In a number of storages, bagasse
similar to that found in layers 1 and 2 has been observed below layer 4. In piles
where the maximum temperature exceeds approximately 70 °C, blackening and
charring of bagasse fibres is clearly evident in the fourth layer below 1000 mm.
The concentration of blackened fibres varies significantly between stockpiles. A
number of stockpiles have continuously cooled after an initial heating period,
with no evidence of bagasse degradation.
The consistency in the physical and thermal characteristics of bagasse stock-
piles suggests that oxygen diffusion may be an important limiting factor in spontaneous combustion. Maximum stockpile temperatures alter an extended period
(approximately 5 months) have been found to vary between stockpiles. Table II
summarises temperature data obtained under various stockpile conditions. The
bagasse moisture content in all stockpiles remained relatively unaltered from the
nominal 50 per cent which existed at the time of pile construction. In the
darkened sections of piles at depths greater than 2 m bagasse moisture content
may increase to 55-60 per cent depending on moisture migration, coverage and
drainage. Partial drying occurs to varying degrees in the surface layer of piles to a
depth of 0.5 m. Bagasse moisture content in this layer can vary between 25 and 45
percent.