Marine algae could replace plastic, massively cut our carbon emissions and help feed billions of people healthily, according to an excellent new book by Vincent Doumeizel
A kelp forest, dominated by giant kelp (Macrocystis pyrifera), grows off the coast of northern California. This is an important habitat for a diverse array of eastern Pacific marine life.; Shutterstock ID 179694674; purchase_order: -; job: -; client: -; other: -
A marine forest, off the coast of northern California, is dominated by fast-growing giant kelp
NEXT time you have maki sushi, consider the nori seaweed it is wrapped in – it might well help save the planet.
As Vincent Doumeizel reveals in his book The Seaweed Revolution, the potential of seaweed, or marine algae, to transform our world is huge. If we could grow it sustainably, he writes, “seaweed could feed people, replace plastic, decarbonize the economy, cool the atmosphere, clean up the oceans”.
It is quite a promise, but can it be fulfilled? Doumeizel is well-placed to find out. He is senior adviser on oceans to the UN Global Compact, the largest bid to get businesses to buy into sustainable, responsible policies and report on their progress.
His premise is that we are filling the atmosphere with climate-warming gases, overcultivating the land and depleting soils, leaving millions of people hungry or malnourished. Yet oceans, covering 71 per cent of Earth, are largely untapped. Of 48 million square kilometres of cultivatable ocean, we use just 2000 for food, contributing only 2 per cent of our calorie intake. Most of us could eat more seaweed and would probably be healthier for it, says Doumeizel. In Japanese cuisine, it already accounts for 10 per cent of daily calories.
Doumeizel details seaweed research, revealing, for example, that nori contains phytosterols, which prevent us from absorbing cholesterol and cut the risk of some cancers. Certain seaweeds also contain a wealth of fibre, vitamins and micronutrients, including omega-3s. Just think of the poor sailors who died of scurvy not knowing that 400 grams of the seaweed below them would have met their daily vitamin C needs.
The book is also persuasive on seaweed’s role in absorbing carbon dioxide, saying it could mop up the equivalent of around 10 billion tonnes of CO2 per year. That is about a fifth of all annual emissions. Giant kelp, in particular, can grow more than 50 centimetres a day, says Doumeizel, and absorbs a huge amount of CO2.
He also points to work showing that adding red algae to the diets of ruminants like cows would alter their gut microbiomes, improve their digestion and could cut their methane emissions by 80 per cent. This alone would have an effect on greenhouse gases akin to banning cars immediately, he says.
Beyond this, there are the emerging uses of kelp to make environmentally friendly clothes, high-density bricks or biodegradable bioplastic, which could replace PET plastic. To do all that, we would need to produce several hundred million tonnes of kelp every year.
As for downsides, Doumeizel says that large-scale farming of one species can unbalance ecosystems, stressing that aquaculture can’t be seen as a local endeavour because the sea carries fertilisers elsewhere, which could cause unpredictable growth surges. It will also transport seaweeds to places where they could spread invasively, so we need robust checks and quarantining.
This doesn’t deter him: in his view, seaweed represents hope, with seaweed “fields” supplying food for billions, absorbing carbon and providing materials. He sees a multi-species aquaculture, farmed by underwater drones. Organic fish waste would be recycled by mussels and scallops, seaweed would mop up inorganic waste, and sea urchins and starfish would absorb leftovers.
We aren’t there yet, though. So far, we have domesticated just 10 to 20 of the 12,000 seaweed species. As Doumeizel says: “What can we do with seaweed? Practically everything! What do we currently know how to do with seaweed? Practically nothing!”
Even so, the market has exploded from very little in 1950 to a global $14 billion now. Since reading this excellent book, my intake of seaweed has soared – even if I am not wearing kelp clothes yet.