Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Results of ANCOVA of different characteristics (Equation 1)_
| Dependent variable (Y) | p-value | Standard error | R2 | Figure |
|---|---|---|---|---|
| Ash content | 0.0032 | 0.4825 | 0.1286 | 3 |
| Net calorific value of dry matter | <0.0001 | 0.1026 | 0.2120 | 4 |
| Net calorific value of moist fuel | <0.0001 | 0.6905 | 0.3940 | 5 |
| Bulk density | <0.0001 | 0.0733 | 0.7789 | 6 |
| Energy density | <0.0001 | 0.3962 | 0.7718 | 7 |
| Shrinkage of diameter | 0.0015 | 1.3550 | 0.0989 | 8 |
Parameter estimates for the relationship between drying shrinkage, storage time, and moisture content (Equation 2 and 3)_
| Species | Parameter | Estimation | p-value |
|---|---|---|---|
| Silver birch | a0 | 3.851 | <0.0001 |
| a1 | 0.02156 | 0.0432 | |
| a2 | 3.572·10−283 | <0.0001 | |
| a3 | −1.944·10−7 | 0.0175 | |
| R2 | 0.240 | ||
| SE | 1. 098 | ||
| p | 0.0010 | ||
| Norway spruce | a1 | 0.15284 | <0.0001 |
| a2 | 0.37387 | <0.0001 | |
| R2 | 0.937 | ||
| SE | 0.990 | ||
| p | <0.0001 | ||
Relationship between moisture content and month number (Equation 4)_
| Sample | a0 | a1 | a2 | p-value | Standard error | R2 |
|---|---|---|---|---|---|---|
| Birch, covered | 58.654 | −7.687 | 0.423 | 0.0235 | 8.289 | 0.415 |
| Birch, uncovered | 78.481 | −11.882 | 0.863 | 0.0967 | 12.862 | 0.284 |
| Spruce, covered | 57.448 | −9.080 | 0.561 | 0.0428 | 8.637 | 0.363 |
| Spruce, uncovered | 65.693 | −10.981 | 0.722 | 0.0407 | 9.484 | 0.367 |
Decline of energy content of logging residues during long-term storage by species and place in pile_
| Storage time, year | Spruce, top | Spruce, middle | Birch, top | Birch, middle |
|---|---|---|---|---|
| 0 | 100.0 | 100.0 | 100.0 | 100.0 |
| 1 | 95.9 | 95.8 | 90.5 | 90.4 |
| 2 | 92.0 | 91.7 | 81.9 | 81.7 |
| 3 | 88.2 | 87.9 | 74.2 | 73.9 |
| 4 | 84.6 | 84.2 | 67.1 | 66.8 |
| 5 | 81.2 | 80.6 | 60.8 | 60.4 |
| 6 | 77.9 | 77.2 | 55.0 | 54.5 |
| 7 | 74.7 | 73.9 | 49.8 | 49.3 |
| 8 | 71.6 | 70.8 | 45.1 | 44.6 |
Estimations and significance probabilities of parameters of ANCOVA Equation 1_
| Dependent variable (Y) | Figure | Parameter | Estimation | p-value |
|---|---|---|---|---|
| Ash content, % | 3 | a0 | 1.561477 | <0.0001 |
| a1 | 0.000941 | <0.0001 | ||
| a2 | 0.315644 | 0.0230 | ||
| a5 | −0.000310 | 0.0045 | ||
| a6 | −0.000140 | 0.0341 | ||
| a7 | −0.000122 | 0.0633 | ||
| Net calorific value of dry matter, kWh/kg | 4 | a0 | 5.323000 | <0.0001 |
| a1 | 0.000085 | 0.0081 | ||
| a5 | −0.000039 | 0.0052 | ||
| a7 | 0.000021 | 0.1380 | ||
| Net calorific value of moist fuel, kWh/kg | 5 | a0 | 4.162196 | <0.0001 |
| a1 | −0.001087 | <0.0001 | ||
| a3 | −0.643537 | <0.0001 | ||
| a5 | 0.000423 | <0.0001 | ||
| Bulk density, g/cm3 | 6 | a0 | 0.571200 | <0.0001 |
| a1 | −0.000160 | <0.0001 | ||
| a2 | 0.173900 | <0.0001 | ||
| a3 | −0.042530 | 0.0013 | ||
| a5 | 0.000046 | 0.0069 | ||
| Energy density, MWh/m3 | 7 | a0 | 3.055000 | <0.0001 |
| a1 | −0.000846 | <0.0001 | ||
| a2 | 0.925200 | <0.0001 | ||
| a3 | −0.232900 | 0.0012 | ||
| a5 | 0.000248 | 0.0068 | ||
| Shrinkage of diameter, % | 8 | a0 | 4.284253 | <0.0001 |
| a2 | −0.791850 | 0.0012 | ||
| a6 | 0.000150 | 0.0973 | ||
Dates of samples_
| No | Date of sampling | Days from the start of the experiment |
|---|---|---|
| 1 | 16.06.2010 | 0 |
| 2 | 02.09.2010 | 78 |
| 3 | 22.11.2010 | 159 |
| 4 | 07.03.2011 | 264 |
| 5 | 02.09.2011 | 443 |
| 6 | 15.02.2012 | 609 |
| 7 | 25.04.2012 | 679 |
| 8 | 04.06.2012 | 719 |
| 9 | 24.08.2012 | 800 |
| 10 | 23.11.2012 | 891 |
| 11 | 16.05.2013 | 1065 |
| 12 | 26.11.2013 | 1259 |
| 13 | 25.06.2014 | 1470 |
| 14 | 12.12.2014 | 1640 |
| 15 | 26.08.2015 | 1897 |
| 16 | 28.08.2016 | 2265 |
| 17 | 18.03.2018 | 2832 |