Scientists in Texas are trying to find a way of reducing carbon dioxide air pollution by capturing the gas, compressing it and then putting it underground. This technique could also yield some benefits for the oil industry by using the gas to force out previously unrecoverable crude.

In a field northeast of Houston, a team of geologists from the University of Texas, four national scientific laboratories and a number of private companies are pumping CO2, or carbon dioxide, into sandstone deposits 1,500 meters below ground. Such attempts at what is known as carbon sequestration are not new. In fact, reducing greenhouse gases such as CO2 in the atmosphere has been a major goal of environmentalists for many years. But Susan Hovorka, a researcher in the Bureau of Economic Geology at the University of Texas at Austin, says this is the first attempt to carefully measure how effective an underground storage strategy might be.

"We are really the first really detailed experiment," said Susan Hovorka. "We have four national labs and the U.S. Geological Survey collecting very detailed measurements with a lot of tools. So, it is a first."

Ms. Hovorka, who serves as the lead researcher at the site near Dayton, Texas, says the effectiveness of this project relies on the rock formations deep in the earth below the field where the scientists are working. She says various types of rock can form a cap over the deposit to prevent almost all leakage.

"There are a lot of things that can hold gas underground," she said. "We are underneath the Anahuac shale, which should be the best seal in the world. So the CO2 should stay underground for thousands of years. No problem."

Ms. Hovorka says carbon dioxide is plentiful in nature and a small amount of leakage from the underground storage site will cause no problem. She says it is the large amounts of CO2 put into the atmosphere by nearby petroleum refineries and factories that cause health problems and contribute to global warming.

In areas like east Texas and Louisiana, which still have many active oil fields, there can be another benefit from pumping carbon dioxide underground. Susan Hovorka says the gas helps move oil out of regions in the porous rock that had defied earlier attempts at extraction.

"The oil is stuck in the pore spaces and the CO2 will act as a solvent to help move it out," explained Susan Hovorka. "So, you can get several decades more life out of a field ending its life."

This use of gas to produce oil could be especially important for future development of greenhouse gas sequestration plans because of the costs involved. Removing carbon dioxide from fossil fuel fumes is an expensive process in itself.

Compressing thousands of tons of that gas into containers and then shipping it to the storage sites to pump it into the ground costs even more. But scientists hope the experiment now under way here in Texas will lead to a cost-effective system for reducing air pollution that can be applied elsewhere in the world as well.