Emissions reductions have not occurred fast enough, nor has decarbonization occurred on a scale large enough to keep global heating below 1.5 degrees Celsius. This means we must find ways to remove carbon from the atmosphere. As such, carbon capture is having a moment. Elon Musk (XPrize) and Bill Gates (Carbon Engineering) have both thrown political and monetary capital behind it, demonstrating its promise. Although carbon capture is not a panacea, is it one of many useful tools that we can help mitigate carbon emissions.
Carbon capture can refer to three main technologies and two main off-take options. The first technology is intended to reduce direct emissions by capturing carbon at its source, such as at a natural gas plant or coal plant. The second type of carbon capture technology is Direct Air Capture (DAC). This is the most well-known type of carbon capture. DAC uses large fans to draw in air and then separate the CO2. This can be done via liquid solvents or solid sorbents that are infused with chemicals which bind with CO2. Once the CO2 is captured, heat is applied to release the CO2 as a solid or a liquid which can then be stored while CO2-free air is released. While the process is relatively simple from a chemistry and engineering perspective, it does require a large amount of power and money to run the machines. Calculations estimate that it will require about 2,000 kWh of energy to remove 1 ton of CO2 from the air. To put that in perspective, 2,000 kWh of energy is about 20% of a typical American household’s energy usage for an entire year while the 1 ton of CO2 removed is about 5% of the typical American’s annual carbon footprint. Therefore, in order for carbon capture to be beneficial, it must be coupled with renewable sources of energy. In addition to the aforementioned monetary and energy costs, DAC also requires a large land footprint to make significant CO2 reductions, and will likely need to be constructed in large open areas similar to how wind farms are currently situated.
The third type of carbon capture is an often overlooked carbon capture mechanism: Direct Ocean Capture (DOC). Ocean absorption of atmospheric CO2 DOC is a relatively simple process that passes seawater through an electrodialysis machine that separates the CO2 from the seawater and returns the seawater to its normal pH balance before returning it to the ocean. The CO2 can then be sequestered or offloaded to industry for use in commodities. The upsides to DOC are numerous, specifically: It does not require as large a footprint as DAC since the largest component of a DOC system are the water pumps. Additionally, DOC can be paired with existing infrastructure such as desalinization plants and it can be located onshore or out at sea on ships or decommissioned oil rigs. It also provides a double benefit of withdrawing CO2 from the ocean (allowing it to absorb more CO2 from the air) but it also returns the ocean to its natural pH balance, thus preventing the collapse of global fishing systems. However, DOC only makes sense to run on renewable, battery or nuclear power and the DOC technology is still years away from being produced at scale.
Conversely, carbon sequestration is the actual storage of carbon that has been captured. The two main types of carbon off-take options are carbon sequestration, where the carbon is pumped into the ground via existing wells or existing rock formations and stored, and carbon liquefaction, where carbon is liquified and used for commodity production such as vodka, perfume, diamonds, cutlery, soap, accessories, as well as synthetic aviation and diesel fuel.
Carbon capture is one of many useful tools that can be intelligently deployed to help, but not totally solve, our national emissions reduction goals. By investing in the different forms of carbon capture and using them effectively, we can maximize the strengths of each while minimizing their limitations. In places where there is abundant renewable energy (wind, solar, geo, hydro, nuclear) and large tracts of unused land such as the U.S. West, DAC is a viable option, while existing fossil fuel plants can and should utilize on-site carbon capture. Finally, along the coasts, on ships or on old oil platforms, or coupled with desalinization plants, DOC should be highly utilized, as its a very attractive solution to remove CO2 from the oceans while making them less acidic all while being less land-intensive than DAC. In short, the U.S. has an opportunity to lead the way in carbon capture by developing the technology and aggressively employing it at scale. It’s simple: capture the carbon wherever we can and either put it underground or put it to work making commodities such as fuel. Carbon capture is not the magic bullet to solve climate change, but used holistically along with other emissions reductions tools and natural climate solutions, it represents an important step forward towards solving the biggest issue of our time.
Climate Security in Focus is a blog series dedicated to exploring key elements of climate security that impact American interests both at home and abroad. The series aims to examine specific aspects of climate security issues in order to better understand climate policy challenges, facilitate conversation, and generate ideas.