Carbon Dioxide Removal (CDR) Technologies and Approaches

In the urgent pursuit of climate mitigation, Carbon Dioxide Removal (CDR) has become a linchpin. This blog post unravels the intricacies of CDR approaches and their pivotal role in aligning with the ambitious goals of the Paris Agreement. Join us in exploring how these strategies, from nature-based solutions to cutting-edge technologies, contribute to our collective commitment to combat climate change!

CDR concept is more popular than it was since efforts to limit the average global temperature rise to 1.5 degrees increased. However, more than implementing CDR will be required to achieve climate goals; reducing greenhouse gas (GHG) emissions must be the first to be considered. 

New CDR technologies and different approaches are emerging, which have various benefits and uncertain environmental and social impacts. CDR approaches can be categorized such as on land and in the ocean.

A few years ago, the three businesses that dominated the CDR market were Carbon Engineering, Climeworks, and Global Thermostat, and these companies focused on direct air capture (DAC). Compared to other technologies, DAC is the most sophisticated and well-understood. DAC can be utilized in cooling towers by feeding back the air in the cooling system to the pipes and carbon dioxide capture equipment and could reduce energy requirements.

In addition to DAC, there are different CDR approaches such as biomass-based CDR, mineralization, ocean-based CDR, and crop enhancement. 

Biomass-based CDR involves innovative techniques like converting crop leftovers into carbon-rich bio-oil for underground sequestration and employing forest management practices, including residual wood burial. 

Mineralization, applicable to land and ocean, utilizes rocks like olivine and basalt for accelerated carbon sequestration through chemical reactions, enhancing soil quality and contributing to ocean alkalinity when spread on beaches. Ocean-based CDR approaches include seaweed cultivation and sinking it into the deep sea, addressing carbon removal and outgrowth. Lastly, crop enhancement utilizes enhanced photosynthesis, employing genetically modified plants and non-genetically modified bred hybrid tree species to increase carbon uptake and sequestration.

Combined CDR Approaches 

Some of these CDR approaches and technologies can be combined to achieve sustainable solutions. For instance, DAC-captured carbon dioxide can be mixed with crushed concrete from building demolition, enabling both mineralization and carbon storage in recycled concrete. Limestone can also be incorporated into this process. Furthermore, a combination of artificial upwelling and seaweed cultivation enhances the efficiency of ocean-based CDR. Artificial upwelling is achieved by pumping nutrient-rich deep-sea water, fostering seaweed growth, and simultaneously mitigating high surface water temperatures that impede natural upwelling.

When removing carbon dioxide through these, measuring and tracking the amount of removed carbon dioxide is essential to understand the impacts on the climate. Measuring processes can be more challenging in some CDR approaches compared to others, such as open systems compared to closed systems like DAC facilities.

Carbon sequestration's long-term permanence or durability is also crucial in understanding how effectively carbon is kept from entering the atmosphere. Biological processes may be less permanent than geological carbon sequestration. Disruptions can cause the release of carbon stored in biological forms, while geologically stored carbon is either transformed into solid minerals or buried deep underground, taking thousands of years to return to the atmosphere naturally.

While having positive environmental and social impacts, CDR approaches also have negative impacts. Each approach must be evaluated individually, taking the impacts and local circumstances into account in which they would be implemented. For example, some businesses combine waste products, such as mine tailings, with CDR techniques to manage harmful compounds and capture carbon dioxide. These methods could, however, have negative impacts, like the requirement for increased mining operations and hazardous trace metals in rock dust. In addition, alkalinity enhancement and other ocean-based CDR techniques, have advantages over local ocean acidification and storm surges, but they also have drawbacks, such as depleting surface water nutrients and harming seafloor ecosystems. Responsible material sourcing is crucial for biomass-based approaches to avoid negative impacts such as climate change, biodiversity loss, and land use alteration. Using waste biomass instead of purpose-grown crops is essential for positive impact.

New carbon dioxide removal (CDR) approaches and technologies show promise, but they require additional research and testing to assess their effectiveness in removing carbon dioxide, understand the timescales of carbon sequestration, and anticipate potential social and environmental impacts. Governments should also engage in these approaches, support the research for further development, and establish stringent guidelines.

Reference:

WRI,(2023)."4 things to know about new developments in carbon dioxide removal."