'Carbon storage' an option
2005-02-08 11:27
Exeter - Less than a decade ago, the idea of capturing and storing the carbon gases blamed for driving the Earth towards climate-change peril was usually dismissed with a laugh.
But a top scientific forum here shows how far the argument for carbon sequestration has come, with a series of experts insisting it can be transformed from fiction to fact.
Driving their case is the fear that time is running out for dealing cheaply with the carbon pollution spewed out by fossil fuels.
These emissions trap the Sun's heat and disrupt Earth's fragile climate system, with potentially catastrophic effects a few decades from now.
Their focus is on power stations which burn oil, gas and coal, and whose pollution is set to soar in coming years as China and India, the two world's most populous countries, meet surging needs for energy.
Sequestrators say carbon dioxide (CO2) would be captured using solvents, either before or after the fossil fuel is burned in the plant.
The CO2 would then be pumped out, sometimes over hundreds of kilometres, to disused oil and gas fields up to one kilometre underground, and stored.
No miracle cure
It would not be the miracle cure to global warming or switch off the dependence on fossil fuels that are the source of the problem, they admit.
Even so, "it can play a global role, making very large and very rapid reductions of CO2 emissions," Jon Gibbins of Imperial College London said on Thursday.
He pointed to a pilot scheme in the North Sea as proof of its feasibility.
An experiment in Norway's offshore field, Sleipner, has been storing a million tons of waste CO2 a year since 1996, pumping it 1 000m below a cap of shale and mudstone.
Another project is in North America, where CO2 is being extracted from a coalgas plant in Wyoming and pumped 300km to Weyburn, in Canada's Saskatchewan province, where it is stored in an empty underground chamber in a working oilfield.
Environmentalists say the answer to global warming is to slash emissions themselves and swiftly wean the world off dirty fossils and onto renewable sources and hydrogen.
They also warn that the stored carbon is simply a bequeathed hazard for future generations. If the geological storage tank leaks or is breached by an earthquake the outpouring of CO2 would instantly damage the world's climate system.
Gibbins says former oil and gas fields in sedimentary basins, but also many types of water aquifers, are excellent options for safe storage: "We are looking at 90% retention [of the gas] for 1 000 years."
'Grow your energy'
Taking out the CO2 from fuel is called "carbon neutral", in other words not adding further to emissions from that source.
But a more ambitious possibility is "carbon negative", or removing CO2 from the atmosphere.
That could be done by biofuels, suggests Peter Read, a professor at Massey University in New Zealand.
Plants suck CO2 out of the air as part of photosynthesis. By growing plants, burning them in fossil-fuel power stations and then sequestrating and storing the carbon, a dent could be made on atmospheric CO2 levels, he said.
"Don't dig for your energy - grow it," he said. "In the right conditions, you could produce all the world's needs for electricity and liquid fuels from biomass."
Typical plants could be willows, pines and other resinous trees, supplemented by seasonal crops such as corn and sugar, he said.