Experts: Wendy Queen (EPFL), Johannes Tiefenthaler (Neustark)
CO2 is a major driver of climate change. For this reason, scientists have developed processes for capturing CO2 from the air and storing it. Such systems are already in operation today. There are questions about their economic viability though. Nevertheless, in order to reach net-zero, science and the business world must push ahead with negative emissions technologies as a matter of great urgency. Such technologies also offer opportunities for Swiss science and industry.
CO2 is one of the main drivers of human-caused climate change. Technologies that capture CO2 from industrial facilities and power stations – also known as ‘carbon capture and storage’ (CCS) – already exist. Other approaches try to filter CO2 out of atmospheric air directly, so-called ‘direct air capture and storage’ (DACS).
These technologies are called ‘negative emissions technologies’ (NETs). Such NETs recapture greenhouse gases that have already been emitted, cancelling them out, so to speak, and thus ensuring, as the name suggests, negative emissions. NETs encompass biological, hybrid and technical approaches. The former include forest and soil management, but also the storage of biochar. One hybrid approach uses the fermentation of plant matter in wastewater-treatment facilities. The CO2 produced during fermentation is captured and stored. It is important that all NETs provide long-term storage for the CO2 they capture. How permanent these storage facilities are depends on the storage method. While mineralised CO2 is stored for a very long time in concrete or other stone and highly unlikely to escape again, the effects of other forms of storage, such as prudent land use with the aim of ensuring that soils are saturated with CO2, can last a few decades.
NETs have now become an important part of climate strategies. They are not intended to compete with the reduction of greenhouse gases though, but to instead mitigate unavoidable emissions – for instance in agriculture, during cement production or from waste disposal.
The first systems to capture CO2 from power stations or to filter it out of ambient air have already been in operation for several years. The CO2 captured in this way can be used as fertiliser or for industrial processes, or stored by means of various procedures. In a pilot project conducted in cooperation with a Bern wastewater-treatment facility, the ETH Zurich spin-off Neustark, which specialises in the production of cement with reduced CO2 emissions, is capturing the CO2 generated during methane production and storing some of it in recycled concrete (see article low-carbon concrete); the rest of it is liquefied and shipped to Iceland, where it is permanently buried underground.
Since 2021, Climeworks, another Swiss start-up and ETH Zurich spin-off, has been operating a facility in Iceland that can annually filter 4,000 tonnes of CO2 out of the atmosphere and store it, mixed with water, underground. In its follow-up project Mammoth, a facility is to be built by 2024 that will annually filter 36,000 tonnes of CO2 out of the air. Climeworks is so far the only company in the world to commercially operate a facility of this kind.
Under the Paris Agreement, Switzerland has committed to reducing CO2 emissions to net zero by 2050. To achieve this goal, CO2 emissions must be cut as much as possible. Even if all avoidable emissions are reduced to zero, there will still be sectors that produce CO2. This CO2 must then either be captured at the source or filtered out of the air using DAC processes. In its strategy for achieving this goal, published in 2021, the Federal Council calculates that around 12 million tonnes of CO2 per year will still have to be offset by 2050. The goal is to filter up to 5 million tonnes out of the atmosphere annually.
The questions that arise differ, depending on the process. With regard to DAC procedures, the questions are about the resources used. The catalysts in use today require rare earths, which may not be available in sufficient quantities to operate such systems on a large scale worldwide. For science though, this also brings pressure to develop new materials that are equally capable of filtering CO2 out of an air stream and capturing it.
Today, DAC systems that filter CO2 out of atmospheric air are still far too expensive to operate, and the current market price of CO2 certificates is far too low to make such procedures worthwhile. Systems that capture CO2 at source (for instance during cement production or in waste-incineration facilities) then store it are in a somewhat better position, even if they reduce the efficiency of power stations. This is because the concentrations in exhaust gas are around 200 to 300 times higher than in atmospheric air.
CO2 emissions are far too cheap today. Accordingly, it is essential to put in place framework conditions that enable industry to reflect the cost of avoiding and capturing CO2 emissions in product prices. At the same time, the example of Climeworks shows that investors believe in the potential of such NETs. In its latest financing round, this company raised 600 million Swiss francs.
As the storage of CO2 remains invisible to end customers, the NETs industry is a trust-based business. In order to build up the necessary trust, there is a need for development of audit standards, measurement procedures and certificates that credibly demonstrate, in accordance with international standards, that the CO2 really is either avoided, or captured and stored.
Despite these challenges, NETs are essential if net zero is to be reached by 2050. Given the size of such projects and the time it takes to get such systems operating, it is very important to prioritise and vigorously pursue CCS and DAC technologies.
Due to ground conditions in particular, Switzerland is probably not suitable as a place to filter CO2 out of the air and bury it underground on a large scale, and is unlikely to become suitable in the future. However, the local university and start-up environment offers a promising opportunity for technology exports.
EPFL and ETH Zurich give Switzerland an extremely strong position in this field and, as the examples of Climeworks and Neustark show, the country is participating in several promising projects. The major cement manufacturers are also involved in projects that are removing CO2 from exhaust air and storing it. Alongside financial support for research projects, science could also benefit from demonstrative and experimental installations, in which the use of such technologies could be tested somewhat more extensively than on a laboratory scale.