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“Comparable to a 40-meter pizza”: the cultivation of seaweed that has the potential to provide sustenance for everyone – with associated expenses.


A large white platform positioned on the Pacific Ocean’s surface is facing a smaller platform located some distance away. Sam Donohue is standing on the larger platform, while Gorio Pepito stands on the smaller one. They both press buttons, causing a high-pitched whirring noise to begin.

Pepito and Donohue stop pressing the buttons, causing the whirring noise to cease. They use a walkie-talkie to communicate that everything is fine. A crab appears on the large platform, which Donohue explains is their pet. They press the buttons once more.

Initially, there is no activity, but suddenly an object arises on top of the water resembling the hump of a whale. It is a sizable circle with numerous lines extending in a star pattern from its center.

The seaweed is illuminated by the early morning sun. Four dolphins gracefully emerge from the water, as if they were summoned for this exact moment.

According to his website, Brian von Herzen has a plan to “save the Earth”. As the founder and director of the Climate Foundation, Von Herzen aims to use advanced platforms to replenish the oceans with seaweed, which would address multiple issues at once: providing food for humanity, restoring ecosystems, and resolving the climate crisis.

2) from the atmosphere

In the previous year, the Climate Foundation was the recipient of the $1 million Milestone award from the Xprize, which was backed by Elon Musk’s foundation. Fourteen other teams also participated in the competition. Currently, these teams are vying to determine which one can successfully remove the most carbon dioxide (CO2) from the atmosphere.2

“The reward for removing carbon dioxide from the atmosphere is $100 million, which Musk has dubbed as the biggest prize incentive in history.”

The elephant in the blue carbon room

The experimental ring can be found approximately 20 miles north of Cebu City in the Philippines. Von Herzen explained the structure as a pizza with twelve slices and a diameter of 40 meters. He had previously described the ring and also suggested appropriate snorkelling equipment for the trip. To him, being in the ring is reminiscent of being in space and performing tasks on a space station. Looking downwards, one can see a depth of 1,000 feet (300 meters) of blue water.

The advanced ring has the appearance of an ancient shipwreck: it has been taken over by the sea. Along its edges, numerous goose barnacles have grown, with their flaps moving like fans.

Ropes covered in seaweed. A person in fins and mask can be seen in the background


At a depth of 120 meters, the water was a cooler 24 degrees Celsius (75 degrees Fahrenheit) compared to the surface temperature of about 30 degrees Celsius. The water at this depth was also rich in nutrients, which are essential for the growth of seaweed. However, Pepito and Donohue must retrieve the ring every morning because the seaweed also requires light for growth. Light is used by the seaweed for photosynthesis of CO2.22

The Climate Foundation is working hard to assist seaweed in converting carbon dioxide into sugar and oxygen, in order to aid in CO2 storage.2.


The IPCC states that in order to mitigate global warming, it is necessary to find ways to sequester CO2. These methods may include planting trees, using crushed rocks to absorb CO2, capturing it from industrial emissions and storing it underground, or cultivating large quantities of seaweed. Each method has potential risks and uncertainties regarding the length of time it can effectively store CO2.2.

Since the pandemic, Von Herzen has not traveled to the Philippines rig. Instead, he communicates from Australia, where he currently resides, through video calls.

According to the speaker, each significant ocean region has a designated exclusive economic zone that extends a minimum of 200 nautical miles from the shore. The accompanying visual shows fish swimming among seaweed. These zones are primarily comprised of uninhabited waters and are often significantly deeper than 300ft (90 meters). Marine permaculture is allowed in all areas deeper than 300ft.

Algae are often referred to as the “elephant in the room” when it comes to blue carbon, due to their rapid growth. For instance, giant kelp can grow up to 50cm in a single day. The seaweed grown by The Climate Foundation is said to grow up to three times faster than surface seaweed, according to Von Herzen.

He suggests that we have the potential to shift the way we interact with the ocean, moving away from taking resources and towards restoring them.

There are only two issues to consider: seaweed, similar to coral, is unable to tolerate high water temperatures. Additionally, the entire endeavor must be profitable.

The sequence of events is hot followed by cold.

For generations, Filipinos have been cultivating seaweed on the shores of their archipelago nation, consisting of over 7,600 islands. They employ a straightforward method: fastening plastic ribbons and attaching seedlings (such as red gracilaria, green caulerpa, or brown gulf seaweed, also called sargassum) to them. They also utilize empty plastic bottles to keep the seaweed afloat.

A young man with a mask and snorkel sits on a boat holding a clump of seaweed

Over one million individuals across the country utilize this method to cultivate seaweed. A farm measuring one hectare could generate approximately €140 (£120) every 45 days. A portion of the harvested seaweed is sold in vibrant baskets at fish markets, showcased with LED lights and kept fresh by fans. However, the most profitable aspect of this industry is the exportation of carrageenan, a food additive extracted from red seaweed. This widely used thickener and stabilizer, commonly known as E407, can be found in everyday products such as toothpaste, candy, spreads, and cream.

The ocean’s temperature has risen to a point where seaweed is unable to thrive, leading to stunted growth or the development of “ice-ice” disease, similar to coral bleaching. In the Philippines, seaweed production has decreased by 20% since 2011 due to these conditions. Additionally, the warmer temperatures prevent the natural mixing of nutrient-rich deep water with surface water, known as upwelling.

There are two choices available: either relocate the seaweed to the deeper water or bring the deeper water to the seaweed.

The second approach is widely debated and known as “artificial upwelling,” which falls under the category of geoengineering. Von Herzen states that they have conducted trials with both methods, but have ultimately decided to focus on the first one, which he refers to as “deep cycling.”

Their creative approach to DIY is impressive. They store energy from the solar panels in 56 motorbike batteries, use discarded car-coolant tanks filled with gas as buoys at the edges of the ring, and have repurposed a maize mill to grind harvested seaweed (although it began to rust from exposure to seawater, they are rebuilding the funnel with stainless steel).

Unfortunately, things don’t always go as planned. Most recently, the team was caught off guard by a thunderstorm and, without a lightning rod, had to take a leap into the water from the platform.

“We utilize only recycled, previously used, or repurposed materials,” states 37-year-old Donohue, who is the head of engineering for the Australian branch. Prior to unexpectedly crossing paths with Von Herzen in the Philippines, he had experience working in gold and silver mines across the globe.

“Ever since I met Brian, I’ve had the chance to make a positive impact on the environment,” he explains. Amidst the workers, there are eight dogs and five puppies that are constantly moving around, often found nestled in toolboxes and fishing nets.

In the nearby island of Bohol, the Climate Foundation utilizes seaweed to create fertilizer and then sells it to nearby rice and fish farmers.

According to Crestito Garcia, a farmer who specializes in aquaculture, he incorporates seaweed into the diet of his fish and shrimp, resulting in improved harvests. Gliceria Limbaga also shares similar success, stating that the use of seaweed fertilizer on her rice farm has eliminated the need for pesticides as it effectively deters insects.

In the past, she utilized a man-made nitrogen fertilizer that not only damages and acidifies the soil, but also contributes to 5% of the world’s greenhouse gas emissions, as stated by Cambridge University researchers.

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According to Pepe Tubal, a member of the foundation, there is a shortage of rice production in the Philippines. He believes that if all rice farmers use their product and increase their yields, the country would no longer need to import rice.

He briefly mentions that the foundation has plans for multiple artificial upwelling initiatives in the area.

Two Filipinas prepare a seaweed at a market stall

Upon further questioning, Donohue and Von Herzen conceded that their plan involves using lengthy pipes to bring water to the surface. However, Von Herzen contests the use of the term “artificial,” stating that they are actually restoring a natural process on a regional scale.

On the other hand, some, such as the Heinrich Böll Foundation, a German think tank, argue that it is incorrect and risky to equate intricate natural upwelling occurrences with man-made ones.


The ocean’s stratification is beneficial as it allows for the storage of a significant quantity of CO2.2 in the depths,” says Andreas Oschlies, head of the biogeochemical modelling research unit at GEOMAR Helmholtz Centre for Ocean Research Kiel.

2 into the22 gets

Upon implementation of artificial upwelling in climate models, it is demonstrated that a significant amount of CO2 is generated.2

“The nutrients are being pumped into it.”


After being released into the atmosphere, this could potentially counter the increase in newly accumulated CO2.2

According to Oschlies, the seaweeds are absorbing certain important nutrients that are lacking in another location.

A bright green field of lush rice plants with a sign advertising “BIG row foliar fertiliser”

There may be a seaweed farmer in one location making a substantial income, but in a neighboring area or even hundreds of miles away, fishermen are experiencing a decrease in their catch due to reduced seaweed growth caused by a lack of nutrients. As a result, there are also fewer fish available.

The issues with upwelling are numerous. While the deep water cools the atmosphere, it also pushes down warmer surface water, potentially causing harm to submerged plants and animals.

This could lead to the growth of harmful, toxic algae, deplete oxygen levels in the water, and disrupt ocean currents, which may impact weather conditions.


Some marine creatures living in seaweed forests, which secrete CO2 through the process of forming calcium carbonate shells, can experience negative impacts despite the initial positive effect.22 emissions

This can eliminate 10-30% of the carbon dioxide emissions produced by the seaweed.2

According to Oschlies, a member of a global panel that advises the UN, the approach has minimal potential for carbon storage and carries a significant risk of adverse effects. He further states, “This method has limited uptake.”

Von Herzen is aware of these dangers. He acknowledges that our actions have already disrupted the Earth’s natural state. Whether we enjoy it or not, every time we use a fossil fuel-powered plane or drive a car, we are essentially participating in geoengineering. Despite being aware of the consequences of increasing carbon emissions, we continue to make choices that contribute to it.

According to him, it is riskier to knowingly contribute to the destruction of the planet than attempting to preserve it. He suggests that, in the worst case scenario, if there are issues with the upwelling, shutting off the pumps would restore the previous state.

2 in the

Regrettably, detractors argue that it is not as simple as it seems. Models conducted by GEOMAR, a marine research facility in Kiel, Germany, revealed that the pumps should not be halted once they are initiated – as this would ultimately result in an increase of CO2 in the atmosphere.2

The temperatures were higher than normal due to the activation of the pumps. Oschlies likens this to the story of the Sorcerer’s Apprentice, who is unable to banish the spirits he conjures.

The reward for saving the world should be worth it.

In the future, the Climate Foundation aims to collaborate with seaweed farmers whose crops are being negatively affected by increasing ocean temperatures. The proposed solution involves leasing systems from the Climate Foundation to these farmers, who will then sell their entire harvest to the organization. The harvested seaweed will be used to create biofertilizer and carrageenan.

A mass of small leaves in various shades of green

2 temporarily

Similar to a land forest, seaweed merely holds onto CO2 for a limited time.22 as possible.
As long as it remains uncollected and treated, the goal is to extract the maximum amount of CO2.22

The Climate Foundation would need to allow seaweed to sink to the seabed in order to remove as much CO2 from the atmosphere as possible. Once at the seabed, the seaweed would either be consumed, decomposed, or buried in sediment. The CO2 removal process is more effective the deeper the seaweed sinks.2
The platform off the coast of Cebu is located at a depth of 220 metres and takes approximately 100 years to reach that depth. At a depth of 900 metres, it takes 1,000 years to reach that depth.


If the seaweed is allowed to settle at the ocean floor, it cannot generate income. The Climate Foundation has been exploring ways to make this financially viable since 2010, such as selling carbon-removal certificates. However, they determined that it would not be profitable on its own. Therefore, only naturally falling seaweed (compared to leaves falling from trees, according to the Climate Foundation) will absorb CO2.2

In the extended period, Von Herzen approximates that this accounts for roughly 20-40% of the harvest.

The Cebu team dons fresh T-shirts featuring an upward-growing seaweed image, with the words “Food security, ecosystems, carbon removal” written on the back in that order. Is it appropriate for climate to be the last concern? “Our priority is to ensure that we can sustainably feed humanity during the climate-affected years ahead,” says Von Herzen.

“We have the ability to determine the amount of seaweed that submerges from the platform. We are able to quantify the reduction of carbon and avoided emissions resulting from agricultural intervention, and record these advantages. However, it is crucial that we also address food security and promote ecosystem restoration in order to establish sustainable environments on both land and sea for the sake of future generations.”

When asked about the community’s response to the Climate Foundation, a staff member stated, “They seem to believe we are involved in the seaweed industry.”

On November 17, 2023, this article was updated to specify that the prototype ring is not composed of metal. A previous version also incorrectly stated that the Carbon Foundation had sold carbon-offsetting certificates, when in reality they had only explored the sale of carbon-removal certificates.

A version of this tale is also featured in the German weekly paper Der Freitag.

Source: theguardian.com