Two-step in situ biodiesel production from microalgae with high free fatty acid content

- An efficient two-step in situ microalgal biodiesel production process is reported.
- The biodiesel yield was dramatically higher than one-step in situ process.
- Amberlyst-15 is suitable for the in situ pre-esterification and can be recycled.
- The use of recyclable Amberlyst-15 reduced catalysts (acid and base) requirement.
- This environmentally benign process has the potential to reduce production cost.