Trees are made of air. Yes, you heard correctly. More than half the weight of a tree, not counting the water in it, comes from the air we breathe.
Today we're going to find out why carbon is nature's battery and what we can do to keep this battery from running out. And who is with us today is Volkswagen, it is the car manufacturer that you already know and that will support our series in which we will discuss a little bit about decarbonization, renewable energies and some technologies that will change a lot the things that we have seen around. Carbon is the fourth most abundant chemical element in the universe and it is essential for life as we know it.
Because it can make connections with several other chemical elements and it can also form huge and complex molecules, like DNA, proteins, which carry out the chemical reactions that keep us alive. But carbon is not just found in living beings, no. It also exists in some rocks and in the atmosphere, in the form of carbon dioxide, or CO2, which I'm representing here with these little balls.
One carbon atom and two oxygen atoms. And look how cool, the plants take carbon dioxide out of the atmosphere and use the sun's energy to transform this invisible gas, kind of dull, into useful things for them. Both in building their bodies, with wood, for example, and to store energy like sugars.
And they do this through a process called photosynthesis. And the name says it all, photo, from light, as in photography, for example, and synthesis means joining. If we could look at photosynthesis very closely, we would see that the plant takes several molecules of carbon dioxide and several molecules of water and transforms it into a glucose molecule, which is a type of sugar that it can use later on.
So here, you can already see that the air has been turned into sugar. And in photosynthesis, oxygen is also generated, O2, what we breathe. This means that photosynthesis is also very useful for generating the oxygen that living things depend on to survive.
One very important thing here is that this glucose molecule has much more energy stored in it than the water and carbon dioxide molecules that formed glucose. And that energy is stored in the bonds that exist here in glucose. But where does all this energy come from?
From the light of the Sun. To show in practice how plants manage to take carbon dioxide from the air and transform it into sugar, we have prepared a very cool experiment here. So, if we take a little plant like this one here that is totally healthy, it stayed there in the sun and everything, will we be able to detect the sugar that is in the plant?
Does it get sweet? Hmm, it doesn't quite work like that. As soon as glucose is formed in the plant, it turns into starch to become an energy reserve.
But the cool thing is that we can detect starch using a very simple test. Iodine reacts with it, giving it a very characteristic dark blue color. To test if there really is starch in the leaf, I'm going to take a healthy leaf, put it for 30 seconds in boiling water, then about 10 minutes in boiling alcohol in a water bath.
It is important to do this in a water bath and with the fire turned off because alcohol is flammable. And the alcohol manages to remove chlorophyll, which gives the leaf its green color, and, therefore, it turns white like that and this will prevent the color from disturbing us to see what is happening in the test. Then, we put it for another 10 seconds in boiling water and drip four drops of iodine on top.
And as we had imagined, the result is positive. And we did the same test with a little plant that was completely in the dark for two days, that is, it hasn't done photosynthesis lately. And guess what?
The result is negative. OK, we've already managed to show that the plant can store energy from photosynthesis in the form of starch and that, for that, it needs light. Now would it be possible for us to know if the carbon that is in the starch really came from the carbon dioxide in the air?
There's a way to know, yes. We just take carbon dioxide out of the air. And there's a chemical way to do it.
So, we are going to use two identical plants that have been left in the dark for two days, that is, they have zero starch. Then, we're going to put each one of them in a closed pot with a beaker on the side. In one of the beakers, we will put water, which will serve as a control, and in the other, we will put caustic soda because it chemically absorbs all carbon dioxide from the air that is inside the pot.
We left these pots in the sun for two days and, after that, we disassembled the experiment and repeated the same thing that we had already done to test the starch. And this was the result. In the plant that was in the control pot with water, photosynthesis was able to take place and, therefore, the plant replenished its starch stock.
But in the plant that was in the pot with the caustic soda, we see that it has much less starch. Because without carbon dioxide, the plant cannot carry out photosynthesis. How cool!
With this experiment, we saw that photosynthesis only happens when there is carbon dioxide and that the starch that we are used to seeing as a white powder, which is a solid thing, really comes from carbon dioxide which is in the air. Now an important question. How does the plant make use of the energy contained in that glucose molecule?
Does it plug a wire here and get electricity? No, the plant will do practically the opposite of photosynthesis. So, it takes the glucose molecule, takes the oxygen from the air, makes the glucose react with the oxygen and in doing so it manages to break these glucose bonds and, in the end, do you know what's left?
Carbon dioxide and water. Which is exactly what we had there at the beginning of photosynthesis. And, there's more!
If you consider the reactants here, which are glucose and oxygen, and the products of this reaction, this is practically combustion, burning. With the difference that this here is extremely controlled inside the cells and the result is not energy in the form of heat. The result is in chemical energy.
Alright, but what do you call this here? Inverted photosynthesis? Really?
No, this is called breathing. These chemical reactions that I showed you, in this case, they are called cellular respiration because it's what happens inside cells. And not just inside plant cells, but inside our cells.
And that's why when we breathe, we have to use the oxygen in the air and when we let it out, carbon dioxide comes out. Going back to our picture here, it means that through respiration, plants return carbon dioxide to the atmosphere. So, at the end of the day, carbon doesn't have just one way out, from the atmosphere to the plant.
No, it also goes from the plant to the atmosphere. We have a cycle here. That's why scientists have named it the carbon cycle.
But there is a detail in this story, it is not all the carbon that the plant absorbs that it returns to the atmosphere because we saw right at the beginning of the video that the plant uses this carbon to grow. So, a part of the glucose that is generated in photosynthesis will be used to be transformed into other things, like the cellulose that makes up the wood of the plant. And as some people there may have already guessed, there are some animals that observed this photosynthesis and know that the plant has energy stored there.
So, they go there and eat the plant to use some of that energy for themselves. This means, then, that a part of the carbon that was in the plant ends up going to the animals that eat that plant. But these animals also breathe, so they send carbon dioxide into the atmosphere.
Some of the carbon will end up being part of the animal itself and, of course, there will be other animals that are interested in that energy that is there and that will eat another animal. That is, one more path that carbon is going through. Of course, this other animal also breathes.
You must have imagined where this is going, right? The plant took carbon dioxide from the atmosphere, a little of the carbon stayed with it, the animal went there, ate the plant, the animal ate the other animal. After all, you ate some animal.
This means that the carbon that is in your cells, the carbon that builds your body, your brain, your blood, your skin, one day it went through this process too. And one day it underwent photosynthesis. So, it means that you and I, we are made a little bit of air too.
But, Iberê, I'm a vegetarian, I don't eat meat, I have nothing to do with that story. You eat plants directly. So, you've only cut a piece of the path.
In the end, then, vegetarians' carbon also comes from photosynthesis. But now we have a question: If no one feeds on human beings, where does the carbon that is in us go when we die? When we pass away, there are fungi and bacteria that are the decomposers that eat what's left of us and these living beings also breathe.
You've seen that the carbon cycle is not just a simple path, right? It's a tangle, it's a spider's web, that's because just from this example we gave, several other connections could be made. Like, the human being can also eat the fungus, and the chicken can eat the plant, but the fungus can also eat the chicken, the fungus can eat the worm, the fungus can eat the plant.
And all this can also catch fire, which is another way of returning carbon to the atmosphere, or even when these living beings die, they can go underground and a part is not decomposed by fungi and bacteria and ends up being there being part of the soil. And, one day, returning to the atmosphere. But the important thing for us to know here is that the amount of carbon on planet Earth is always the same.
What happens is that carbon circulates between different places, and we have large carbon reservoirs. The atmosphere, for example, is one of those reservoirs because it has a lot of carbon dioxide. In the sea, we will have a lot of carbon dioxide dissolved in the water and also in marine beings, because carbon is part of their body.
On land too, forests are a huge carbon reservoir. And underground too because oil is another carbon reservoir. In nature, the amount of carbon that each of these reservoirs has is more or less constant because over time things have been balancing.
So, in the atmosphere, for example, the amount of carbon that leaves is supposed to be more or less the amount of carbon that comes back and things adjust over time. But all this takes into account the things that happen in nature: decomposition, animal feeding, plant photosynthesis. .
. Human beings began to do things a little differently. We started to use a lot of fuel, burn things for energy, generate a lot of garbage.
. . and what ends up happening as a result of all this?
We mess up this whole cycle, we take carbon dioxide out of several reservoirs, we end up sending everything into the atmosphere. And we kill plants, which reduces the amount of carbon dioxide they would be able to extract from the atmosphere. Putting too much CO2 into the atmosphere is a problem because carbon dioxide is one of the gases that regulates the temperature of our planet.
And if you have too much of this gas, the average temperature of the planet as a whole will rise. This is what we call global warming. That is why, in 2016, several countries around the world, including Brazil, signed a document called the Paris Agreement.
And in that document, these countries pledged not to let the global average temperature rise more than two degrees from the time when people started messing up carbon deposits and warming the planet. And that happened when industries spread around the world, in the middle of the 19th century, 1850, around. .
. But how can we do that? Several goals were set for each country, but the general idea is to reduce the carbon footprint, reduce the emission of greenhouse gases.
They are gases that warm the planet, such as carbon dioxide, methane, nitrous oxide. One of the main ways to do this is to generate clean energy in these countries, renewable energy that emits less carbon dioxide into the atmosphere. As much as these actions are focused on countries, several institutions, such as companies, and even individuals can contribute to make this happen.
Volkswagen was the first car manufacturer to join the Paris agreement and has committed to becoming carbon neutral by 2050. It makes sense to explain that this does not mean that they will never emit carbon dioxide again, but the moment carbon dioxide is emitted, there has to be some mechanism to remove this carbon dioxide from the atmosphere so that it does not accumulate here. And they're doing it on a global scale with their Way to Zero strategy, which is focused on reducing emissions throughout the entire product lifecycle, from beginning to end, from supplier to recycling.
And for that, the company is also supporting and investing in research with biofuels. Ethanol, for example, has a very low carbon footprint because the carbon dioxide that is emitted when ethanol is burned had already been absorbed by the sugarcane when the sugarcane carried out photosynthesis. That is, the carbon dioxide from ethanol goes back and forth.
And they told us that they are creating a research and development center for biofuels in Brazil that will be located at their factory in São Bernardo do Campo. The objective is to develop and export solutions in this area to complement the solutions they already provide for combustion, hybrid and even electric vehicles. Yes, Volkswagen is already working on electrification, which is one of the paths to decarbonization.
And the cool thing is, when you use that word electrification, you don't just mean making electric cars. It is also thinking about the entire structure that these vehicles need to travel across the country. The whole process for neutralizing carbon dioxide is a long one, not least because it does not depend only on automakers.
But Volkswagen is already going down that path. That's why they invited us to make this new series at Manual do Mundo and try to explore a little more this world of biofuels and technologies to reduce carbon emissions.
