How can we capture CO2 in a way that is not harming the environment? I use flowerpots in the lab as one way of finding out.
First: Why should we capture CO2 in the first place?
Carbon dioxide (CO2) is known as one of the culprits behind human made global warming and as a necessary means for its reduction, capture of it is essential. The Norwegian Carbon Capture and Storage research Centre (NCCS) is working on developing more efficient ways of, as the name states, capture and, safely and permanently, store carbon (here: CO2), for it not to be released into the atmosphere.
Amine solvents to the rescue
CO2 forms during industrial processes like the burning of fossil fuels or the production of steel and cement. One major way of capturing CO2 in this case, is the use of amine solvents: The gas containing CO2 is bubbled through a solution with amines, which captures the CO2 from the flue gas and allows us to collect and store it.
Amine solvents have been industrially used to capture CO2for many years, and I am working on finding better solvents for this purpose. One of the things that I am trying to understand, is why we often see “degradation” of the solvent over time, meaning that it no longer works as it should. Additionally, it is of course very important, that the solvent that is used does not harm the environment. I am therefore looking for two main qualities in the solvent:
- The perfect solvent should be environment friendly.
- The perfect solvent must be able to withstand the harsh process conditions.
What about the environment?
The solvent should not be toxic to people, animals or the environment. In case some of it were to leak from the gas cleaning plant, it should be able to degrade in to all-natural harmless new compounds in the nature.
To investigate how different solvents will act in nature and how they will degrade, I am making little ecosystems confined to flowerpots filled with soil and grass.
To these little microcosms, I am adding the amine solvent that we are investigating, and we can study where the solvent distributes itself; in the soil, the plants, or the surplus water that drips through the soil and also see how the plants are doing after we add it.
The degradation processes going on in these microcosms are quite complex, as both the plants, the bacteria and fungi in the soil, and the other elements that exist in, and close to the system can have an influence on them! With some advanced analytical instruments though, I can hopefully identify the degradation compounds that the environment breaks the amines down to, and with that understand what could happen if a solvent is released into nature. Once we know which compounds can be formed in nature, we can assess the safety of the solvent.
Another important aspect: Oxidative degradation
We want a solvent that can do the job of capturing CO2, but without being damaged while it is doing it. One of the other solvent qualities I am investigating, is therefore its ability to withstand the harsh process conditions. This includes elevated temperatures and presence of other gas components, like oxygen.
Contact with oxygen can lead to oxidation, and oxidation leads to degradation, whether it is a solvent for CO2 capture or the fruit tissue of a bruised apple. Just as the bruised apple cannot turn red again, there is no easy way to go back to the non-oxidized state of the solvent. In most of the capture processes, there is some oxygen present in the CO2 containing flue gas; and we are trying to find a solvent that can handle this.
Hard durability tests
When investigating this, we are putting the solvents through some hard durability tests, checking how they react when oxygen is bubbled through them at a elevated temperatures over a long period of time. Following all these experiments, we are analyzing all compounds that emerge from degradation reactions and determine their chemical and physical characteristics, to see if also these are harmless to people, process and nature.
- Industrial opportunities and employment prospects in large-scale CO2 management in Norway (#SINTEFblog – in English)
- Sammendrag: Industrielle muligheter og arbeidsplasser ved storskala CO2-håndtering i Norge (SINTEF – på norsk)
- Global Warming of 1.5 ºC – Special report (IPCC – Intergovernmental Panel on Climate Change)
This blog text is written by Vanja Buvik. She is a PhD candidate in the Environmental Engineering and Reactor Technology research group at the Department of Chemical Engineering,