Technical and political perspectives in carbon management

Climate protection remains one of the key factors shaping technical and economic development in the EU and large parts of the world. EU regulations stipulate that greenhouse gas emissions in the EU must reach net zero by 2050. Germany is aiming to achieve climate neutrality even earlier, by 2045. Yet the transformation towards using renewable resources must not have a negative impact on the EU’s status as an industrial location, nor on its prosperity.

Text: Richard Backhaus | Photos: Stefan Bausewein

A key component in implementing these goals is carbon management. Professor Roland Span, head of the Chair of Thermodynamics at Ruhr University Bochum, is calling for carbon dioxide (CO₂) to be seen not only as harmful to the climate, but also as a potentially useful raw material. Working in a global network of research facilities, he and his team are looking for ways to establish concepts and ecosystems for carbon capture and storage (CCS) as well as carbon capture and utilisation (CCU) on a large industrial scale as part of comprehensive carbon management.

As Span noted in his keynote speech at FVV’s spring conference, the focus in politics, society and industry must remain on preventing CO2 emissions. Generating energy from renewable sources is the key to the developments that need to happen. After all, for much of the energy used for mobility, in homes and in industry, electrification is the most economical and therefore the best way to reduce CO2 emissions. »In reality, however, the situation is much more complex, as carbon will remain a core element of industrial production. This means we are talking about defossilisation rather than decarbonisation,« Span said. Of the around 650 million tonnes of CO2 currently emitted in Germany every year, researchers believe that around 80 million tonnes are economically unavoidable, including 45 million tonnes of CO2 from industry. According to Span, CCS/CCU concepts will be essential in dealing with these emissions. Industrial carbon management (ICM) has already seen a great deal of political activity in this context, he said, but this is not far-sighted enough, given that carbon management is also relevant to sectors of mobility that cannot be effectively electrified – such as heavy goods transport, shipping and aviation.

Carbon capture and utilisation

In carbon management, it is important to distinguish between CCS and CCU, as the two approaches have different value chains. CCS aims to directly reduce atmospheric, climate-relevant emissions through the permanent geological storage of captured CO2. CCU primarily relates to the provision of carbon in a defossilised society. Whether CCU is effective in helping to reduce atmospheric CO2 emissions depends largely on the source of the CO2, the type of products being produced, and whether they can be kept within in the carbon cycle.

© Eidsmo, EERA JP CCS

Some see carbon dioxide merely as harmful to the climate, but Professor Span and his team take a different view. They put the potential of CO2 emissions that are difficult or impossible to avoid at the heart of their work and collaborate with international research networks to reduce the costs and risks associated with a large-scale use of CCS systems.

There are three known methods for capturing CO2: pre-combustion capture, post-combustion capture, and the oxyfuel process. Although post-combustion capture is an established technology, system integration has its challenges, especially in connection with mobile applications such as ships. Span emphasised the need for more research in this area. »The pre-combustion process also raises issues regarding system integration that have to be resolved. Since the process always involves the combustion of hydrogen, research activities on the use of hydrogen as an energy carrier, such as in hydrogen engines, and in other areas are relevant here.« The third method, oxyfuel combustion, is comparatively straightforward in terms of the capture process itself, Span continues, but requires significant changes to the engine/turbine design to convert the combustion process to the nitrogen-free gas. Direct air capture (DAC) is a special case in this context. This process is very ineffective in energy terms but will continue to play a role in the future, as it is required for industrial-scale production of carbon-based sustainable fuels such as methanol. »Process industrialisation today is focused on the post-combustion capture approach with absorption, i.e. amine scrubbing. To achieve the best possible results across the entire system, the capture method and process need to be developed in an integrated way. The markets for the process and plant technology required for this are currently taking shape,« said Span, describing the current state of progress.

Transport networks and infrastructure

The transport of CO2 is an important aspect of carbon management that has long been underestimated. Original CCS concepts were all based on point-to-point transport, with a pipeline connecting the CO2 source at one end to the storage location at the other end. The CO2 is primarily stored in offshore reservoirs. Norway, Denmark, Sweden, the United Kingdom, the Netherlands and other countries already have plants like this in operation or have initiated their first commercial storage projects. Suitable storage reservoirs include saline aquifers, which are often located under oil and gas storage facilities. For CO2 emitters in industrial locations far away from the coast, such as in Central Europe, offshore storage as significant disadvantages. »Concepts for lower-cost storage on land are therefore being considered, which are estimated to cost around 60% less than offshore storage across the entire system. In addition, the EU is planning to set up a Europe-wide backbone pipeline for CO2 transport,« explains Span. But the network will not be extensive enough to allow all emitters and storage facilities to be connected directly to a long-distance pipeline. This issue is to be resolved with a multimodal transport network that includes the transfer of solid and gaseous CO2 in pipelines and the transport of liquids in tanks on trains and ships.

Technical hurdles in implementing the pipeline and transport system include both the interfaces between the various modes of transport and the handling of the captured raw CO2, for example compression, expansion, liquefaction and purification. Higher levels of contamination, typically N2, Ar and O2, have an impact on the vapour pressure curve, which needs to be taken into account when designing the pipelines and storage tanks. In homogeneous states, low-level SOX, NOX or H2O contamination in the ppm range does not have a significant impact on density or other properties, but can trigger the formation of a highly corrosive second phase. In addition, mixing of CO2 from different emitters is inevitable during transport, which leads to contamination with fluctuating concentrations and can cause chemical reactions. »Limit values still need to be defined here in order to ensure that substances can be transported smoothly and safely. Intense discussions about the permissible level of contamination are ongoing at CEN level, and I expect to see at least a preliminary solution by the end of the year,« Span predicted.

Given the problems with the transport infrastructure, many companies who want to use carbon capture, for example in the cement industry, are considering CCU as an alternative. As Span explained, assessing the economic viability of CCU is much more complex than for CCS. CO2 storage becomes profitable when the certificate prices exceed the storage costs. For CCU, the economic viability depends on the process chain, the market price and the market volume of the end product. In any case, CCU is only sustainable if the carbon comes from organic sources or DAC, or if the product is recycled. Span predicts that acquiring CO2 certificates for CCU will therefore be difficult in most cases. The high consumption of hydrogen and green electricity also needs to be considered.

Outlook: Where CCS can be used

Span anticipates that CCS will be used primarily for processes that cannot be made climate neutral in any other way, such as the production of cement, lime and perhaps steel. Some countries are considering CCS in connection with base load supply through coal-fired power generation. »This is not a clever idea, as the amount of CO2 will be very high and more competitive alternatives already exist today,« said Span. Germany sees CCS as a short-term option for gas turbine power plants in the grid reserve, with green hydrogen replacing the fossil natural gas in the long term. For mobile applications like ships, CCS can be used as an alternative to synthetic fuels, ammonia or hydrogen. Because the individual applications differ so widely, the technology assessment yields very different results and no process will prove to be fundamentally superior. Bringing his speech to a close, Span reminded the audience of the urgency with which affected companies need to address the issue of CCS. »Setting up and integrating the infrastructure required may present certain challenges, but it also offers market potential. Furthermore, we can already see that demand for CO2 storage capacity will outstrip supply in just a few years. Large storage capacity is available, but there will be a transitional period in which its development will struggle to keep up with demand. Industrial companies should therefore create a carbon management concept and acquire access to the CCS infrastructure now if required, so that they are not playing catch-up later,« Span appealed.