It’s not CO2 itself that is the sinner. It’s the high concentration of it in our atmosphere that is problematic. CO2 is released in the atmosphere when all material is burned. It is, together with other greenhouse gasses, contributing to the containment of heat on earth, which causes our planet to warm up slowly, but inevitably.
If we continue business as usual, we won’t be able to live up to the Paris Agreement to limit the global temperature rise to 1,5 degrees. Cities all over the world have gotten the message that the planet is sending us. There are many major cities that have set ambitious goals to become CO2-neutral within a few years from now. But it won’t happen without new measures.
We must therefore turn to new technologies and methods that can help us clean the air. The past several years NIRAS has been working on a number of innovative projects, that map the best possibilities to capture CO2 and handle it responsibly.
To capture CO2
Basically, there are three ways we can decrease the concentration of CO2 in the atmosphere. We can limit our energy consumption and thereby reduce our CO2 output. We can also capture it and store it underground, which is called Carbon Capture and Storage (CCS), or we can capture CO2 and exploit it in different ways, called Carbon Capture and Utilisation (CCU). The latter can indirectly reduce CO2 emissions if the utilisation substitutes fossil based CO2 and thus avoids fossil CO2 emissions.
If we want to store or utilise the CO2, we have to start by capturing it. That means that we first and foremost have to decide where we want to capture the CO2. CO2 is not only to be found in the air that we breath, but also in the sea, in flue gas, biogas and in landfill gas.
There are many major cities that have set ambitious goals to become CO2-neutral within a few years from now, but it won't happen without new measures
Research, that NIRAS has contributed to, shows that it is attractive to start by capturing CO2 from biogas and flue gas, for example waste incineration plants. Flue gas has a CO2 concentration of up to 10 per cent, and it can be captured by already existing technologies. NIRAS has mapped these technologies in April 2019 in a report commissioned by the municipality of Copenhagen and Amager Ressourcecenter (ARC).
Capture CO2 from the chimney
ARC is the waste treatment plant that covers the greater Copenhagen area – the one with the ski slope on its roof. ARC is owned by five municipalities: Dragør, Tårnby, Hvidovre, Frederiksberg and Copenhagen.
The municipality of Copenhagen ambitiously aims to become CO2-neutral in 2025 and is therefore interested in reducing the CO2-outlet from its waste incinerator. Even though the citizens living in Copenhagen separate their waste in different categories, ARC will still be burning a large portion of trash that is fossil -based. This could be all from sneakers to nylon jackets or diapers. Waste of this type cannot reasonably be recycled.
It’s in the chimney, where NIRAS suggests to capture the CO2. Our technology screening shows that this is best done by amine absorption technology. The flue gas will be ‘washed’ with an amino acidic solution, which can absorb the CO2. The harvested CO2 is released in a desorber and converted into a liquid state.
Sailing liquid CO2 to the North Sea
In the report for the municipalities and ARC we also recommend what to do with the CO2, once we have captured it from the flue gas. This has led ARC to work with NIRAS to dig deeper in order to arrive at the optimal solution. In a sequential study, which we are currently working on, we are researching if it would be a realistic scenario to store the CO2 in abandoned oil- and gas fields or via new drillings in suitable geological structures in the underground.
We are investigating if it is feasible to sail the liquid CO2 to depleted oil and gas fields in the North Sea. Here we could pump the many tons of CO2 in reservoirs, which we know for certain are tight, since they have contained oil or gas for millions of years.
While we set out to map opportunities in a study like this, we also cover possible threats and insecurities associated with it. One of the crucial questions that need answering is: who will be responsible for the stored CO2? Who will ensure that the CO2 remains in the underground, also in the long term? Is it the state? Is it the party that shipped the CO2? Or will it be a third party? This is work in progress, but it is of the utmost importance that all scenarios are discussed, so decisionmakers can base their decisions on a proper knowledge base.
Expensive to utilise CO2
An alternative to CO2-storage is to utilise it instead. CO2 can be converted to something else, something useful. This we call CCU.
If we want to convert CO2 to something beneficial and make it available on a large scale, we need hydrogen. Hydrogen is the most common element on our planet, but it is not to be found in free form, only in molecules, such as in water (H2O). This means that you have to release the hydrogen first. This is done by electrolysis, a process where water is split into oxygen and hydrogen by electricity. If the hydrogen is to be green, which it should be, then the electrolysis process needs to be performed with energy from renewables. Green energy comes from for example sun cells, wind turbines or tidal power.
If large scale deployment of CCS and CCU technologies is to be a reality, then it's crucial that politicians worldwide dare to set the agenda
Once the hydrogen is released, it can be combined with the carbon in the captured CO2, and then it can be transformed to hydricarbons, such as methane, methanol or even aviation fuel . Unfortunately, utilisation technologies are not commercially viable at the moment but on their way. This has several reasons. The most important of them being that CCU-technologies require extremely large amounts of energy in order to be able to create hydrogen by electrolysis.
If we were to create all the jet fuel that is used in Denmark for intra- and intercontinental flights by producing hydrogen and combining it with CO2, we would have to use the energy of three times as many wind turbines as we have right now in Denmark. This is expensive to establish, but without green electricity there is no green hydrogen and without hydrogen we cannot produce synthetic hydrocarbons - also called e-fuels.
It is commonly agreed that large scale deployment of CCS and CCU technologies are crucial to achieving the goal of the Paris Agreement to limit global warming to 1,5 degrees Celsius on average. It is crucial that politicians worldwide dare to set that agenda. We need technology research that can map the best possibilities for the removal of greenhouse gasses from the atmosphere.
NIRAS is a frontrunner and we collaborate with highly specialised companies to collect and apply knowledge. We must create solutions that add value to both businesses and the environment. One of our employees has recently presented our findings on an international conference in Munich.
It is everyone’s business to act and to address the climate crisis. Fortunately, several European capitals have realised this. NIRAS is currently drafting a report for five European capitals - Amsterdam, Copenhagen, Helsinki, Oslo and Stockholm - to map the best possible ways to capture, store and utilise CO2.
It is of the utmost importance, that we keep on developing and start to implement all the innovative solutions we can use to capture, store and utilise CO2 to everyone’s benefit. Europe needs to be the frontrunner and catch CO2 before it takes us to prisoners. It’s an essential part of combatting global warming and the climate crisis.