Climate change and CO2 – the greenhouse gas carbon dioxide – are inextricably linked. But researchers are working hard on a solution to try and capture and recycle CO2. One way of doing that is by using miniature versions of chemical reactors small enough to fit in your pocket, a method currently being developed by the industrial engineers at Campus Diepenbeek.
CO2 is released when we burn fossil fuels, such as petrol or diesel. It’s also a by-product of large-scale logging and cattle farming. The gas accumulates and forms a blanket, as it were, in our atmosphere, causing the earth's temperature to rise and disrupting the climate. The good news is that we can turn the waste product that is CO2 into a raw material, but we first have to 'capture’ it.
Methods to capture CO2 already exist, but they sometimes do more harm than good. After all, this equipment also requires energy, which is not always renewable, and water. This water then needs to be separated from the CO2 again and this, too, requires energy. At the end of the day, it needs to be worth the effort, and the end result should benefit the climate.
Professor Mumin Enis Leblebici of the Centre of Industrial Process Technology (CIPT) in Diepenbeek feels that the solution to climate change lies with chemistry. His research team is studying new chemical reactors that can capture or recycle CO2.
The standard chemical reactor is a glass vessel that works as follows: chemicals are introduced, mixed, heated up or cooled down. This causes a chemical reaction, creating a new product that is the precursor for most paints, plastics and medicines.
But a new type of reactor can also purify air and, as a result, capture CO2. This is what’s called an aerosol reactor. No more of the big glass vessels standard for a chemical reactor, an aerosol reactor is a small nebuliser like the ones you can get at the pharmacy. Only this one isn't meant for inhaling medication, but rather for capturing carbon dioxide.
Atomised droplets actually form a net for CO2, explains Professor Leblebici: “We atomise droplets with chemicals in them. These react with the light, allowing the droplets to capture CO2 in the air. The trick is to atomise drops of the right size that – like the mesh of a fishing net – have to be just big enough to catch a particular fish, or in this case the CO2. The next step is collecting the droplets containing the CO2. And we’re very successful at this.”
The aerosol reactor is a good candidate solution for the capture of CO2, Leblebici continues. "Compared to standard capturing equipment, our reactor is cheaper to produce and it needs less water, for example. That means 60% less energy costs. The goal is that the aerosol reactor will become a standard filter in industrial chimneys."
With the aerosol reactor we atomise droplets with chemicals in them. These react with the light and capture CO2.
The researchers are also experimenting with another new chemical reactor: the monolith reactor. Not the massive rock you would imagine, on the contrary, the reactor is small enough to fit inside your pocket. Leblebici shows a few prototypes that were made – in one piece, hence “monolith” – with a 3D printer: small, almost transparent blocks with tubes less than a millimetre in length running through them.
"You let a liquid or a gas continuously flow through the tubes while irradiating the reactor with light. The light triggers a chemical reaction, transforming the liquid or gas into the product you want to make. Our monolithic reactor is the most energy-efficient reactor that works on the basis of light."
The liquids or gases flowing through the tubes of the monolithic reactor can be waste products such as glycerol, for example, a residual product from biodiesel: "The photochemical reaction of the light with the glycerol flowing through this sort of monolithic reactor results in other useful chemicals, such as acids and solvents, like acetone." And what's interesting is that this reactor can also convert CO2 into something else that can be used as a raw material, such as a biofuel, or raw materials for construction materials or medicines.
Both the aerosol reactor and the monolith reactor work on the basis of sunlight: “You could call our reactors chemical solar panels. We don't use the sunlight to generate electricity, but to produce chemicals directly.” Light is climate-friendly and a cheap energy source.
From the CO2 in factory chimneys to a new raw material: biofuel or raw materials for construction materials or medicines.
Leblebici thinks it will be possible, in time, to combine his two types of reactors to recycle CO2. "From the CO2 in factory chimneys to a new raw material. With the aerosol reactor we can capture CO2 and at a later stage convert it to a useful raw material using our monolithic reactor."
Leblebici's research is part of the Flemish government's Moonshot programme, which aims to make the Flemish industry CO2 neutral by 2050. “We’re running out of time. The challenge now is to translate what we’re able to do in the lab in very small quantities to a large, industrial scale. How do you capture tons of CO2 per minute and convert it efficiently into something else? Together with our partners in this project, we want to test a prototype in a factory by 2025. We’ll do it here in Diepenbeek, and aspiring industrial engineering students who want to help us with this are welcome to do so!"