Burying CO2 Under the Ocean?

Carbon capture is the most promising technology for reducing emissions from coal-fired power plants, by capturing it and injecting it in geological formations underground. Now, one of Canada’s foremost experts on carbon capture says that we could also store the CO₂  in gigantic inflatable bags that could be stored several miles below the ocean’s surface. 

Dr. David Keith is the director of the Energy and Environmental Systems Group at University of Calgary-based Institute for Sustainable Energy, Environment and Economy, and he sees this solution as a potentially useful complement to CO₂ storage in geological formations, particularly for CO₂ emanating from sources near deep oceans. The flat plains that cover deep oceans are good storage environments, he argues, because they have little life and are benign.

For CO₂ to be stored there, the gas must be captured from power and industrial point sources, compressed to liquid, and transported via pipelines. When the liquid CO₂ is pumped into the deep ocean, the intense pressure and cold temperatures make it negatively buoyant.

“This negative buoyancy is the key,” explains Keith. “It means the CO₂ wants to leak downwards rather than moving up to the biosphere.”

There are currently no power plants that use a full capture and storage system, primarily due to the cost of implementation and the inefficiency of the current systems, which would increase energy costs from 20 to 90 percent. When implemented, a CCS applied to a modern conventional power plant could reduce CO₂ emissions to the atmosphere by approximately 80-90 percent compared to a plant without CCS.

There are other carbon capture projects underway in the U.S., and a professor at the University of Texas in Austin has developed a system that received a $1.8 million, six-year grant from TXU Power to develop. Chemical Engineering Professor Gary Rochelle is an expert on reducing industrial emissions, and has two decades of experience developing and testing similar technology to remove hyrdogen sulfide and carbon dioxide from natural gas.

His technology involves two steps for treating carbon dioxide produced by burning coal. First, carbon dioxide gas is absorbed into a special chemical solution, so it can be collected. The next step concentrates and isolates the carbon dioxide so it can be compressed to high pressure and cooled to form a liquid. With the same decades-old process now used to recover oil from reservoirs, the liquid carbon dioxide can then be injected underground into sandstone formations for storage. The system could be ready for testing in small, coal-fired plants in 2009, and larger plants in 2015.

Although these carbon capture technologies sound like a reasonable solution for reducing power plant emissions, I have to wonder if the research money wouldn’t be better spent on  developing alternative energy sources. In fact, there are suggestions that the end is near for coal-fired power plants, as new emissions regulations are on the table in D.C., and there is a growing public discontent with pollution caused by burning fossil fuels.