The Compost Bomb: Peat and Global Warming
Posted by Unknown in Biofuel, Environmental Issues, Fire, Global Warming, Manure and Composting on Sunday 27 January 2013
(Oil Price)
Peat, or turf, is an accumulation of partially decayed vegetation
matter. Peat forms in wetland bogs, moors, and peat swamp forests. Peat
is harvested as an important source of fuel in certain parts of the
world. Peat has a high carbon content and can burn under low moisture
conditions. Once ignited by the presence of a heat source, it smolders.
These smoldering fires can burn undetected for very long periods of time
(months, years and even centuries) propagating in a creeping fashion
through the underground peat layer. The rate of global warming could
lead to a rapid release of carbon from these peat lands that would then
further accelerate global warming. Two recent studies published by the
Mathematics Research Institute at the University of Exeter highlight the
risk that this 'compost bomb' instability could pose, and calculate the
conditions under which it could occur.
Peat
fires are emerging as a global threat with significant economic, social
and ecological impacts. Recent burning of peat bogs in Indonesia, with
their large and deep growths containing more than 50 billion tons of
carbon, has contributed to increases in world carbon dioxide levels.
Peat deposits in Southeast Asia could be destroyed by 2040.
Peat-Bog |
In
1997, it is estimated that peat and forest fires in Indonesia released
between 0.81 and 2.57 Gt of carbon; equivalent to 13-40 percent of the
amount released by global fossil fuel burning, and greater than the
carbon uptake of the world's biosphere. These fires may be partially
responsible for the increase in carbon dioxide levels since 1998.
Underground
peat fires are fairly common and world wide. In 2008 there was an
underground peat fire in North Carolina triggered by a lightning strike
and aided by a prolonged drought. In Australia (Victoria province)there
has been a peat fire raging for 13 years. In 2010 Russia is suffering
from a prolonged peat fire.
A peat fire, like any fire, requires fuel (peat), air, and ignition.
The
first Exeter paper by Catherine Luke and Professor Peter Cox describes
one of the basic potential ignition sources. When soil microbes
decompose organic matter they release heat -- this is why compost heaps
are often warmer than the air around them.
The
compost bomb instability is a runaway feedback that occurs when the
heat is generated by microbes more quickly than it can escape to the
atmosphere. This in turn requires that the active decomposing soil layer
is thermally-insulated from the atmosphere.
Catherine
Luke explains: "The compost bomb instability is most likely to occur in
drying organic soils covered by an insulating lichen or moss layer."
The
second paper led by Dr Sebastian Wieczorek and Professor Peter Ashwin,
also of the University of Exeter, proves there is a dangerous rate of
global warming beyond which the compost bomb instability (i.e. ignition
or spontaneous combustion occurs) occurs.
Spontaneous
combustion occurs when materials self-heat to a temperature high enough
to cause them to ignite. Typically, composting materials ignite at
temperatures between 150 and 200°C.
As
the temperature rises, the speed of temperature increase also rises.
For example, heat is generated about 16 times faster at 100°C than at
60°C because the reaction rate approximately doubles with each 10°C rise
in temperature.
The
Exeter team is now modeling the potential impact of the compost bomb
instability on future climate change, including the potential link to
the Russian peat land fires.It is also working to identify other
rate-dependent tipping points.
By. Andy Soos of Environmental News Network
This entry was posted on Sunday 27 January 2013 at 22:15 and is filed under Biofuel, Environmental Issues, Fire, Global Warming, Manure and Composting. You can follow any responses to this entry through the RSS 2.0. You can leave a response.
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