Within the scope of CCU technologies capture is understood as the process by which CO₂ is filtered out of industrial waste gases. The goal here is that, following the capture process, the CO₂ is available in sufficiently high purity in order to allow it to be used or geologically compressed.
Carbon capture technologies
There is currently one class of technology which is currently the benchmark for a large-scale capture of CO2: wet-chemical washing processes with the aid of strong alkaline solutions, in particular, so-called “amine scrubbing”. Wet-chemical processes involve diverting an exhaust stream through a so-called absorber solution. The CO2 contained in the exhaust stream is then absorbed by the molecules of the absorber solution and separated from the remaining exhaust stream. In the case of amine scrubbing, this absorbing mixture is based on a solution of amines.
The term catalysis defines the act of influencing a chemical reaction with the aid of a catalyst, with the goal of initiating a reaction, accelerating a reaction or reducing the necessary energy for a reaction, as well as causing specific reaction processes. For CCU processes, breakthroughs in catalysis research were essential. They made first processes feasible and/or energetically sensible, thus enabling further processing on the inert material CO₂.
CCS/geological storage of CO2
Carbon Capture and Storage (CCS) defines the capture and subsequent geological storage of carbon dioxide from industrial waste gases, with the goal of removing CO₂ durably from the atmosphere. Storage is regarded as feasible, for example, in underground salt water layers and former crude oil and natural gas sites.
Circular economy/(Closed loop) recycling management/German Life-Cycle Resource Management Act (Kreislaufwirtschaftsgesetz)/Recycling (Closed loop)
Recycling management defines a concept of leading resources that are completely utilised in production into further utilisation. Recycling processes are part of this concept, but are also supplemented by other forms of further use, such as cascade utilisation. In this study, both terms are used: (closed loop) recycling management stands for the conception of the objectives while recycling is a concrete process on the way to this. The European Guidelines for dealing with waste were determined by law in the German Life-Cycle Resource Management Act (KrWG) in 2012.
Delay of emissions
After a particular period of time, the used CO2 will be emitted again. Depending on the lifetime of the respective CCU product, the CO2 can be stored for days or weeks (e.g. synthetic fuels), years (e.g. polymers) or decades or centuries (e.g. cement).
Direct use/direct utilisation of CO2
The usage of carbon dioxide in industrial processes without chemical transformation is defined as direct utilisation of CO₂. This type of utilisation can take place in solid or liquid form and is already commonplace in diverse production processes, for example, carbonic acid in drinks, dry ice for cooling of foods, in fire extinguishers or as fertiliser in greenhouses.
End of life
The term “end of life” denominates the final phase in the life cycle of a product. This includes processes like the incineration of a product, its disposal on a landfill or its entering in a recycling process.
Life Cycle Assessment/ecological balance/life cycle analysis
A Life Cycle Assessment or LCA is a systematic analysis of the possible effects on the environment of a production process of an interim or end product. Ideally, this analysis should include the complete lifetime of a product (“cradle to grave”) or up to the point in time of the finished manufacture of an (interim) product (“cradle to gate”). For CCU products, this means, in particular, the inclusion of all of the processes upstream and downstream from the actual CCU core process, in order to make a holistic assessment of the possible effects on the environment possible.
Material utilisation of CO2
CO₂, if chemically transformed, can serve as a raw material for the production of carbon compounds of energetically higher or of lower value. This so-called material utilisation of CO₂ as a component of materials, chemicals and minerals has been common for some time in special pharmaceutical products (e.g. headache tablets), solvents or, on the larger scale, fertilisers (urea). Furthermore, the material utilisation of CO₂ is already currently technically feasible in the manufacture of plastics and foams, paints and coatings, and building materials similar to cement (so-called minerals). These new procedures usually involve innovative processes to replace conventional production processes, but which are currently still in very early stages of development or have only recently become feasible due to breakthroughs in catalysis research, and which will now, first of all, have to be demonstrated on an industrial scale.
Mineralisation is a process of material utilisation of CO₂, with the aid of which, for example, industrial waste such as ash and sand can be processed with CO₂ from waste gases to so-called minerals. Such minerals can be, for example, cement-like or other building materials similar to concrete for road works or other similar purposes.
Permanent storage/binding of CO2
Permanent storage here refers to a duration of more than 1000 years.
Power-to-X defines, as a generic term, all the processes which transform energy from renewable sources, for example, in the form of hydrogen or electricity, together with CO₂, to diverse energy sources (for example Power to gas – PtG, or Power to liquids – PtL). This technology plays an important role in the energy transition policies as an option for flexible deployment and storage at peaks within the scope of the production of renewable energies, but is also open to other possibilities for large-scale application of CCU technology. Due to the low prices of fossil energy, these new technologies are, however, currently not competitive options to conventional fuels.
Savings potential/emission savings
It must be considered that the evaluation for usable CO2 emissions are not to be considered equal with actual saved CO2 emissions, since all conversion technologies also require energy. For each individual CO2 utilisation technology, it is therefore necessary to determine the potential for CO2 savings individually – this can be higher or lower than the amount of CO2 which can be used. It is even possible that an increase in emissions will occur.
Synthetic fuels/energy carriers
Generally, it is also feasible to use carbon dioxide as a raw material in order to manufacture energy carriers. It is possible, for example, to produce the following energy carriers from CO2 by means of diverse processes:
- liquid fuels such as methanol, diesel
- gaseous fuels such as methane/synthetic gas.
Such energy carriers can directly serve the mobility sector or could find future use as energy storage, in order to use peaks in the generation of renewable energies.
- Dechema study: Low carbon energy and feedstock for the European chemical industry.
- Preliminary results booklet of the funding measure CO2Plus by the Federal Ministry of Education and Research (BMBF) [only available in German]: CO2Plus – Stoffliche Nutzung von CO2 zur Verbreiterung der Rohstoffbasis
- Circle chart
- Scientific Opinion by the Group of Chief Scientific Advisors, European Commission: Novel carbon capture and utilisation technologies
- Science Advice for Policy by European Academies (SAPEA) report: Novel carbon capture and utilisation technologies: research and climate aspects
- Report: CO2 Utilisation Today
- Report: Techno-Economic Assessment & Life Cycle Assessment Guidelines for CO2 Utilization
- Flyer by CO2 Value Europe: A condensed guide to carbon capture and utilisation (CCU)
- Flyer by CO2 Value Europe: CO2 Mineralisation: A way to transform CO2 emissions into useful construction materials
- IASS fact sheet: CO2 as an asset?
- IASS working paper: CO2-Recycling – An option for policymaking and society?
- Short brochure by the Federal Ministry of Education and Research (BMBF) [only available in German]: Vom Abfall zum Rohstoff – Kann CO2 in Zukunft Erdöl ersetzen?
- Flyer about the funding measure CO2Plus by the Federal Ministry of Education and Research (BMBF) [only available in German]: Kohlendioxid als Ressource – Vom Abfall zum Rohstoff – CO2Plus-Forschung macht mehr aus Treibhausgas
- Paper: The German R&D Program for CO2 Utilization - Innovations for a Green Economy