Stuff the Earth
By Stela Susic

OTTAWA — What goes up, must come down. Scientists around the world are taking ownership of the cliché and applying it to atmospheric pollution. How? By taking gas pollutants in the air and piping them into the earth and oceans.

The global climate has changed in the past few decades because of the GHG effect.

Finding answers to the great puzzle of pollution isn’t easy, says Danae Voormeij, a researcher at the University of Victoria. “Geological sequestration is one way to do it,” Voormeij adds.

One of the main contributors to the problem of air pollution is carbon dioxide (CO2). According to Statistics Canada, CO2 accounts for 78 per cent of Canada’s greenhouse gas (GHG) emissions.

Increased emissions of greenhouse gases make them act as pollutants, changing global climate beyond what is considered normal, says Voormeij. “Most of CO2 is produced by humans through the burning of fossil fuel. If we produce so much of it, then it stands to reason we can reduce it as well.”

This is where carbon sequestration comes in, says Don White, a geology expert at Natural Resources Canada. “It is essentially defined as the disposal of excess carbon dioxide which will, hopefully, help us meet our Kyoto goals."

In 2002, Canada ratified the Kyoto Protocol, committing to cut CO2 emissions by six per cent relative to the levels in 1990. To help realize this goal, Natural Resources Canada last year invested over $25 million to study geological sequestration. The funding will be used over the next five years.

Though not a universally accepted idea, sequestration is a step forward in improving the environmental health of our planet, says Voormeij. “...sequestering these emissions is a viable method ... People are not going to change their ways; most drive large vehicles and use large amounts of energy.”

While carbon management will help Canadians reduce pollution, the reverse is not true, says Stefan Bachu, a geoscience advisor for the Alberta Geological Survey. “The general population is not likely to support sequestration. It costs money and people aren’t interested in electricity price hikes,” he explains.

What is it that makes the process of carbon management expensive?

“First of all, you have to understand that there are two types of sequestration: indirect and direct,” explains Carolyn Preston, an engineer with the CANMET Energy Technology Centre.

Indirect sequestration involves removing CO2 from the atmosphere through forestation and agriculture practices, she says. “This is basically using the natural exchange of CO2 and oxygen in plants to store carbon,” adds Bachu. Trees, or plants, act like sponges, soaking up the CO2 from the atmosphere and storing them until they decay or encounter natural disasters such as fire.

Direct sequestration is what really costs money, says Preston. It involves the capture and storage of CO2 before its release into the atmosphere; equivalent to imprisoning the criminal prior to crime. The rainbow of approaches used to capture carbon includes amine scrubbing and cryogenic separation, which use high amounts of energy. After capture, the carbon is transported, usually through pipeline, to a storage site.

Storing CO2

Carbon dioxide storage sites are simply called sinks, says NRC's White. Just like an ordinary kitchen sink, geological formations suck up materials that, through a series of pipes, are stuffed under the surface, he explains.

Oil reservoirs have good storage potential, says Preston. “And they’re cheaper because the petroleum industry has the machines already in place that can inject CO2 into the reservoir.”

Oil reservoirs are good sinks because the infrastructure needed to store carbon is already in place.

The bonus with oil reservoirs, says Voormeij, is purely commercial. “When injected into an active oil reservoir, CO2 can improve oil recovery.” At high pressures underground, the carbon and oil become miscible, speeding up the migration of the oil towards the well.

The Shaquile O’Neal of geological sinks, oceans can also store carbon dioxide. In its liquid form, it can be transported by pipeline and dropped on the ocean floor. “This is not very effective because the liquid CO2 is less dense than seawater,” Voormeij says. This means it will float to the surface and possibly circulate into the atmosphere.

The more effective method is transporting the gas by ship and dropping it at a depth of over 3000 metres.

Transporting carbon by ship and dropping it to the bottom of the ocean is one way to dispose of the gas.

The pressure at that depth turns the CO2 into a clathrate. This ice-like mixture of carbon dioxide and water has higher density than seawater, thus remaining at the bottom of the ocean.

Though sinking carbon dioxide looks like a good way to reduce greenhouse gas emissions, opinion on the long-term issues with this practice are varied.

“My primary concern is that there is no technology to monitor how the carbon interacts with materials under the surface,” says Bachu. “What if it escapes from the surface?”

There are monitoring technologies being developed in Canada, says Preston, referring to the $42 million Weyburn Project in Saskatchewan designed to study the effects of storing CO2 in oil reservoirs. The main concern should be reducing the cost of carbon management, she adds. “If it’s not economically feasible, it won’t survive long enough to be replaced by new energy efficient technologies.”

Voormeij agrees, “The deciding factor...is economics,” but “oil and gas will eventually run out and cleaner forms of energy will take over in the future."