A research team exploring the untapped potential of seaweed farming for carbon sequestration is positioning Taiwan to play a role in offsetting global carbon emissions.

Carbon sequestration is an industry with a global revenue of over US$95 billion, according to the World Bank. Yet it hasn’t exactly trended or hit buzzword status.  

This business is blissfully free from celebrity endorsements, cute mascots, and Hollywood agencies clamoring for film rights – in short, it’s not sexy, nor is it hip. But it is cutting-edge science, and the individuals involved are driven by a profound goal: to save the planet. Arguably, there is little else that carries such immense importance and gravity. 

Annual emissions from fossil fuels have rapidly increased since the middle of the 20th century. In the 1960s, we were burning almost 11 billion tons of carbon dioxide annually. By 2022, that number had more than tripled to an estimated 36.6 billion, according to the Global Carbon Project. As the severity of the situation becomes jarringly apparent, more countries are setting out on journeys toward becoming carbon neutral.  

On January 10, 2023, Taiwan took a leap toward carbon neutrality when the Legislative Yuan passed the Climate Change Response Act. The Act established a legally binding target of no net greenhouse gas emissions by 2050, meaning any emissions would need to be balanced by initiatives to offset them. Such a move sets Taiwan up for the potential to become an important player and advocate in Asia’s climate policy and is a boon to fostering scientific research. 

Capturing carbon from the atmosphere is a way to start reversing our impact on the environment and keeping rising temperatures – and associated effects – to a minimum. From 2020 to 2022, global investment in new carbon dioxide removal capacity totaled around US$200 million, according to an independent report by the University of Oxford. Meanwhile, some US$4 billion has been funneled into publicly funded research and development since 2010. Current carbon capture methods include reforestation and the more expensive and energy-intensive direct air-capture method.  

But there is also a potential new solution – carbon sequestration by seaweed. Like trees, seaweed photosynthesizes, turning sunlight and carbon dioxide into energy. There are many species of seaweed, all of which draw in carbon to build their biomass.  

To qualify for scientists’ definition of long-term carbon storage, seaweed must lock carbon away from the atmosphere for at least 100 years. This can be done by sinking the seaweed into depths of 500 meters or more, becoming buried in sediment, or drifting in deepwater currents. The majority of the seaweed sunk into the deep ocean will eventually decompose back into CO2. However, since water at these depths does not return to the surface for a period ranging between a hundred and a thousand years, the CO2 remains sequestered for a sufficiently long duration. 

In Taiwan, it is Academia Sinica that fronts the conceptualization, associated research, and implementation of seaweed carbon sequestration. The academy’s effort is spearheaded by Abby Ren, associate professor of the Department of Geoscience at National Taiwan University (NTU).  

“We only started in July 2023, modifying abandoned ponds that used to grow abalone,” she says. “We’re growing various types of seaweed to assess growth rates and see which is best suited to Taiwan’s waters.”  

Japan, Korea, Indonesia, and the Philippines all have long-established seaweed farming operations primarily for food and medicinal industries. Ren believes that while Taiwan lacks the same long-term experience with growing seaweed, the island’s unique conditions are advantageous.  

“Seaweed has some characteristics that make it very interesting for Taiwan – it’s a relatively fast-growing marine macroalgae,” says Ren. “And then the eastern side of Taiwan is very deep and fed by the nutrient-rich Kuroshio current, meaning we can both grow and sink any seaweed we farm.” 

Ren and her team are assessing two locations for potential long-term commercial operations. The team is also testing in the ocean, using seven tube nets with around two kilograms of seaweed in each net, placed several hundred meters offshore. “We’re not using a great deal of seaweed because we want to be able to keep a close eye on the growth and ensure we can quantify the carbon flux,” she says. 

As the temperature of ocean surfaces rise and waters become more stratified, the unique characteristics of warm, buoyant water on the surface and cold, dense water deeper down come into play. Given that the ocean depth off Taiwan’s east coast reaches 4,000 meters, these conditions create an ideal environment for long-term deep-sea storage. 

For other commercial avenues, however, there are still challenges. Seaweed growth and harvesting for uses such as food, fertilizer, animal feed, and medicine mainly occurs in shallow water to give farmers easy access to the produce. For Taiwan, this factor presents problems.  

“Unlike aquaculture on land, offshore farming cannot ensure the production of a single species,” says Ren. As a result, offshore-farmed seaweed would be better suited for applications that do not require a single species.” 

Additionally, regardless of the cultivation method – whether on long lines of rope, as is common in most seaweed farms worldwide, or in tube nets – constant monitoring is crucial. This vigilance ensures that the type of seaweed being grown doesn’t become a host to another variety. Still, Ren and her team are exploring the potential of this type of cultivation in Taiwan, and the single species that the team is focusing on has shown promising results in terms of growth and resilience. 

Why not simply plant more trees to sequester carbon? It would be easier than working in the ocean. The answer is simple – land in Taiwan is in high demand, and crops, buildings, and infrastructure projects take up most of the space that isn’t dominated by steep mountains. Additionally, rainfall – or a lack thereof – soil depletion, erosion, and typhoons are all potential problems for forests. However, Ren readily admits that gathering data on land would be much easier than in the ocean, where everything is constantly moving.  

“It’s challenging, but it’s also fascinating for scientific reasons,” says Ren. “I get this opportunity to do a real-world experiment in the ocean – most of the time we do experiments in the lab. But we also recognize there are cha-llenges and uncertainties.”  

In addition to having a unique concept that is proven through solid scientific data, scalability is an essential aspect of any new commercial enterprise. A primary objective of Academia Sinica’s project is to perform rigorous testing and ensure all data is peer-reviewed to certify that the methodology employed can be exported worldwide. 

The price of carbon sequestration by seaweed is subject to production costs and the value of CO2 capture, which in turn is dependent on whether a carbon credit scheme has been implemented. Essentially, a carbon credit system allows a company to purchase carbon credits as a means to offset its carbon emissions, with the goal of achieving carbon neutrality or even a negative carbon footprint over a specified period.  

Carbon credits also have the potential to be traded within systems, a notable example being the European Carbon Credit Market. Taiwan established the Taiwan Carbon Solution Exchange (TCX) last year for this purpose. The first sale on the exchange only included international carbon credits, as regulations governing domestic emission reduction carbon fees are expected to be finalized in the first quarter of 2024. But for Ren and her team, this development provides potential for future funding. 

“We have a lot of interest from investors, but we’re still at the research stage,” says Ren. “We want to prove growth rates, ensure there are no adverse environmental impacts, and quantify how much carbon is being sequestered.”  

Though challenging, the team’s journey is a testament to the power of science and determination to make a significant impact on our planet’s future. As this initiative continues to unfold, it may well pave the way for an era in environmental conservation where seaweed becomes more than just an aquatic plant.