Carbon Sinks

Carbon sinks and negative emissions play a limited but nevertheless indispensable role in achieving climate neutrality. In agriculture in particular, but also in specific industrial processes, residual GHG emissions will still remain in 2050. These emissions will be offset by removing CO₂ from the atmosphere and subsequently storing it via CCS technology. On balance, Germany can become climate neutral.

Carbon sinks include natural sinks, such as carbon uptake by forests and soils, as well as so-called negative emissions via CCS technology, which are achieved by removing CO₂ from the atmosphere and depositing it.

Natural carbon sinks include carbon sequestration from land use, land use change and forestry (LULUCF). These natural sinks absorb and store CO₂, e.g. in trees in forests or in peat soils. If poorly managed, sinks can become GHG emission sources.

Negative emissions from the use of CCS-technologies are mainly achieved through biomass CCS, Direct Air Carbon Capture And Storage and the material binding of CO₂ in green polymers.

Bioenergy with carbon capture and storage (BECCS) is the capture and geological storage of CO₂ created through the combustion of biomass. Since biomass is largely CO₂-neutral when sustainably cultivated and used as a waste material, BECCS can remove CO₂from the atmosphere in the long term. The use of BECCS is limited by the amount of sustainably available biomass.
Direct Air Carbon Capture and Storage (DACCS) refers to the capture of CO₂ directly from the air and its subsequent storage in suitable geological formations. Ambient air is sucked in by fans and CO₂ is bound by a sorbent. The CO₂ is deposited in the same way as in CCS. The energy consumption and costs for DACCS are significantly higher than for BECCS.
Green naphtha / material binding of CO₂in green polymers: Green naphtha or other hydrocarbons can be produced by using biomass or CO₂ extracted from the air via direct air capture in combination with renewables-based hydrogen, e.g. in Fischer-Tropsch plants. These can be processed into polymers and plastics. Through an improved recycling system, the plastics are permanently kept in the material cycle. Combined with CCS in waste incineration, it can be avoided that carbon previously captured from the atmosphere is re-emitted.

Prognos, Öko-Institut, Wuppertal Institut (2020): Towards a Climate-Neutral Germany. Executive Summary conducted for Agora Energiewende, Agora Verkehrswende and Stiftung Klimaneutralität

Industry will play an important role in the use of BECCS. Especially the high concentrated heat requirements of the steel and chemical industries are well suited for using biomass on a large scale and capturing the resulting CO₂. The carbon can then be stored via the CO₂ infrastructure needed for the cement industry anyway. The almost complete recycling of plastics, especially through chemical recycling, is a further important contribution of the industry to climate neutrality.

For CCS, infrastructure as well as spatial planning issues are of major importance. In the future, the availability of CO₂ infrastructures and corresponding storage sites will be a central location requirement for several industrial sectors. We will need massive learning curve effects for the technology of extracting CO₂ from the atmosphere.

Data and forecasts regarding natural sinks, i.e. the carbon uptake by forests and soils, are still very imprecise. In addition, due to climate change, forests and soils could threaten to turn into CO₂ sources instead of sinks in the coming decades. Therefore, the contribution of natural sinks to climate neutrality is difficult to quantify and is not considered by us to achieve climate neutrality.

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Residual GHG emissions and their compensation in 2050

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Prognos, Öko-Institut, Wuppertal Institut (2020)

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