Carbon capture is gaining steam as a potential climate solution, with governments devoting funding to and scientists researching technology that can pull carbon dioxide out of the air and halt its global warming effects.

In some carbon capture cases, the greenhouse gas is pulled from the air and stored so it doesn’t affect the atmosphere, also known as carbon capture and sequestration.

But carbon can also prove useful for making a variety of products. With carbon capture and utilization technology, CO2 can be sucked up and used in chemicals, plastics, fuels like ethanol, and building materials like concrete or foam insulation. 

A University of Michigan study analyzed 20 ways CO2 could be captured and used and ranked them by which product bears the most climate benefits. According to a news release, it’s the first comprehensive study comparing a wide range of CCU-derived products.

“Our rankings will help prioritize R&D strategies toward products with the greatest climate benefit while avoiding pathways that incur a significant climate burden and that offer little hope for improvement,” Dwarak Ravikumar, former postdoctoral researcher at the University of Michigan, said in a news release.

The study

Carbon capture and utilization technologies can source carbon by pulling it from flue gases at facilities like power plants or cement factories, or it can be removed from the air via direct air capture. The UM study assumed the CO2 is captured from a natural gas power plant.

The researchers chose 20 products CCU could be used to make across three categories: concrete, chemicals, and minerals. Products in those three categories could gobble up to 6.2 gigatons of carbon dioxide annually by 2050, previous studies have shown.

The team crunched the numbers for nearly 200 datasets to determine which technologies create a net climate benefit, meaning the emissions captured outweigh the emissions generated while making the final product.

They determined the lifecycle carbon dioxide footprints of the materials and energy needed to make the CCU products. Next, they compared those CO2 footprint values to the footprints produced when making conventional versions of the products. And finally, the researchers developed a metric to rank and prioritize the CCU products in terms of climate return on investment.

Results

The researchers discovered that only four of the 20 CCU applications have a greater than 50% chance of generating a net climate benefit: Two use CO2 for creating concrete, one produces formic acid, and one makes carbon monoxide from methane.

Still, the researchers explained that many of the other technologies they studied will exhibit climate benefits under the right conditions, such as if renewable sources powered the CCU technology. “It’s just that the options to achieve these benefits are more restricted,” said Volker Sick, UM professor of mechanical engineering.

Right now, renewable energy typically has a greater climate benefit if it goes to the grid to offset fossil fuel emissions instead of being used to make CCU products, the team found. But that should change over time as fossil fuels are phased out and clean energy becomes cheaper and more widespread.

“This study is important for prioritizing and guiding the future development and deployment of CCU technologies, particularly as energy supplies decarbonize,” said Greg Keoleian, director of the Center for Sustainable Systems at UM.