What happens if a natural disaster strikes one of these huge algae farms? Wouldn't the impact be much worse than for a traditional soil-based farm? These algae tanks would seem to require a much more significant capital investment than a plain corn or wheat field.
How much water is needed to support the process? The TV show pointed out that H2O is a byproduct of burning hydrocarbons, but if I remember correctly it's not a huge emission component. Wouldn't you need a lot more water in which to culture the algae?