New carbon capture system could cut the cost of decarbonisation

A new system that efficiently captures carbon dioxide and converts it into methanol could make the process more affordable and widespread, according to its developers.

Scientists at the US Department of Energy’s (DOE) Pacific Northwest National Laboratory (PNNL) created the system, which uses CO₂ to produce one of the world’s most widely-used chemicals.   

The largest emitters need incentives to adopt carbon capture technology, the researchers said, with high costs creating a longstanding barrier to widespread use.

Methanol could provide that incentive, the team said. The chemical holds many uses as a fuel, solvent, and as an important ingredient in plastics, paint, construction materials and car parts. Converting CO₂ into methanol offers a path for industrial organisations to capture and repurpose their carbon.

“Instead of extracting oil from the ground to make these chemicals, we're trying to do it from CO₂ captured from the atmosphere or from coal plants, so it can be reconstituted into useful things,” said PNNL chemist David Heldebrant, who led the research team. “You're keeping carbon alive, so to speak, so it's not just ‘pull it out of the ground, use it once, and throw it away.’ We're trying to recycle the CO₂, much like we try to recycle other things like glass, aluminium and plastics.”

The new system is designed to fit into coal, gas, or biomass power plants, as well as cement kilns and steel plants. Using a PNNL-developed capture solvent, the system ‘snatches’ CO₂ molecules before they’re emitted, then converts them into useful products.

Different systems can be used depending on the nature of the plant or kiln, but in every set up solvents wash over CO₂-rich flue gas before it is emitted, leaving behind CO₂ molecules bound within the liquid.

By using renewably-sourced hydrogen in the conversion, the team produced methanol with a lower carbon footprint than conventional methods that use natural gas as a feedstock.

Commercial systems soak up carbon from flue gas at roughly $46 per tonne of CO₂, according to DOE analysis. The PNNL team achieved a cost of $47.10 per tonne in 2021. Using the methanol system with different PNNL solvents has cut that figure to less than $39, according to a new study in the Journal of Cleaner Production.

“We looked at three CO₂-binding solvents in this new study,” said chemical engineer Yuan Jiang, who led the assessment. “We found that they capture over 90% of the carbon that passes through them, and they do so for roughly 75% of the cost of traditional capture technology.”

Other target materials for the conversion process include polyurethanes, which are found in adhesives, coatings, and foam insulation, and polyesters, which are widely used in fabrics for textiles.

“Once researchers finalise the chemistry behind converting CO₂ into materials that keep it out of the atmosphere for climate-relevant timescales, a wide web of capture systems could be poised to run such reactions,” a research announcement said.

A significant amount of work remains to optimise and scale the process, with commercial deployment likely several years away. Displacing conventional chemical commodities might only be the beginning, however, according to Casie Davidson, manager for PNNL’s Carbon Management and Fossil Energy market sector. “The team’s integrated approach opens up a world of new CO₂ conversion chemistry. There’s a sense that we’re standing on the threshold of an entirely new field of scalable, cost-effective carbon tech. It’s a very exciting time.”

The carbon capture and conversion research was published in Advanced Energy Materials.