An Illustrated Guide to Seaweed Farming
Words by Mathew Bate
Illustrations by Liz Rowland
This illustrated guide is featured in Issue 2. Order your copy or become a yearly subscriber today.
Building up our ocean's underwater forests and farming seaweed could be the most effective way to sequester carbon from our atmosphere and combat climate change. This illustrated guide, featured in Issue 2, tells us how.
Seaweed farming
Due to the unprecedented rise of CO2 in our atmosphere, which is largely to do with our obsession with industry and economic growth, we are experiencing a drastic change in global climate. Let’s assume you already know this. If you don’t, well, go snorkelling at the Great Barrier Reef and see what you find. Hint: it won’t be coral. 25 percent of all CO2 emissions are absorbed by our oceans. We used to thank our lucky stars that we had the ocean to take so much of our CO2 until we realised...
more CO2 in the ocean raises the acidity (lowers the pH) of the water. Over the past 150 years, the catastrophic rise in CO2 emissions has seen the acidity of oceans rise by 30 percent.
The greater the acidity of water, the harder it is for shellfish and other crustaceans to deposit calcium on their shells, making it incredibly difficult for them to survive. If we remind ourselves of the trophic pyramid, all sea life relies on the bottom rungs of the pyramid for food, therefore, if shellfish suffer, so do smaller fish, as do larger fish, as do seals, whales, sharks, birds and, of course, us (humans). In the Atlantic Ocean, due to ocean acidification and warmer waters from global warming, scientists have observed a decrease in marine biological activity of four to eight percent per year.
Back to the trophic pyramid. At the very bottom of the pyramid we have tiny micro-organisms called phytoplankton (around 0.25 billion can fit in one cup of seawater) and other seaweed species, like kelp. Just like trees, kelp and phytoplankton pull CO2 from the atmosphere; trees pull carbon from the air and kelp pulls carbon from the water. Kelp and phytoplankton make up half of the world’s organic matter and produce at least half of the world’s oxygen. Kelp also grows 30 times faster than most land plants. By pulling CO2 from the water, kelp lowers the water’s acidity.
So, it follows that by building up our underwater kelp forests, known as Ocean Afforestation, we can lower the CO2 in our oceans, lower acidity and consequently benefit all other sea life. Not only is kelp great for the ocean, it’s great in miso soup and sushi would be quite bland without it (the global kelp market is estimated to be worth over $5 billion). We can also turn it into bio-methane, a viable alternative to burning fossil fuels, which (ironically) catalysed this entire problem in the first place. It’s even been found that particular strains of kelp can significantly reduce methane emissions if added to a cow’s diet (more on that at the end).
Antoine De Ramon N’Yeurt, a researcher and lecturer at the University of the South Pacific in Fiji, who has studied marine plant biodiversity of the Pacific Islands for the past 25 years, published a groundbreaking paper in 2012. Titled ‘Negative Carbon via Ocean Afforestation’, the paper estimated that if we turned nine percent of our ocean (a size as big as 4.5 Australias) into seaweed farms we could sequester enough carbon from the atmosphere to get us back to pre-industrial CO2 levels. In addition, we could produce 12 billion tonnes of bio-methane, which would make the entire fossil fuel industry redundant and would create enough biomass in our oceans to produce, per year, 200 kilograms of fish/shellfish for 10 billion people.
Can the ocean take that much carbon though? The short answer is yes. The ocean holds 55 times more carbon than is stored in our entire atmosphere. Meaning that if we took all the carbon from the atmosphere and stored it in the ocean, it would only result in a net increase of two percent of the ocean’s carbon. Whatever kelp we don’t consume, turn into fuel or use in any other productive way can literally be chopped off and left to sink to the bottom of the ocean. This is because kelp turns into carbonates and dissolved carbon, which can be stored for around 1,000 years, until it returns back into the water and can be absorbed, again, by our booming kelp forests. Having said that, scientists are currently undertaking tests to see what would happen if we sunk huge amounts of carbon into the depths of the ocean. At this point we're not entirely sure if there are any adverse consequences of using the ocean as a carbon sink.
So, how in the heck do we farm kelp at a massive scale? Well, Brian Von Herzen, a US scientist and the executive director of the Climate Foundation, has come up with an ingeniously simple idea that he calls Marine Permaculture Arrays (MPAs).
Marine Permaculture Arrays
Von Herzen has a PhD in computer science and has been developing ways in which we can naturally sequester carbon from the atmosphere since his tenure at Princeton University in the 80s. More recently, the Bill and Melinda Gates Foundation has funded his work into a land-based carbon sequestration model for developing nations and the early stages of the MPA infrastructure has been trialled with terrific success off the coast of Hawaii. His not-for-profit, the Climate Foundation, has carbon sequestration projects all around the world, both underwater and on land.
Von Herzen’s MPA is a kelp farm that sits around 25 metres underwater so that large boats and ocean liners can pass above with minimal impact — they can even withstand the force of the most severe hurricanes. At around 650m2, the farms are built using a lightweight lattice structure that is submerged and attached to buoys that rise and fall with the swell.
The movement of these buoys powers pumps that draw up the water from the depths, drenching the kelp in nutrients. Kelp grows so fast that Von Herzen suggests that farmers could harvest it every 90 days.
These floating kelp forests could not only tackle our CO2 emissions, but could also provide the world with a viable renewable fuel, enormous amounts of food and literally breathe new life into our suffering oceans.
Cows on a beach
If you didn’t think seaweed could get any better, well, it does. Not only is seaweed a fantastic solution to sequestering carbon from our oceans, it may also be the solution to the methane emitted by animal agriculture.
Methane emissions from cattle in Australia account for around 10 percent of total greenhouse gas (GHG) emissions. Globally, methane from cattle accounts for four to five percent of total GHG emissions. If seaweed could play even the slightest role in methane reduction, it could have a massive impact on global emissions. How can seaweed possibly reduce methane emissions from livestock? Well, the story starts on a farm in Canada...
Joe Dorgan, a Canadian cattle farmer, noticed that his cows pastured on land with access to the ocean were doing a lot better than those that were landlocked. He discovered that the cows were grazing on seaweed and when he introduced his landlocked herds to the seaweed he noted significant improvements. Dorgan founded North Atlantic Organic to commercialise this seaweed, but regulations required scientific testing. He approached Canadian scientist and researcher, Rob Kinley, to study the seaweed. Kinley reported a 20 percent reduction in methane emissions from the seaweed-eating bovine. Lower methane production by cows means that more energy is being put into muscle and milk development. Cows that eat seaweed emit less methane, produce more muscle and are therefore more efficient at converting energy. Kinley then joined the CSIRO and James Cook University in Australia, who were already testing the effects of seaweed on livestock nutrition.
Kinley and his team found a specific strain of seaweed that grows off the coast of Queensland called Asparagopsis taxiformis. Kinley initially tested it using an artificial rumen that mimics the digestive system of a cow. They found that if this specific seaweed made up only two percent of the cow’s diet it would reduce the methane emitted by a staggering 99 percent. The implications for emission reductions simply from adding this seaweed to a cow’s diet are massive.
Because Asparagopsis taxiformis doesn’t grow in abundance, and is yet to be commercially farmed, it could encounter scalability issues. But it still presents a powerful opportunity. If Asparagopsis taxiformis could be farmed using MPAs and fed to cattle, then we might have found a legitimate solution to combating livestock methane emissions.
