The proximate analysis shows that volatiles and fixed carbon
content in the char decrease as temperature is increased, which
is explained by the higher content of ash in the residue. This conclusion
is also reflected in the elemental analysis because total carbon
content is also lower when temperature is raised. The main
consequence of the high ash content is that the calorific value of
the char decreases as pyrolysis temperature is increased. Nonetheless,
these trends are just the opposite of those found in other lignocellulosic
chars in which the heating value and carbon content
increase with temperature [20]. In fact, the ash yields obtained in
the pyrolysis of other lignocellulosic waste materials are lower,
generally below 5 wt.%. In view of these results, it can be concluded
that combustion of this char is an undesirable option due to the
large amount of ash that must be handled, which causes serious
environmental and health problems [43,66]. Moreover, the calorific
value (16.1 MJ kg1 for the char obtained at 450 C) is low
compared to other solid fuels, such as lignite (28 MJ kg1) or coke
(29 MJ kg1).