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Geology Matters When it Comes to Storing Carbon

By Tara Thean

 

For all the promise of carbon capture and storage to reduce carbon dioxide emissions, the technique faces an uphill battle to becoming widely adopted. That's because like most things, carbon capture and storage – also known as CCS – does not fit well into any one-size-fits-all formula.

A recent study looked at three prominent CCS sites to see how they responded to the process, and the results suggest that environmental engineers need to be extra careful when selecting locations for storing the gas securely.

The Vattenfall carbon capture and storage facility at Schwarze Pumpe, Germany.
Credit: Vattenfall/Flickr

At a sufficiently large scale, CCS is a technique that may allow power plants to operate without adding greenhouse gases to the atmosphere – though so far, policy and regulatory hurdles and high costs have prevented that scale from becoming a reality. CCS efforts capture emissions at their source and inject them into an underground reservoir of porous rock.

Current CCS technology could lower carbon dioxide emissions by 80 to 90 percent. For a typical 500-megawatt coal power plant, that’s the equivalent of planting an extra 62 million trees and leaving them to grow for 10 years, according to the Environmental Protection Agency.

"In reality, we know that it is technically feasible to put several million (metric) tonnes of carbon dioxide in the ground and have it stay there," said James Verdon, the study's lead author and a research fellow at the University of Bristol in the U.K., in an email. "But not all sites will be successful."

Leakage is a central concern, with critics concerned that continuous leakage will undermine any climate mitigation that might have come from CCS in the first place. Many point to the disaster in Lake Nyos, Cameroon in 1986, when a naturally released cloud of carbon dioxide asphyxiated 1,700 people and 3,200 animals, as a sign of the serious local risks CCS also poses.

For the study, published in the Proceedings of the National Academy of Sciences, Verdon and his colleagues examined three commercial-scale CCS sites that receive upwards of 1 megaton of carbon dioxide injection per year, and thus represent some of the world’s largest-scale CCS projects, to see how they reacted to having gas pumped underground. The sites include the Sleipner Field in the North Sea, the Weyburn Field in Canada, and the In Salah Field in Algeria.

The In Salah site turned out to be a questionable site for carbon injection. Its rocks have low permeability, which led engineers to "push" carbon dioxide into the Earth harder to ensure that the rocks soak it up. However, using higher pressure at injection points has caused fracturing and uplift of several centimeters.

The Weyburn site has proven to be something of a middle ground: 45 years of oil production before its first carbon dioxide injection mean there’s extra space to store the gas underground. However, numerous stress changes to the site caused by water and carbon dioxide injection occurring simultaneously with oil production have led to counterintuitive locations for small seismic events: at Weyburn, these events occur in production wells rather than injection sites – rather than the other way around – because previous activity has altered how stress changes around the reservoir upon production or injection.

In contrast, Sleipner showed hardly any fracturing or uplift because the reservoir where carbon dioxide is being pumped is large enough to provide ample space for the gas to move in without disturbing the land above it.

The researchers' characterization of the three fields adds an important dimension to the debate. Indeed, Vernon and his colleagues found motivation for their work in a 2012 Proceedings of the National Academy of Sciences paper that criticized the strategy, arguing that forcing gas into the brittle rocks of the Earth's interior would cause earthquakes that could then breach seals and bring the gas back to the earth's surface. The more recent investigation of three CCS sites suggests that appropriate locations do exist. Scale is still one of the main issues going forward, Vernon said.

"For CCS to make a dent on global carbon dioxide emissions, we need to be storing billions of tonnes of CO2 a year," Vernon said, adding that such a sizable need for storage means some failure is inevitable.

To limit such failures, CCS initiatives will need to conduct detailed appraisals of each site before gas injection and ensure comprehensive monitoring thereafter, according to Donald White, one of the study’s co-authors and a Geological Survey of Canada senior research scientist. White sees studies like this one as part of an ongoing effort to help define what "adequate" characterization and monitoring should look like.

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Comments

By Lewis Cleverdon (Wales)
on July 17th, 2013

“At a sufficiently large scale, CCS is a technique that may allow power plants to operate without adding greenhouse gases to the atmosphere – though so far, policy and regulatory hurdles and high costs have prevented that scale from becoming a reality. “

I wonder if the coal industry in the US, like that in the UK, has also been pushing this ‘Clean Coal & Jam Tomorrow’ hype since the 1970s ? The advocates’ claims that capturing and disposing of ~85% of a power station’s CO2 output will ‘only’ require 30% of its power output seems a notable demerit. As does the fact that the new infrastructure needed to process and transport just 10% of present anthro-CO2 output being captured and liquefied would be equal to the last 80-years-worth of the oil industry’s global infrastructure.

So how about a best case appraisal of Native Afforestation for Carbon Recovery & Interment for Farm Fertility Enhancement and Methanol [NACRIFFEM] ? For this approach we at least have the 2,000yr trials in the Amazon’s huge “Terra Preta” areas as a baseline of practical utility, as well as the prospect of two income streams, as well as easy verifiability, as well as the benefits of huge rural employment globally and of massive gains in high-biodiversity habitats.

Sadly the fact that it doesn’t provide a fig-leaf for the fossil lobby as it should obviously be used for Carbon Recovery, that is, for lowering airborne CO2 concentrations, rather than for rip-offsets to serve continued fossil lobby profits, means it somehow doesn’t seem to get much attention.

Regards,

Lewis

Reply to this comment

By Dave (Basking Ridge, NJ 07920)
on July 17th, 2013

If a wind turbine or solar panel fails then it is no big deal for safety and the environment. If instead a practically large CO2 storage site containing say a billion tons of this colorless odorless asphyxiating greenhouse gas were to experience a catastrophic failure then the same thing cannot be said. Notwithstanding that specific and ultimately thorny issue of the feasibility of safe storage and just how safe is safe enough, the net engineering challenges to achieving widespread cost effective implementation of CCS also remain very significant.

In the best possible scenario, and if CCS R&D investment continues, then effective CCS solutions of dubious long term potential safety would still be decades away. The motivation for ‘greening up’ fossil fuels is obvious. An energy hungry world matched up to politically powerful fossil fuel business interests are formidable forces. CCS is a way for energy companies to say that they are working on making their fossil fuel cleaner and more environmentally friendly. We have all seen the ads. Today that’s about all CCS is ‘good’ for.

Reply to this comment

By Conodo Mose (Spokane, WA 99208)
on July 23rd, 2013

Most dummies realize that carbon dioxide need not, should not be stored, sequestered at any location outside of the atmosphere or biosphere except in plants and carbonate sediments, i.e. limestone, trees, grasses, including plants especially those to grow our food as carbon dioxide is a natural fertilizer. Farmers, horticulturalists as myself hail CO2 for food production. Historic carbon dioxide levels have reached tens or more times their current level yet the biosphere did not implode/explode. Beyond the useful secondary recovery purpose, the irrational’ short-sighted wish to “hide” carbon dioxide should examine two realities: first is the carbon cycle to consider how hare-brained a fools mission is CCS. Secondly, the biosphere fail-safe is at work without need of mindless CCS madness. Its called carbon dioxide solubility. One can only conclude that CCS-promoters have no knowledge of basic chemistry, which is sufficient reason to reject CCS craziness and to consider the underlying motive in this propaganda.

Reply to this comment

By Philip (Opelika, AL 36804)
on July 25th, 2013

It is of deep concern that most everyone misses the point.  The earth has inefficiently put carbon in storage for over 4 ½ billion year or so.  The carbon atom is stored in numerous ways and most storage is in the form of fossil fuels (i.e., coal, oil, gas, etc. in the form of hydrocarbon chains) and in rock form (i.e., carbonates, etc.).  I have never seen a scientific budget of oxygen discussed in politics.  To burn a carbon chain will result in the consumption of four oxygen atoms per one carbon atom: (i.e., CH4 + 2O2 = CO2 + 2H2O).  Another words, we essentially losing 4 oxygen atoms per one carbon atom to the atmosphere and water.  By the continuum of burning carbon at unprecedented rates way beyond the Earth’s capacity to replace the atmosphere’s oxygen by photosynthesis or equivalent, the Earth’s atmosphere has only one direction and that is to revert back in geologic time (i.e., less oxygen and more CO2 among others).  Going back to a primitive atmosphere is a place that most plants and animals do not need to go because we all have adapted to where we are today.  Now you want to sequester CO2 and inject it permanently into the ground???  You have just sequestered oxygen at 4-times the rate of carbon sequester.  We are simply losing our oxygen supply.  I know some will argue this is impossible, but please think about it closely and crunch the numbers.  Answer is STOP burning fossil fuels period.  I have not even mentioned climate change, acidification, loss of coral reefs worldwide, genetic changes, rise in sea levels, etc.

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By David Dockstader (Louisville, KY)
on July 29th, 2013

Philip says crunch the numbers. Did you? Oxygen is about 20% of the atmosphere while CO2 is about .038%, up about .01% in the last 150 years. It would seem that the necessary sequestration to maintain reasonable levels of atmospheric CO2 will not make much of a dent in atmospheric oxygen. On top of the 20% of the atmospheric oxygen also accounts for 50% of the Earth’s crust. Oxygen is not rare or scarce.

Reply to this comment

By Bob Barnwell (Montgomery, AL)
on August 6th, 2013

David has pointed out the abundance of oxygen but should not take lightly any proportional change with elements.  Measurement of CO2 in atmosphere started about 90 years ago, statistical changes are always questionable.  You may have 50% percentage oxygen in the earths crust (silicates) and even higher percentages in the ocean but you can’t breathe rocks and water.  There is much oxygen to breathe as David indicated but we should not be mindless/unaware of the impacts to our growing world.  Hate to think we will need those stem-cell burgers.

Whether you sequester or not, CO2 amounts have exponentially increased since our industrial age. Modify the equation,  things change….  We will probably just see wild weather patterns in our lifetime.  However, as our atmosphere gets to detrimental levels that are recognized by all, it will be too late to reverse the curse in any short time span.

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