There are a number of carbon removal or negative emissions technologies (NET) that can use biological or technological approaches to remove CO₂ from the atmosphere and store it on a more or less permanent basis.
Essentially, CO₂ can be captured in biomass (through photosynthesis) or by chemical means (using air filters or mineral sequestration). The CO₂ is then stored in biomass on the earth's surface (e.g. in wood), in the soil, in the geological substrate, in minerals or in the seabed.
For these technologies to generate negative emissions to a degree that affects the climate, the CO₂ must be stored for a long time, preferably for thousands if not millions of years.
CO₂ stored in forest biomass or in humus in the soil is more liable to end up back in the air than CO₂ sequestered deep underground or in minerals, due for example to exceptional events (such as forest fires) or intensive soil tillage.
There is a need to shift to technology-based removal while maintaining historical nature-based carbon sinks. Why? Because nature-based sequestration has its limitations in permanence as well as capacity. There is a clear need for additional tech-based removal, the potential of which is abundant.
For more information, see Swiss Federal Office for the Environment’s classification: factsheet.