FROM GREENHOUSE GAS TO RAW MATERIAL: carbon capture & utilisation AS A WEAPON AGAINST GLOBAL WARMING

CO₂ contains carbon, so it can be used as a basic raw material for chemicals, synthetic fuels, building materials and many other applications. Carbon capture & utilisation is still mostly only available on a lab scale, so it is currently too early for upscaling and a broad rollout. With its rich expertise, VITO is contributing to CCU research through all of its research domains: from scientific and technical considerations to the economic aspects.

In the 2015 Paris Agreement it was agreed that global warming should be limited to a maximum of 2 degrees – and ideally 1.5 degrees – by 2100. That is easier said than done, as it means that global greenhouse gas emissions will have to be drastically reduced over the coming decades. This decade, a reduction of 900 million tonnes of CO₂ emissions (the most significant greenhouse gas) would already need to be achieved every year (current annual CO₂ emissions are 35 billion tonnes). By 2050, these emissions should not exceed 13 billion tonnes, and by 2070 they should be zero. The latter might seem completely unrealistic, if not for the fact that these are net emission figures. So-called negative emissions, with CO₂ being removed from the atmosphere, are included in the calculation.

Carbon capture: economic and ecological added value

Until recently, technologies for negative emissions were mainly assigned to the category carbon capture & storage, or CCS. But in recent years, an expansion to this with greater potential has emerged: carbon capture & utilisation, or CCU. Here the captured carbon is processed and recycled as much as possible, preferably in applications with both economic and ecological added value. In a certain sense, this goes back to the natural process of photosynthesis, as planting trees or certain crops can be viewed as a natural version of CCU.

CCU thus differs from CCS, where carbon is stored on a massive scale, e.g. underground – this still is a highly sensitive matter and would not appear to be economically feasible either. When using CCU, CO₂ is (and often remains) stored in products and applications. Another difference with CCS is the complementary nature of CCU with (other) emission-reducing strategies, like advanced decarbonisation of electricity production, increased carbon efficiency in the process industry and maximum carbon recycling during the manufacture of plastics.

Turning CO₂ into fuel thanks to CCU

CCU is highly interesting in terms of making the chemical industry more sustainable and greener. After all, this industry not only emits vast quantities of CO₂ – both through energy generation and production processes – but it also relies heavily on carbon as a raw material. Although greenhouse gas emissions from the chemical industry are relatively limited on a global scale (in Europe it produces 4 percent of greenhouse gases), this share is much higher in the highly industrialised region of Flanders. The chemical industry in our region is responsible for no less than 11.7 percent of Flemish emissions. Apart from increasing the efficiency of processes and advanced electrification, our chemical industry could also benefit from CCU.

By allowing CO₂ to react with hydrogen in a controlled manner using a catalyst, various chemical building blocks can be created, like syngas and methanol. These can then be further converted into renewable fuels or chemical products like plastics – this is the thermocatalytic route. By using electrolysis, CO₂ and water can also be converted into building blocks for bulk chemistry, like formic acid – this is the so-called electrocatalytic route. Catalysts play a leading role within both routes, so the link to materials research is never far away. VITO is working very hard on a new generation of heterogenous catalysts that may substantially increase the efficiency of these processes. Among other things, this is being done by 3D printing catalysts, CO₂ capture equipment and gas diffusion electrodes.

Chemical sector key stakeholder in carbon capture

There is no doubt that the chemical sector – which is energy-intensive and has high CO₂ emissions – is a key stakeholder in the CCU development process. Furthermore, it can use its traditional role of innovator to kick-start the rollout and development of CCU technologies and projects in other sectors. This will also allow the chemical industry to strengthen its position of enabler in the renewable energy transition – for example, by providing simplified storage and transport of energy in the shape of ‘green’ molecules produced with intermittent power sources like solar and wind. Methods to connect CCU with the future supply of renewable energy are being studied by VITO. Note that the CO₂ streams required for this may also come from other sectors, like the steel industry.

Carbon neutral building materials thanks to CCU

The building and construction sector may also benefit from CCU to become more sustainable. After all, the production of building materials contributes greatly to global warming. The share of concrete in human CO₂ emissions is between 5 and 8 percent worldwide – which is mainly the result of cement production. Here CCU can also help to reduce the emissions.

Accelerating a reaction called carbonation – which causes the formation of new rock in the earth’s crust – in optimum conditions and at high CO₂ concentrations allows alternative building materials to be created without having to use cement. VITO is actively working on the development of these “CO₂-neutral building and raw materials”. They typically use mineral raw materials that contain calcium or magnesium and come from various industrial sectors (energy, steel, construction, etc.).

An additional advantage of this technology is that it also offers an important contribution to the sustainable use of raw materials. This connects CCU to the transition towards a circular economy and a more sustainable materials policy, which are two key spearheads of the Flemish and European economy.

Smart upscaling of electrochemical reactions

Improving the process efficiency of catalytic reactions is the greatest challenge right now. In this field, VITO can use the expertise gained during a long-term collaboration with the Applied Electrochemistry and Catalysis (ELCAT) research group of the University of Antwerp. Both at VITO and the University of Antwerp, efforts are taken to scale up electrochemical reactions that work well in a lab (see “Capturing CO₂ from flue gases or ambient air – VITO research focus” box). This is done both in terms of conversion (more active reactions, allowing more end product to be made with less energy) and time (faster and more stable reactions).

At the same time, VITO is unleashing its expertise in techno-economic analyses on this upscaling process, allowing the various parameters to be optimised to ensure the economic feasibility of the final application. In this way, VITO is gradually moving the technology from a lab scale to a pilot scale.

Turning the Flemish economy and industry more sustainable and stronger is part of VITO’s core mission. The research into CCU should also be viewed in that light. That is why this is being done from various units and research domains to cover all the aspects of CCU: the fundamental chemical aspect, the engineering aspect, the techno-economic aspect, etc.

The focus here is not only on Flanders, but on Europe as well. The research focuses on the entire value chain, from CO₂ capture at chimneys or from the air all the way to the marketing of the end product. This makes CCU the subject of a very broad field of research. But at its core the challenge remains the same: reducing greenhouse gas emissions and converting CO₂ into products with economic value.

Direct air capture to meet emissions targets

For the time being, most of the CO₂ required for potential CCU applications is still being captured above chimneys of plants (so-called industrial point sources). But the greenhouse gas can also be collected directly from the air, although its concentration is obviously several orders of magnitude lower there. This approach is called direct air capture, or DAC.

By providing negative emissions, DAC may help to achieve the prescribed emission targets for CO₂. Seeing that this technology is still expensive at the moment, VITO is looking for strategies and developments to reduce the costs of CO₂ capture and accelerate its preliminary implementation in the field.

Carbon capture research at UAntwerpen, UGent and VITO

In 2019, a multidisciplinary partnership was established between the University of Antwerp, Ghent University and VITO to accelerate radical technological innovations within Flanders. Within this Capture initiative, various research programmes involving the capture, separation and conversion of CO₂ can be set up within the various stages of technological development.

The strategic partnership between the University of Antwerp and VITO, which dates back further, is also embedded within this initiative. It mainly focuses on catalysis (by the University of Antwerp) and supporting competencies like upscaling and techno-economic analyses (by VITO). “It is a combination of things,” explains Tom Breugelmans of the University of Antwerp. “There are many available technologies and possible CCU solutions. Joining forces allows us to go looking for the ideal combination. The whole life cycle analysis must be right.”

The ultimate goal is to valorise the knowledge gained and in this way serve industry in Flanders. This will be done by granting both SMEs and major corporations primary access to the research results and by including them in a vibrant and diverse business community.

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