Carbon Removal and Storage

Carbon dioxide is the primary greenhouse gas contributing to climate change. Despite environmental efforts, the level of global carbon emissions continues to rise. Convincing the world to change technology and phase out carbon-polluting fuel sources has proven near-impossible… but what if there was another way? A different direction that would allow us to mitigate carbon pollution without halting all fossil fuel usage overnight, a way to give communities time to adjust to more environmentally friendly changes? Scientists have begun removing carbon dioxide directly from the air we breathe, and it looks like a ray of hope we all need right now.

Note: to read about carbon dioxide as a greenhouse gas, click here.

Before the dawn of humans, planet Earth still produced and removed carbon. Volcanic eruptions, fires, even the act of breathing adds carbon to the environment. Carbon cycles from the atmosphere to the Earth, landing in rocks, the ocean, and living organisms, before being cycled back to the atmosphere. This continuous cycle should balance the carbon levels of our planet, but the human footprint has weighed heavily on Earth’s ability to remove carbon from the atmosphere. In 2015, the United Nations Paris Agreement declared the goal of keeping global average temperatures below 1.5 ºC. As of 2023, climate model scenarios show that the only way to keep rising temperatures to 1.5 ºC is by using carbon removal methods; let’s break some of them down.

First, the term “carbon removal” refers to removing carbon dioxide (CO2) from the atmosphere and locking it away… somewhere. Trees participate in carbon removal, they suck carbon from the air and store it within their branches, leaves, and roots. This is why burning wood releases so much carbon. “Carbon capture” is useful in the industrial world; this method captures carbon directly at the source to prevent the emissions from entering the atmosphere.

“Direct air capture” is the next term, in which giant fans take in air, trap the carbon dioxide, and release the purified air back into the environment. The captured carbon can be reused as fuel or building materials, or it can be stored underground. Direct air capture requires substantial power, meaning the factories need low-carbon energy sources (such as solar or wind power) to successfully have a negative carbon net. As of 2022, 19 direct air capture facilities existed around the world.

One Swiss company, Climeworks, uses direct air capture to remove carbon from the atmosphere, then sends the trapped CO2 to Carbfix in Iceland. The CO2 is then dissolved in water and turned to stone underground after coming into contact with basalt (lava rocks). This storage technique is called “carbon mineralization”, also known as enhanced weathering. Turning gaseous or liquid CO2 into stone allows it to be permanently stored.

Outside of carbon mineralization, storage options for captured carbon include oil and gas reservoirs, coal beds, geological formations, and even within the ocean. Phytoplankton consumes CO2, making them a focus of new carbon sequestering approaches. A concept called the “iron hypothesis” proposes that iron limits phytoplankton growth, meaning phytoplankton colonies would bloom if iron was added; this would suggest that carbon would be removed quicker with the addition of iron. Since experiments on ocean iron fertilization have only been conducted on small scales, today it remains more of a theory than a definite solution.

The iron hypothesis is merely one of many approaches being studied to help mitigate the effects of climate change through carbon removal. As new scientists enter the field and as technology advances, we are seeing a new age of environmental protection begin. Now is not the time to put our feet up, but hopefully this news lets you breathe a bit easier today.

References

Carbfix. (n.d.). How it works. Carbfix. https://www.carbfix.com/how-it-works/

Climeworks. (n.d.). Direct air capture: A technology to fight climate change. Climeworks. https://climeworks.com/direct-air-capture

Mulligan, J., Ellison, G., Levin, K., Lebling, K., Rudee, A., & Leslie-Bole, H. (2023, March 17). 6 ways to remove carbon pollution from the atmosphere. World Resources Institute. https://www.wri.org/insights/6-ways-remove-carbon-pollution-sky#:~:text=Carbon%20removal%20strategies%20include%20familiar,air%20and%20sequesters%20it%20underground

NOAA. (2019). What is the carbon cycle?. National Ocean Service website. https://oceanservice.noaa.gov/facts/carbon-cycle.html#transcript

Stoll, H. (2020). 30 years of the Iron Hypothesis of Ice Ages. Nature, 578(7795), 370–371. https://doi.org/10.1038/d41586-020-00393-x