Meher Sanku is turning air into plastics
2020-04-16 Meher Sanku, researcher at the Department of Chemical Engineering at Lund University, has just defended her PhD thesis. Her work focuses on how to capture and utilise carbon dioxide – to create new building blocks for plastics. She is a researcher in STEPS work package one, which focuses on production of polyester building blocks from renewable feedstocks, including surplus biomass streams and carbon dioxide.
In recent years, carbon capture has started to attract an increasing interest, not only from researchers, but also from industry and policymakers. Countries need to drastically cut emissions, and capturing carbon is seen as a solution to reduce global warming. But, currently capturing carbon is both costly and energy intensive. That is why more and more researchers, including Meher Sanku, have become concerned with not only removing carbon from the atmosphere, but also to utilise it.
Yet, as a molecule, carbon dioxide is a challenge to work with, explains Meher Sanku. It is the last thing that is formed when you burn carbon-based resources such as oil and gas because it has very low chemical potential. One could draw an analogy to water flow. Water flows from higher to lower potential (or it flows with gravity). To utilise carbon dioxide is like making water flow upwards.
– I would say it is challenging but not impossible to work with carbon dioxide. The advantage of working with carbon dioxide is that it is a surplus compound, people want to get rid of it, says Meher Sanku.
So far, Meher Sanku and her group have succeeded in creating a system that could both capture and utilise carbon dioxide at the same time. They have used the compound amine, which contains basic nitrogen atoms, to create a reaction with the carbon dioxide. This process captures the carbon dioxide. By controlling the amount of carbon dioxide in the amine solution, the carbon dioxide can be bound either into the liquid solution or into a salt form. This liquid is then used to make building blocks to create polyester plastics.
– We came up with the idea to use the amine as a reactant for both processes. We combined the capturing process with the catalysis process for the utilisation step, to both capture and then utilise the carbon dioxide.
– If we can separate plastic production from the capture and utilisation of carbon, it is a good thing. We would then avoid having to build several plants and systems in the same place, for example, and more companies can contribute to the production and distribution of new plastic polymers.
Around the world, some companies have already started to use carbon dioxide to produce plastics, for example foams for mattresses, and shoes. This indicates that there is a growing market to use carbon dioxide as an alternative feedstock. Plastics made from carbon dioxide can attain different properties, depending on the amount of carbon dioxide incorporated. For example, a small amount of carbon dioxide makes for softer, more malleable plastic, whereas larger amount yields a plastic which is harder and more durable.
– Today, plastic production in general is not sustainable. It could be sustainable based on how the plastics are produced and the rest of their life cycle. In the context of plastic production, using carbon dioxide as a feedstock has a lot of potential.
– The big hurdle to carbon capture is to create a market which is willing to pay for it. This can be done by decreasing the cost of capture and/or combine capture with processes of economic benefit like utilisation of carbon dioxide to produce plastics.
– We are trying to do both decrease the cost of capture and give it an economic value by producing value added products from it. The size of the market for products based on carbon dioxide is very small. But if sustainable plastics are produced from carbon dioxide, that market share can be increased. If we concentrate our efforts in decreasing the emissions of carbon dioxide and simultaneously utilise the emitted carbon dioxide in sustainable plastics production, we can have a sustainable yet economically viable society, concludes Meher Sanku.