‘Like a 40-metre pizza’: the seaweed farms that could feed us all – at a cost

A white metal platform on the surface of the Pacific Ocean faces another, smaller one some distance away. Sam Donohue stands on the big platform, Gorio Pepito on the small one. They press buttons, and a high-pitched whirring sets in.

Pepito and Donohue release the buttons. The whirring stops. They communicate by walkie-talkie. Everything’s OK. A crab walks across the big platform: that’s their pet, Donohue says. They press the buttons again.

At first nothing happens, but then it appears on the surface of the water, cresting like the back of a whale: a large ring, from which countless lines are stretched out in a star shape.

It’s seaweed, glowing in the light of the rising sun. Four dolphins leap from the water as if they had been ordered there for this moment.

This is Brian von Herzen’s plan for “saving the Earth”, according to his website. The founder and director of the Climate Foundation, Von Herzen wants to use highly engineered platforms to…