Carbon mineralization examined as storage strategy

It’s a familiar refrain among Carbon Management Canada’s HQP. In conversations and interviews, when asked ‘why carbon management research,’ they respond that it’s not only the science that draws them. It’s also the issue.

Anna Harrison, a PhD student examining ways to accelerate carbon mineralization in mine tailings, and Ian Power, a post doc working with an enzyme that converts gaseous CO2 into an aqueous form, say concerns about climate change fuel their passions for research.

Issue of the day

“Climate change is the issue of the day,” says Ian who, like Anna, works for Greg Dipple, professor and head of UBC’s Department of Earth and Ocean Sciences. “The research has an applied side to it – that’s something that drove me toward doing this work.”

Anna, who has an undergraduate degree in environmental earth science, says part of the reason she was drawn to Dipple’s lab was the opportunity to undertake work that would make a difference. “It’s a relevant issue and it’s important to look for solutions.”

Research promising

Based on early results, their research looks promising. Both are examining ways to accelerate the sequestration of CO2 in mine tailings – albeit from different angles. Carbon mineralization relates to the formation of carbonate minerals that are a long-term, stable strategy of storing atmospheric CO2. In nature, this process aids in stabilizing the concentration of atmospheric CO2 over geological time scales. If researchers can find ways to speed up this process, carbon mineralization may help reduce levels of atmospheric carbon and mitigate the impacts of climate change.

Anna’s work involves increasing the concentration of CO2 supplied to a slurry similar in chemical composition to tailings process water. She alters the amount of CO2 passed through the slurry and measures the speed of mineralization. The results have been exciting.

“You don’t need to go to 100% CO2 to get significant acceleration. You can get a 200 fold rate increase over atmospheric levels just by increasing the concentration of CO2 to 10%” she said.

Cost effectiveness key to uptake

Enabling the mineralization process using levels of CO2 typically found in flue gases, as opposed to requiring a pure stream of the gas, is more cost effective which will make the technology more attractive for industry.

Ian focuses on using an enzyme, carbonic anhydrase, that catalyzes the hydration of aqueous CO2 to a form that can be mineralized.

“That hydration step is rate limiting. We ask what is the slowest step, and we find ways of speeding it up,” says Ian.

Dual approach planned

Ian and Anna are going to combine their work – using higher concentrations of CO2 with the enzyme. They anticipate the dual approach will lead to a greatly enhanced acceleration rate.

“If you get a complete reaction within 75 hours (with increased CO2), with the enzyme we are hoping after 7 hours you get 100 per cent conversion of the original minerals into carbonates,” he says.

Public attitudes toward the geological sequestration of carbon are mixed with concern over leaks often cited as reasons against CCS. Sequestering CO2 through carbon mineralization eliminates that worry because the carbon will be stored in solid, mineral form for thousands to millions of years.

As Ian says, “Carbonate minerals are a solid thing you can hold on to.  We’re confident the carbon will be locked in for quite some time.”