Algae have become one of the spearheads of geoengineering. These aquatic plants are, naturally, one of the lungs of the planet: When they carry out photosynthesis they absorb CO2 from their environment and give us back oxygen that we can breathe. So, the more algae, the better for the planet, right?
Well it depends. The potential of some geoengineering projects may be less than we initially believed, at least that is what some experts who are more critical of these measures consider.
One of the latest controversies has had as its protagonist the planting of algae. These projects have certain parallels with those for the fertilization of ocean waters but represent a separate category. This technique is based on the development of crops of these plants for subsequent discharge into the sea.
To understand the idea, it may be useful to explain the maritime carbon cycle. This cycle begins with photosynthesis carried out by various marine organisms such as the algae themselves. These organisms use carbon for their vital functions, including growth, so they accumulate carbon.
This carbon enters the trophic pyramid, can be consumed by animals and then exhaled back into the atmosphere, but can also end up on the ocean floor, for example through the phenomenon known as marine snow. The increase in biomass and sedimentation on the seabed are therefore two potential carbon sinks to take into account when measuring the evolution of CO2 concentrations in the atmosphere.
The idea behind algae farming projects is a little different: after making these algae grow by feeding on environmental carbon, the plants are dumped into the sea, not to continue growing but to sink directly into the depths and become themselves a carbon sink.
Not all scientists agree that this is a good idea. In a recent article in the magazine One Earthan international group of researchers did a call to establish a moratorium about this practice. The group argued that this practice “is not an ecological, economic or ethical response to climate change mitigation through carbon ‘sequestration’.”
The group indicated that the technique is a distraction from more appropriate techniques and highlighted the lack of scientific knowledge
What could happen? Some reasons to be skeptical are intuitive: for example, it can be expensive to make algae sink because of its low natural density. Another example is the possible ecological impacts that the multiplication of a species in a specific environment may generate, potentially altering the ecological balance in the region.
some buts
There are more issues to take into account. In an article in the magazine ScienceWarren Cornwall addressed some. We must consider, for example, that algae, difference from terrestrial plantsalgae do not directly absorb CO2 from the atmosphere, but rather feed on carbon dioxide from the water.
When aquatic plants absorb the gas, two things can happen: one, that the “decarbonized” water stays on the surface and absorbs carbon from the atmosphere, or that it sinks, losing contact with the atmosphere, which would imply that atmospheric carbon will stay in place.
Algae can also have “carbon losses” that we must take into account. some algae will be consumed by aquatic animalsothers will break up or decompose, returning carbon to the ocean cycle.
Finally, it is also worth remembering that the proposed algae “landfills” are also ecosystems in themselves and it is impossible to know how they would react to the sudden dumping of organic matter.
All these factors do not in themselves imply the invalidity of the technique, but they can make it inefficient. But not taking them into account can lead experts to make wrong decisions, leaning towards options that are not entirely effective or, at least, that are not the most efficient.
There are alternatives. For example, bury these algae in the ground. This is what some projects propose, such as Brilliant Planet, which proposes grow and bury these algae in desert areas. This would avoid some, but not all, of the problems noted above.
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Image | Lachlan Ross
