SkyClean: Well-known technologies can be the big gamechanger

1. August 2022

Properly used, pyrolysis can both remove CO2 from the air, obtain new green fuels and deliver green improvements to agriculture.

“Pyrolysis is one of the greenest methods there is, and we have known about it for many years. It is only now that you see the climate potential in it,” says Jesper Ahrenfeldt, Project Director at Stiesdal SkyClean, who together with colleague Jesper Noes is working on developing 20 MW pyrolysis plants in an innovation project in Energy Cluster Denmark.

The SkyClean innovation project will be able to remove 20 percent of agricultural CO2 emissions and do about the same for air traffic. Pyrolysis is good, old news for the climate.

When the government announced a target of 70% CO2 reductions by 2030, the Danish Minister for Climate, Energy and Utilities, Dan Jørgensen, repeatedly stressed that not all the green solutions that would contribute to achieving the goal were yet known.

New innovation and new technological solutions were needed – and the 70 percent ambition was to help develop them, it said.

When it comes to pyrolysis and the contribution to CO2 reductions, it is not so much about new innovation and new technological solutions.

It is more of a new view of known technologies.

“We have known and used pyrolysis for many years, among other things to produce coke for fuel,” says Jesper Ahrenfeldt, Chief Engineer at Stiesdal SkyClean:

“What’s new is to consider pyrolysis as a source of capture CO2, to see pyrolysis as a climate action and to leverage technology to make a positive contribution.”

Dark green

Pyrolysis has a huge potential to contribute to the climate fight, and the innovation project SkyClean explores the possibilities of lifting off the big blade.

In SkyClean, biomass is pyrolyzed in an oxygen-free environment. The biomass can be residual products from agriculture – straw from fields or residual fibres from biogas production, for example – which absorbed CO2 while it was growing. When biomass is pyrolyzed, the absorbed CO2 becomes two end products: Biochar, which can be ploughed into the soil by the farmer and act as soil improvers for the next 500 years; as well as pyrolysis gas, which can be a steppingstone on the road to biofuels.

When the pyrolysis gas is converted to biometanol or similar and burned, green CO2 is released, which in turn is absorbed by the biomass and included in the cycle:

“It’s not just green, it’s dark green. There is even an environmental benefit on top of that,” says Jesper Ahrenfeldt.

Displaces 20 percent

Pyrolysis eases the climate pressure from two of the major sources of CO2 emissions in Denmark. In total, agriculture and transport will each account for a third of the CO2 emissions we expect to have by 2030 – pyrolysis is good news for both, says Jesper Noes, Project Manager at Stiesdal SkyClean:

“We expect that by 2030 we will have between 80 and 100 pyrolysis plants that convert biomass into biochar and biogas. This will displace 20 percent of agricultural CO2 emissions and could do about the same for air traffic or heavy road transport,” he says.

To get there, you have to develop a 20 MW plant, and the innovation project is suitable for that.

“Even though we know the technology, we don’t know the scaling,” says Jesper Ahrenfeldt:

“The advantages of the innovation project are that we can scale it at a pace that ensures a positive progress. In close collaboration with DTU and other partners, we can develop the steppingstones that will make the project achievable,” he says.

Green oil fields

The project is anchored in Energy Cluster Denmark, and project manager Christian Munk Jensen sees great potential in it.

“We take a residual product – straw – which would otherwise rot in the fields and make it into CO2 storage in the form of biochar and CO2-neutral fuel,” he says.

“And when we use the fuel, the straw absorbs the CO2 again. This is CO2 negative and contributes to turning Danish fields into the new, green oil fields,” says Christian Munk Jensen.