3.4. Ash content and calorific value
The ash content influences the energetic quality of the pellet;
therefore, the energetic value is greatly related to this parameter.
In Fig. 5 the variability of ash content in the different pellet
blends is shown; the ash percentage in the 2 PH pomace pellet is
nearly double (4.3%) than 3 PH one (2.4%), due to the extremely
high values of ash-forming elements as Fe, Mg, K.
Nevertheless, all the pellets blends are in compliance with the
Technical Standard [17] since the ash content is less than 5% on a
dry basis, the maximum acceptable value.
The main parameter to define the energetic quality as the fuel of
the pellets is the heating value, as the maximum amount of energy
that can be gained by converting completely a unit mass of fuel in
standard conditions.