Switzerland has committed itself to meet the internationally agreed goal of limiting global climate warming well below 2° C, preferably to 1.5° C, compared to pre-industrial levels, as defined in the Paris Agreement. To reach this goal and, consequently, limit the effects of climate change is of high importance for Switzerland. Global warming is caused by the emission of greenhouse gases, with carbon dioxide (CO₂) accounting for the largest share. To achieve the global temperature goal, emissions need to reach net-zero by 2050. Net-zero means reducing greenhouse gas emissions as close to zero as possible and offsetting those CO₂ emissions which are hard to abate (s. Q 5).

Atmospheric CO₂ is the CO₂ that has been released into the atmosphere and therefore causes the increase in global temperature. Atmospheric CO₂ can be of different origin. In the context of net-zero, there is fossil and biogenic CO₂.

Fossil CO₂ is emitted from the combustion of fossil resources, such as coal, oil, or gas. The fossil CO₂ has been stored underground for millions of years. By burning fossil fuels, this large amount of stored CO₂ is released back into the atmosphere. Additionally, also other industrial and chemical plants such as the production of cement emit fossil CO₂.

Biogenic CO₂ is CO₂ released by combustion or decomposition of organic material (biomass such as compost, burned wood, or residual sludge) that took up the CO₂ from the atmosphere via photosynthesis.

CCS stands for Carbon dioxide Capture and Storage. CCS refers to the capture of CO₂ from point-emission sources, such as waste-to-energy, chemical, or cement plants, and permanent storage in underground geological formations or in building materials (e.g. concrete). The source of the CO₂ captured thereby can be of fossil or biogenic origin (s. Q 2).

In DemoUpCARMA, we focus on and distinguish two specific CCS approaches, which are referred to as CCUS (Carbon dioxide Capture, Utilisation and Storage) and CCTS (Carbon dioxide Capture, Transport and Storage). In these two acronyms, the letters “U” and “T” are added to emphasize the “utilization” and “transport” components of these two approaches.

CCUS involves three steps: (i) CO₂ capture from point-emission sources, (ii) utilization of CO₂ as a feedstock to produce a range of products, such as concrete, methanol, ethanol, carbonates, plastics etc. DemoUpCARMA investigates a CCUS pathway that optimizes permanent CO₂ storage in building materials, i.e., recycling concrete. In DemoUpCARMA, a CCUS pilot is investigated and demonstrated, in which biogenic CO₂ captured at a biogas plant is utilised and stored in concrete that is then used as a building material.

Similarly, CCTS involves three steps: (i) CO₂ capture from point-emission sources, (ii) transportation of CO₂ by truck, train, ship/barge, or pipeline, and (iii) permanent CO₂ storage in a geological reservoir. In DemoUpCARMA, a CCTS pilot is investigated and demonstrated, in which biogenic CO₂ captured at a biogas plant is transported from Switzerland to Iceland, where it is dissolved in seawater and stored underground in a basalt formation.

If CCUS or CCTS approaches are based on fossil CO₂ (e.g., CO₂ captured from a chemical plant), they result in CO₂ emissions being avoided. On the contrary, if CCUS or CCTS approaches are based on biogenic CO₂ (e.g., CO₂ captured from a biogas plant), negative emissions are generated (CO₂ removal). In the latter case, the CCUS or CCTS application would be categorized as a negative emission technology (NET; for details, see Q4). This also applies to the two DemoUpCARMA pilots outlined above.

NETs stand for negative emission technologies. NETs encompass all manmade solutions that permanently remove CO₂ from the atmosphere, including landscape management solutions such as soil carbon management and reforestation. This process is also called carbon dioxide removal (CDR). The solutions that are predominantly discussed, developed, and implemented are biochar, soil carbon sequestration, afforestation and reforestation, bioenergy with carbon capture, permanent CO₂ storage (BECCS), and direct air capture and permanent CO₂ storage (DACCS). When biogenic CO₂ is permanently removed from the atmosphere via NET, negative emissions are generated.

More information can be found here: Swiss Carbon Removal Platform; or here: FOEN/negative-emissions-technologies.

According to Switzerland’s long-term climate strategy, remaining, hard to abate greenhouse gas emissions from industry, waste management, and agriculture will amount to around 12 million tonnes of CO₂ equivalents. These can be offset by either CCS or NETs. Around 5 million tons of these CO₂ emissions shall by reduced from large point-emission industrial sources by CCS efforts. The remaining 7 million tons per year shall be offset via NETs such as bioenergy with CO₂ capture and permanent storage (BECCS) and direct air capture and permanent CO₂ storage (DACCS).

Carbon dioxide is mineralized in concrete. Thereby, the CO₂ binds with the concrete aggregate and is in consequence stored in solid form. This is regarded as a safe storage technique.

The average lifetime of modern Swiss buildings is about 70 to 100 years depending on their usage. In general, carbonated concrete can be recycled and put into use again. In any case, once the CO₂ is mineralized in concrete, it remains there indefinitely also when the building is dismantled.

The biogas at the waste-water treatment plant ARA Bern consists of a gas mixture of methane (60%) and CO₂ (40 vol%), which must be separated to obtain high purity methane, so-called bio-methane. After being captured, CO₂ is conditioned to a liquid state. The liquid CO₂ is then loaded into dedicated ISO tank containers (or ISOtainers, see Q10) and transported to the storage site at conditions of -35°C and maximum 22 bar.

For the DemoUpCARMA pilot, the captured CO₂ is dissolved in seawater and injected into basalts (a reactive rock formation) for permanent mineral storage. DemoUpStorage monitors both the response of the Icelandic underground to the injection of CO₂ dissolved in seawater, and the mineralization process.

This storage method has already been implemented using fresh water: once injected, the carbonated water reacts with the rock formation underground, releasing calcium, magnesium, and iron into the water stream. Over time, these elements combine with the dissolved CO₂ to form stable carbonates.

This differs from other methods of CO₂ storage that inject CO₂ into subsurface reservoirs, such as sedimentary basins, where CO₂ is physically trapped in porous rocks below an impermeable cap rock.

The potential for storing CO₂ in geological storage formations has been investigated within the SCCER-SoE project (Swiss Competence Center for Energy Research – Supply of Electricity) as well as the international research project ELEGANCY. The research in these projects showed that the first estimates of the geological storage potential in Switzerland is limited and not available in the near future. Consequently, exploring alternative storage options abroad are important.

Iceland has both, favourable geological characteristics (basalt formations) as well as the know-how and experience to store CO₂ underground. In DemoUpCARMA, Carbfix will implement and operate the CO₂ injection system. The Icelandic company has been pioneering CO₂ storage in basalts since 2012 and has demonstrated that CO₂ can mineralize within a few years after injection by turning into stone. DemoUpCARMA together with its partner projects DemoUpStorage and CO2SeaStone aim at investigating the feasibility of injecting CO₂ dissolved in seawater for permanent mineral storage. Using seawater instead of fresh water is expected to decrease the environmental impact of the storage technology, specifically its water footprint, and to allow its implementation offshore, thus unlocking a larger storage capacity worldwide.

DemoUpCARMA also assesses the ecological footprint of this option, see Q16.

The risks related to underground storage of CO₂ depend on the selected geological formation and the chosen procedure. So far, commercial scale CO₂ storage has targeted deep saline aquifers or depleted oil and gas reservoirs. Currently, there are about 30 operation projects worldwide that store CO₂ in such formations, with about 100 additional projects being planned. These successful projects demonstrate that a properly designed and operated underground CO₂ storage is safe, but every project must be accompanied by a detailed and project-specific risk assessment. Two of the risks that need to be carefully evaluated in aquifer storage projects are the risk of leakage through geological formation or existing boreholes, and the risk of induced seismicity (see Q14) and/or surface deformation.

In DemoUpCARMA and in its partner projects DemoUpStorage and CO2SeaStone, a host formation of basaltic rocks at depth of 300 – 500 m is used for storage. This technology promoted by Carbfix differs from the above described approaches and potentially offers several advantages with respect to safety.

• The CO₂ is dissolved in seawater and injected at low pressures into highly permeable and already fluid saturated formations. Because of the shallow depth, and because the injection does not require substantial overpressures, the risk of induced seismicity is low.
• The risk of leakage is also lower compared to the injection as a supercritical fluid (the current practice in running projects), because the CO₂ is dissolved in water.
• Finally, mineralisation processes of CO₂ dissolved in water and injected into basalts have been shown in laboratory experiments to be much faster when compared to injection into deep saline aquifers in sedimentary layers. In basalts, CO₂ will mineralize into carbonates and hence be permanently immobilized within a few years, a process that takes hundreds to thousands of years in other storage options.

One of the key objectives of DemoUpStorage is to observe in-situ the fluid propagation and mineralisation processes with geophysical and geochemical monitoring techniques. This will provide important and independent input for risk and safety assessments, monitoring strategies, and up-scaling of future sequestration projects.

Induced seismicity has been observed as a consequence of oil and gas production, geothermal projects, mining related activities, or hydro-dams. Induced seismicity related to CO₂ storage poses a risk in itself (the actual shaking), but an earthquake can potentially also create leakage pathways and also can negatively influence public acceptance of CCS projects, especially onshore ones.

There are only few reported cases of minor induced seismicity related to CO₂ storage in saline aquifers or depleted reservoirs so far, and none related to storage in basalts. In Iceland, the risk of induced earthquakes when injecting CO₂ dissolved in seawater is very low, because of the shallow depth of injection and because the overpressures are low. Nevertheless, the Swiss Seismological Service at ETH is installing a network of seismic sensors near the injection site capable of observing micro-earthquakes with magnitudes starting from 0.5.

As responsible for the injection site, Carbfix and DemoUpStorage partner Eawag will perform in chemical and CO₂ flux monitoring using dedicated wells to determine the post-injection CO₂ mineralisation efficiency. In addition, in the framework of DemoUpStorage, the Swiss Seismological Service at ETH Zurich will install a seismic monitoring network (see Q14) to monitor seismicity. DemoUpStorage will also conduct geophysical measurements between the boreholes, with the objective to track the migration and potentially the mineralisation of the CO₂ injected.

To assess the environmental impacts as well as the actual and final carbon footprint of both pilots, a Life Cycle Assessment will be conducted. Thus, the entire chain will be assessed from capturing, transporting, and using or storing the CO₂. This for example includes the energy needed to transport and store the CO₂ underground.