Bayerische Landesanstalt für Wald und Forstwirtschaft

Fuel Quality Changes and Dry Matter Losses during the Storage of Wood Chips

49th International Symposium on Forestry Mechanization

Nicolas Hofmann (LWF), Theresa Mendel (TFZ), Fabian Schulmeyer (LWF), Dr. Daniel Kuptz (TFZ), Dr. Herbert Borchert (LWF), Dr. Hans Hartmann (TFZ)

Warsaw, September 7, 2016

Part 1: Field Trials to Examine the Storage of Wood Chips under Practical Conditions

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Joint research project

Bavarian State Institute of Forestry (LWF)

Technology and Support Centre (TFZ)

Funding

Bavarian State Ministry of Food, Agriculture and Forestry

Cooperation

Bavarian State Forest Enterprise

several forest service companies

FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Research Project Quality Preserving Storage of Wood Chips from Forests

Introduction/Aims

almost 5 million lcm of wood chips from forests in Bavaria each year

important role of storage

dry matter losses

energy losses

impact of storage on fuel quality

moisture content, ash content (d), heating value (d)

consideration of Bavarian conditions

type of wood (Norway spruce, Picea abies)

climate

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FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Experimental Setup

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2 experiments (winter + summer)

4 chip piles of 200 lcm (mainly spruce)

forest residues (FR)/energy roundwood (ER)

uncovered/covered (fleece)

unchipped piles from FR and ER

sampling with balance bags (144 per pile)

wood chip pile N. Hofmann

N. Hofmann forest residue chips energy roundwood chips N. Hofmann N. Hofmann

balance bag for sampling T. Mendel

FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Experimental Setup

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FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

segment

Experimental Setup

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N. Hofmann

FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Results: Initial Fine and Moisture Content

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Winter Summer

Fine content (w-%)* 24.9 (±8.7) 15.1 (±1.8)

Moisture content (w-%)

51.1 (±0.6) open

50.7 (±0.7) fleece

50.4 (±0.7) open

56.8 (±0.5) fleece

Winter Summer

10.0 (±2.2) 7,5 (±2.4)

56.6 (±0.8) open

55.1 (±1.2) fleece

47.9 (±0.5) open

53.2 (±1.0) fleece

FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

N. Hofmann N. Hofmann

*mixed samples uncovered/covered pile

Results: Temperature

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Winter 2014/15 Summer 2015

FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Precipitation: Winter 2014/15: 234 mm Summer 2015: 244 mm

Results: Moisture, Dry Matter and Ash

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FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Winter trial Summer trial

FRC no fleece

FRC fleece

ERC no fleece

ERC fleece

FRC no fleece

FRC fleece

ERC no fleece

ERC fleece

Moisture content before storage (w-%)

51.1 (±0.6)

50.7 (±0.7)

56.6 (±0.8)

55.1 (±1.2)

50.4 (±0.7)

56.8 (±0.5)

47.9 (±0.5)

53.2 (±1.0)

Moisture content after 5 months of storage (w-%)

52.7 (±5.0)

36.9 (±0.8)

58.7 (±0.7)

52.8 (±0.5)

34.1 (±2.8)

34.2 (±0.8)

36.5 (±1.6)

31.0 (±0.5)

Dry matter losses after 5 months of storage (w-%)

7.8 (±0.1)

8.0 (±0.1)

3.4 (±0.6)

4.2 (±0.2)

7.0 (±1.4)

11.1 (±1.1)

6.8 (±0.3)

6.9 (±0.4)

Change in ash content after 5 months of storage (w-%, abs., d)

0.60 -0.04 0.19 0.16 0.23 0.26 0.05 -0.03

Results: Influence of Factors on Moisture Content

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FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Factors Deg. of

Freedom MS F p

Partial eta-

squared

Season 1 1432.76 517.67 0.0000 0.89

Storage duration 3 251.34 90.81 0.0000 0.81

Assortment 1 555.73 200.79 0.0000 0.76

Fleece 1 416.28 150.41 0.0000 0.70 effe

ct s

ize

summer stronger drying than winter

longer storage duration stronger drying

FRC dried stronger than ERC

with fleece stronger drying than without

highest decrease in MC: -22.6 w-%. (summer, 5 months of storage, FRC, fleece)

final absolute MC around 35 w-% in summer

Results: Influence of Factors on Dry Matter Losses

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FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Factors Deg. of

Freedom MS F p

Partial eta-

squared

Storage duration 3 143.54 187.64 0.0000 0.90

Assortment 1 286.83 374.95 0.0000 0.85

Season 1 19.10 24.96 0.0000 0.28

Fleece 1 8.18 10.69 0.0017 0.14

longer storage duration higher loss

FRC decomposed stronger than ERC

summer higher loss than winter

with fleece higher loss than without

highest loss: 11.1 w-% (summer, 5 months of storage, FRC, fleece)

effe

ct s

ize

Results: Usable Energy Content

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Winter 2014/15 Summer 2015

change in usable energy content primarily influenced by dry matter loss and moisture content change, net calorific value (on dry basis) changed only marginally

FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Results: Unchipped Storage (21/22 weeks)

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Winter trial Summer trial

Parameter Forest residues Energy roundwood Forest residues Energy

roundwood*

Moisture content before storage (w-%)

49.2 (±2.0) [n = 44]

52.7 (±4.3) [n = 41]

52.5 (±3.0) [n = 35]

-

Moisture content after storage (w-%)

48.7 (±2.5) [n = 10]

47.2 (±2.2) [n = 24]

39.5 (±2.2) [n = 9]

24.2 (±0.5) [n = 19]

Dry matter loss (w-%), decomp.

2.5 0.1 6.6 -

Trickling-loss (w-%)

4.6 0.2 5.2 -

Total dry matter loss (w-%)

7.1 0.3 11.8 -

Change in usable energy content (%)

-6.7 2.6 -5.8 -

Change in ash content (%)

-2.5 -0.3 -0.5 -

* error in initial condition of the pile FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Conclusion

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self-heating is higher in FRC than in ERC

change in moisture content and dry matter loss are significantly dependent on storage duration, season, assortment and rain protection (fleece)

in winter only little loss of usable energy, except for uncovered FRC

in summer even slight increase of usable energy content possible

ash content and net calorific value (on dry basis) only change marginally during storage of wood chips

storage of unchipped wood in regard to energy content mainly recommendable for energy roundwood; however, significant decrease in ash and fine content during storage of unchipped forest residues possible

FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Thank you for your attention!

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FORMEC 2016 − Wood Chip Storage Trials under Practical Conditions − Nicolas Hofmann

Bavarian State Institute of Forestry Forest Technology, Business Management, Timber Hans-Carl-von-Carlowitz-Platz 1 85354 Freising, Germany www.lwf.bayern.de

N. Hofmann

Nicolas Hofmann +49 (0) 8161 / 71 – 4175 nicolas.hofmann@lwf.bayern.de