Why carbon dioxide is both friend and foe

The gas is an essential part of life on Earth—but right now we have too much of a good thing.
Cineca in Bologna, Italy, is a computing center with one of the most powerful supercomputers in Europe. The center often collaborates with organizations such as the European Centre for Medium-Range Weather Forecast, or Copernicus, the European Union's atmospheric monitoring program, which use supercomputing to perform simulations from large amounts of data collected from weather stations around the world.
Photograph by Sergio Ramazzotti
By Marco Boscolo
photographs by Sergio Ramazzotti
Published 5 Dec 2022, 11:33 GMT

If carbon dioxide (CO₂) were a politician, it would be worried about its bad press. The greenhouse gas is the primary pollutant responsible for climate change. Not only are scientists, leaders, and activists trying to halt its production, but they also want to capture it directly from the air and lock it underground where it will do less harm.  

This gas, however, also plays a key role in life on Earth.  

How CO2 supports life  

Carbon helps form the protein and DNA found in living things. In the atmosphere, it combines with two oxygen molecules to form carbon dioxide.  

Carbon dioxide is a crucial ingredient in photosynthesis, the process by which plants turn energy from the sun to turn water and carbon dioxide into sugar. In return, plants emit oxygen.  

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A gentoo penguin during low tide in Mikkelsen Harbor, in the Antarctic Peninsula. Antarctica contains about 70 percent of the world's fresh water and the Antarctic Ocean absorbs almost a third of the carbon dioxide emissions captured by the world's oceans.
Photograph by Sergio Ramazzotti
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While activities such as producing oil, gas, and coal produce large quantities of greenhouse gasses, wasted food rotting in landfills also creates pollution. Landfills are particularly potent sources of methane, a greenhouse gas even more potent than carbon dioxide.
Photograph by Sergio Ramazzotti
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Acid rain results from a buildup of carbon dioxide in the atmosphere. The result is corrosive precipitation that can corrode stone or, in the case of this statue in Milan, bronze.
Photograph by Sergio Ramazzotti

As carbon dioxide concentrations increase in the atmosphere, scientists are trying to hack photosynthesis to supercharge plant growth. 

Laboratory studies show a higher concentration of the gas is making some plants grow more quickly in certain conditions, but in the wild and on outdoor farms the overall benefit is unclear.  

In the Netherlands, some commercial greenhouses are experimenting with ways to route carbon dioxide emitted from industry into greenhouses where plants use the excess gas as fertiliser.  

Early discoveries  

The first person to hypothesise the existence of carbon dioxide was 16th-century Belgian scientist Jean Baptiste van Helmont. After coal was burned, he noted, the weight of the remaining ashes was lower than the coal’s initial weight, meaning some mass had been lost in the process. Van Helmont was the first scientist to discern different gases present in the air we breathe.  

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Locatelli Meccanica is an Italian company that specializes in the production of dry ice, the solid form of carbon dioxide.
Photograph by Sergio Ramazzotti
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In Milan, firefighter illustrates how carbon dioxide compressed into a fire extinguisher is used to squelch gas-powered flames.
Photograph by Sergio Ramazzotti

In 1772 English scientist Joseph Priestly was also curious about the different gases in our air and identified the element oxygen. Priestly developed a way to inject water with carbon dioxide, effectively inventing sparkling water. He later isolated carbon monoxide.    

It wasn't until 1896 that Swedish scientist Svante Arrhenius linked the carbon dioxide emitted from burning fossil fuels to atmospheric warming.

A modern ingredient in the food industry  

Carbon dioxide sold for commercial use is made as a byproduct of fermenting fuel like ethanol or producing ammonia.  

When frozen, it forms dry ice, which is used to keep food cold over extended periods of time and quickly cool down hot machinery used during food production. Unlike water, which moves from a solid to a liquid to a gas as it warms, carbon dioxide moves directly from a solid to a gaseous state, avoiding messy puddles. 

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Freediving athlete Massimiliano Pampaloni trains to keep his diaphragmatic contractions under control to help prevent hypercapnia, a buildup of carbon dioxide in the body as a result of too little breathing. Carbon dioxide is a product of the body’s metabolism and is normally expelled through the lungs.
Photograph by Sergio Ramazzotti

Once food has been produced, carbon dioxide is essential for preserving it in its packaging. High concentrations of the gas prevent bacteria from spreading. In baked goods, it penetrates air bubbles, preventing mould and fungus from forming. 

When carbon dioxide comes into contact with any water present in packaging, the chemical reaction of the two substances lowers the environment’s pH, which also helps preserve baked goods.  

And when that fresh, packaged food arrives at the grocery store, it's a sustainable alternative to commercial refrigerants that help prolong shelf life. Since the 1980s, a potent greenhouse gas called hydroflourocarbons has been used as a refrigerant, but new refrigeration systems are able to effectively chill food with carbon dioxide.  

Surprising uses 

From aiding surgeons to physicists, carbon dioxide plays a surprising role in modern science.

Pure carbon dioxide is sterile and non toxic; it has a number of applications for surgical procedures. When surgeons perform an abdominal procedure called a laparoscopy, they inflate the abdomen with the gas, allowing them to make a smaller cut and resulting in quicker recovery. 

Similarly, during colonoscopies, it's used to inflate the colon to more easily conduct the procedure.  

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At Papa Giovanni XXIII Hospital in Bergamo, Italy, Dr. Paolo Bertoli and his team perform a laparoscopy. Medical-grade carbon dioxide is used to dilate the abdominal cavity. CO2 is used primarily because it is an inert gas, therefore not at risk of combustion in the presence of electrical charges, from tools like an electric scalpel.
Photograph by Sergio Ramazzotti
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Scientists at labs owned by Eni, an Italian oil company, experiment with ways to make photosynthesis—and uptake of carbon dioxide—more efficient by exposing microalgae to different wavelengths. Engineer Vasco Di Castro, seen here, experiments with plant materials that could be used as fuel or in cosmetics.
Photograph by Sergio Ramazzotti

The oil industry captures some of the carbon dioxide it emits and uses it to tap oil fields dry. When a well is almost exhausted, carbon dioxide is pumped in to increase pressure and force remaining oil up to the surface. It also makes the oil less viscous and allows for easier removal. 

In Meyrin, Switzerland, carbon dioxide is essential at the European Council for Nuclear Research’s (CERN) Large Hadron Collider, a particle accelerator that helps scientists study the particles that make up everything in the universe. Here, carbon dioxide is employed in certain types of instruments as a refrigerant gas, similar to what occurs in commercial refrigeration facilities, and as tool to study subatomic particles called muons.  

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At a mountain observatory near Modena, Italy, the country's National Research Council and Air Force monitor air quality daily, observing the concentration of carbon dioxide in the atmosphere. Concentrations of carbon dioxide in the atmosphere have risen 47 percent since the Industrial Revolution.
Photograph by Sergio Ramazzotti
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Producing crops and raising livestock is a large source of carbon dioxide. Globally, the food sector is responsible for a third of the world's greenhouse gas emissions.
Photograph by Sergio Ramazzotti
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On a beach in Azerbaijan's capital of Baku, children play within view of abandoned oil rigs stranded on the Caspian Sea. The UN's Intergovernmental Panel on Climate Change (IPCC) estimates that fossil fuel extraction, refining, and transport account for at least 10 percent of annual global emissions.
Photograph by Sergio Ramazzotti

In short supply   

Just like when it was first injected into water to form carbonated beverages 200 years ago, carbon dioxide is essential for today’s wine and beer industry. It makes wine sparkle and beer froth, and it helps prevent the oxidation process responsible for making drinks taste flat.  

Yet, despite its abundance in the atmosphere, commercially produced carbon dioxide has been scarce because of rising energy costs. As a result, some brewers have had to raise prices or scale down production. The shortage reveals just how important carbon dioxide is. 

Both friend and foe, carbon dioxide is essential to life on Earth but crucial to limit.

A version of this story appeared in National Geographic's Italian edition.

Italian photographer Sergio Ramazzotti has written and photographed stories for some of the world's leading magazines. He has a special interest in covering wars and humanitarian crises. He and Marco Boscolo reported this story together.

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