The Saskatchewan prairie is so featureless and flat that people here say you can watch your dog run away for three days. Fields of canola and wheat fill the vastness before falling off the horizon in a landscape punctuated by oil pump jacks bobbing lazily like old men in rocking chairs.
But deep underground, an ambitious experiment is underway to determine whether carbon dioxide can be safely buried. If so, carbon sequestration, as the process is called, could prove to be an effective way to reduce one of the biggest contributors to global warming.
Carbon dioxide emissions from power plants, auto tailpipes, factories and other sources are contributing significantly to global warming, scientists have found. Without sizable reductions in this and other so-called greenhouse gases, the trend is expected to continue, bringing with it tumultuous weather patterns, melting glaciers and rising sea levels.
The Weyburn oil field, 70 miles south of Regina and 50 miles north of the U.S. border, can hold an estimated 21 million tons of carbon dioxide over the project's 25-year lifespan. Saskatchewan's oil fields have enough capacity to store all the province's carbon dioxide emissions for more than three decades, according to the Petroleum Technology Research Center, which manages the project.
The Canadian government believes that carbon gas storage will go a long way toward helping the country meet its emissions reduction targets under the 1997 Kyoto Protocol, of which it is a signatory. The pact requires industrialized nations to cut emissions of greenhouse gases by an average of 5% between 2008 and 2012.
The Weyburn project began four years ago and has the backing of international energy companies and the United States, European Union and Canada, which have contributed $21 million.
"When I first heard about this, my reaction was, 'Wow, this is really nuts.' But the more I looked at it, I began to start believing that, on a small scale, this is something that is achievable," said Sally Benson, deputy director at Lawrence Berkeley National Laboratory in Northern California.
An essential ingredient of the atmosphere, carbon dioxide keeps the Earth warm enough to sustain life. It is only during the last century that scientists have begun to fear that the industrial world is creating too much of it and started to look for ways to lower CO2 production or dispose of the excess.
But it is a tricky molecule to get rid of. It doesn't always stay buried.
In 1986, 1,700 people in the West African nation of Cameroon suffocated when a giant bubble of naturally occurring carbon dioxide suddenly erupted from Lake Nyos and displaced all of the available oxygen in the immediate area.
Deep-well injection of the gas can force briny water to the surface, potentially polluting streams and aquifers. Earthquakes have been reported in places where deep-well injection has occurred. And carbon dioxide can convert to an acid in groundwater.
"With geological sequestration, we need to know that the carbon we put in the ground isn't going to come back up," said Klaus Lackner, a scientist with the Earth and Environmental Engineering Department at Columbia University.
Burying the gas is one of several remedies for global warming that include energy conservation, emissions reductions and greater reliance on alternative energy. But carbon storage offers a unique incentive. Buried in an oil field, the gas boosts oil production by forcing residual deposits to the surface. At Weyburn, oil production is up 50% since carbon dioxide injection began four years ago.
The Weyburn site was selected because, during 44 years of oil exploration, Saskatchewan required oil companies to keep copious geological records. Core samples from 1,200 bore holes provide a comprehensive look at subsurface conditions and a way to track movement of oil and gases. Carbon dioxide is injected nearly a mile underground beneath a thick rock layer.
Researchers keep track of buried carbon dioxide by checking vapors in wells, sampling groundwater and conducting seismic tests that depict subsurface conditions. So far, no leaks have been detected and none of the gas has escaped to the surface, said Mike Monea, who manages the Weyburn project for the Petroleum Technology Research Center.
But the Weyburn site is pocked with hundreds of oil wells over a 70-square-mile area. Each well shaft can act as a conduit to channel carbon dioxide to the surface. Some wells are being closed off, and others are being watched for traces of carbon dioxide. Scientists are trying to forecast how the site will hold up over several millenniums. One computer model showed that carbon dioxide could migrate upward about 150 feet in 5,000 years -- though it would still be far below the surface. A final report is due in June.
Each day, about 5,000 tons of liquefied carbon dioxide arrives from a plant near Beulah, N.D., operated by the Dakota Gasification Co., which converts coal to natural gas. The liquid CO2 crosses the prairie in a 220-mile-long pipeline before it is pumped underground in Canada.
Separating carbon dioxide from other exhaust exiting a smokestack is expensive. The process can use up to one-third of the energy produced by the power plant. Scrubbers must be installed, pipelines must be built, carbon dioxide must be carefully watched underground.
It costs about $30 a ton to separate carbon dioxide from industrial exhaust, though technology exists to cut that expense nearly in half, said Curt White, carbon sequestration science leader for the U.S. National Energy Technology Laboratory. He said the Energy Department's goal is to get the cost down to $8 a ton, a price at which the emissions could be captured and stored in the United States without increasing the cost to produce electricity by more than 10%.
"It's always going to be cheaper to put carbon dioxide into the air than somewhere else," said Howard Herzog, principal research engineer at the Massachusetts Institute of Technology. "It costs a lot more than anybody seems willing to pay now, but if we decide we really want to solve the climate problem, then it's going to be a cost-effective option."
President Bush has endorsed carbon capture and burial as a way to reduce greenhouse gas emissions while promoting energy development. The Energy Department has a goal for power plants to capture 90% of their carbon emissions by 2012.
Experts caution that sequestration, alone, is only part of the solution.
The United States -- which has not signed the Kyoto Protocol -- is the world's leading emitter of carbon dioxide, with 1.6 billion tons of emissions annually, about one-quarter of the worldwide total. About 80% of the U.S. emissions come from fossil fuel combustion, according to the Environmental Protection Agency.
Worldwide CO2 emissions could triple over the next 100 years, reaching 20 billion tons annually, according the Intergovernmental Panel on Climate Change, the United Nations body that brings together scientists to study global warming.
"We need increased reliance on energy efficiency and increased reliance on renewable energy," said David Hawkins, director of the climate center for the Natural Resources Defense Council, a leading U.S. environmental group. "Carbon storage could provide a third side of the triangle that would allow us to get deep reductions in global warming pollution, but you can't rely on it as the silver bullet."
"We've got to find a way to get industry to get their emissions into the ground instead of into the atmosphere," said Monea, the Weyburn project manager. "One of the most destructive greenhouse gases is carbon dioxide, and mitigation of that greenhouse gas is happening here. We are dealing with this problem, right here, by burying it underground. What's happening here is huge."
California probably has enough capacity in depleted oil fields and subsurface saline deposits to store all the carbon dioxide the state's power plants can produce for the next few centuries, said Benson at the Lawrence Berkeley laboratory. Pilot projects using carbon dioxide injection to enhance oil recovery have been conducted in Kern County, she said.
A consortium of eight partners, including Canada, the United States, the European Union and BP -- formerly British Petroleum -- have launched a $25-million project to explore new technologies to capture and store carbon gas.
The effort so far has found techniques that reduce costs for geological carbon storage by up to 60%, although more savings are needed before the economics favor doing so on large scale, said Gardiner Hill, manager of BP's environmental technology group.
"Geological storage is one option that could play a material part in helping us remove emissions and helping the world move forward to a stable amount of carbon dioxide in the atmosphere," Hill said. "The carbon originated from under the ground. We're putting it back."