Saturday, August 1, 2009

Storing carbon underground can have unintended consequences

From Greenpeace - "FALSE HOPE

One of the key challenges for CCS is the safe and permanent storage of captured carbon. Even very small leakage rates could completely undermine any climate mitigation efforts.

The world has no experience of the long-term storage of anything, let alone CO2.
As the results of a 2006 United States Geological Survey (USGS) field experiment1 show, there is every chance that carbon dioxide will behave in ways that are totally
unexpected. The USGS scientists were testing deep geological disposal of carbon dioxide at a pilot project in Frio, Texas.

The researchers were surprised when the buried CO2 dissolved large amounts of the surrounding minerals responsible for keeping it contained. The CO2 reacted with salty water (brine) in the geological formation turning it as acidic as vinegar. This acidified brine then dissolved other minerals, including metals such as iron and manganese, organic material and relatively large amounts of carbonate materials. Carbonates naturally seal pores and fractures in geological sites; the reaction of the acidic brine with them is extremely concerning. Carbonate is also found in the cements used to plug abandoned oil and gas wells. If these open, CO2 could leak into the atmosphere and/or the contaminated brine could leak into the aquifers that supply drinking and irrigation water.

In an interview with Greenpeace, lead scientist Yousif Kharaka warned that the results are “a cautionary note: for detailed and careful studies of injection sites, and a well thought out monitoring program to detect early study show that we simply do not know enough about how stored carbon will behave to be able to assure its safe and permanent storage.

1 Kharaka Y K, Cole D R, Hovorka S D, Gunter W D, Knauss K G & Freifeld B M, ‘Gas-water-rock interactions in frio formation following CO2 injection:
Implications for the storage of greenhouse gases in sedimentary basins’, Geology, vol., 34, no. 7, 2006, pp. 577–580.
2 Kharka, Yousif, 2007, USGS, Research Hydrologist, Interview conducted over e-mail.