It's true that collecting algae requires effort to collect and transport. But my ultimate point is that the total energy and resource costs of directly convert

It's true that collecting algae requires effort to collect and transport. But my ultimate point is that the total energy and resource costs of directly converting seaweed to fuel would be far lower than in OP's proposal. Just as in your power plant anecdote. And you achieve the same goal of removing CO2 from the ocean. Drying pond algae with solar heat is tricky because you can't concentrate the sunlight too much or you get ash instead of dry algae. But with dry distillation the objective is to pyrolize the input, so you can efficiently use concentrated sunlight. >you need cellulosic ethanol tech to work better first. Still didn't break even against solar My proposal isn't competing with solar electricity (which doesn't remove CO2 from the ocean), but with OP's proposal to use solar electricity to produce methanol from CO2 extracted from seawater.