Global warming “can be reversed", scientists claim

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A biofuel plant, Lockerbie
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Hi-tech new bio-energy plants could “reverse” global warming by pumping carbon dioxide into old gas wells - lowering temperatures by 0.6°C per century, according to a study.

There are already 16 projects around the world working on the technology - aiming to generate power for local homes by burning vegetation such as wood or straw and then burying the carbon dioxide it produces deep underground.

“It’s like drilling for natural gas, but in reverse,” says Niclas Mattson of Chalmers University, Sweden, co-author of the study.

Because trees and other plants absorb carbon dioxide while they grow, the technology, known as BECCS - Bioenergy with Carbon Capture and Storage - is “carbon negative”.

The bio-energy plants will capture thousands of tons of CO2 per day, and then pipe the gas down into rock formations, or depleted oil and gas wells. By 2050, the researchers believe, the BECCS plants could bury billions of tons of CO2 per year.

[Related: World energy agency sees "record" oil demand]

The first BECCS plants will be here within a decade, Mattson says. They are likely to be expensive relative to coal-burning power stations - but the researchers say that even if the technology only becomes widespread in 2050, it would enable governments to beat current climate goals.

Study author Professor Christian Azar said: “We can reverse the warming trend and push temperatures back below the 2°C target by 2150.”

Around 60 per cent of global CO2 emissions come from power plants fuelled by coal, natural gas and oil.

“Bioenergy plants are already widespread, especially here in northern Europe,” says Mattson. “The new part is applying carbon capture. This could be done by retrofitting existing plants, but we believe this will primarily happen by building dedicated new plants.”

“After being separated in the power plant, the CO2 needs to be transported (by pipeline or shipped in liquid form) to an underground storage facility. Alternatively, you can build new power plants directly by the storage sites. Then you pump the CO2 underground (same as drilling for natural gas, but in reverse). Suitable storage sites that can keep the CO2 intact underground can be: depleted oil and natural gas wells, coal beds or possibly saline aquifers.”
Plants that burn a mixture of coal and vegetation (such as straw or wood), could also be “carbon negative”.
“Carbon dioxide separation, transport and storage are already being done for various purposes on a fairly large scale, but only individually,” says Mattson. “The first combined full-scale power plants will probably be here within a decade, so it will take several decades for this to become significant on a global scale. We consider this delay in our model, however, and still find that the technology has the potential to help us meet or even beat the two-degree target.”

“Even if current political gridlock causes global warming in excess of 2°C, we can reverse the temperature trend and reach targets later,” Azar says.

Azar says that the technology shouldn’t be used as an argument against reducing emissions.

Azar says: “BECCS can only reverse global warming if we have net negative emissions from the entire global energy system. This means that all other CO2 emissions need to be reduced to nearly zero.

“To do so requires both large-scale use of BECCS and reducing other emissions to near-zero levels using other renewables – mainly solar energy – or nuclear power.”

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