Reported by Staff

PARIS - Dreams of slowing global warming by storing carbon emissions from power plants could be undermined by the risk of leakage, according to a study just published by Nature Geoscience.

Major industrialized countries have earmarked huge investment dollars toward the still largely unproven technology of carbon capture and storage (CCS). In fact, the European Union plans to invest billions of Euros within the next ten years to develop facilities that would extract CO2 at power plants and other combustion sites, and pipe it to underground storage units (land-based and oceanic), or unused gas fields.

In the U.S., coal-reliant states like Wyoming are funding new CCS plants in hopes of maintaining longterm energy  relevance in a reduced carbon world. 

Supporters say the sequestered carbon would slow the pace of man-made warming, and buy time for politicians to forge an effective treaty on greenhouse gases. Critics, however, say CCS could be dangerous if the stored gas returns to the atmosphere. They also argue that its financial cost, still unknown, could be far greater than tackling the source of the problem itself.

The research by the Niels Bohr Institute and published in Nature Geoscience sheds lights upon these issues. Large scale use of carbon sequestration could help to avoid extreme global warming that would otherwise occur in the near future unless fossil fuel emissions are reduced significantly. But it is not clear how effective different types of sequestration are in the long run, owing to leakage of stored CO2 back into the atmosphere. Nor is it clear what would be the long-term consequences of such leakage for the Earth’s environment.

Gary Shaffer, professor at the Niels Bohr Institute, and leader of the Danish Center for Earth System Science, made long model projections for a number of sequestration/leakage scenarios. His results show that leakage of the stored CO2 may bring about large atmosphere warming, large sea level rise and oxygen depletion, acidification and elevated CO2 concentrations in the ocean.

Storage of CO2 in the deep ocean is a poor choice since this creates grave problems for deep sea life and since CO2 stored this way returns to the atmosphere relatively quickly, bringing back the global warming.

Geological storage may be more effective in delaying the return of the warming and associated consequences but only if a CO2 leakage of 1 % or less per thousand years can be obtained.

“CO2 sequestration has many potential advantages over other forms of climate geoengineering. It makes good sense to modify the Earth’s radiation balance by putting carbon back in where it came from. Atmospheric CO2 is long-lived and evenly-distributed globally making it possible to manage it in a long-term, controlled way with less chance for unpleasant climate surprises. However, one should not underestimate potential short and long-term problems with leakage from underground reservoirs. Carbon in light form will seek its way out of the ground or seabed. The present situation in the Gulf of Mexico is a poignant reminder of that”, says Gary Shaffer.

Professor Shaffer concludes that “the dangers of carbon sequestration are real and the development of this technique should not be used as an argument for continued high fossil fuel emissions. On the contrary, we should greatly limit CO2 emissions in our time to reduce the need for massive carbon sequestration and thus reduce unwanted consequences and burdens over many future generations from the leakage of sequestered CO2.”