Carbon Capture

Carbon dioxide is responsible for 76 percent of the world’s warming, and it stays in the atmosphere for years. As the world struggles to wean off of fossil fuels, capturing carbon dioxide from the atmosphere is emerging as a key part of stopping climate change.

There are several methods of carbon capture, but all of them have a common goal: to remove carbon from the air. To ensure the gas is not released back into the air, scientists must either store it or convert it to a non-gaseous form. 

Natural Carbon Capture

For life to thrive, carbon dioxide must be naturally regulated. When the Earth was first formed, carbon dioxide’s high quantities prohibited any life, until a small microbe called cyanobacteria (or blue-green algae) started absorbing the gas and releasing oxygen into the air, through the process of photosynthesis. Over millions of years, these tiny beings changed the planet’s atmospheric composition drastically. In this climate crisis, cyanobacteria could help life thrive once again, acting similarly to trees as a natural carbon capture strategy.

Cyanobacteria can bloom wherever conditions are favorable — in warm water, in the presence of light, or where there are excess nutrients. One acre of cyanobacteria absorbs about 2.7 tons of carbon dioxide per day — twice as much as plants. To multiply this effect, we can grow blue-green algae in ponds, or sink some in the ocean. However, cyanobacteria can only be deployed away from human populations, as it often causes rashes and irritation. In an effort to mimic the natural effects of cyanobacteria, artificial bioreactors have also come into play, which can soak up 400 times more carbon dioxide than a typical tree.

Trees are another, more traditional form of carbon capture. They also use photosynthesis, taking carbon dioxide from the atmosphere and converting it into oxygen. However, trees are less efficient and more expensive because of the space that they require. Though they are often heralded as the saviors of carbon capture, scientists have found cyanobacteria to be far more effective. Still, trees and forests maintain important and irreplaceable ecological benefits, forming the basis for many ecosystems across the planet.

These natural carbon capture strategies are called carbon sinks — areas into which carbon sinks from the atmosphere. While carbon sinks have played an important role in developing life on Earth, they are still not effective enough to counteract the rapid rate of greenhouse gas emissions. That is when human ingenuity comes into play.

Artificial Technologies

Innovators have been developing a technology called Direct Air Capture (DAC), which has two types: solid and liquid. In solid DAC, air passes through a filter in a very low-temperature and high-pressure environment. Under these conditions, the filter is able to separate the carbon, trapping it on the surface and thus removing the gas from the air. Meanwhile, in liquid DAC, air passes through an alkali solution such as potassium hydroxide (KOH), causing the acidic carbon dioxide (CO2) to react (carbon dioxide is actually acidic!) and form calcium carbonate (CaCO3) with water (H2O). DAC takes relatively little space for the amount of carbon it takes out of the air, compared to the natural solutions. DAC plants have been commissioned in Europe, North America, Japan, and the Middle East.

The more difficult part, however, is storing carbon. Carbon, once captured, needs to be stored deep underground, which can be expensive. It takes $135 to $345 to store one ton of carbon dioxide. Financial incentives for carbon capture can make it profitable — and that’s where governments come into play. When governments help pay for the implementation of carbon capture systems, private companies are more likely to enter the business. 

Lil Fuhr, the director of the climate and energy program at the Center for International Environmental Law, says that carbon capture is not a technology that should be reserved for the future, and instead, we should take action now. However, developing carbon capture has led to some groups advocating for it to replace methods of reducing greenhouse gas emissions. They claim that if we remove carbon dioxide from the atmosphere, there is no need to end fossil fuel use. This is false — carbon capture cannot replace greenhouse gas reduction. Ending emissions is key to stopping climate change because carbon capture cannot collect all emissions, and is not efficient enough to directly counteract fossil fuel production, explains Friederike Otto, a lead author for the International Panel on Climate Change, the United Nations’s chief climate body. 

Instead, carbon capture gives us one invaluable resource: time. Carbon capture can reverse the effects of global warming, and experts refer to this as negative carbon emissions. Think of it like this: for every one ton of carbon we use, we take back half of that. This method can decelerate global warming, and we can get more time to react to the rising temperatures.

Despite the potential that carbon capture has to reduce climate change, there are only 40 carbon capture plants worldwide. The International Energy Agency (IEA) reports that despite slow progress, development is increasing. Through 2023, there were 400 new projects in the works, one hundred more than the year before.

As we move into a world so conscious about climate change, the future of carbon capture is bright. Per the IEA, there will be 50 new carbon capture plants by 2030, processing around 125 megatonnes of carbon dioxide per year, but that’s still much less than the 1.2 gigatonnes of carbon capture required to achieve net zero emissions.

It is almost certain that a green and sustainable future is one with both responsible emissions and innovative technologies. We cannot rely solely on carbon capture, but we can use it to support emission-reduction efforts. We need to follow nature’s one, true principle — balance.