Carbon Capture And Storage/Sequestration (CCS)
Many people still aren’t aware of what Carbon Capture and Storage (CCS) is, so I thought I’d publish an article outlining it – and some of its associated problems.
CCS is one of a suite of so-called “clean coal” technologies that will supposedly allow us to continue burning coal for electricity generation but with drastically reduced carbon emissions.
How Carbon Capture And Storage Works
– Carbon dioxide is extracted through one of three processes (information from GreenFacts):
Post-combustion: carbon dioxide is captured after the coal is burned by injecting the flue gases into a special solvent, which is then reheated to release the CO2.
Pre-combustion: the coal is heated in steam and air or oxygen, creating hydrogen and carbon dioxide. The hydrogen is separated out for use as a fuel and the remaining carbon dioxide captured.
Oxy-fuel combustion: the coal is burned with oxygen, resulting in steam and carbon dioxide. Cooling and compressing of the gas stream separates the steam from the CO2.
– In whichever capture scenario, the carbon dioxide is compressed and either stored in vessels on site for shipping later or piped away.
- The compressed carbon dioxide is then injected underground, below the ocean floor or into the ocean itself.
It’s all very complex, energy intensive and fraught with potential dangers.
CO2 Capture – The Energy Hog
To capture, transport and sequester the carbon dioxide takes energy – and a lot of it. I’ve read various figures, ranging from 25 – 40% more energy required just for the capture and compression aspect that occurs at the power plant.
Even at 25%, that means a lot of extra coal needs to be burned. It’s great news for coal mining companies, but not so good for the environment as coal mining is incredibly destructive in itself, even before the product is shipped and burned.
Add to that the energy required to transport the compressed CO2 and then finally store it underground and it all becomes quite an energy hog. While renewable energy resources could be used in some cases and aspects of CCS to supply power for associated processes, it’s somewhat of an unholy alliance with dubious outcomes.
Carbon Sequestration – Nature’s Warning
In terms of storing the carbon dioxide, CCS is essentially the same as sweeping dirt under a rug – something humanity has become quite good at – but with one important difference.
Potential storage sites for the CO2 include old oil and gas fields. What happens if all that compressed CO2 leaks? Nature has already provided us with an important precedent we should take note of.
In 1986 at Lake Nyos in Africa, a massive natural release of carbon dioxide occurred that killed around 1,700 people and thousands of animals. Since carbon dioxide is denser than air, the CO2 stayed close to the ground; forming a layer that suffocated anything in its path.
While storage points may be well away from human habitation, that’s little comfort in terms of local ecosystems where they are situated. Claims of injection points of being safe are fine; but how many times have we been told a potentially dangerous and polluting activity is safe, only for disaster to occur?
The Ocean As An Emissions Dumping ground
Other forms of sequestration include injecting it into the ocean itself. One method is to pump it down to a level where the CO2 will be naturally dissolved in seawater before reaching the surface. However, our oceans are already working overtime in mopping up carbon dioxide from the atmosphere to a point they are now becoming measurably more acidic and affecting marine organisms.
Another option is to release it even deeper where the pressure will keep the compressed carbon dioxide down – but again, also impacting on the surrounding ecosystem and it’s not guaranteed 100% it will stay where it’s put.
What Carbon Capture And Sequestration Won’t Do
Extracting carbon dioxide from the gases of a coal fired power plant does nothing to address another issue – mercury emissions. Power plants are the world’s major source of atmospheric mercury and the contamination has spread to every point on the planet.
Aside from mercury, burning coal releases other toxic materials such as arsenic, lead and radium. While other “clean coal” technologies used in conjunction with CCS can address particulate pollution; they do not address these pollutants.
Once the extra coal to provide energy for CCS processes is burned, fly ash is created – huge quantities of this stuff are stored around the world. Fly ash contains more of the above toxins.
CCS – A Dangerous Diversion?
Millions of dollars have been poured into carbon capture and sequestration and we still aren’t even close to a commercially viable solution.
CCS is all about more coal, more mining, more expensive electricity, more toxic emissions, more control for “Big Energy”, more danger and more damage. The promise of a CCS solution is also providing what may be false hope, therefore impacting uptake and stealing support from other cleaner sources of power.
Even if carbon capture and storage does become commercially viable, a very valid concern is that rather than being used as an interim solution to buy time while we wean ourselves off the filthy fossil fuel, it will then provide an excuse for business as usual; again to the detriment of clean, renewable energy – and the environment.
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