The Mølleå wastewater treatment plant in Lyngby is one of the many plants in Denmark that produce biogas from wastewater. Here, DTU’s mobile carbon capture plant is to demonstrate over the next couple of months that it is possible to upgrade the gas in an energy-saving way, so that it becomes profitable to use it for other purposes than heating.
Biogas consists primarily of the greenhouse gases methane and CO2. It can be burned off immediately to generate heat, but it is also possible to upgrade it by separating the two gases. Methane can, for example, be used in natural gas supply, while CO2 is usually simply emitted into the surroundings. But CO2 is actually a valuable resource, and researchers from DTU are therefore now examining how the carbon can instead be captured effectively. This is done in the BioCO2 project headed by Associate Professor at DTU Chemical Engineering Philip Fosbøl. And it has now reached the stage in which the mobile plant is to be tested in reality.
The most characteristic feature of the plant is its tall tower. Here, the CO2 is passed through long pipes where it comes into contact with a liquid containing various additives. When the CO2 has been absorbed into the liquid, it is captured, and it will be extractable again in a purer form without sulphur and other biogas residues. It is thus transformed into a resource, i.e. a product that can be resold and utilized for other purposes
“Instead of seeing CO2 as an unwanted waste product, we can thus view it as a commodity. Today, CO2 is already being used for a wide range of purposes, including in the food and pharmaceutical industries, for welding and other industrial processes. At DTU Chemical Engineering, we’re also examining whether CO2 can be used for the production of synthetic aviation fuel,” says Philip Fosbøl.
Magic dust and heat pumps
The researchers are constantly optimizing the carbon capture liquid.
“It’s our magic dust that we’re trying to improve with new additives that can reduce energy consumption. We’re also working with new ways of regenerating the heat, and, most recently, an integrated heat pump has been installed in the plant,” says Philip Fosbøl.
A stringent plan has been laid for how the mobile plant will be tested in different contexts over the next few years. Among other tests, it will be connected to a Funen farm plant and to the Copenhagen incineration plant Amager Bakke. And it will then probably visit the cement company Aalborg Portland.
“In a more long-term perspective, the intention is that our partner Pentair Union will take some of the ideas developed in the project and turn them into a business. We’re aiming high and imagine that the technology will become internationally competitive, so that it can form the basis of a new export adventure for Denmark,” says Philip Fosbøl.