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

Allar Padari; Risto Mitt; Linnar Pärn; Vahur Kurvits; Sander Kaasik; Peeter Muiste

doi:10.2478/fsmu-2023-0012

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

Forestry Studies

Volume 79 (2023): Issue 1 (December 2023)

By: Allar Padari, Risto Mitt, Linnar Pärn, Vahur Kurvits, Sander Kaasik and Peeter Muiste

Open Access

|Apr 2024

Figures & Tables

Table 1.

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

Table 2.

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

Table 3.

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
Net calorific value of dry matter, kWh/kg	4	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
Net calorific value of moist fuel, kWh/kg	5	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
Shrinkage of diameter, %	8	a₂	−0.791850	0.0012
a₆	0.000150	0.0973

Change of net calorific value of dry matter.

Change of net calorific value of moist fuel.

Shrinkage of diameter of sample branches.

Variation of moisture content during the year.

Table 4.

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

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 Norway spruce logging residues.

Table 5.

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

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

Table 6.

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

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DOI: https://doi.org/10.2478/fsmu-2023-0012 | Journal eISSN: 1736-8723 | Journal ISSN: 1406-9954

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Language: English, Estonian

Page range: 51 - 65

Published on: Apr 13, 2024

Published by: Estonian University of Life Sciences

In partnership with: Paradigm Publishing Services

Keywords:

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© 2024 Allar Padari, Risto Mitt, Linnar Pärn, Vahur Kurvits, Sander Kaasik, Peeter Muiste, published by Estonian University of Life Sciences
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 79 (2023): Issue 1 (December 2023)

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

Figures & Tables

Figure 1.

Figure 2.

Table 1.

Table 2.

Table 3.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Table 4.

Figure 10.

Figure 11.

Table 5.

Figure 12.

Figure 13.

Figure 14.

Table 6.

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