Why carbon removal is important. Now.

Carbon dioxide removal (CDR), commonly also referred to as carbon removal, is a process that involves extracting carbon dioxide from the atmosphere and harmlessly sequestering (i.e. storing) it in geological, terrestrial, or ocean reservoirs – also known as natural carbon sinks – or by using the CO₂ for another purpose where it is stored permanently.

The amount of CDR we will need depends on our choices: how much we choose to limit the rise in global temperature, how much we choose to reduce emissions, and in which timeframe.

The Special Report on 1.5°C by the IPCC underlines that pathways that limit global warming to 1.5°C will require carbon and other GHG removal on the order of 100–1000 billion tons of CO₂ over the 21st century.

See chart below: Necessary order of magnitude for carbon removal for emission path of 1.5°C (data source: Network for Greening the Financial System Scenario Explorer. Model: REMIND-MAgPIE 1.7-3.0; provided by IIASA).

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.

Current research shows that there is no single solution that could be deployed at scale to remove hundreds of gigatons of CO₂ from the atmosphere by the end of this century.

Some proposals for carbon removal are at a very early stage in their development, others are more established. They vary in cost, how much they can remove and in the resources they require (such as land, water and energy). Some carry risks, for instance due to costs of land conversion and biodiversity loss, particularly if deployed on very large scales. Some bring co-benefits, for instance generating power, reversing biodiversity loss or providing useful materials. Some may prove unsuccessful in scaling up. Importantly, there is still much scope for innovation and improvement, and some techniques will work better in some contexts than others.

The answer is in the mix – and with a focus on solutions that have been proven both ecologically and economically feasible and can make a significant impact in the next decade.

CDR removes carbon from the atmosphere, thus removing previous emissions – enabling us to address both unavoidable and historic emissions.

CCS prevents carbon from entering the atmosphere – making it a concept that focuses on reducing emissions.

Neustark sources CO₂ from biogas production sites and stores it in demolished concrete permanently.

The CO₂ sourced from the biogas sites is biogenic CO₂, i.e. if released into the atmosphere by the biogas plants, the process would be carbon-neutral (as the plants combusted in the process already absorbed CO₂ earlier in their life cycle).

By capturing and storing this biogenic CO₂, neustark removes carbon-neutral emissions that would otherwise have gone into the atmosphere – hence creating negative emissions.