The Benefits of Cultivating Seaweed

By Cecilia Drury (ESB S3ENA) 

When someone says ‘seaweed,’ what is the first thing you think of? Do you remember how you freak out when slimy fronds of seaweed wrap themselves around your ankles when you go swimming? Do you conjure up images of mystical underwater forests? Or does the word seaweed just make you want to order sushi? Everyone can relate to one or all the above, but we need to start recalibrating how we think of this sea vegetable, because seaweed is also a valuable ally in our fight against climate change in more ways than one. 


Over the last couple of hundred years, livestock farming has started to pose a significant issue to the environment, causing air and water pollution and contributing to around 15% of global greenhouse gas emissions. Due to the increasingly high demand for meat and dairy, livestock farms are being expanded progressively, with around 10,000 acres of woodland (about half the area of Manhattan) being cleared worldwide every day to make way for animal grazing fields, that would, ironically, otherwise be extracting the carbon dioxide produced by farms from the air.  

Cattle themselves are also bad for the environment, as when they inevitably burp, they release considerable amounts of methane into the atmosphere, produced by a digestive process called ‘enteric fermentation’ where microbes in the upper stomach chamber predigest starches and fibers, releasing gases when they exhale. Moreover, one cow produces about 37 kilos of feces every day and their waste either ends up littered all over farms or is disposed of in bodies of water. Over time, this water becomes contaminated, resulting in nitrate contamination because cattle feces contain a lot of nitrogen. This consequently prevents any wildlife from living in this water, affecting the food webs in the surrounding areas. 

However, there is an obvious solution to the problem. As is with many problems humankind has been faced with, nature has provided us with a solution that has been under our noses the entire time. Seaweed. This macroalgae is completely underrated, seaweed is not only a natural carbon dioxide neutraliser, but is equally environmentally beneficial to livestock agriculture and our own health. It is also an effective water purifier that does not require pesticides or fresh water to grow, making it the perfect place for marine biodiversity to thrive.  

So how is seaweed going to drop cows’ methane emissions?  

Researchers have proved that by including a supplement of as little as 80g of dried asparagopsis armata (a type of feathery red macroalgae) to dairy cows’ diets it reduces their methane emissions by as much as 85%, which not only scales down their methane footprint, but also means that the cattle can put more energy into milk development. An added benefit is that this new seasoning in the cows’ fodder does not seem to affect the taste of their produce. 


What is carbon sequestering and how does it work? The term ‘carbon sequestration’ refers to a process (natural or artificial) in which carbon dioxide is extracted from the atmosphere and stored in a solid or liquid form. CO2 can be stored in the Earth under our feet, but also buried in layers of sediments deep in the ocean over thousands of years. Theoretically, unless disturbed, the carbon dioxide should stay sequestered in the ground, but as humans excavate the ground for fossil fuels, it releases these stores of CO2 into the air, polluting the atmosphere and adding to the greenhouse gases responsible for global warming.  

The ocean is one of our greatest allies in our fight against the greenhouse effect and global warming. The ocean creates a huge carbon sink (‘a forest, ocean, or other natural environment viewed in terms of its ability to absorb carbon dioxide from the atmosphere.’) which is, according to a 1994 – 2007 study, capable of absorbing 1/3 more carbon dioxide than all terrestrial ecosystems combined. But the ocean itself is not alone. A vast variety of its inhabitants naturally help us restore the planet, namely kelp and phytoplankton.  

Kelp has an astoundingly fast growth rate of up to two feet a day. Because of this, kelp can afford to export a large portion of its biomass into the ocean, to put down more roots and hopefully start new underwater forests and as it undertakes photosynthesis, it naturally absorbs CO2 to produce its nutrients, and releases O2 into the atmosphere. If humans could take advantage of this, it would play an even bigger part in solving the climate crisis. 

Phytoplankton are also useful to us. Phytoplankton is a broad term. They can be bacteria, protists but most are single-celled plants. Phytoplankton are mainly producers, providing their own nutrients through photosynthesis, sequestering CO2 and releasing oxygen, but some also consume other microscopic organisms as another source of energy. Like kelp, phytoplankton also grows incredibly fast when conditions are right, and when this happens in a population of phytoplankton it is known as a ‘bloom’, which can be seen easily from satellite images. These blooms only last around a week or two, but with the astronomical numbers of plankton all photosynthesizing every minute of the day, they can sequester equally vast amounts of CO2. 

All these carbon-sequestering solutions just prove that, although science and technology will play an equally huge role in solving the climate crisis, sometimes one has to turn to mother nature, because if you look hard enough, there is always a solution to be found that was there all along.