Carbon Dioxide Removal (CDR) span a large variety of methods that remove carbon dioxide from the atmosphere (so-called negative emissions technologies). This includes fixing carbon in plants, the soil and building materials – but also the storage of captured CO₂ in permanent disposal sites.
Currently, Switzerland is a leading player in some of these areas, such as the production of carbon-negative cement or direct air capture. However, the widespread application of negative emissions technologies is challenged by a lack of testing and funding, high costs and power demands, land-use and food security conflicts, the safety and reversibility of the carbon storage, and the availability of input resources. Therefore, avoiding CO₂ emissions in the first place is usually less costly than removing CO₂ from the atmosphere.
The following CDR methods are discussed, developed and being implemented at present:
Afforestation + Reforestation
Forest management measures that optimize and increase the CO₂ uptake of woodlands by expansion, protection or reforestation. A sustainable management ensures that the carbon is bound in the soil and living biomass of healthy forests for a long time. Further, this approach can include using wood for long-lived products or energy production in cascaded use.
Biochar + Soil Carbon Sequestration
Conversion of biomass (e.g. harvest residues) into mineral-rich charcoal at high temperatures and in the absence of oxygen (i.e. pyrolysis), making it resistant to decomposition. Allows to sink C in agricultural soils, with various co-benefits. This approach includes further agricultural practices that aim to increase the soil carbon content and thus uptake of CO₂ from the atmosphere.
Direct Air Carbon Capture & Storage (DACCS or DAC+S)
Removal of CO₂ from ambient air through various chemical or engineering processes, e.g. adsorption, methanation or via hydroxide solutions (powered by residual heat or renewable energy). Captured CO₂ may then be stored long-term, e.g. by injecting it into depleted oil and gas fields or saline aquifers, or used in consumer goods and other applications.
Enhanced Weathering + Carbon Uptake in Cement
Application of minerals, such as rock powder, that naturally absorb CO₂ by chemical weathering, in terrestrial or aquatic systems. Depending on the used rock, nutrients are released and soil properties can be improved. This approach also includes enhanced CO₂ uptake in cement by means of concrete recycling technologies, e.g. the carbonation of crushed concrete materials, that allow long-term storage of captured CO₂ in built structures.
Bioenergy with Carbon Capture + Sequestration (BECCS)
Integration of carbon removal technologies in a wide range of industrial processes that convert biomass (i.e., put simply, carbon stored by/in plants) into products, such as fermentation, gasification or combustion. Carbon captured in e.g. combined heat and power plant, in biogas plants, the paper and pulp industry or during ethanol production may then be stored long-term.
Cultivation + Restoration of Wetlands
As a natural carbon sink, wetlands generate biomass that conserves carbon dioxide, e.g. through the formation of peat in raised bogs. Thus, cultivating and restoring wetlands, peatlands and coastal habitats have the potential to combine long-term carbon absorption and storage with nature conservation.
Literature Focusing on Switzerland
The Role of Atmospheric CDR in Swiss Climate Policy
Risk Dialogue Foundation (2018)
Selected Research + Background Information
Negative emissions—Part 1: Research landscape and synthesis
Minx et al. (2018)
Technologies and policies to decarbonize global industry: Review and assessment of mitigation drivers through 2070
Rissmann et al. (2020)
Climate scientists: concept of net zero is a dangerous trap
Dyke, Watson and Knorr (2021)
Global Warming of 1.5 °C
Intergovernmental Panel on Climate Change (2018)
Policy Brief: Negative Emissions
Mercator Research Institute on Global Commons and Climate Change (2016)
Net expectations: assessing the role of carbon dioxide removal in companies’ climate plans
Greenpeace UK (2021)
Detailed background information, assessments & recommendations for action on the topic of NET, in particular on the role of negative emissions in corporate climate plans.