Greenhouse gases buried at sea

Greenhouse gases buried at sea
Published: 10 May 2005

Scientists at BP are working with officials from the Department of Trade and Industry (DTI) on plans to bury millions of tonnes of carbon dioxide (CO2) under the bed of the North Sea. The aim? To try to reduce the amount of harmful greenhouse gases emitted into the atmosphere which lead to global warming. The capture and storage of CO2, or carbon sequestration, is not new but the Miller project would be Britain’s first. Under the scheme, carbon dioxide emitted by power stations would be liquified, pumped back out to the North Sea via a disused oil pipeline and stored in the depleted Miller field.

The discussions are still at an early stage but if an agreement is reached, the potential benefits could be huge. Scientists estimate that, on average, just one such project could remove 1m tonnes of CO2 from the atmosphere every year - the equivalent of the combined emissions pumped out by 100,000 4x4 cars every 12 months. BP, meanwhile, would also benefit since the CO2 pumped into the field would help to flush out the last reserves of oil. A similar technique known as "enhanced oil recovery" is already used in several oil fields around the world. According to industry analysts, carbon sequestration could actually extend oil production from North Sea fields by 15 to 20 years. "The best option is, of course, energy efficiency but [carbon sequestration] is an attractive option as you can reduce CO2 emissions by 85 per cent to 95 per cent for a specific plant or process," says Dolf Gielen, a senior energy analyst at the International Energy Agency (IEA) in Paris. "You can use it with gas or coal-fired processes and we are going to be using significant amounts of fossil fuels for the next 50 years at least."

Under the BP scheme natural gas would continue to be fed to the Peterhead power station near Aberdeen. However, before being burnt, it would be converted into hydrogen and CO2. The hydrogen would replace the gas used to fuel the power station, while the CO2 would be separated, liquified and pumped out to the Miller field.

While the attractions of carbon sequestration may be clear, several big hurdles remain. The biggest is costs. Last week a report by Norway’s Petroleum Directorate concluded that carbon sequestration was currently too expensive and too risky to be used on the Norwegian Continental Shelf. One way to offer incentives, says Gielen, could be through the European Union’s emissions trading system. Under this scheme, power plants have to buy "renewable obligation credits" if they exceed the amount of CO2 they are allowed to emit - effectively paying a pollution penalty. The price of the credits is determined by the demand. However, under the current scheme the gas is trading at between euros7 to euros15 per tonne - still too low to make carbon sequestration worthwhile.

Dr Lynn Orr, the director of the Global Climate and Energy Project at Stanford University, is convinced that carbon sequestration will play a key role in the future, but he cautions it is not the only solution to global warming. "It is potentially one element but the challenges are so big it is by no means the panacea. The volumes of CO2 we generate are so huge, we need to think of a lot of different ways if we are going to make a dent in the emissions." (Abstracted from the Sunday Telegraph, UK)