The role of marine vegetation as a sink for atmospheric carbon has been well recognized. Angiosperm-based habitats, such as mangrove forests, intertidal salt marshes, and coastal meadows are recognized as extremely important carbon reservoirs; it is estimated marine primary producers contribute to over half of the worlds carbon fixation and account for as much as 71% of all carbon storage (6, 5). However, marine macroalgae have been largely excluded from discussions of marine carbon sinks, and only recently have they been recognized for their carbon sequestration potential (6). Recently, Scientists from The University of Technology, Sydney and Deak University used thermal analysis to demonstrate that the structure and cell walls of seaweed make it extremely stable and thus prove its potential as a marine carbon sink (11). They reported, “Until now, seaweeds have been thought to break down rapidly and therefore not be significant contributors to long-term carbon sequestration; however, what we have shown is that not all seaweeds are equal and some show great potential for long-term sequestration” (10).
As a result of these and other recent findings, the topic of seaweed farming has gained immense traction within the environmental field as an extremely beneficial potential for climate change mitigation. Seaweed farming is currently a global multi-billion dollar industry, with more than 25 million metric tonnes farmed annually, mostly in the developing world (1). However, research is just beginning to recognize the great environmental benefits of seaweed aquaculture, and there is now a growing trend of seaweed farming in the U.S as a sustainable agricultural initiative. In 2017, acclaimed scientist and author Tim Flannery published Sunlight and Seaweed: An Argument For How To Feed, Power, and Clean Up the World, which argues that the successful production of seaweed can help solve many major issues facing the globe, such as climate change, food production, and toxic pollution (4). It’s interest comes from the fact that Seaweed plays a huge role in carbon sequestration, has a low/positive ecological footprint, and grows extremely quickly. In this post, I outline the potential of macroalgae in climate change mitigation, outline some of the other environmental, social, and economic benefits of seaweed farming, and address some of the concerns of the growing industry.
Macroalgae and Climate Change Mitigation
Macroalgae and seaweed farming have the potential to contribute greatly to climate change mitigation in two ways: (a) as a “blue carbon” sink and (b) by reducing dependency on fossil fuels. Macroalgae sequester atmospheric CO2 through primary production near the ocean’s surfaces and then deposit that carbon in their sediments on the ocean floor (2). Additionally, many people are currently discussing the possibility of using seaweed as a biofuel. This could potentially reduce fossil fuel dependency by providing a sustainable source of biofuels (1). This would also take pressure off of terrestrial sources of biofuels, such as canola from palm and bioethanol from sugarcane and corn, which are having severe ecological and social costs (1).
In a comprehensive study in the Journal of European Federation of Chemical Engineering, it is estimated that if 9% of the world’s ocean surface was used for seaweed farming, it could produce 12 gigatonnes of biofuel, and remove 53 billion tonnes of CO2 per year from the atmosphere. (3)
Additional Benefits of Seaweed Farming
- Improves local ecosystem health
- Reduces the effects of ocean acidification and de-oxygenation (6)
- Increases ocean primary productivity and biodiversity (6)
- Provides important habitat for fish and shellfish
- Seaweed used as livestock feed reduces methane release from cows by up to 20%-90%. (4).
- Grows 30 to 60 times the rate of land-based plants (12)
- Has diversified economic market potential:
- Human consumption, livestock consumption, cosmetics, pharmaceuticals, fertilizers, biofuels and more.
- Has reduced overfishing and dependency on fisheries in coastal nations in developing nations (1)
- In many areas, women are the primary farmers of seaweed, which has given economic independence and opportunity to women (1)
Concerns of a Growing Industry
- Limited availability of suitable areas and competition (3)
- The need for engineering systems capable of coping with rough ocean conditions (3)
- Unregulated seaweed farming has the potential to lead to reduction of genetic diversity of native seaweed stocks and harm local environments as a result of unfavorable practices such as mono-cropping and the illegal use of algicides/pesticides (1)
- Most of the current seaweed aquaculture industry is taking place in developing nations, which often have little/no regulations which could lead to exploitation of both people and environments (1)
Macroalgae is an important contributor to “blue carbon”, and today seaweed farming is seen as an extremely feasible tool for climate change mitigation and adaptation. Since the 1950’s, seaweed farming has increased exponentially, primarily because of market opportunities, and the seaweed aquaculture industry is already delivering some of the many benefits listed above. However, we have identified possible limitations and concerns regarding the fast-growing industry. What does the future look like for seaweed farming, and can we successfully utilize this natural resource to help sequester anthropogenic carbon emissions, reduce ocean acidification, clean up local ocean ecosystems, provide important ocean habitats, and provide a livelihood to many coastal communities?
- Braun, David Maxwell. 2016. Booming Seaweed Farming Exposes Producers and Environment to Risks, Experts Warn. National Geographic Changing Planet.Web. Retrieved from https://blog.nationalgeographic.org/2016/09/03/booming-seaweed-farming-exposes-producers-and-environment-to-risks-experts-warn/
- Chung, I.K., Beardall, J., Mehta, S. et al. J Appl Phycol (2011) 23: 877. https://doi.org/10.1007/s10811-010-9604-9
- De Ramon N’Yeurt, Antoine & P. Chynoweth, David & Capron, Mark & Stewart, Jim & A. Hasan, Mohammed. (2012). Negative Carbon Via Ocean Afforestation. Process Safety and Environmental Protection. 90. 467-474. 10.1016/j.psep.2012.10.008.
- Battaglia, Michael. 2016. Seaweed could hold the key to cutting methane emissions from cow burps. The Conversation. Web. Retrieved from https://theconversation.com/seaweed-could-hold-the-key-to-cutting-methane-emissions- rom-cow-burps-66498.
- Duarte Carlos M., Wu Jiaping, Xiao Xi, Bruhn Annette, Krause-Jensen Dorte. 2017. Can Seaweed Farming Play a Role in Climate Change Mitigation and Adaptation? Frontiers in Marine Science, Vol. 4. 10.3389/fmars.2017.00100 Retrieved from https://www.frontiersin.org/articles/10.3389/fmars.2017.00100/full
- Duarte, C. M., Middelburg, J. & Caraco, N. 2005. Major role of marine vegetation on the oceanic carbon cycle. Biogeosciences 2, 1–8.
- Flannery, Tim. 2017. How farming giant seaweed can feed fish and fix the climate. The Conversation. Web.
- Mosbergen, Dominique. 2016. Seaweed Not Green Enough, UN Researchers Warn. Huffington Post. Web.
- Trevathan-Tackett, S. M., Kelleway, J., Macreadie, P. I., Beardall, J., Ralph, P. and Bellgrove, A. (2015), Comparison of marine macrophytes for their contributions to blue carbon sequestration. Ecology, 96: 3043–3057. doi:10.1890/15-0149.1
- University of Technology, Sydney (UTS). 2015. Study Backs Seaweed’s Carbon Capturing Potential. PhysOrg. Retrieved from https://phys.org/news/2015-05-seaweed-carbon-capturing-potential.html
- Climate Council. 2016. How seaweed can kelp us tackle climate change. Web. Retrieved from https://www.climatecouncil.org.au/seaweed-climate-change.