What is the Carbon Cycle?

Carbon is a life-sustaining element that’s available in all living organisms, from the smallest microbe to the largest and most complex animal. This element is primarily stored in rocks, but is also abundant in the atmosphere and carbon reservoirs (also known as carbon sinks), which are ecosystems where carbon is stored. The largest carbon sinks are forests and oceans. These reservoirs will cycle carbon from the atmosphere to Earth and back, exchanging carbon atoms in a never-ending loop. 

Since the carbon cycle takes place in a closed system, the planet doesn’t gain or lose carbon. As a result, this cycle will remain balanced when left undisturbed. However, human activities such as fossil fuel combustion and environmental events, like erupting volcanoes and forest fires, increase the amount of carbon in the atmosphere, impacting the natural carbon cycle. 

In order to better understand the carbon cycle, it can be helpful to break it down into a few stages.

• Carbon enters the atmosphere 

• CO₂ is absorbed 

• Animals eat plants

• Decomposition

Let’s take a closer look at the carbon cycle steps below:

Carbon enters the atmosphere

Carbon enters the atmosphere through different human and natural processes, including:

• Burning fossil fuels: When fossil fuels (i.e.,natural gas, coal and oil) are burned, they release significant amounts of carbon dioxide into the atmosphere—electricity alone is responsible for 34 billion tonnes annually worldwide. The burning of fossil fuels is one of the most prominent human-induced ways that carbon enters the atmosphere.

• Deforestation: Through photosynthesis, plants, trees and other forms of vegetation absorb CO₂ and produce  oxygen. However, when they are cut down or burned, the CO₂ stored within them is released into the atmosphere. 

• Respiration: Humans, animals and other living organisms breathe in oxygen and exhale CO₂.

• Waste: Carbon dioxide is emitted into the air when organic waste decomposes. This happens because during the process of decomposition, microorganisms consume and break down organic waste, releasing CO₂ as a result. 

• Environmental events:  Some naturally occurring environmental events including volcanic eruptions, wildfires and permafrost thawing will emit CO₂ into the atmosphere. About 100 billion tons of CO2 cycle through the atmosphere this way.
  

CO₂ is absorbed

CO₂ that is present in the atmosphere is naturally absorbed by plants and other organisms. In most cases, carbon will be absorbed by carbon sinks, which are ecosystems that store more CO₂ than they release. 

Here are just a few examples of how CO₂ is absorbed on Earth through natural processes.

• Oceans are the largest carbon sinks on the planet, absorbing significant amounts of CO₂, thanks to the phytoplankton—or microscopic plants—that float in the water. Phytoplankton soak the carbon dioxide at the surface of the ocean. They sink down to the deep ocean floor when they die and release CO₂. 

• Plants will absorb carbon dioxide from the atmosphere during photosynthesis, allowing them to turn the CO₂ into glucose for energy. This process also emits oxygen back into the air, a necessary component for all life on earth. Forests are one of the most abundant carbon reservoirs and can absorb 2.6 billion tonnes of carbon annually.

• The soil is also a powerful carbon sink that absorbs CO2 from the organic plant matter it contains.
  

Animals eat plants

When animals consume plants, they also ingest the CO₂ stored in the plants from photosynthesis, increasing the amount of carbon in their bodies. 

These animals may then be eaten by other organisms, allowing the carbon to continue moving up the food chain. This process is known as bioaccumulation and can act as a carbon sink because the CO₂ will only be released when the animal dies and decomposes.

Decomposition

When an organism such as a plant or animal dies, its body will go through the process of decomposition. As a result, microorganisms, such as bacteria and fungi, will break down the organic material and release CO₂ into the atmosphere. However, some amounts of carbon will remain in the soil, where it can be stored for years.

Carbon is exchanged at different rates, which influences the speed of the process. The fast carbon cycle refers to the quick transfer of carbon between living organisms. In contrast, the slow carbon cycle refers to a process that takes longer and is driven by natural and human activities. 

The fast carbon cycle

The fast carbon cycle will exchange carbon in a few years or decades. The main reason carbon can be transmitted faster is due to plants, living organisms and the process of respiration.

The slow carbon cycle

In the slow carbon cycle, carbon will move through the lithosphere (the outer part of the earth), atmosphere and ocean at a slow rate. The exchange of carbon between different stages can take approximately 100 to 200 million years, a direct contrast to the fast cycle which can occur over decades. 

The slow carbon cycle takes longer to transfer carbon because it primarily depends on geological processes, such as the disruption of tectonic plates, weathering and erosion. However, it can be easily influenced by human activities, including deforestation, burning fossil fuels and mining. 

Despite their differences, fast and slow carbon cycles play an important role in the transfer of carbon and help to regulate the amount of CO₂ on earth.

While carbon is vital to maintaining life on Earth, excess CO₂ exacerbates climate change and global warming patterns that influence biodiversity/habitat loss and other environmental burdens, as well as the social, economic and political aspects of life. More CO₂ in the atmosphere causes the planet to retain more heat, leading to rising temperatures and other environmental consequences. It’s more critical now than ever to look at ways to reduce CO₂ emissions and remove excess CO₂ from the atmosphere.

There are several decarbonization methods that can help us reduce carbon dioxide and work towards achieving a state of carbon neutrality. These methods include:

• Reforestation: Revitalizing depleted forests by planting trees and other forms of vegetation is a valuable way to create more space for natural carbon sequestration. While this method is valuable and removes CO₂ from the atmosphere, relying solely on natural processes is no longer effective because carbon is generated by industries at a rate that natural removal processes cannot keep up with.

• Carbon capture, utilization, and storage (CCUS): Carbon capture, utilization and storage technologies are a suite of systems used to capture and convert CO₂ into products of value or permanently store it underground. CCUS technologies can be used to capture CO₂ from power plants and the industrial sector (e.g., cement, steel manufacturing) and other carbon-emitting sources before it’s released in order to reduce CO₂ emissions that enter the atmosphere. The captured carbon can be stored underground or used to produce valuable products that can displace fossil fuels-based goods and materials. AIR COMPANY’s Carbon Conversion Reactor is an example of a CO₂ utilization technology that converts CO₂ into alcohols and fuels.

• Direct air capture (DAC): Direct air capture technology extracts carbon dioxide directly from the air rather than from industrial facilities like CCUS technologies. This carbon can be stored underground or utilized. 

It’s important to note that CCUS and DAC technologies have not yet been adopted at a large scale. However, both have an important role to play in effectively decreasing the amount of CO₂ in our atmosphere. In fact, the scientific community has reached a consensus on the critical role these technologies will play.

The carbon cycle is a complex series of processes that exchange carbon between the atmosphere, ocean, lithosphere, and living organisms. Ultimately, under natural conditions, the carbon cycle works to keep the amount of carbon on our planet stable and maintain a habitable environment. However, human activities have dramatically increased the volumes of carbon released into the atmosphere, disrupting the delicate balance of the carbon cycle. Fortunately, innovation has paved the way for a solutions-oriented approach to reducing carbon emissions and putting them to a good use. 

At AIR COMPANY, we work with nature rather than against it, using a process that mimics photosynthesis to convert CO₂ into products of value. Using our AIRMADE™ Carbon Technology  we create carbon-based products including sustainable aviation fuel, methanol and ethanol, for applications across consumer and industrial verticals. By turning the most harmful pollutant into a useful building block, we can lower the amount of carbon emitted into the atmosphere and create practical, environmentally-responsible products and materials.