COP28: What is Carbon Dioxide Removal?
Ecology and Environment
3rd Dec, 2023
CDR methods require appropriate governance and policies as they can also cause adverse side-effects apart from the predicted benefits.
COP 28 and CO2 removal:
Ahead of the 2023 Climate Summit, the United Nations Environment Programme (UNEP) in a press release said that countries must go further than the current pledges under the 2015 Paris Agreement to limit global warming to 1.5°C with no or low overshoot during this century.
According to the Emissions Gap report, delaying greenhouse gas (GHG) emissions reduction will further increase the future dependence on carbon dioxide removal (CDR) from the atmosphere.
Carbon Dioxide Removal:
- CDR: Carbon dioxide removal, or CDR, is using technologies, practices, and approaches to remove carbon dioxide from our atmosphere through deliberate and intentional human actions.
- Traditional Methods: This includes traditional methods like afforestation, as well as more sophisticated technologies like direct air carbon capture and storage (DACCS).
- Natural Processes: Natural processes, like the growth of a natural forest, are not CDR methods.
- Carbon Storage: CDR also includes durable and efficient storage of extracted carbon dioxide in natural reservoirs like soil and vegetation, or in manufactured products like carbonated drinks.
- Afforestation/reforestation: Converting abandoned or degraded agricultural lands into forests can contribute to negative emissions. Additional plants and trees can sequester more carbon dioxide from the atmosphere into the soil.
- According to the Intergovernmental Panel on Climate Change (IPCC), afforestation is a relatively cheaper method of CDR, costing approximately under $240 per tonne of CO2. The storage time can last from decades to centuries.
- Biochar: Biochar is the substance produced by burning organic waste from agricultural lands and forests in a controlled process called pyrolysis. Although it resembles common charcoal in appearance, the production of biochar reduces contamination and is a method to safely store carbon.
- IPCC estimates biochar as a CDR method costs $10-345 per tonne of CO2. The downside of the technology includes negative impact from dust, and increased competition for biomass.
- BECCS: Bioenergy with carbon capture and storage, or BECCS, is similar to biochar in the sense that it also uses biomass to produce energy while preventing the release of carbon dioxide into the atmosphere. However, BECCS involves bioenergy production, often through combustion to generate electricity or heat. The resulting CO2 emissions from this combustion are captured and stored underground, preventing them from contributing to the greenhouse effect.
- According to IPCC, BECCS costs $50-200 per tonne of CO2. Growing energy crops for BECCS can also lead to increased competition for land.
DACCS: Direct air carbon capture and storage, or DACCS (also called DACS), extracts CO2 directly from the atmosphere at any location. This captured CO2 is then permanently stored in deep geological formations or used for other applications.
- According to an update from the International Energy Agency (IEA), 27 DACCS plants have been commissioned worldwide till 2023, capturing almost 0.01?Mt?CO2/year.
- DACCS is also the most expensive form of CDR. Atmospheric CO2 exists in a very diluted form, leading to high costs and energy needs for efficient extraction.
Enhanced rock weathering: This CDR method involves pulverising silicate rocks to bypass the conventionally slow weathering action. The resultant product, usually a powder, has higher reactive surface area, which is then spread on agricultural lands for further chemical reactions.
- Estimated cost for enhanced rock weathering stands at $50-200 per tonne of CO2, according to IPCC. Dust emissions and potential for increased GHG emissions from energy generation are a few drawbacks of the technology.
Ocean alkalinity enhancement: Like forests and green patches on land, oceans are also vast natural sinks for carbon. Ocean alkalinity enhancement is a CDR method that involves adding alkaline substances to seawater to accelerate this natural sink.
- The process costs approximately 40-260 Dollars per tonne of CO2, according to IPCC. However, it also comes with certain risks, like potential for increased GHG emissions from mining, transport, and deployment. Weathering of alkaline materials can also release byproducts like trace metals, impacting fragile marine ecosystems.
Way Forward: CDR as a policy
According to IPCC, CDR methods require appropriate governance and policies as they can also cause adverse side-effects apart from the predicted benefits. To accelerate research and development and incentivise CDR deployment, a political commitment to formal integration into existing climate policy frameworks is required, including reliable measurement, reporting, and verification of carbon flows.
- According to IPCC, CDR methods require appropriate governance and policies as they can also cause adverse side-effects apart from the predicted benefits.