Can Carbon Capture Stop Climate Change?
Six billion tons of carbon dioxide a year pour into the atmosphere from sources such as power stations, chemical plants and steel foundries. And this gas contributes to global warming by trapping the sun’s rays in the atmosphere.
"If we fail to catch our carbon dioxide, then the planet will change beyond our recognition," warns Stuart Haszeldine, Professor of Geology at Edinburgh University.
Professor Haszeldine and his fellow researchers are investigating ways of interrupting the emission of carbon dioxide into the atmosphere, and storing the gas in a way that does not promote global warming.
Power stations produce bulk of world’s CO2
The first and biggest step, he says, is to deal with power stations. The burning of fossil fuels to generate electricity is the source of fully one third of the world’s C02 emissions. The technology of capturing the bulk of this is now well established.
The waste gases are fed through a solvent that absorbs the carbon dioxide. "This takes out roughly ninety percent of the carbon dioxide," Haszeldine explains.
"And that solvent can be taken away and heated up and the pure carbon dioxide taken out."
But what happens then with the C02? There have been numerous suggestions. Scientists at London’s Carbon Dioxide Centre have been investigating some of them.
Dumping CO2 at sea questionable
One of the most bizarre proposals is literally dumping the C02 at sea by pumping to the bottom of the ocean and parking it there.
Below 5000 meters, carbon dioxide changes into a liquid. And as liquid CO2 is denser than water, it would settle on the bottom of the ocean and form a lake. Then a chemical called a cathrate forms over the top of this lake, storing the CO2 beneath it.
But the center’s director Stef Simons concedes that this solution is problematic because scientists don’t fully understand the ecosystem of the deep ocean. It would also contravene every ocean dumping and disposal treaty.
And there’s another major obstacle. Every attempt to test this procedure has been blocked by public opinion.
"So at the moment that’s almost defunct, that type of research program," says Professor Haszeldine.
CO2 helps oil production
A far better option, says Dr. Stefani Brandini of the Carbon Dioxide Centre, is to use CO2 commercially, such as in a method called "enhanced oil recovery". This means pumping CO2 into ageing oil wells. The carbon dioxide raises the level of the oil, Brandini explains, and also has a "double effect."
"It also improves the viscosity, the way the liquid flows, so it’s easier to extract more oil from an oil reservoir once you inject the C02," says Brandini.
In the Wayburn oilfield in Saskatchewan, Canada, C02 is pumped 1400 meters underground in order to flush out more oil.
This process is expected to extend the life of this field by 20 years as well as storing 30 million tons of carbon dioxide underground.
The CO2 comes from an energy company called Dakota Gas, 360 kilometers away. Traditionally, this carbon dioxide produced from burning coal would have been discharged into the air.
The company’s director Fred Stern says it makes "economic sense" to capture the C02 and sell it to the Canadians instead.
Coal good CO2 absorber
Back at the Carbon Dioxide Centre in London, Stef Simons points out that another way of storing the gas and extracting more valuable energy is by pumping carbon dioxide into old coalmines. This is because coal is a very good absorber of CO2.
"If you pump carbon dioxide into a coalmine," says Simons, "the coal will capture the carbon dioxide and emit methane in its place, so it’s actually quite a nice production process for methane and keep the carbon dioxide down underground."
The idea is that the oil company or the coalmine operator would continue recycling the C02, and in this way keep it permanently out of the atmosphere. Enhanced oil production and generating methane from coal are obviously attractive carbon capture technologies since they will yield a healthy profit as well as burying the CO2.
But on their own, they would only absorb a relatively small percentage of total emissions. And, of course, they would be assisting in the production of more greenhouse gas emitting fuels.
Underground CO2 reservoirs another option
Fortunately, says Professor Haszeldine, there are many underground sites around the world where C02 could be securely parked. This means identifying sites of porous rock, and pumping liquid carbon dioxide deep underground, where it would "spread out and fill up these microscopic pores."
Hazseldine says the CO2 could stay deposited in the rocks for tens of thousands of years.
The British oil giant BP has already embarked on a project of this kind -- capturing C02 at a natural gas plant in Algeria. The C02 released by the gas processing would normally be vented into the sky.
Under this project, the carbon dioxide is pumped into porous rock beneath the Sahara Desert and stored there. BP’s Ian Wright finds it "frustrating" that this technology isn’t being given tax breaks and other financial incentives.
"We have a relatively cost-effective way of making a significant dent in greenhouse gas emissions and we’re not deploying it today because there’s no long-term, stable incentives that will allow us to do this."
Carbon capture affordable?
There are scientists who say that carbon capture is not horrendously expensive. According to one estimate, the whole process of capture and storage would add about 300 euros a year to the energy bill of a typical European household.
The scientists argue that if governments made carbon expensive to emit through taxation and regulation, these costs would be easily affordable.
Professor Haszeldine says governments are not acting with sufficient urgency. The European Union for example, has plans to look at deploying carbon dioxide storage initially by 2015 with the potential for large-scale projects in 2025. Haszeldine thinks this is "quite late."
"I’d want to see this really rolled out immediately," Haszeldine says, "and we should be looking to have a lot of these working by 2015, maybe 12 or 15 plants in Europe. We should be looking to build all of our plants in this way by 2020 at the latest.’’
The Carbon researchers say a fundamental shift in the climate of political opinion is required, especially in the United States.
If this happened, it could transform the economics of carbon capture and lead to the largest single reduction in greenhouse gas emissions and save the planet from some of the worst effects of global warming.