|
| Measure | Potential | Operational costs in $US/tCO2 | Main investment requirements | Uncertainties | Side-effects | Sources |
|
| Biological-based carbon dioxide removal |
|
| Biochar production | 5 Gt CO2/year | 45
(15–76) | Bio-char production units | Net carbon storage potential due to use as energy source; use as fertilizer may reduce costs | Use as fertilizer increases net primary production; residuals from pyrolysis process might limit application for food production | [36–44] |
|
| Southern Ocean iron fertilization | 5 Gt CO2/year | 45
(8–82) | Iron sulfate production and treatment, ship fleet for spreading (20–500 ships) | Necessary amount of iron sulfate; coagulation of iron sulfate; increase in export production; leakage (even though accounted for in the estimate for potential) | Impacts on marine biogeochemistry, ecology, and biodiversity; increases nutrient supply for fish stocks, change in oxygen minimum zones, temporary acceleration of oceanic pH value (faster acidification) | [26–28, 45–51] |
|
| Afforestation | 4 Gt CO2/year | 60
(19–101) | | Measurement of carbon uptake and leakage varies between studies; unintended carbon release due to fire, storms; impact on albedo | Ecological effects and implication for biodiversity; land requirements | [6, 52–54] |
|
| Chemical-based carbon dioxide removal |
|
| Spreading pulverized olivine | 4 Gt CO2/year | 42
(27–57) | Exploitation, transport, pulverization, and spreading infrastructure | Access to target area (tropical catchment areas of large rivers) for spreading | Increase in soil and oceanic pH value (reduced ocean acidification); ecological impacts (e.g. input of silicic acid into oceans) | [55–57] |
|
| Spreading pulverized calcium hydroxide | 1.5 Gt CO2/Gt CaCO3 | 50
(45–54) | Exploitation, transport, thermal treatment, storage for separated CO2, fleet for spreading (about 3000 ships) | Exploitation and spreading logistics, uptake limited due to ocean circulation, storage of separated CO2 | CCS-related side-effects; increase in oceanic pH value (reduced ocean acidification) | [58–60] |
|
| Spreading pulverized lime | 0.3 Gt CO2/Gt CaCO3 | 65
(57–72) | Exploitation, transport, pulverization infrastructure, fleet for spreading (between 4000 and 6000 ships) | Exploitation and spreading logistics, uptake limited due to ocean circulation | Increase in oceanic pH value (reduced ocean acidification) | [59] |
|
| Air capture (sodium hydroxide) | 1.0–1.2 Mt CO2/unit/year | 250
(69–430) | $US 247–480 M/unit | Storage of captured carbon, energy provision | Carbon-Capture-and-Storage- (CCS-) related side-effects | [61–66] |
|
| Comparison to existing abatement measures |
|
| Conventional emission control for limitation to 2°C increase by 2050 | 21 Gt CO2
(in 2035) | 90–120
(in 2035) | $US 940 B/year (2020–2035) $US 1280 B/year (2030–2035) | Simulation results | Side-effects associated with nuclear power, CCS, and biofuel production | [2] |
|
