By Tara Prakash
Since the beginning of the industrial era in 1850, human activities have raised atmospheric concentrations of carbon dioxide by nearly 49%. In 2019, global carbon emissions reached a high of 36.44 billion metric tons. The concentration of carbon dioxide in Earth’s atmosphere is currently at nearly 412 parts per million and rising. As we begin to run out of time, carbon dioxide removal (CDR), might be a necessary tool.
Carbon dioxide is a greenhouse gas in the atmosphere. The term “greenhouse” refers to the essential and natural process that warms Earth by trapping heat in our atmosphere. Without carbon dioxide, the planet would be inhospitably cold; plants and animals alike would be unable to survive.
Despite the clear ecological necessity of carbon dioxide, rapidly increasing levels of greenhouse gas emissions present danger. Excessive carbon dioxide creates a cover that traps the sun’s heat energy in the atmosphere, exorbitantly warming the planet and the oceans. We have already seen the effects of this with longer heat waves, melting ice caps, and rising sea levels.
Carbon dioxide is not our enemy, as it serves an important biological function. However, when in excess, the greenhouse gas leads to catastrophic events associated with global warming. Now, it is just about finding a healthy middle. If we do not rapidly halt our rate of emissions, we might need to get a bit more creative. This is where CDR comes into play.
The first and most popular method of carbon removal is natural forest regrowth, in which trees grow back inland previously cleared for agriculture or industrial use. Forests currently absorb 30% of carbon dioxide, while the remaining 70% end up in the ocean or the atmosphere, where they fuel climate change. Natural forest regrowth could absorb another 23% of carbon dioxide emissions, so 55% of all carbon dioxide would be absorbed across natural forest regrowth and current forests. The other 45% would end up in the ocean and atmosphere. The rates at which these forests can remove carbon dioxide from the atmosphere vary by order of magnitude around the world. Tropical countries have the highest sequestration rates, while countries in Central Europe and the Middle East have the lowest. This method certainly has upsides. Planting one trillion trees could store 225 billion tons of carbon, or two-thirds of the carbon released by humans into the atmosphere since the Industrial Revolution began. Yet nature-based carbon removal, like natural forest regrowth, may conflict with policies and programs already in place, like food production and industrial growth. Plus, old forests store much more carbon than new ones, meaning that planting new trees will not have much of an impact if we continue our deforestation practices.
Another potential method for CDR is direct air capture and carbon storage, a process in which carbon dioxide is removed from the air, bound to filters, and when these filters are heated, the carbon is then captured and stored underground.
A third method is creating bioenergy with carbon capture. In this practice, forests grow and create a “carbon sink” to absorb the carbon dioxide. Then, the plants and trees are burned to produce heat, or bioenergy. During combustion, carbon emissions are captured and stored underground.
A fourth method is mineralization, in which carbon dioxide reacts with rocks and crystallizes. The carbon dioxide is then removed from the air, and the mineralized carbon dioxide is stored underground.
Many of these methods and similar carbon removal methods have not been implemented on a large scale; nonetheless, they serve as hopeful solutions to many climate activists. Carbon dioxide removal may not be the answer to all of our problems, but it might help us get closer to that middle of the spectrum we all are searching for.
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