Open Access

The impact of extra long-term storage of logging residues on fuel quality in Estonian conditions – a case study

Allar Padari
Allar Padari
, 
Risto Mitt
Risto Mitt
, 
Linnar Pärn
Linnar Pärn
, 
Vahur Kurvits
Vahur Kurvits
, 
Sander Kaasik
Sander Kaasik
 and 
Peeter Muiste
Peeter Muiste
   | Apr 13, 2024
Forestry Studies's Cover Image
About this article
Previous Article
Next Article
Cite
Article Category: Research paper
Published Online: Apr 13, 2024
Page range: 51 - 65
DOI: https://doi.org/10.2478/fsmu-2023-0012
Keywords
© 2023 Allar Padari et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1.

Sample pile of spruce logging residues.
Sample pile of spruce logging residues.

Figure 2.

Sample pile of birch logging residues.
Sample pile of birch logging residues.

Figure 3.

Change of ash content during storage.
Change of ash content during storage.

Figure 4.

Change of net calorific value of dry matter.
Change of net calorific value of dry matter.

Figure 5.

Change of net calorific value of moist fuel.
Change of net calorific value of moist fuel.

Figure 6.

Change of bulk density.
Change of bulk density.

Figure 7.

Change of energy density.
Change of energy density.

Figure 8.

Shrinkage of diameter of sample branches.
Shrinkage of diameter of sample branches.

Figure 9.

Variation of moisture content during the year.
Variation of moisture content during the year.

Figure 10.

Diameter drying shrinkage relationship with storage time and moisture content in birch logging residues.
Diameter drying shrinkage relationship with storage time and moisture content in birch logging residues.

Figure 11.

Diameter drying shrinkage relationship with storage time and moisture content in Norway spruce logging residues.
Diameter drying shrinkage relationship with storage time and moisture content in Norway spruce logging residues.

Figure 12.

Bulk density during storage of birch residues (ρbm – bulk density with oven-dry mass and volume at the base moisture content; t – days from the start of the experiment).
Bulk density during storage of birch residues (ρbm – bulk density with oven-dry mass and volume at the base moisture content; t – days from the start of the experiment).

Figure 13.

Bulk density during storage of spruce residues (ρbm – bulk density with oven-dry mass and volume at the base moisture content; t – days from the start of the experiment).
Bulk density during storage of spruce residues (ρbm – bulk density with oven-dry mass and volume at the base moisture content; t – days from the start of the experiment).

Figure 14.

Decline of energy content of logging residues during long-term storage.
Decline of energy content of logging residues during long-term storage.

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
eISSN:
1736-8723
Language:
English
Publication timeframe:
2 times per year
Journal Subjects:
Life Sciences, Plant Science, Ecology, other
Journal RSS Feed