Remove CO2 from the atmosphere?
Carbon Removal, also Carbon Dioxide Removal (CDR), is the process of capturing CO2 from the atmosphere and trapping it in carbon sinks. Some techniques are already being used on a small scale, while others are still in the early stages of development.
For a process or technology to be considered carbon removal, four conditions must be met:
- CO2 is physically removed from the atmosphere.
- the removed CO2 is permanently stored outside the atmosphere.
- emissions generated during the process are included in the overall balance.
- emissions generated during the process are less than the negative emissions produced.
Carbon Removal should not be confused with Carbon Capture and Storage (CCS) or Carbon Utilization (CCU). CCS refers to a process in which CO2 produced by the utilization of fossil resources is captured and trapped underground. CCU uses CO2 to make short-lived products such as plastics or synthetic fuel. Sooner or later, the CO2 ends up back in the atmosphere. Only Carbon Removal allows for permanent CO2-removals and thus contributes to decreasing CO2 concentrations in the atmosphere.
Emission reduction alone is not enough!
In order to meet global climate targets, the avoidance and reduction of emissions is a priority. However, the technologies needed for achieving this are not available in the medium term, so according to the Intergovernmental Panel on Climate Change (IPCC), large-scale removal of CO2 from the atmosphere is also necessary.
The magnitude of this removal is expected to be between 4.5 and 15 Gt of CO2 per year from 2030 until the end of the century. This is equivalent to about 15 to 50 percent of today’s annual global anthropogenic CO2-emissions.
Regardless of whether the global community wants to limit global warming to 1.5 °C or 2 °C, the use of carbon removal technologies is inevitable.
Which technologies can help?
Negative emission technologies (NETs) for biological, chemical, or physical removal of carbon differ in terms of the final reservoirs of CO2, the durability of storage outside the atmosphere, their cost structure, and their environmental and socio-economic side effects. The spectrum ranges from purely technological solutions such as direct air capture to nature-based techniques such as changed land use practices.
NETs can be differentiated according to various dimensions, for example, the CO2-removal process (nature-based removal, technological removal), the Earth system in which CO2-removal takes place (land or ocean), or the storage medium (geological reservoir, building materials, biomass, soil, sediments in oceans).
The technologies exhibit differences, sometimes significant ones, in their costs (from to) and potentials (from to), but also in their secondary impacts on ecosystems. Many of the carbon removal solutions have both positive and negative secondary effects. It is likely that a mix of technologies will prevail depending on local availability and socio-economic structures.
Afforestation involves the planting of trees on previously unforested areas. Reforestation means resettling forests on former forest areas. Photosynthesis converts CO2 into biomass.
Potential and costs
3,6 Gt CO2/year until 2050, cumulative 80-260 Gt CO2 untill 2100
5-50 $/t CO2
+ Biodiversity, soil quality, flood and erosion control, local economy
– Land use competition, reversibility, saturation, monoculture plantations