As far as I know
Nereocystis leutkeana, or bull kelp, is the fastest growing. It has been known to grow more than 2 feet a day. As for which produces the most hydrolyzable cellulose, I'm not sure.
Space/Science » in reply to Re: Good question for a biologist
Nereocystis leutkeana, or bull kelp, is the fastest growing. It has been known to grow more than 2 feet a day. As for which produces the most hydrolyzable cellulose, I'm not sure.