Some areas of ocean in the Southern Hemisphere do not contain sufficient nutrients to support large seaweed farms.

When a seaweed plant is burned, it releases an amount of carbon dioxide comparable to the amount it has absorbed in its lifetime.

Even if seaweed farms prove effective, some people will be reluctant to switch to this new fuel.

Each year about seven billion tons of carbon dioxide are released into the atmosphere but only about five billion tons are absorbed by plant life.

Seaweed farms would make more money by farming seaweed to sell as nutritional supplements than by farming seaweed to sell as fuel.