Hydrotreating (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 hydrogenated or hydrotreated vegetable oil (HVO). Hydrogen is added to the oil feedstock in the presence of a catalyst to convert triglycerides into long-chained hydrocarbons that can be considered a renewable diesel (drop-in). The main technical challenge with this technology is producing algae with high lipid content and then extracting the lipids efficiently. A major benefit of algae-based biofuels is their potential to produce biofuels without competition with food, as algae can be grown on non-arable land, though it has high land/nutrient/energy/water usage.