Types of carbon sequestration and their climate change mitigation potential

In recent years, many countries and companies have announced net zero targets to reach climate targets and limit global warming to well below 2°C. Thereby the “net” refers to emissions that cannot be removed – or are too costly to be removed – and are instead balanced by removing CO2 directly from the atmosphere. This process is called carbon sequestration. 

In this blog post we will take a brief look at the different types of carbon sequestration and their potential to contribute to reaching our climate targets as set out by the Paris Agreement. 

Types of carbon sequestration

Carbon sequestration is the process of capturing and storing atmospheric CO2 in a carbon pool. There are two main categories of carbon sequestration. Firstly, biologic carbon sequestration and secondly, artificial carbon sequestration. 

Biologic carbon sequestration. Under this category fall all biological processes where CO2 is naturally captured from the atmosphere and stored in vegetation, soils, woody products, and aquatic environments. The most prominent example is the large-scale planting of trees due to their cost-efficiency in terms of storing carbon while potentially also delivering co-benefits in terms of biodiversity and health, among others. 

Artificial carbon sequestration. Over the last couple of years, two main approaches have been seriously pursued. Firstly, geological carbon sequestration where CO2 is stored in geological underground formations through injection into porous rock. This process is also called carbon capture and storage (CCS) Secondly, direct air capture where CO2 is directly captured from the air by means of a large fan. 

Potential to help limit global warming to well below 2°C 

Most of all climate change mitigation pathways – such as the Shared Socioeconomic Pathways (SSP) from the IPCC – rely significantly on negative emission technologies enabling carbon sequestration on a large-scale. Nevertheless, as of today, the main negative emission technologies discussed above are still early stage and not profitable. Hence, for now tree planting is the main viable solution to enhance natural carbon sinks on a large scale. 

And while reforestation should be encouraged, there are also limitations to its contribution to reach climate targets. An in-depth study conducted in the UK in 2020 on the potential of reforestation to reach the net zero target by 2050 found that ambitious reforestation plans could add 22MtCO2e in carbon sink capacity. This contrasts with 452MtCO2e emissions in the same year. 

Moreover, another concern is that putting too much hope in negative emission technologies diverts from the actual goal of reducing emissions in absolute terms by phasing out fossil fuels, while also incentivizing business-as-usual.