No matter what kind of action the U.S. or rest of the world takes on climate change, we’ll continue to burn coal for decades. And we face more than 2 degrees Celsius of warming (3.6 degrees Fahrenheit), and the risk of unstoppable sea level rise, unless 80 percent of the world's coal reserves remain in the ground. One of the ideas for mitigating climate change, then, is removing carbon pollution from the air and burying it deep underground. It’s called carbon capture and storage (CCS), and the technology still has a long way to go before it's feasible. CarbFix, a $10 million project in Iceland, is working on a solution to one of the major challenges of this approach: How to make sure the carbon stays in the ground. 

According to a New York Times article Tuesday, CarbFix injects the gas into water (25 tons of liquid per ton of gas) and pumps it into basalt, a reactive rock that makes up 90 percent of Iceland's underground. Using basalt speeds up a natural chemical reaction, which turns the carbon into a harmless solid—a rock. But under natural circumstances, the process can take centuries. Before that can happen, carbon would bubble up to the surface, and leak into the atmosphere. CarbFix, though, is studying how to speed up this process so it occurs in a matter of years. What's unique about CarbFix's process is how it combines the gas with water, an extra step that makes storage both more effective and more expensive. Other forms of carbon storage condense carbon into a liquid-type substance without water, leaving it more likely to escape to the surface.

Proponents of the technology say that just like scrubbers "clean" coal to lower sulfur and nitrogen emissions from power plants, carbon capture can cut down on carbon emissions. 

But even if CCS science develops, it likely won’t reach the kind of scale—billions of tons of stored carbon—that's necessary to fight climate change. The technology faces two major obstacles: Economic cost and political indifference. It is extraordinarily expensive to capture and store carbon. It not only requires power plants to install equipment for capturing and transporting the carbon, but also necessitates huge water reserves. Coal companies have no incentive to invest in the technology on their own, when it’s inexpensive to let carbon escape into the air. That’s why there are only a handful of large projects around the world. The Times says CarbFix's method costs $17 per ton of carbon dioxide, which is "about twice the cost of transporting and injecting the gas alone."

Of course, regulation and the right policies can compel companies to do this, too. For example, an aggressive tax on carbon—essentially fining companies for polluting—would help to make CCS more appealing. The Obama administration’s proposed regulations on power plants also require future plants to invest in CCS technology to capture between 30 and 50 percent of their carbon emissions. 

But investing in renewables and energy efficiency makes more sense than mandating an unproven technology that doesn't solve long-term warming. According to a report Tuesday from the National Research Council and National Academy of Sciences, "most carbon dioxide removal strategies have limited technical capacity, and absent some unforeseen technological innovation, large-scale deployment would cost as much or more than replacing fossil fuels with low carbon-emission energy sources." When it comes to mitigating climate change, the report said, "There is no substitute for dramatic reductions in greenhouse gas emissions."