DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/2013 str. 40     <-- 40 -->        PDF

determined for samples of wood and bark of tested clones according to standard methodology in the bomb calorimeter.
Caloric value of wood and bark of tested clones ranged from 18.542 MJ·kg–1 in clone 457 to 19.554 MJ·kg–1 in clone 618 (table 5). According to these data the heating value of bark was higher than that of wood and it ranged from 18.545 to 20.106 MJ·kg–1 and deviations were positive in all clones in relation to wood (Table 5). These results were similar to the mean values of heating value of trunks aged 3–5 years Ciria et al.(1996), and they were somewhat lower in comparison to the appropriate value of 20.239 MJ·kg–1 of grown up trees (Klašnja et al. 1998).
Energy value of biomass is directly related to the heating value of wood of tested clones, and also with other factors influencing the quantity and quality of produced biomass. The main objective of biomass combustion is to release the large amount of heating energy, and only harmless products of combustion through chimney (water vapor and carbon dioxide), and to retain only ash in furnace as noncombustible materials adopted from soil in the process of biomass production. All tested clones belonged to the group of Eastern cottonwood (Populus deltoides Bartr. ex Marsh.) and their caloric values were similar and ranged from 18.542 MJ·kg–1 in clone 457 to 19.554 MJ·kg–1in clone 618 (Table 5). These results were similar to literature data obtained by Klašnja et al (2009) for the group of clones. Benetka et al (2002) provided data of heating values ranging from 18.60 MJ·kg–1 to 19.27 MJ·kg–1 for poplar trees aged 1–3 years.
Values of estimated quantity of energy that would be obtained in two two-year cycles depending on clone and planting density are given in Table 6 and Figure 1.
It is evident from these data that the quantity of energy produced in the second cycle was significantly greater compared to the first cycle, which was the result of better rooting ability and strong regeneration force of selected clones.
The greatest amount of heating energy of 364.02 GJ·ha–1 would be obtained by combustion of biomass of the above ground part of clone 55/65, subtreatment (c) at density of 1.2 × 0.5 m in the first cycle, and 659.83 GJ·ha–1 in the second or a total of 1023.85 GJ·ha–1.
Within the group of tested clones of Eastern cottonwood (Populus deltoides Bartr. ex Marsh.) the minimum quantity of heating energy of 202.38 GJ·ha–1 would be obtained for clone 618, subtreatment (c) at density of 1.2 × 1.0 m by combustion of biomass of the above ground part in the first cycle, and 440.75 GJ·ha–1 in the second, or the total of 643.13 GJ·ha–1 (Fig. 1).
It is evident from the mentioned figure that there were no significant differences in the quantity of the produced energy in the first cycle, while in the second cycle clone 450 had significantly higher values at density of 1.2 × 0,75 m, and clone 55/65 at density of 1.2 × 0.5 m.
These differences probably occured due to stronger regeneration force in the second cycle compared to other clones.