What is it?
Carbon dioxide removal (CDR) is the process in which CO₂ is captured from the atmosphere with the intention of storing it for long periods of time (~1,000+ yrs). There are pathways that rely on nature, such as photosynthesis, and those that employ engineered methods, such as chemical reactions to remove the CO2 from the atmosphere. However CDR is achieved, it is important that it is done in a way that will be impactful to climate change, results in CO₂ being net-removed from the atmosphere, and upholds ecological and cultural ecosystems.
How does it work?
There are many pathways that result in CDR, some naturally occurring such as planting trees, and some engineered pathways, such as direct air capture via chemicals. Some of these pathways include:
- Afforestation/Reforestation : Afforestation is the planting of trees where there were none previously. Reforestation is the planting of trees where there were before.
- Mineral Carbonation: CO₂ binding with rock formations to form new minerals.
- Direct Air Capture (DAC): Capture of CO₂ from the atmosphere using special chemicals. Two primary methods to achieve this are the use of liquid solvents and solid sorbents.
- Bioenergy for Carbon Removal and Storage (BiCRS): Using biomass, which captures CO₂ during its lifetime to create energy and use CCS to capture CO₂ from the flue gas produced.
- Coastal Blue Carbon: Protection and restoration of coastal wetlands to increase their uptake of CO₂ from the atmosphere.
- Soil Carbon Sequestration: land management practices that result in soil uptaking CO₂ out of the atmosphere and storing it deep in the soil ecosystem.
Although it is evident that these pathways often have very different requirements (i.e., energy, land area, etc.), there are aspects of these solutions that should be emphasized to ensure they result in high-quality CDR.
- The CO₂ that is physically removed is additional. For removal to be considered additional, it should not have taken place without the intention to do so. An example of this would be that there is no additional removal for trees that are already planted, however, if new trees are planted, or those already planted are protected against imminent deforestation, these activities would be considered additional.
- CO₂ storage needs to be durable. For CO₂ storage to be durable, there needs to be minimal risk of CO₂ being re-released back into the atmosphere. This re-release could occur if there is a leak in a geologic reservoir, a forest fire, or CO₂ released from soils once they are tilled.
- Accurate CO₂ accounting has been completed to include both upstream and downstream emissions. The total amount of CO₂ that is physically removed from the atmosphere must be greater than the CO₂ emissions produced by the process.
- Do No Harm. CDR operations should have minimal negative environmental impacts (i.e., biodiversity, water quality, etc.) and impacts on local communities.
Why is it important and what are the major barriers?
A framework that determines if CDR is high-quality will be crucial in the fight against climate and it will also carry a lot of nuance. Ultimately, CDR efforts should not contribute to or be pursued to justify further environmental damages. Guidelines such as these assist to ensure that the proper care is taken before CDR efforts are deployed.
Although these guidelines seem to be pretty straightforward, ensuring and verifying all CDR projects meet them is not. Some of the barriers that stand in the way of projects meeting these guidelines are monitoring, measurement, and verification methods and agreed-upon CO₂ accounting procedures.
What we do.
In the Clean Energy Conversions Lab (CECL), we often analyze and assess leading CDR technologies within the realm of DAC and mineral carbonation. These analyses are typically techno-economic assessments, life cycle analyses, mapping/siting studies that contribute to better understanding how these CDR efforts can best be deployed at large scale. We have furthered the field by completing techno-economic assessments for various DAC approaches powered by multiple different energy sources and using mapping strategies to illustrate places where DAC may be best deployed for access to low-carbon energy and CO₂ storage.