Carbon Capture and Storage

by Delores Broten

Carbon capture and storage is the latest trendy “solution” to the impacts of burning oil and gas. Poli­ticians and many environmental or­ganizations around the world and in Canada are banking on it. The idea is to capture cabon dioxide (CO2) from refineries and coal burning power plants, and pipe it to geologi­cal deposits where it will be injected underground and stored forever.

To some extent, this is not a new trick. For decades the oil and gas industry has used carbon dioxide as a “flush” to pressurize older fields and force the remaining deposits to the well head. But in those cases the industry is not even trying to lock up the gas, which eventually eats away at the concrete well seals. It’s the permanent storage part that may be tricky, since so far only two full scale experimental sites have actually tried to keep the CO2 locked away.

The capturing part isn’t going to be as easy as writing a political speech either. “Clean Coal” is based on cre­ating synthetic gas from the coal in order to capture sulphur compounds, nitrogen oxides, mercury and other pollutants, as well as the CO2. How­ever, a successful and economical operating model remains as elusive as the Grail, despite several attempts and significant subsidies.

Getting the captured gas from the industrial facilities to the reburial sites will also be cumbersome and expensive, since it would involve con­struction of another massive series of pipelines with all the attendant emis­sions and expenses. The Energy Jus­tice Network, in their excellent fact sheet, “The Myth of Clean Coal,” notes that if 60% of the CO2 were to be captured just from the almost 500 coal fired power plants in the US, and compressed to a liquid for under­ground injection, “its volume would equal the US oil consumption of 20 million barrels a day.”

Then there is the issue of where and how to bury the CO2. This is where the two experiments mentioned come in. Since 1996, the Norwegian company, Statoil, has been injecting 1 million tonnes of CO2 a year un­derwater into deep saline aquifers at the Sleipner offshore gas field in the North Sea without leakage. Statoil has constructed special plants at the site to capture the CO2 from the gas as it is pumped so it does not need to pipe the CO2 to the site. The other ongoing ex­periment, at EnCana’s Weyburn Sas­katchewan site, pipes CO2 from North Dakota for injection into the depleted oil field. So far about 5 million tonnes has been disposed of and is staying safely underground without leaking.

This is just as well, since the CO2 is mixed with 3.5% hydrogen sul­phide and would be extremely toxic if it escaped. To put it all in perspective, one million tons represents one third of the carbon dioxide from one large coal power plant for a year.

There are some tried and true carbon storage methods. The deep sea deep well injection for operating off­shore oil and gas fields seems a prac­tical option. Soil enhancement with charcoal, first discovered in studying agriculture in the Amazon, promises to boost yields, retain nutrients in the soil, and sequester carbon, as does or­ganic farming in general. And then, of course, there are all the original “carbon sinks” of functional ecosys­tems, from peat bogs to coral reefs to old growth forests. But that’s not where the politicians are putting their money, not yet.


[From WS September/October 2008]

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