Dec. 5, 2008 -- Burning peat bogs in a controlled way may be a good way to sequester carbon from the atmosphere, according to new research.
Peatlands are dense carbon storage units -- as the woody plants growing on top of the peat die, they fall into oxygen-poor, water-logged soil that keeps their carbon-rich remains preserved indefinitely. Around the world, peat contains 30 percent of all carbon buried in soils, equivalent to slightly less than all of the carbon in the atmosphere today.
"Peatlands suck up between 1 and 2 percent of all anthropogenic carbon emissions in the U.K. annually," Fred Worrall of Durham University in the United Kingdom said.
In the United Kingdom, private land managers burn peatlands regularly to clear space for grouse habitat and sheep grazing. This is no tree-hugging exercise -- the grouse are cultivated for recreational hunting -- but Worrall and Gareth Clay, also of Durham University, think the burning may have the beneficial side effect of enhancing carbon sequestration in the bogs.
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When the vegetation growing on top of peat bogs burns, some of it turns into black carbon charcoal. The charcoal can sink into the murky depths where it is preserved. In a computer simulation, the researchers found that if controlled burns were applied to optimize this process, the bogs could absorb 20 to 30 percent more carbon than when they were left to grow naturally.
"The key is that only the top heather vegetation can be burned -- what we call a 'cool burn.' Once you start burning down into the litter and soil, all bets are off. It's definitely a carbon source," Worrall said.
There's also a risk that a burn could get out of control and turn into a wildfire, devastating the peat.
"This is kind of an up and coming idea," said Andrew Zimmermann of the University of Florida. "Making what is called 'biochar' to enhance carbon sequestration has potential to be used all over the world."
Zimmermann pointed to forests as having even more potential to store carbon by making charcoal, because as trees die, their carbon-rich wood and leaf litter are broken down by microorganisms and released back into the atmosphere.
"Peat is already preserving plenty of carbon. What we need is to preserve what is not already being preserved," he said.
But poor land management has severely damaged peat bogs, Worrall said, and erosion is already releasing up to 400 tons of carbon per square kilometer of peat each year from its sodden layers. To reverse that trend, close attention to the bogs is needed -- and perhaps even a fire every now and then.
"If you do nothing, peatlands are sure to become part of our greenhouse gas emissions," Worrall said. "But if we do something and it's the right thing, we can turn this system around and make it part of the solution."
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