Technology

Converting CO2 to rock

 By RP Siegel

A very important development in the battle against climate change took place in Iceland last month…

(Cover pic by Moyan Brenn, CC-By-2.0)

In a press conference on October 11, representatives of the public utility Reykjavik Energy (OR) and the Swiss company Climeworks, announced the launch of their partnership project called Carbfix2 in which CO2 collected from the atmosphere is injected underground where it mineralizes in basaltic rock formations, achieving a highly stable durable state.
According to the latest UN Emissions Gap Report, the current emission reduction trajectory reaches only roughly one-third of the 2030 target established in Paris. Therefore, it’s more important than ever to not only double-down on efforts to reduce emissions, but to establish a program of negative emissions, using both technology as well as natural systems to aggressively pull carbon dioxide from the air and to store it in solid form.
The Carbfix project began back to 2007, when Reykjavik Energy, in partnership with the University of Iceland, CNRS in Toulouse and the Earth Institute at Columbia University in New York, decided to investigate the idea of re-injecting the CO2 that was rising out of geothermal wells, in hopes of making them carbon neutral. After some years of design and development, several injections took place around the Hellisheidi geothermal plant in 2012. With the first injections, in which pure CO2 was injected into basaltic rock at a depth of 500 meters, researchers were surprised to find that CO2 mineralized quickly. In the second injection, where CO2 gas was mixed with hydrogen sulfide (H2S) gas, the mineralization occurred even more quickly. Analysis of the site found that 95 percent of the CO2 had mineralized, essentially, became rock, within a year after injection, while 100 percent of the H2S mineralized within four months.

A section of the mineralized carbon dioxide (or.is)

This is significant because it is unlike most other carbon sequestration efforts, which inject highly pressurized, supercritical CO2, and depend on impermeable cap rock to keep the buoyant gas from escaping, the fact that the carbon solidifies shortly after being injected, all but eliminates the risk of fugitive emissions. The Carbfix approach takes the additional step of dissolving the CO2 in water before injection, which eliminates the buoyancy effect during the injection process which further reduces the chance of escaping gas.
The second phase of the project, Carbfix2, added the capabilities of Climeworks, who has demonstrated the ability to pull CO2 directly out of the air with their modular, direct air capture (DAC) plants. Each module captures roughly 300 pounds of CO2 per day. Therefore, a plant consisting of 36 modules can remove approximately 4 million pounds of CO2 annually. The combination of the Climeworks technology with the Carbfix injection process provides a robust path to pulling carbon dioxide directly from the air and safely sequestering it away. The effort received funding from European Union’s Horizon 2020 research and innovation program.
According to Edda Sif Aradóttir, CarbFix project leader at Reykjavik Energy, “We have developed CarbFix at a unique location here in Iceland and proved that we can permanently turn this greenhouse gas into rock. By imitating natural processes this happens in less than two years. By integrating the Climeworks and CarbFix technologies we create a solution that is deployable where we have basalt but independent of the location of emissions. This is important to scale up the CarbFix approach on a global level.”

How Climeworks technology works (climeworks.com)

Now that the pilot plant, containing a single module, is in operation, the plan is to scale it up to industrial size by 2019, then to aggressively build more of these plants around the world, with the ambitious goal of capturing and sequestering 1 percent of global emissions by 2025.
What is the global potential of this approach?
First, it must be understood that it’s the unique composition of basaltic rocks, which contain substantial levels of calcium, magnesium and iron that make them particularly well-suited to convert CO2 dissolved in water into solid carbonate rocks. Basaltic rock covers roughly 10 percent of the Earth’s continental surface, as well as most of the ocean floor. Analysts at Reykjavik Energy estimate that the active rift zone in Iceland could store over 400 Gt CO2. The theoretical capacity of ocean ridges globally is anywhere between 100,00 and 250,000 Gt, as much as a decade or more of global emissions. As emission levels decline, that number of years could become greater.
Of course, nothing comes for free. A significant amount of water and energy are required to perform this operation. The good news is that salt water can be used, meaning that if the facilities are located near the ocean, there should be little impact on the fresh water supply. As for the energy, most of it is low grade heat. That is why locating the plants near operations such as power plants, or geothermal wells, or using solar facilities can do much to reduce the impact. Significant electric power is also needed to run the fans and pumps, but as the technology continues to develop, efficiency gains are likely to occur.
When combined with afforestation efforts, projects like these can be expected to slowly reverse the trend of ever-increasing greenhouse gas concentrations in the air, and perhaps walk us back from the brink of what could be some extremely challenging scenarios.

READ MORE: Turning CO2 into fuel by Rob Davies

about the author
RP Siegel
Skilled writer. Technology, sustainability, engineering, energy, renewables, solar, wind, poverty, water, food. Studied both English Lit.and Engineering at university level. Inventor.