We have heard a lot about greenhouse gases in recent decades. While right now CO2 emission represents a threat to the planet's climate stability (anthropocentric stability), it is not a new feature in the Earth's atmosphere. Co2 has maintained a self-regulating equilibrium through geological and astronomical events, which manifest a cyclical character. This has buffered too many drastic changes in the earth's climate, which have ultimately preserved life.
Not without difficulty, since there were also mass extinctions resulting from ocean acidification (the cause of which is also found in CO2 suddenly expelled by volcanoes, which dissolves in water into carbonic acid by Le Chatelier's principle) and glaciations (of complex origin, although mainly due to Milanković's cycles).
The current problem is not that the climate is not changing, because it will change eventually. The problem is that it is changing prematurely due to human action. While these changes occur in incredibly long cycles for the human scale, the contribution of CO2 emissions through the burning of fossil fuels has been exponential since the 19th century and the industrial revolution.
We have practically doubled CO2 ppm since 1950, which is extremely worrying. The reason why this is a disruption of the functioning of natural geological cycles is because these fuels had been sheltered from the atmosphere. This is where biotechnological science comes in, using the photosynthetic mechanism to try to rescue that anthropogenic atmospheric CO2.
Plants or microorganisms?
Despite what is commonly said, the Amazon is not as effective a lung for the world as are the oceans full of diatoms. Recent studies have in fact concluded that the damaged forest, both natural and human-caused is now worsening climate change.
The polite does not take away the brave, and all the biomass we see from trees and plants comes from the carboxylase action and photolysis of water, i.e., its anabolism is due to the ability to integrate atmospheric CO2. It is an incredibly ingenious mechanism that has allowed the biological diversity we enjoy on Earth today. Although it must be said that photosynthetic performance in terrestrial plants leaves much to be desired, so it is better to design a system using microorganisms to capture atmospheric CO2.
The advantages of using them are many. Starting with scalability due to their small size, the quadratic/cube law favors microorganisms, since they have more surface area in relation to their volume, so they are in greater contact with atmospheric gases. Their reproduction is much faster, and they are easily genetically editable, since, in general, their physiology is several orders of magnitude simpler. In addition, many photosynthetic organisms are really easy to cultivate, unlike plants. For all these reasons, microorganisms have been chosen as the cutting edge of atmospheric CO2 recovery. There are several ways to use them, and here are some very promising ones.
Biofuels are an option that takes full advantage of the knowledge of living beings and the planet's geochemical cycles. Although they are fossil fuels and their burning produces the same CO2 (in terms of energy released), they are considered carbon-neutral. This is possible thanks to the very concept of biofuel. Instead of removing material full of carbonaceous skeletons - the product of incomplete oxidation - from the bowels of the lithosphere, this material is produced from the CO2 we have already released into the atmosphere by burning it, allowing us to recycle this CO2 continuously by adding energy. That energy addition is mostly solar, which is where the photons that excite the photosystems in the thylakoid membrane come from. This ingenious way of understanding combustion to produce energy is destined to be a key step in the transition of our energy consumption model, replacing conventional fossil fuels.
Of course, optimal biofuels do not yet exist, and the strategies to increase their performance and scalability are many since these are biological systems that have a great deal of variability and possible routes of action. Liquid, gaseous and solid wastes are also generated, most of which are easily recyclable for this or other industries. Generating a circular economy more than interesting for the world’s future.
In physiology, the parts of the plant where photoassimilates accumulate are usually referred to as "sinks". This concept is important because there is another way to use microorganisms other than biofuel to recover CO2. It simply consists of the accumulation of carbon dioxide in the biomass, but it is not intended to be burned, but rather to solve other problems, such as soil or chemical industry pollution. Many millionaires are betting on developing the formula for this form of CO2 fixation. It turns out that there are organisms that are not even photosynthetic, such as Nitrospira that can fix CO2 by a rather rare molecular mechanism in biology, called the reverse Krebs Cycle. This is just one example of the thousands of microbes that have evolved to take advantage of a fundamental feature of our planet: that the most basic food is ubiquitously found in the air and water!
Current Research & Start-ups
One such curious and promising startup is Air Protein, an initiative that has really taken advantage of NASA's scientific efforts. The idea is to use CO2 from the atmosphere to produce protein without the photosynthetic mechanism, but using hydrogenotrophs, a type of microorganisms found in bitumen.
This trend is a hotbed of ideas right now. There are too many ideas, and many of them will necessarily end up disappearing because they are ineffective or because of the competition in the niche. All public and private efforts are remarkable, although perhaps not enough in many countries, as major changes in global economic models such as ours are complicated.