Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2010
Volume 13
Issue 4
Topic:
Wood Technology
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Nicewicz D. , Danecki L. 2010. WOOD FROM PALLETS AND CONTAINERS AS RAW MATERIAL FOR THE PRODUCTION OF FIBERBOARDS, EJPAU 13(4), #03.
Available Online: http://www.ejpau.media.pl/volume13/issue4/art-03.html

WOOD FROM PALLETS AND CONTAINERS AS RAW MATERIAL FOR THE PRODUCTION OF FIBERBOARDS

Danuta Nicewicz1, Leszek Danecki2
1 Faculty of Wood Technology, Warsaw University of Life Sciences – SGGW, Poland
2 Research and Development Centre for Wood-Based Panels Industry in Czarna Woda, Poland

 

ABSTRACT

Recovered wood from palettes and containers was disintegrated to the form of chips. Pulps to the production of fiberboards: insulation boards, hardboards and MDF at variable defibration and rafination parameters were obtained from these chips. Chips and pulps were characterized by determination of percent shares of fractions obtained by sorting on a sieve sorters. The fractional composition of chips and pulps from recovered wood was compared with fractional composition of standard chips and pulps, respectively. The effect of addition of pulp from recovered wood on the properties of insulation boards, hardboards and MDF boards was examined.

Key words: chips, pulps, palettes, containers, fibreboard properties.

INTRODUCTION

Economical development brings not only increasing welfare of people but also a growth in the quantity of produced wastes. It is estimated that the quantity of wastes in the form of used wood products in Poland amounts to over 5 million m3 (2.8 million tons) yearly. These wastes are diversified with regard to their form, material composition and content of chemical substances [7].Therefore, there is no single method of their utilization. From the experience of Western countries it is known that they should be utilized in industry and power engineering rather than stored on waste storage yards [3].

Management of recovered wood in Poland is at the initial stage of development. In last years, there arose first centers for collection of recovered wood, assigned for alternative fuel [9,10]. Researches on application of this wood in wood-based panels industry are carried out as well. In other countries, recovered wood has been already utilized on industrial scale in the production of particleboards [5]. There are definitely less reports on utilization of this wood in the production of fiberboards [1,8].

It results from a conducted market analysis that the quantity of recovered wood possible to obtain from containers and pallets reaches in Poland the level of about 3.5–3.8 million m3 yearly, in that about 500–700 thousand m3 from wooden containers only. The resources of this assortment of recovered wood can satisfy the raw-material demand of particleboard and fiberboard industry in even as much as 20% [2,6].

Relatively low moisture content of recovered wood can be both an advantage and a drawback in the production of wood-based materials. In the case of fiberboards manufactured by the dry and wet methods, low humidity of the raw material is a drawback. In the production process of these boards, wood is chipped and chips in turn are submitted to defibration to the form of fibers. The operation of defibration proceeds correctly when the humidity of chips is above the fiber saturation point. Thus, chips from recovered wood must be moistened before they are submitted to defibration.

MATERIALS AND METHODS

In the researches, there was used a batch of recovered wood of mass 500 kg coming from used containers and pallets. The composition of the material of the study was the following: exotic wood 32%, local wood 64%, in that: hardwood 34%, softwood 30%, and particleboards 4%. Foreign matter (nails and steel stitches) made about 0.8% of wood mass.

From pallets and containers, there were removed fasteners and in this way they were divided to components which subsequently were disintegrated to the form of chips in a wood chipper. Chips were immersed in water of temperature 30°C for 4 h and brought to the humidity of 48%. At the next stage, chips were disintegrated to the form of wood fibers in a laboratory defibrator. In order to establish the optimum conditions of defibration, there were applied variable defibration parameters: time of heating of chips (2–5 min) and defibration temperature (140–160°C); the time of defibration of chips amounted to 2 min in each case. Obtained pulp was refined in a laboratory refiner.

Chips and pulp obtained from wood of containers and pallets are marked as RW (recovered wood), while chips and pulp obtained from fresh softwood in industrial conditions as standard ones. The freeness of pulp used for insulation boards amounted to 42 DS, for hardboards – to 23 DS, for MDF boards – to 52 DS.

Particular kinds of pulp obtained from RW were added to standard pulp in relations: 0, 25, 50, 75 and 100%. After mixing, appropriate chemical agents were spread on fibers and insulation boards, hardboards and MDF were produced.

Insulation boards were produced only with an addition of a hydrophobic agent (1% of paraffin); hardboards – with an addition of 1% of PF resin (phenol formaldehyde resin) and 1% of paraffin, while MDF boards – with an addition of 10% of UF resin (urea formaldehyde resin) and 1% of paraffin.

Assumed properties of boards:

Technological parameters during production:

Properties of obtained boards (30 in each series) were tested according to the obligatory standards PN-EN 622/1 - 622/5. Significance of results was examined by means of the Student's criterion.

RESULTS AND ANALYSIS

Chips were characterized by: determination of percent shares of fractions obtained by sorting chips on a sieve sorter, humidity of chips within each fraction, content of bark in standard chips. Results are presented in Table 1.

Table 1. Shares of fractions in chips from recovered wood and from forest wood

Sieve slot width [mm]

Chips from
RW
[%]

Relative humidity
[%]

Standard chips
[%]

Content of bark
[%]

Relative humidity
[%]

40

16.9

12.6

 

20

35.1

12.9

19.1

7.0

52.1

10

31.6

11.7

38.0

27.3

55.9

4

12.5

12.9

34.6

25.8

53.6

2

2.3

16.9

4.4

8.6

52.6

1

0.5

14.4

2.6

50.0

0.5 mm

0.9

18.8

0.7

41.3

Fines and dust

0.2

14.3

0.6

24.6

Total

100%

mean = 14.3

100%

 

mean = 42

Generally, it can be concluded that size of chips depended on the type of raw material they originated from. From containers and pallets, there were obtained almost 17% of chips retained by a 40-mm sieve, while there were no such chips from forest wood. The sieve 20 mm retained 35% of chips from pallets, and barely a half of that in the case of chips from forest wood (19%). In standard chips, in fractions 2–20 mm there was bark in the proportion of several to twenty percent while in chips from containers and pallets there was no bark at all. The humidity of standard chips amounted to 42%, while that of chips from RW – to only 14%, so they were moistened before defibration.

It results from the presented data that from wood of low humidity (that from containers and pallets) there arose more big chips (retained by sieves 20–40 mm) than from fresh wood. In chips from recovered wood, there was a relatively small content of fine fractions (the through fraction made only 0.2%).

Then the fractional composition of pulps obtained from chips was examined, separately in pulps for insulation boards, hardboards and MDF.

In Table 2, there are presented shares of fractions in pulp for insulation boards obtained as a result of sorting on a standard sorter with slotted sieves.

Fractioning of pulp gives a general idea of phenomena taking place during a 2-stage production of pulp. It results from the data in Table 2 that in the pulp from RW after defibration there were 7 times as much fiber bunches (retained by sieve 1 mm) as in standard pulp. During refination, a considerable proportion of fiber bunches were separated, both in RW pulp and in standard one. In the standard pulp after refination most fibers were retained by the sieve ≤ 0.15 mm (97%), while in the pulp from containers and pallets there were about 80% of such fibers.

Table 2. Fractional composition of pulps for the production of insulation boards

Sieve slot width (mm)

Pulp from RW
after defibration
[%]

Standard pulp
after defibration
[%]

Pulp from RW
after refination
[%]

Standard pulp
after refination
[%]

1

40.3

5.7

1.3

0.3

0.5

12.9

2.4

9.7

0.9

0.3

9.6

6.7

8.7

1.8

0.15
and smaller

37.2

85.2

80.3

97.0

In Table 3, there are presented selected properties of pulp destined for insulation boards, obtained in the MorFi LB01 apparatus [4].

As visible, pulps differed not only in the length of fibers but also in the content of shives. In the standard pulp, fibers were on average by about 50% longer than fibers obtained from pallet wood. There can have been at least two causes of this fact. The first one is the species composition of wood from which both pulps were produced. In the pallet wood, there were about 30% of exotic wood and about 30% of local hardwood. The industrial pulp was produced from pine wood. So the anatomic structure of wood had probably an influence on the length of obtained fibers. The second important parameter was probably susceptibility of chips to defibration. Chips from pallet wood (of lower initial humidity –  about 14%) were probably plasticized in the heater of defibrator to a lower degree and could be more shortened during defibration. Their lower plasticization was additionally proven by a much higher (by about 45%) quantity of shives in the secondary pulp. On the other hand, the proportion of fines was on a similar level in the analyzed pulps. This result was an effect of not only anatomical structure of wood and humidity of chips, but also of a presence of bark in standard chips (Table 1).

Table 3. Properties of pulp from container and pallet wood as well as of standard pulp destined for insulation boards

Properties of:

Pulp from RW

Standard pulp

average length of fibers [mm]

563

857

average width of fibers [mm]

34

38

quantity of  shives [pieces]

192

106

quantity of shives [% surface]

13

10

It results from the conducted analysis that wood fibers obtained from wood of containers and pallets differ in size from fibers in standard pulp. However, it seems that they can make a useful raw material for the production of insulation boards.

Characteristics of pulp destined for hardboard production are presented in Table 4.
In the fractional composition of the analyzed pulps after the first stage of defibration, there are visible significant differences, especially in fractions retained by the sieves 1 mm and '0.15 and smaller'. However, these differences considerably diminished as a result of pulp refination. In the pulp from RW, there remained a relatively high proportion (almost 20%) of fibers retained by the sieve 1 mm. On the other hand, the percent shares of other fractions did not differ significantly. Hence it can be concluded that fibers obtained from wood of containers and pallets can be utilized in the production of hardboards.

Table 4. Fractional composition of pulps for the production of hardboards

Sieve slot width [mm]

Pulp from RW
after defibration
[%]

Standard pulp
after defibration
[%]

Pulp from RW
after refination
[%]

Standard pulp
after refination
[%]

1

67.7

3.5

19.7

2.9

0.5

12.7

14.5

7.5

7.4

0.3

8.5

4.7

7.8

3.0

0.15 and smaller

11.1

77.3

65.0

86.7

Fractional composition of pulps destined for MDF boards are presented in Table 5. Pulp from container and pallet wood was obtained in laboratory conditions by defibration of chips and refination of pulp. Standard pulp was produced in industrial conditions in a process of one-stage defibration of chips in a new-generation defibrator.

Table 5. Fractional composition of pulps for the production of MDF

Sieve slot width [mm]

Pulp from RW
after defibration
[%]

Pulp from RW
after refination
[%]

Standard pulp
after one-stage defibration
[ %]

1

5.7

0.3

1.3

0.5

2.4

1.7

5.6

0.3

6.9

2.3

38.8

0.15 and smaller

85.0

95.7

61.2

It is visible from the data presented in Table 5 that as a result of refination the share of fibers retained by sieves 1, 0.5 and 0.3 mm decreased and at the same time the share of fibers retained by the sieve '0.15 and smaller' increased by about 10%. However, a comparison of pulp from recovered wood after refination with standard pulp destined for MDF boards reveals significant differences in percent shares of particular fractions. Hence it can be concluded that pulp from wood of containers and pallets will be applicable at the most as a certain addition to the standard pulp in the production of MDF boards.

In the first place, there are presented properties of insulation boards obtained from RW pulp and from standard pulp. Results are shown in Table 6. In that table, apart from board properties tested according to the standard PN-EN622/3, there is presented also the thickness of boards. Thickness of hardboards and MDF has not been presented because mats from which these boards were made underwent pressing and the thickness of boards was obtained according to the assumptions. Mats for insulation boards were dried directly after forming, so their thickness depended only on the alignment of fibers in the mat.

Table 6. Properties of insulation boards obtained with different proportions of standard pulps and pulps from wood of containers and pallets

Proportion of RW
[%]

Thickness
[mm]

Density
[kG/m3]

MOR
[N/mm2]

Standard deviation
[N/mm2]

Thickness
swelling after 2 h
[%]

Standard deviation
[%]

0

14.3

200

1.00

0.28

2.4

0.3

25

14.0

200

0.65

0.07

1.5

0.5

50

13.4

200

0.66

0.13

2.1

0.3

75

12.8

220

0.74

0.11

2.0

0.4

100

11.7

240

0,96

0.11

2.1

0.4

It results from the data in the table that with a growth of share of pulp from recovered wood the thickness of boards was decreasing and their density was growing. It was mentioned that fibers from recovered wood were considerably shorter than those in standard, hence they created a more compact structure of boards. These fibers affected also bending strength of boards. The strength of insulation boards with an addition of recovered pulp in proportions of 25, 50 and 75% was lower by about 30% in relation to the strength of boards made from standard pulp. However, the exact proportion of added pulp from RW had no influence on the bending strength – in all cases the strength was at the level of 0.7 N/mm2. Only boards made in 100% of RW pulp had a bending strength of 1.0 N/mm2, i.e. the same as boards made from standard pulp. Probably the values of bending strength of boards made from RW pulp were affected by their density.

Addition of pulp from containers and pallets did not significantly affect swelling of insulation boards. On one hand, it could be expected that an addition of pulp containing fibers of hardwoods will cause a growth of swelling, because these species contain more hemicelluloses in comparison with softwood. On the other hand, wood was dried during production of containers and pallets, to moisture content 15%, which caused probably a partial hornification of xylem and fibers were absorbing less water. Eventually, swelling of boards with additions of pulp from wood of containers and pallets in all analyzed variants slightly decreased, but this decrease was statistically insignificant.

To summarize, it can be stated that wood from used containers and pallets can be a raw material in the production of insulation boards, however, before defibration, chips obtained from this raw material should be wetted. Attempts at defibration of chips after sprinkling with water in a laboratory defibrator ended with a failure. There arose too many incompletely defibrated chips and the consumption of electric power significantly increased.
Properties of hardboards made from RW pulps and from standard pulp are presented in Table 7.

It results from data shown in Table 7 that an addition of pulp from wood of containers and pallets did not significantly affect the board properties. From among all analyzed properties, only tensile strength perpendicular to surface was lower in the tested boards in relation to the value given in the standard PN- EN 622-2 (0.5 N/mm2), except for the boards made exclusively from the RW pulp.

Table 7. Propertes of hardboards obtained at different shares of standard pulp and pulp from wood of containers and pallets

Proportion of
RW and PF
[%]

Density [kG/m3]

MOR
[N/mm2]

Standard deviation
[N/mm2]

IB
[N/mm2]

Standard deviation
[N/mm2]

MOE
[N/mm2]

Standard deviation
[N/mm2]

Thickness
swelling after 24 h
[%]

Standard deviation
[%]

0.0      1.0

953

31.7

5.0

0.27

0.03

2832

637

23.6

1.8

25      1.0

955

35.3

4.1

0.23

0.02

3526

162

26.0

2.0

25      1.5

951

41.6

4.1

0.41

0.04

4478

508

25.5

2.1

50      1.0

993

40.7

4.3

0.30

0.02

4444

376

22.8

1.4

75      1.0

956

40.5

5.6

0.4

0.01

4711

498

25.2

3.2

100      1.0

967

46.8

3.8

0.5

0.02

4478

601

24.2

2.1

In order to improve this property, boards of higher freeness of pulp (28DS) were produced. Results are not shown in a table, because there was no improvement in the analyzed property. Therefore, there was produced an additional variant of boards with a 25-percent addition of pulp from wood of containers and pallets in which the amount of PF resin was increased to 1.5%. As visible from the data in the table, increased addition of resin caused a growth in all strength properties of tested boards. Tensile strength perpendicular to surface increased from 0.2 to 0.4 N/mm2, but still it was lower than required. Nevertheless, it seems that recovered wood from containers and pallets can be utilized also in the production of hardboards.

Properties of obtained MDF boards are presented in Table 8.
It is visible from the data presented in the table that with a growing addition of pulp from wood of containers and pallets, all analyzed strength properties were deteriorating.

Table 8. Properties of MDF boards produced with different shares of pulp from recovered wood and standard pulp

Proportion of  RW and UF [%]

Density
[kg/m3]

MOR
[N/mm2]

Standard deviation
[N/mm2]

IB
[N/mm2]

Standard deviation
[N/mm2]

MOE
[N/mm2 ]

Standard deviation
[N/mm2]

Thickness
swelling after 24 h
[%]

Standard deviation
[%]

0.0  10

741

33.9

3.3

0.78

0.06

2297

119

14.8

0.7

25  10

695

28.4

4.1

0.69

0.11

2263

206

14.1

2.1

50  10

698

25.6

4.9

0.61

0.01

2203

159

20.0

1.6

75  10

721

22.2

1.1

0.50

0.05

1751

52

26.9

0.4

In the case of bending strength, a difference in values of this property was observed  between boards made of standard pulp and those with a 25-percent addition of pulp from recovered wood . The bending strength diminished by 5.5 N/mm2 (i.e. by 16%) and this decrease was statistically significant. With a growth of the share of pulp from recovered wood in boards to 50% and 75%, bending strength fell by 25% and 35% correspondingly. This decrease in bending strength was statistically significant in relation to boards made from standard pulp, but insignificant between variants (boards with addition of pulp from recovered wood of 25, 50 and 75%).

Tensile strength perpendicular to surface decreased with a growing share of pulp from recovered wood in boards as well. Strength satisfying the standard was reached for the boards with 25 and 50% addition of pulp from recovered wood. Boards with a 50-percent share of pulp from recovered wood had a tensile strength of 0.61 N/mm2. In relation to the strength of boards made from standard pulp, it was a decrease by 22% and it was statistically significant. Boards with a 75-percent share of pulp from recovered wood reached a tensile strength of only 0.50 N/mm2.

Changes in modulus of elasticity of boards with different additions of pulp from wood of containers and pallets showed a similar pattern as changes in bending strength.

Thickness swelling of boards after 24h of soaking in water increased with a growing share of pulp from recovered wood in boards. Only boards with a 25-percent share of this pulp satisfied the requirements of the standard. Therefore, there is a possibility of producing MDF boards with a 25% addition of pulp from wood of containers and pallets.

CONCLUSIONS

It is commonly known that insulation boards, hardboards and MDF are produced from wood fibers. From the data presented above it is visible that depending on the type of produced boards characteristics of standard pulps are different. Due to this fact, it is possible to produce boards of diversified properties.

It also results from the presented data that pulps obtained from wood of containers and pallets, even though they differ from considered standard pulps. It seems that in the first place this wood should be applied to the production of boards by the wet method, so insulation boards and hardboards. Addition of this wood in the production of boards by the dry method (MDF) is possible as well.

REFERENCES

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  2. Danecki L., Paluchewicz Z., 2009. Opracowanie danych dotyczących ilości drewna poużytkowego z opakowań, palet i płyt o budowie włóknistej [Develop data on the amount of recovered wood packaging, pallets and boards of fiberboard pulps]. Typescript ODRPPD Czarna Woda [in Polish].

  3. Hillring B., Canals G., Olsson O., 2007. Market for recovered wood in Europe – an overview. 3rd Eur. COST E31 Conf. Management of Recovered Wood. Austria, 201–213.

  4. Klimczewski M., Nicewicz D., Danecki L., 2009. Properties of fiberboard pulps manufactured from selected types of recovered wood. Symp. Proceedings of the International Panel Products. Nantes, France 16–18.09.

  5. Merl A.D., Humar M., Okstad T., Picardo V., 2007. Amounts of recovered wood in COST E31 countries and Europe. 3rd Eur. COST E31 Conf. Management of Recovered Wood. Austria, 79–116.

  6. Nicewicz D., Danecki L., 2009. Wood from pallets and wooden containers as a potential source of raw material for the wood-based boards industry. Ann. Univ. Life Sci. SGGW For. Wood Technol.69, 115–118.

  7. Ratajczak E., Szostek A., Bidzińska G., 2003. Drewno poużytkowe w Polsce [Recovered wood in Poland]. Wyd. Instytutu Technologii Drewna, Poznań [in Polish].

  8. Roffael E., Behn C., Dix B., Bär G. 2009. Recycling of UF-bonded fiberboards. Conf. IPPC Nantes in France, 253–262.

  9. www.oberlandia.pl

  10. www.univerpal.com.pl

This work is financed by the Polish Department of Education and Science, Project no N N309136435.

 

Accepted for print: 9.09.2010


Danuta Nicewicz
Faculty of Wood Technology,
Warsaw University of Life Sciences – SGGW, Poland
Nowoursynowska 159, 02-776 Warsaw, Poland
email: danuta_nicewicz@sggw.pl

Leszek Danecki
Research and Development Centre for Wood-Based Panels Industry in Czarna Woda, Poland
Mickiewicza 10a, 83-262 Czarna Woda, Poland
email: leszek.danecki@obrppd.com

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