Monday, October 10, 2016

‘We’d Have to Finish One New Facility Every Working Day for the Next 70 Years’—Why Carbon Capture Is No Panacea - by Bulletin of the Atomic Scientists

Site close to the Hellisheidi geothermal powerplant, where CO2 was injected into volcanic rock. In two years it was almost completely mineralised. (Photograph Credit: Juerg Matter/Science) Click to Enlarge.
A recent experiment in Iceland garnered a lot of press lately, including The New York Times and the Latest News section of Science.  It’s easy to see why: Scientists showed that carbon dioxide injected more than 1,000 feet underground into formations of basalt rock—which much of Iceland is made of—reacted very quickly with the minerals present in the rock to form new minerals that remain stable essentially forever. Chemically speaking, they turned carbon dioxide (CO2) into calcite (CaCO3), the principle constituent of marble and limestone.  Or, at the risk of oversimplifying, the researchers converted gas into stone, using what is essentially soda water.

At first glance, this approach promises to achieve a long-sought goal:  to remove carbon dioxide emissions—one of the chief greenhouse gases behind global warming—from the atmosphere, and lock them away deep underground in a carbon “sink,” where they can do no more harm.  Known as carbon capture and sequestration, or CCS, the work in Iceland with basalts marks an important technical advance in a line of attack that scientists have long pursued.  

The timing couldn’t be better.  For years, many scenarios used in the computerized simulations of carbon emissions mitigation have called for a big contribution from CCS.  Indeed, the models used by the Intergovernmental Panel on Climate Change (IPCC) require the large-scale deployment of this technology, while the Paris Agreement specifically calls for “removals by sinks of greenhouse gases in the second half of this century.”  This language stems from the growing recognition that the world is likely to overshoot the carbon budget required to hold the increase in global average surface temperatures to “well below 2 degrees Celsius above pre-industrial levels” and avoid the problems of rising sea levels, droughts, extinction events, mass migrations, and other disastrous consequences of climate change.  As a matter of fact, of the 400 IPCC scenarios that keep warming below the Paris agreement target, 344 involve the deployment of negative emissions technologies, wrote Kevin Anderson in Nature Geoscience.
Sequestering CO2 in basalts.
To get a better idea of the current situation, we first need to  better understand the CCS process in these rock formations.
For rock weathering to help solve the climate crisis in the immediate coming decades, a way has to be found to greatly speed up these reactions.  One solution may be to expose the rocks to concentrated doses of CO2 at high temperatures, in the presence of water—which is what the scientists in Iceland did.

In a peer-reviewed article in the journal Science, Juerg Matter—associate professor of geoengineering at the University of Southampton—and his colleagues reported on their experiment, in which volcanically-sourced CO2 was dissolved in water and injected into basalts at depths between 400 and 800 meters.  Using isotopic and chemical tracers, they were able to demonstrate that 95 percent of the CO2 they injected had become mineralized in the space of two years—much faster than expected.  Once CO2 has reacted with the calcium, magnesium, and iron-rich minerals naturally present in the basalt, stable and benign carbonate minerals like calcite are formed.  This process holds out the hope that CO2 sequestration can be permanent, and that long-term monitoring can be dispensed with. This is in line with some of the latest thinking about solving the climate crisis.
There certainly are some key snags that need to be overcome if CCS is to be used on a wide scale in basalts.  (There are several different ways in which to approach carbon capture and storage; we are focusing primarily here on the method that has caught the most attention lately:  converting carbon dioxide gas to solid form in basalt rock formations.)

For one thing, whatever type of CCS technology that is used, human beings would have to develop a huge carbon capture and sequestration industry that is about triple the size of the entire current fossil fuel industry.  And we’d have to do it fast—at a rate of about one new CCS plant completed every working day for the next 70 years, or from now until the year 2087.

For another thing, the CCS-in-basalts process used in the Iceland experiment requires almost unimaginable amounts of water.  And once the water and CO2 have been processed, an equally large area must be found to store that volume of resulting material.  And at this point it is unknown how well the results in Iceland can be applied at large scale in other locales.
If CCS is to provide a solution to the climate crisis, then over the span of 60 to 70 years, a new industry about three times the size (measured as mass) of the current fossil fuel industry would have to be developed.
There is currently no economic case for deploying CCS.  There is at least one other hitch to the use of any kind of carbon capture and storage:  The economics of CCS are marginal, even in cases where CO2 is stripped from natural gas—which has to be done anyway to make the gas saleable—and then injected into ailing oil fields to enhance recovery.  To extract CO2 from the combustion exhausts of fossil fuel or biofuel power stations and sequester it can cost from $50 to $100 per ton of CO2.  In the absence of carbon pricing or enhanced oil recovery, there is no economic case to be made for undertaking this.  Private capital is likely to avoid funding CCS until there are clear signs that a high carbon price, or equivalent emissions cap regulations, are imminent.
Some application of CCS, in some form, is likely to eventually be necessary.  To stabilize rising global temperatures requires not just greatly reducing emissions, but getting them to zero. 
But because of delays in reducing emissions, and the likely consequent overshoot in safe carbon emission budgets, there will be a need for a range of technologies capable of reducing the concentrations of carbon dioxide in the atmosphere.  But all negative emissions technologies will take time to implement, and time is the one commodity that humans are certainly squandering.

Read more at ‘We’d Have to Finish One New Facility Every Working Day for the Next 70 Years’—Why Carbon Capture Is No Panacea

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