Earth CO₂ flows & budgets
- Orange, red and purple arrows (numbered 1–10, as described in Table 1) represent cycling, closed and open pathways for CO₂ utilization and removal.
- Teal block arrows represent annual flows to and from the atmosphere, with estimates averaged over the 2008–2017 period. Estimates of stocks in the Earth’s spheres (lithosphere, biosphere, hydrosphere and atmosphere, labelled in bold) and selected stock subcategories are given.
- All estimates are based on IPCC estimates except where noted, and are converted from C to CO₂.
- Carbon stocks in the hydrosphere comprise seawater, sediment, and dissolved organic carbon (not shown, around 2,600 Gt CO₂).
- The vast majority of carbon stocks in the lithosphere are locked in the Earth’s crust, with estimated accessible fossil fuel reserves and resources of more than 45,000 Gt CO₂.
- Atmospheric stocks are converted from the 2017 estimates of atmospheric CO₂ of 405 ppm using a conversion factor of 2.12.
- From: The technological and economic prospects for CO2 utilization and removal
CO₂ Utilization pathways
1. Chemicals from CO₂
3. Products from microalgae
1. Chemicals from CO₂
Catalytic chemical conversion of CO₂from flue gas or other sources into chemical products
2. Fuels from CO₂
3. Products from microalgae
1. Chemicals from CO₂
Catalytic hydrogenation processes to convert CO₂ from flue gas or other sources into fuels
3. Products from microalgae
3. Products from microalgae
4. Concrete building materials
Uptake of CO₂ from the atmosphere or other sources by microalgae biomass
4. Concrete building materials
6. Bioenergy with carbon capture and storage (BECCS)
4. Concrete building materials
Mineralization of CO₂ from flue gas or other sources into industrial waste materials, and CO2 curing of concrete
5. CO₂-EOR
6. Bioenergy with carbon capture and storage (BECCS)
6. Bioenergy with carbon capture and storage (BECCS)
Injection of CO2 from flue gas or other sources into oil reservoirs
6. Bioenergy with carbon capture and storage (BECCS)
6. Bioenergy with carbon capture and storage (BECCS)
6. Bioenergy with carbon capture and storage (BECCS)
Growth of plant biomass
7. Enhanced weathering
9. Soil carbon sequestration techniques
7. Enhanced weathering
Mineralization of atmospheric CO₂ via the application of pulverized silicate rock to cropland, grassland and forests
8. Forestry techniques
9. Soil carbon sequestration techniques
7. Enhanced weathering
Growth of woody biomass via afforestation, reforestation or sustainable forest management
9. Soil carbon sequestration techniques
9. Soil carbon sequestration techniques
9. Soil carbon sequestration techniques
Increase in soil organic carbon content via various land management practices
10. Biochar
10. Biochar
9. Soil carbon sequestration techniques
Growth of plant biomass for pyrolysis and application of char to soils