Undersea volcanic rocks offer storage for greenhouse gases

Posted by Samantha Rose

Chicago (IL) - A group of scientists has conducted experiments utilizing deep ocean-floor drilling to show that volcanic rocks located off of the West Coast of the U.S. and in other areas could potentially be capable of securely capturing and storing large amounts of global-warming causing carbon dioxide that is captured from power plants and other sources. According to the scientists, natural chemical reactions under 30,000 square miles of ocean floor off of the coast of Oregon, California, Washington and British Columbia could potentially be capable of trapping as much as 150 years worth of U.S. carbon dioxide production.

The process has been deemed carbon sequestration and the interest in the process is beginning to grow worldwide. As of yet, there are no large-scale projects underway, and other geological settings could potentially pose problems. For example, the petroleum industry has been pumping carbon dioxide into voids that were left by old oil wells on a small scale. Some individuals fear that these could eventually leak, which would allow gas to seep back into the air which could be harmful for individuals in the area.

However, lead author David Goldberg, a geophysicist at Columbia University's Lamont-Doherty Earth Observatory, called the study "the first good evidence that this kind of carbon burial is feasible."

"We are convinced that the sub-ocean floor is a significant part of the solution to the global climate problem," said Goldberg. "Basalt reservoirs are understudied. They are immense, accessible and well sealed - a huge prize in the search for viable options." One of the main advantages, he said, is a chemical process between basalt and pumped-in carbon dioxide that would convert the carbon into a solid mineral.

In their study findings, Goldberg and the scientists he worked with, Taro Takahashi and Angela Slagle, utilized findings from pervious deep-ocean drilling studies at the Jauna de Fuca plate, which is located about 100 miles off of the Pacific coast. They used the findings to chart a vast basalt formation they feel could be used for this type of pumping. Basalt is the basic component of the ocean floors: It is hardened lava that has erupted from volcanoes and fissures under the oceans and seas. Off of the Pacific coast, the majority of the basalt is located in a depth of 2700 meters (8850 feet) and below 200 meters (650 feet) or more of overlying fine-grained sediment.

The Integrated Ocean Drilling Programs apparently has shown that the rock is porous and honeycombed with watery channels that could provide space for pressurized carbon dioxide. The scientists created a map of specific sites that are isolated from earthquakes, hydrothermal vents, or other factors that might upset the system.

Ongoing experiments that have been conducted by Lamont scientists on land have shown that when carbon dioxide is combined with basalt, the gas and components of the rock react together naturally, creating a solid carbonate like chalk. To demonstrate the effect, a separate team that will be lead by Lamont geochemist Juerg Matter plans to pump will into a basalt formation on land located at a power plant near Reykjavik, Iceland.

While basalts exist at or near the surface of other land areas such as the northeast United States, the Carribean, North and South Africa and southeast Asia, Goldberg claims that undersea basalts, which tend to be widespread, could be potentially larger and better than the ones available on land. It is believed that the carbon dioxide that does not actually react with the rock will be heavier than the seawater and won’t be able to rise back to the top. And even if it did escape, the rock would actually hit the overlying impermeable cap of clay like sediment in areas such as the Juan de Fuca plate.

Individuals that are skeptical of the process have pointed out that getting the carbon dioxide to the particular sites would be difficult and expensive. But Goldberg feels that the West Coast formations should be close enough to the land that delivery via pipelines or tankers would be feasible. He has called on the government to study and survey the details of how the idea might be possible, and whether or not the economics work out. Currently, the United States spends about $40 million a year on the study of carbon sequestration, but the majority of it goes to land based research. "Forty million is about the opening-day box office for Finding Nemo," Goldberg said.

The concept of ocean carbon sequestration could be a big deal in our opinion. What are your thoughts? Let us know by writing a comment below.