The high heating values of semi-dried and wet banana leaves
were 19.8 MJ/kg and 5.5 MJ/kg, respectively. The low high heating
value for wet banana leaves is due to high moisture content in the
samples. The semi-dried banana leaves have high heating value
close to wastes used as biomass in energy generation showed in
Table 1 and proposed in the literature references previously mentioned.
The exception was for vegetal coal with high heating value
of 29.7 MJ/kg and this fact is in part due to the generally higher
moisture content and in part due to the high oxygen content for
vegetal biomass, as observed in Table 2.
Carbon, hydrogen and oxygen are the main components of biomass
fuels. Carbon and hydrogen become oxidized during combustion
by exothermic reactions (formation of CO2 and H2O) and
therefore influence the higher heating value of the fuel. The organically
bound oxygen provides a part of the oxygen necessary for the
combustion process, additional oxygen must be supplied by air
injection. The semi-dried banana leaves presented carbon, hydrogen
and oxygen contents of 43.5, 6.3 and 48.7%, respectively, much
close to some tree-fruit leaves, sugar cane straw, elephant grass
and briquettes, as showed in Table 2. However, the carbon content
was lower than values for wood (51.6%), sugar cane bagasse
(57.2%) and vegetal coal (79.3%) and bigger than value for rice husk
(35.6%), showing rice husk has poor energy density. The oxygen value
for semi-dried banana leaves (48.7%) was close to tree leaves,
sugar cane straw, elephant grass and briquettes and much bigger
than value for vegetal coal.
The nitrogen (