burning, largely resulting from the activities of man, accounts
for around half a million tonnes of nitrous oxide-N emission each
year. Nitrous oxide emissions arising from biomass burning are
a result of incomplete combustion and significant amounts can
be produced during large scale burning of woodlands, savanna and
In savanna regions of the world, burning is often carried out
every few years to promote regeneration of the vegetation. An
important biomass burning related source of nitrous oxide emission
is that of crop residue burning.
The high nitrogen and water contents of many crop residues mean
that the burning of such material can produce a relatively high
percentage (around 1 percent) emitted as nitrous oxide.
Though fires caused by lightning strikes have, and still do,
account for some large biomass burning events, the activities
of man in the last 100 years have dwarfed nitrous oxide emissions
from such natural biomass burning. Huge areas of woodland and
grassland are now periodically burned for land clearance and agricultural
Burning of agricultural waste also produces significant amounts
of nitrous oxide due to its generally high water content. Additionally,
wood burning as a domestic fuel source and for charcoal production
can release significant amounts of nitrous oxide on a global scale.
Potential for control
Reductions in crop residue burning give a direct route for reductions
in biomass burning related nitrous oxide emissions. Similarly,
careful management of any necessary crop residue burning to ensure
emissions of nitrous oxide are kept to a minimum may help to reduce
the strength of this nitrous oxide source. On a large scale, the
uncontrolled way in which most biomass burning happens means that
the only real route to reducing emissions from this source is
to reduce the amount of burning itself.
Some biomass burning is required if environments such as the
savanna are to be retained, but it is the large scale destruction
of forest areas for cash crop agriculture and urban spread which
stand out as areas to be tackled. Biomass burning is currently
being developed as an alternative to traditional fossil fuel energy
production methods, with power stations fuelled by wood chips
and the like already a reality.
By making use of a renewable resource, like pine wood chips,
and avoiding uncontrolled and incomplete combustion, these biomass
power stations are able to have a much reduced net greenhouse
gas impact compared to equivalent coal, oil and gas fired power