Algae farm field in Nusa Lembongan, Indonesia

In recent years, seaweed has gone from being a tasty Japanese side dish, to a way to rewild the seas, feed livestock, make plastics and absorb carbon. Can this wonder plant really help fix the planet?

Harvesting seaweed is nothing new. It’s been gathered for centuries in Britain for the production of soda ash – used in glass and soap production, and for bleaching linen. This was a significant industry in the 17th and 18th centuries. Later, it was collected for extracting iodine and for use as a gelling agent. By the turn of the 21st century though, interest had waned.

But now there’s a resurge of interest in seaweed farming, with new enterprises springing up around the coasts of northern Europe. Why? Simple, says Cait Murray, co-founder of a new Scottish seaweed business EcoCascade. “It’s the fastest-growing biomass on the planet and flourishes without the need for land, fresh water, pesticides or fertilisers. Its sustainability is outstanding.”

Author of The Seaweed Revolution Vincent Doumeizel and senior adviser on oceans and food to the U.N. has studied the potential of seaweed more than most, and says firstly as a food, its a great source of nutrients – not just for people but animals too.

“It’s richer in protein than soybean meal, it’s naturally anti-bacterial, anti-inflammatory, anti-viral, and it’s the best natural prebiotic in the world.”

As such, it curbs the need for the routine antibiotic treatment of livestock – a practice many believe is compounding the problem of antibiotic resistance in humans.

And the advantages don’t stop there.

Locally sourced seaweed beats imported soy meal on any number of sustainability metrics – why deforest the Amazon, asks Doumeizel, when we can harvest the stuff from our own waters?

There’s excitement too about the potential of some seaweeds to curb methane emissions from cows by up to 90 per cent when added to their feed.

Then there’s its potential as a fertiliser to boost plant growth; and as a clean, green, biodegradable substitute for plastic.

It’s also highly promising as a medicine: scientists at the Shanghai Institute of Materia Medica, drawing on traditional Chinese medicine, have developed a drug from it to treat Alzheimer’s, while recent studies by scientists in India, Japan, Europe and elsewhere appear to confirm the potential of seaweed to inhibit cancer as practised in Ayurvedic and ancient Japanese medicine.

And unlike most modern agriculture, seaweed can act – in certain instances – as a carbon sink, not a source.

Put all those elements together, and the vertiginous upsurge of interest in farming seaweed comes as no surprise.

Devon county council in England, along with the Eden Project and Plymouth Marine Laboratories, is backing a major new seaweed farm and processing site off the north Devon coast.

Nordic countries are catching on as well. In waters off the western coast of Sweden, the newly established Nordic Seafarm is setting out tens of kilometres of ropes to grow sea lettuce (Ulva).

Meanwhile, Amazon is investing around $1.5m (£1.24m) in an experiment off the coast of the Netherlands. Its aim: to see whether commercial seaweed production can thrive in an area of offshore wind farms, while at the same time sequestering large, measurable amounts of CO2.

There’s something of a gold rush feel to it all, and like any pioneering sector, there are pitfalls too. Doumeizel points to the fact that for all seaweed’s potential, “it’s not like it’s skyrocketing. We need to grow demand and to grow the market.” For now, production is threatening to outpace demand.

Will seaweed save the world? On its own? Most certainly not. Are we perhaps, even in danger of becoming victims of a hype cycle?

Like any fast growing green industry (think EVs, think biomass as fuel), some of the claims of seaweed enthusiasts should be taken with a pinch of (presumably seaweed infused) salt. Yet, there’s no doubt there is substantial potential there.

For Doumeizel, there’s an overwhelming logic in looking to the seas. “We cannot carry on feeding the world with the food systems we have in place now [with all their massive environmental impacts]. The oceans cover 70 per cent of the world’s surface yet contribute less than 3 per cent of our food. So if we want to maximise the potential of our planet to feed its people, let’s do it in the ocean.”