Agriculture Reference
In-Depth Information
Chapter 2
Fundamentals
Fire's the sun, unwindin' itself out o' the wood
David Mitchell, author
2.1
Fire and Fuel Basics
2.1.1
Fuel Chemistry
Wildland fuels are mostly created from plants, sunlight, water, and nutrients to be
eventually burned by fire. Fuels are created by plants as a product of photosynthesis,
a chemical process where carbon dioxide (CO
2
), water (H
2
O), and energy from the
sun (solar radiation) are used to produce organic compounds of the chemical form
(C
6
H
10
O
5
)
y
and also oxygen (O
2
). This can be expressed in the general formula:
5
HO CO SolarEnergyCHO O
2
+
6
+
→
(
)
+
6
.
(2.1)
2
6
10
5
y
2
The substances that compose biomass (C
6
H
10
O
5
)
y
are quite susceptible to burn be-
cause of their organic chemical constituency. The primary substances found in plant
biomass are cellulose, hemicellulose, and lignin. In general, wood, an important
fuel in forest ecosystems, is composed of around 40-55 % cellulose, 15-25 % hemi-
cellulose, 15-30 % lignin, and 2-15 % other matter, while needles have less lignin
but more cellulose than wood.
Gisborne (
1947
) said “all fuels have pretty much the same chemical constituents
(cellulose, starch, and lignin) and when these organic fuels burn in a wildland fire,
they combine with oxygen to create carbon dioxide, water, and heat” as denoted in
the following formula:
(
CHO6Oheat
)
+
→
5H O6CO Heat
+
+
+
secondary compounds
(2.2)
6 05y
2
2
2
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