Everybody talks about the rain forests and their importance for world climate in general and their capacity for CO2 fixation in particular.
What is less well known is that there are forests under water which are just as important when it comes to CO2 fixation and which are just as under threat as their counterparts above the water line, the kelp forests.
Algae...
... are an enormously diverse class of species in terms of size, distribution, and (possible) uses.
Their size ranges from a few micrometers in the case of micro-algae which are found in the plankton to several dozen meters in the case of the giant kelp.
They are found all around the world, mainly in sub-aquatic environments (both fresh and sea-water), some in wet environments (such as beaches), and some on land.
Their common feature is that they are photosynthetic, i.e. they consume carbon dioxide to produce oxygen.
This way the kelp forests and algae help to maintain the ecological equilibrium in the various habitats.
However, these kelp forest are under threat from pollution and catastrophic storms.
What are algae used for?
A potential solution to the world food crisis?
Algae have been farmed as food for thousands of years.[1]
While seaweed is somewhat frowned upon in Europe, especially in Asia algae form an important part of the cuisine.
Probably the best known example for this are the dark green mats called nori that sushi is rolled in.
Algae contain many vitamins (including Vitamin C) and trace elements such as iodine, potassium, magnesium, and calcium.
The use of algae as food is seen by some as a potential solution to the world food crisis, and people like the World Economic Forum are promoting this idea.[2]
Feeding everybody on this world a daily steak is not sustainable and other food sources will have to be found, not just in terms of calories but also in terms of nutritional value.
For example, fish are an excellent source of omega-3 fatty acids.
Here the proponents of seaweed-based food see a substantial advantage.
The argument goes like this: Fish are good food, both calorifically and nutritionally.
Where do the fish get their carbon from (to form things like the aforementioned omega-3 fatty acids)?
And the answer is: From small algae.
So, why not cut out the middle-fish and eat algae directly?[3]
What else?
There are many other uses for algae and seaweed already in use or under active research.
Remediation
One is the use of sea-weed in the remediation of contaminated land or water body.
The general principle here is to grow plants in contaminated areas which extract and incorporate the contaminants in question into their biomass.
The plants are then harvested and treated appropriately, leaving the once contaminated area clean (or, at least, less contaminated).
Researchers in California have investigated the use of algae as "hyper-accumulators" in the remediation of selenium contaminated soils.[4]
The contamination resulted from the leaching of selenium compounds from the soil caused by repeated irrigation and evaporation.
The researchers found algae to sequester the selenium compounds and transform them into less harmful ones.
A related use is to grow algae in basins that collect the run-off from agricultural fields.
The water from fields is often very rich in (artificial) fertilisers which can lead to uncontrolled and detrimental algae growth in fresh water bodies such as rivers and lakes (eutrophication).
Catching the fertiliser run off and using it to grow harvestable algae is therefore a form of controlled eutrophication.
Healthcare industry
Another use of algae is the extraction of compounds used in the healthcare industry.
Carrageenans, alginates, and galactans derived from algae have been investigated as agents against numerous diseases ranging from influenza to HIV.[5]
One of the most spectacular (literally) projects is undertaken at the Institut de la vision in France, where researchers are working on introducing light sensitive cells derived from algae into the retina of blind patients in order to restore their vision.[6]
Fuel source
Probably the most sizeable possible application of algae (along with their use as food) is their use as a fuel source.
Algae produce oils which can be extracted and used as fuel or the biomass can be converted into bio-gas in biorefineries.
The advantage of producing fuel from algae is that it does not require farming land. Instead, the algae can be grown in areas unsuitable for other agri- or aquacultural activities such as brackish water bodies.
In particular, it can be used in tandem with remediation projects as outlined above.
Algae-derived fuel is carbon-neutral in nature as their combustion only releases the amount of CO2 previously consumed by the algae in photosynthesis.
At present, however, producing fuel in this way is not yet economically viable and more research has to be undertaken in order to reduce costs.
Their photosynthetic activity makes algae also a promising candidate for Carbon Capture and Utilisation (CCU) projects.
The French energy company Suez is running an experimental CO2 scrubber in the Parisian suburb of Poissy and report promising results.[7]
In addition, just as plastics can be made from fossil fuels, they can be made from algae-derived fuels as well.
Is there any challenges?
It goes without saying that where there's light there's also shadow.
Some areas where algae are traditionally grown are close to mangrove forests.
Depending on the practices used by the algae farmers this can have detrimental effects on these mangrove forests with all the rat's tail of consequences that follow when an important part of an ecosystem is damaged.
So, could algae contribute to a more sustainable future?
The answer is yes.
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01) Buschmann, A.H. et al., European Journal of Phycology, 2017, 54 (2), 391
02) https://www.weforum.org/agenda/2017/10/how-marine-algae-could-help-feed-the-world, last accessed 2021.06.13
03) Moomaw, W. et al., Industrial Biotechnology, 2017, 234
04) Lin, Z.-Q. et al., Journal of Environmental Quality, 2002, 31, 2104
05) https://www.researchgate.net/profile/Bitu-Gartia/publication/325924731_The_Role_of_Algae_in_Pharmaceutical_Development/links/5b2ce207a6fdcc8506bd145f/The-Role-of-Algae-in-Pharmaceutical-Development.pdf, last accessed 2021.06.13
06) https://www.institut-vision.org/en/news1/214-gen-armd-3.html, last accessed 2021.06.13
07) https://www.suez.com/en/who-we-are/innovating-for-the-future/pollution-and-carbon-sink, last accessed 2021.06.13
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