Transesterification (biodiesel)

Micro-algae are grown to produce lipids. They can be grown in open ponds, closed photobioreactors, or in heterotrophic bioreactors (no light required). Once the lipids (oils) are extracted from the algae, the process is similar to traditional fatty acid methyl ester (FAME) biodiesel production, in which the oil feedstock is reacted with methanol in the presence of a catalyst to produce biodiesel and glycerine. The main challenge with micro-algae is the high cost of cultivation and harvesting (lipid extraction) compared to terrestrial biomass; other issues arise from lipid content, reducing energy/water/nutrient/land footprint, and integrating the full process pathway at demonstration scale. On the other hand, algae can be grown on non-arable land, avoiding competition with food. It can also be grown rapidly, and exhibits high photosynthetic efficiency, potentially leading to greater biofuel per unit area yields compared to terrestrial biomass.