cr.what
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.
cr.why
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.
cr.how
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.
Fact Sheet
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
Side effects
+ Biodiversity, soil quality, flood and erosion control, local economy
– Land use competition, reversibility, saturation, monoculture plantations
Fact Sheet
When carbon is sequestered in the soil, CO2 is removed from the atmosphere as changes in land use (reduction of soil disturbances, changes in crop rotation or pasture use through grazing) increase the carbon content of the soil.
Potential and costs
2-5 Gt CO2/year until 2050, cumulative 100 Gt CO2 until 2100
-20 – 100 $/tCO2
Side effects
+ Soil quality and climate resilience, reduced use of fertilizers
– Reversibility and management practices, soil saturation, measurability
Fact Sheet
Biochar is obtained through thermal breakdown of organic material in the absence of oxygen (pyrolysis). When added to the soil, biochar increases the amount of carbon in the soil and improves soil fertility and other ecosystem properties.
Potential and costs
0,5-5 Gt CO2/year until 2050, cumulative 100 Gt CO2 until 2100
30-120 $/t CO2
Side effects
+ Soil quality, energy production
– Reversibility, measurability
Fact Sheet
BECCS stands for bioenergy with carbon capture and storage and describes a process in which energy is obtained from biomass in industrial processes and the resulting carbon dioxide is then separated and stored. The feasibility, scalability, and other environmental impacts depend heavily on whether biomass waste or biomass from dedicated BECCS plantations is used.
Potential and costs
0,5-5 Gt CO2/year until 2050
20-200 $/t CO2
Side effects
+ Energy production
– Loss of biodiversity, land, water and fertilizer consumption
Fact Sheet
Technologies from the area of Direct Air Capture (DAC) include a series of chemical and mechanical processes in which CO2 is washed directly from the air and then pressed and stored in the ground.
Potential and costs
0,5-5 Gt CO2/year in 2050
100-600 $/t CO2
Side effects
+ high-purity CO2 for material use, permanence
– Energy consumption, requires suitable infrastructure and storage locations
Fact Sheet
With improved mineralization, also known as enhanced or accelerated weathering, the natural processes of rock weathering are used and accelerated to bind CO2 from the atmosphere in stable minerals. Certain rocks are ground and applied on the ground as a powder.
Potential and costs
2-4 Gt CO2/year until 2050, cumulative 100-360 Gt CO2 until 2100
50 – 200 $/t CO2
Side effects
+ Soil quality
– Environmental problems from mining, milling and transport, depending on the application, soil and groundwater pollution
Fact Sheet
Restoration or terrestrial peatlands and coastal wetlands and mangroves can sequester CO2 back into plants and sediments.
Potential and costs
No reliable data on global potentials
10-100 $/t CO2
Side effects
+ Biodiversity and water quality, flood control and tourism
– Emissions of other natural greenhouse gases, saturation, reversibility, measurability.
Fact Sheet
Ocean alkalinization (or ocean liming) is the marine counterpart to enhanced weathering. The addition of alkalinity to marine areas (such as via Ca(OH)2) converts CO2 to stable carbonates and silicates and increases the local CO2 buffering capacity of the ocean.
Potential and costs
1 Gt CO2/year until 2050, cumulative approx. 100 Gt CO2 until 2100
50 – 180 $/t CO2 (high uncertainty)
Side effects
+ Counteracts ocean acidification
– Possible biogeochemical side effects on oceans, environmental problems from mining, milling, and transportation
Fact Sheet
Ocean fertilisation is based on the effect of biological production enhancement resulting from the selective addition of macro- or micronutrients to the upper ocean water. The resulting algae could sequester CO2 from the atmosphere, which is subsequently stored in the ocean sediment.
Potential and costs
0,2 – 2 Gt CO2/year until 2050, cumulative up to 300 Gt CO2 until 2100 (high uncertainty)
50 – 500 $/t CO2 (high uncertainty)
Side effects
– Unknown impact on marine biology and nutrient budget, Possible oxygen depletion in surface waters
