizing the solvent. However, lipids may be damaged by prolonged exposure to heated solvent (Topfer et al. 1995). 

Microwave extraction is an alternative approach. It saves energy by not heating the solvent but instead heating only the biomass, rapidly exciting whatever water remains inside. This increases the pressure within the biomass particles and thus expels the desired chemicals, sometimes by exploding cell walls. With this method, diffusion is no longer the limiting factor. Expelling chemicals into unheated solvent also preserves them. Additionally, microwave extraction is a single-stage process and greatly reduces overall extraction time (Armstrong 1999).

Once the lipids are extracted, they can undergo esterification or transesterification to become biodiesel, or they might be used as pharmaceuticals, flavorings, fragrances, colorings, or oils. Radient Technologies has licensed the microwave extraction technology and a new company, NaturNorth Technologies is looking at lipid extraction from birch bark.