AFAIU algae fuel has been researched since the 70'ies, with little to show for it.

Recently Exxon quietly cancelled their algae fuel project. One wonders if it was ever supposed to achieve something or was it just greenwashing.

Algae fuel makes little sense. To grow enough algae for fuel usage, you would have to use a lot of fertilizer. The fertilizer would be made from natural gas. So it would just be a giant scheme of hiding natural gas usage behind green fuel, but worse since it would take more natural gas than just using it directly.