Tag Archives: Carbon capture & sequestration

Signs of forests adapting to growing CO2 levels

FOR IMMEDIATE RELEASE LONDON, 9 August – Trees may be getting more efficient in the way they manage water. They could be exploiting the higher levels of carbon dioxide in the atmosphere, growing foliage from a lower uptake of groundwater. If so, then the carbon dioxide fertilisation effect – predicted by theorists and observed in laboratory experiments – could be real. This is a provisional finding, because it is pretty difficult to measure the precise economy of a whole forest or an open wilderness. But Trevor Keenan  – of Macquarie University in Australia and at present at Harvard University in the US – and colleagues report in Nature that they used an indirect measure, called the eddy-covariance technique, to monitor the way managed forests handle two important gases: carbon dioxide and water vapour. Carbon dioxide levels in the atmosphere were once 280 parts per million; they are now 400 ppm and still rising. For more than 20 years, rigs have towered above the world’s forests recording eddy co-variance, measuring carbon uptake and water-use over areas of a square kilometre. Keenan and his fellow-researchers looked at the data from 21 temperate and boreal forests in the northern hemisphere and found a remarkably consistent trend: as the years rolled by, and carbon dioxide levels rose, forests used water more efficiently, and this was true for all 21 sites. This so-called fertilisation effect has been independently confirmed in arid zones, again by indirect research, through the work of an Australian team studying satellite data, and also seems consistent with a finding reported in Nature Climate Change that tropical forest trees are now producing more flowers, even though the observed temperature rises in the tropics have so far only been modest. The implication of the most recent research from the boreal and temperate forests is that plants could be partially closing their stomata to keep their carbon levels at a constant level. This finding, like much in science, raises as many questions as it answers. How plants “know” what to do in such circumstances, and how they do it, is still a mystery: Plants exploit atmospheric carbon dioxide so it should be no surprise that a better supply leads to more efficient growth. But more carbon dioxide also means higher temperatures, more evaporation, more precipitation and more cloud cover, so it has been difficult to observe the impact. Whether this will turn out in the long run to be a positive feedback that could, to some slight extent, slow global warming is uncertain. Plants are also sensitive to extreme heat and drought, two other unwelcome companions of climate change due to human emissions of greenhouse gases such as carbon dioxide, so it is too soon to suggest that forests will emerge as the winners. Other scientists still have to confirm the effect, and measure its scale more accurately. But the latest research does suggest trees are responding to change. “Our analysis suggests that rising atmospheric carbon dioxide is having a direct and unexpectedly strong influence on ecosystem processes and biosphere-atmosphere interactions in temperate and boreal forests,” says one of the authors, Dave Hollinger of the US Forest Service. – Climate News Network  

FOR IMMEDIATE RELEASE LONDON, 9 August – Trees may be getting more efficient in the way they manage water. They could be exploiting the higher levels of carbon dioxide in the atmosphere, growing foliage from a lower uptake of groundwater. If so, then the carbon dioxide fertilisation effect – predicted by theorists and observed in laboratory experiments – could be real. This is a provisional finding, because it is pretty difficult to measure the precise economy of a whole forest or an open wilderness. But Trevor Keenan  – of Macquarie University in Australia and at present at Harvard University in the US – and colleagues report in Nature that they used an indirect measure, called the eddy-covariance technique, to monitor the way managed forests handle two important gases: carbon dioxide and water vapour. Carbon dioxide levels in the atmosphere were once 280 parts per million; they are now 400 ppm and still rising. For more than 20 years, rigs have towered above the world’s forests recording eddy co-variance, measuring carbon uptake and water-use over areas of a square kilometre. Keenan and his fellow-researchers looked at the data from 21 temperate and boreal forests in the northern hemisphere and found a remarkably consistent trend: as the years rolled by, and carbon dioxide levels rose, forests used water more efficiently, and this was true for all 21 sites. This so-called fertilisation effect has been independently confirmed in arid zones, again by indirect research, through the work of an Australian team studying satellite data, and also seems consistent with a finding reported in Nature Climate Change that tropical forest trees are now producing more flowers, even though the observed temperature rises in the tropics have so far only been modest. The implication of the most recent research from the boreal and temperate forests is that plants could be partially closing their stomata to keep their carbon levels at a constant level. This finding, like much in science, raises as many questions as it answers. How plants “know” what to do in such circumstances, and how they do it, is still a mystery: Plants exploit atmospheric carbon dioxide so it should be no surprise that a better supply leads to more efficient growth. But more carbon dioxide also means higher temperatures, more evaporation, more precipitation and more cloud cover, so it has been difficult to observe the impact. Whether this will turn out in the long run to be a positive feedback that could, to some slight extent, slow global warming is uncertain. Plants are also sensitive to extreme heat and drought, two other unwelcome companions of climate change due to human emissions of greenhouse gases such as carbon dioxide, so it is too soon to suggest that forests will emerge as the winners. Other scientists still have to confirm the effect, and measure its scale more accurately. But the latest research does suggest trees are responding to change. “Our analysis suggests that rising atmospheric carbon dioxide is having a direct and unexpectedly strong influence on ecosystem processes and biosphere-atmosphere interactions in temperate and boreal forests,” says one of the authors, Dave Hollinger of the US Forest Service. – Climate News Network  

CO2 storage 'needs tailoring to geology'

FOR IMMEDIATE RELEASE
Perhaps we’ll be able to lessen the climate impact of CO2 emissions by trapping and storing them underground. But researchers say potential sites vary so much that each will need separate appraisal.

LONDON, 9 July – Anybody planning carbon capture and storage  (CCS) – one way to burn fossil fuels without releasing greenhouse gases – will have to think long and hard about where to put the carbon dioxide:  long, because it must be kept secure for thousands of years, hard because even the hardest rocks yield under pressure.

The technology exists and CCS is already one potential amelioration of the greenhouse problem. Energy companies have been condensing carbon dioxide from power station exhausts and gas and oil fields, and finding places to store it, usually deep underground.

But deep burial may not be a permanent solution, which is why James Verdon, an earth scientist at the University of Bristol in the United Kingdom, and colleagues report in the Proceedings of the National Academy of Sciences that they decided to take a more careful look at three cases of long-term disposal.

Three million tonnes of carbon dioxide (think of this as the exhausts from 500,000 cars) have been buried every year since 2000 in an oil and gas reservoir below Weyburn, in Saskatchewan, Canada.

Around a million tonnes of liquefied CO2 each year is now stripped from natural gas and pumped back into the Sleipner field under the Norwegian North Sea, and in the last seven years almost four million tonnes has been put back deep under a natural gas field at In Salah in Algeria.

In each case, the gas exerts pressure on the surrounding rocks, in the case of the Weyburn field permeating pores and colonising gaps left by more than five decades of oil extraction; what geologists need to know is how the rocks react to this new pressure and whether the gas will migrate.

“There is not likely to be a one-size fits all approach to CCS”

They also need to understand whether there is a history of faulting, and whether the process is likely to trigger earthquakes. This last possibility presents what the researchers delicately describe as a “significant ‘own goal’ from a public relations and political perspective”, so the stakes are high.

The risks also include the opening of existing fractures; damage to the rocks that cap the reservoirs, failures of the wells bored into the storage site and the deformation of the entire geological structure. And since nothing in geology happens in a hurry, the scientists have to calculate probabilities of hazard for thousands of years.

They found enough geomechanical deformation to clear up one point: every deep storage and burial site is likely to be different, and anyone who chooses the CCS solution will have to think carefully.

The authors don’t use the Goldilocks metaphor – not too big, not too hot, just right – from the children’s fairy story, but the intent is clear enough. Each case needs to be considered on its merits; each burial site will need long-term monitoring. To make a difference to total emissions, billions of tonnes must be stored each year, and the industry must find at least 3,000 sites like the Sleipner field.

“Every future CCS site will have a different geological setting, and our study has shown that this can lead to very different responses to CO2 injection,” Dr Verdon warns. “There is not likely to be a one-size fits all approach to CCS.” – Climate News Network

FOR IMMEDIATE RELEASE
Perhaps we’ll be able to lessen the climate impact of CO2 emissions by trapping and storing them underground. But researchers say potential sites vary so much that each will need separate appraisal.

LONDON, 9 July – Anybody planning carbon capture and storage  (CCS) – one way to burn fossil fuels without releasing greenhouse gases – will have to think long and hard about where to put the carbon dioxide:  long, because it must be kept secure for thousands of years, hard because even the hardest rocks yield under pressure.

The technology exists and CCS is already one potential amelioration of the greenhouse problem. Energy companies have been condensing carbon dioxide from power station exhausts and gas and oil fields, and finding places to store it, usually deep underground.

But deep burial may not be a permanent solution, which is why James Verdon, an earth scientist at the University of Bristol in the United Kingdom, and colleagues report in the Proceedings of the National Academy of Sciences that they decided to take a more careful look at three cases of long-term disposal.

Three million tonnes of carbon dioxide (think of this as the exhausts from 500,000 cars) have been buried every year since 2000 in an oil and gas reservoir below Weyburn, in Saskatchewan, Canada.

Around a million tonnes of liquefied CO2 each year is now stripped from natural gas and pumped back into the Sleipner field under the Norwegian North Sea, and in the last seven years almost four million tonnes has been put back deep under a natural gas field at In Salah in Algeria.

In each case, the gas exerts pressure on the surrounding rocks, in the case of the Weyburn field permeating pores and colonising gaps left by more than five decades of oil extraction; what geologists need to know is how the rocks react to this new pressure and whether the gas will migrate.

“There is not likely to be a one-size fits all approach to CCS”

They also need to understand whether there is a history of faulting, and whether the process is likely to trigger earthquakes. This last possibility presents what the researchers delicately describe as a “significant ‘own goal’ from a public relations and political perspective”, so the stakes are high.

The risks also include the opening of existing fractures; damage to the rocks that cap the reservoirs, failures of the wells bored into the storage site and the deformation of the entire geological structure. And since nothing in geology happens in a hurry, the scientists have to calculate probabilities of hazard for thousands of years.

They found enough geomechanical deformation to clear up one point: every deep storage and burial site is likely to be different, and anyone who chooses the CCS solution will have to think carefully.

The authors don’t use the Goldilocks metaphor – not too big, not too hot, just right – from the children’s fairy story, but the intent is clear enough. Each case needs to be considered on its merits; each burial site will need long-term monitoring. To make a difference to total emissions, billions of tonnes must be stored each year, and the industry must find at least 3,000 sites like the Sleipner field.

“Every future CCS site will have a different geological setting, and our study has shown that this can lead to very different responses to CO2 injection,” Dr Verdon warns. “There is not likely to be a one-size fits all approach to CCS.” – Climate News Network