That was an initial thought of mine about a decade ago. The energy densities don't work out.

At present rates of per-capita energy consumption, population, and rates of plant growth, there is either not enough primary productivity, or too large an environmental impact. Humans simply use immense amounts of energy.

Other sources, lower per-capita usage, and/or fewer people, are the options.

https://dothemath.ucsd.edu/tag/biofuels/

https://link.springer.com/article/10.1023%2FA%3A102639131768...

https://old.reddit.com/r/dredmorbius/comments/2cvap7/the_int...

https://old.reddit.com/r/dredmorbius/comments/1wo2hl/boeings...