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April
27, 2007 The
consortium
brings together a unique combination of expertise and facilities
enabling the
design and execution of a novel experiment. Plants were grown in a
facility
containing atmospheric carbon dioxide almost exclusively with a heavy
form of
carbon (13C). This makes the carbon released
from the plants
relatively easy to detect. Thus, if plants are able to emit methane, it
will
contain the heavy carbon isotope and can be detected against the
background of
lighter carbon molecules in the air. Six
plant
species were grown in a 13C-carbon dioxide
atmosphere, saturating
the plants with heavy carbon. 13C-Methane
emission was measured
under controlled, but natural conditions with a photo-acoustic laser
technique.
This technique is so sensitive that the scientists are able to measure
the
carbon dioxide in the breath of small insects like ants. Even with this
state-of-the-art technique, the measured emission rates were so close
to the
detection limit that they did not statistically differ from zero. To
our
knowledge this is the first independent test which has been published
since the
controversy last year. Conscious
of
the fact that a small amount of plant material might only result in
small
amounts of methane, the researchers sampled the
‘heavy’ methane in the air in
which a large amount of plants were growing. Again, the measured
methane
emissions were negligible. Thus these plant specialists conclude that
there is
no reason to reassess the mitigation potential of plants. The
researchers
stress that questions still remain and that the gap in the global
methane
budget needs to be properly addressed.
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