EFFECT OF WOOD WASTE DISPOSAL ON DYNAMIC
ISSN: 1579-4377
EFFECT OF WOOD WASTE DISPOSAL ON DYNAMICS OF SOIL
CHEMISTRY
AND WOOD BIOPOLYMERS IN A FOREST AREA SITUATED ON
BISTRITA AND BICAZ VALLEY, NEAMT COUNTY, ROMANIA
1
Carmen – Alice Teaca1, Ruxanda Bodirlau1, Iuliana-Gabriela Breaban2
“Petru Poni” Institute of Macromolecular Chemistry, 41 A Gr. Ghica-Voda Alley, Iasi, RO-700487, Romania
2
“Al. I. Cuza” University, Department of Geography, 1Carol I Blv., Iasi, RO-700503, Romania
ABSTRACT
Wood waste represents a significant proportion of the waste stream. Forestry/saw mills and
the pulping industries produce wood waste, as well as the construction and demolition
activities. Wood waste, principally a relatively inert, but organic material becomes a priority
material, considering the rapidly evolving field of processing and end markets of this waste
material. Wood wastes (sawdust, wood chips, etc.) present disposal problems for industries
that generate such wastes. In our country, there are many districts that have significant
sawmilling and timber harvesting industries. One of them-Neamt district- generates a large
quantity of wood residue (especially, sawdust composed from 80 % softwood and 20 %
hardwood) that is now being landfilled as waste. Experimental data on wood biopolymers
for sawdust specimens assayed from wood waste dumpsites, located in different areas on the
Bistrita and Bicaz Valley, Neamt County, Romania, are presented here. Besides chemical
analysis, IR and DTG investigations were also performed in order to evidence the wood
biodegradation process. The study of soil dynamics from the wood waste disposal sites
included humus, mineral elements (N, P, K), pH, and total soluble salts content values
(CTSS) determination
KEYWORDS
wood waste disposal, soil dynamics, wood biopolymers, IR spectra, thermogravimetry
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
INTRODUCTION
Biodegradable natural materials are permanently exposed to degradation processes of an
environmental, chemical or microbial nature. The extent of the deterioration depends on the
environment in which these materials are usually found. Among biodegradable materials,
wood is considered to be a durable material that withstands weathering well without lossing
much of its structural properties (except for microbial attack). However, a number of
environmental (non-biological) parameters contribute significantly to the degradation of
wood, including humidity, temperature, solar light irradiation time, atmospheric ozone
content, and pollution. Another important aspect that may significantly affect the
degradation rate of wood is the kind of wood, i.e. softwood or hardwood. Hardwood and
softwood differ in several aspects, like fiber dimensions, chemical component composition
and lignin and cellulose content. The hardwood presents a vessel element and lignin with
both guaiacyl and syringyl units. Softwood does not contain vessel element, the lignin being
composed mostly of essentially only guaiacyl units [1]. In the present paper, data on a
chemical investigation of the softwood specimens (sawdust) assayed from wood waste
disposal sites (situated on Bistrita and Bicaz Valley, Neamt County, Romania), as different
profiles, are presented having mainly in view the biodegradation process. A dynamic
evolution of nutrients in the soil bed, including nitrogen, phosphorus, potassium contents, as
well as the humus, the extractives salts total content and pH values, was also approached.
MATERIALS AND METHODS
Study site
The wood waste disposal sites considered here are located in the Neamt County, northeastern Romania, in a mountain region (Bistrita and Bicaz Valley), being surrounded by
mixed coniferous and decidous forests. The soils are typical brown earths, with a structure of
siliceous sandstones and stones. The forests are mainly composed by coniferous tree species,
such as fir (Abies alba L.) and spruce (Picea abies L.), being also present some decidous
tree species, namely beech (Fagus sylvatica) and birch (Betula alba). The wood wastes
landfilled as dumps in this region are generated through forestry and sawmilling activities.
Soil dynamics analysis
Determination of pH, humus, mineral elements (N, P. K), and extractives salts total content
was performed for evaluating the soil dynamics at the wood waste disposal sites. Soil
samples preparation for analysis (drying, grounding) was achieved through the standard
method according to the SR ISO 11464-1997. Values for pH soil solution and salinity (total
concentration of soluble salts CTSS) were determined by using an InoLab Multilevel 1
(multiparameter- pH, conductivity, the dissolved oxygen) device according to the standard
SR ISO 10390-99. Humus content was determined by titration (standard method 7184 2185). An Inkjel automat Kjeldahl system was used to evaluate the total nitrogen content of
soil samples. A MOM Budapest device was used for determining the soluble potassium
content, while the phosphorous values were determined by using a Shimadzu 1601 PC
photocolorimeter.
2696
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Chemical investigation on the wood waste from disposal sites
In Table 1 are presented the wood sawdust specimens analyzed, the height of the wood
waste dumps ranging in the 1.5 – 2.0 m domain.
Table 1. Wood waste dump profile sections used for the sawdust specimens’assay
Wood waste dump
profile section
Bicaz (P1)
0-12 cm (P209)
0-18 cm (P206)
Geographical location (Neamt district)
Tasca (P2)
Borca (P3)
0-4 cm (P200)
0-20 cm (P213)
4-8 cm (P200a, P200b)
20-60 cm (P214)
60-80 cm (P215)
The wood sawdust specimens were preliminary washed and sieved for removing soil,
and further let air-dry thoroughly. The experimental methodology included the specific
techniques used by the wood chemistry [2]. To determine the wood biopolymers and
extractives content by the standard procedures, the fraction passed through the sieve having
0.40 mm mesh size has been used [3-7]. All the results are relative to the dry matter content
(%DM).
The wood sawdust specimens and their major chemical components (cellulose and
lignin) were further investigated through IR spectroscopy method and thermogravimetry
(DTG) in order to evaluate the biodegradation process. IR spectra were obtained by using a
SPECORD M-80 Carl Zeiss Jena spectrophotometer model, on samples in KBr pellets. A
MOM derivatograph (Paulik-Erdey type, Budapest, Hungary) was used in order to perform
the thermal analysis for wood sawdust specimens and cellulose component (sample weight
50 mg, under a dynamic air flow, at a constant heating rate of 12 0C/min up to the maximum
heating temperature of 600 0C). The device recorded simultaneously the following curves: T
– temperature curve for each moment, TG – weight of sample at each moment, and DTG –
rate of weight loss. The kinetic parameters for the main thermal decomposition reaction
were determined by the Coats-Redfern method [8].
RESULTS AND DISCUSSION
Soil analysis
The study of soil dynamics at wood waste disposal sites has evidenced some differences for
soil parameters, as it is shown in Table 2.
Table 2. Data on soil parameters for samples assayed from wood waste disposal sites
2697
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Soil horizon
pH
P1 (Bicaz)
A0m (18-28 cm)
A0 (28-62 cm)
humus, %
CTSS
N, %
P, ppm
K, ppm
7.94
3.36
106
83
0.18
0.27
15
13
242
82
7.7
8
P2 (Tasca)
A0 (8-31 cm)
A02 (31-48 cm)
G0 (48-52 cm)
Gr (52-62 cm)
R (63 cm)
8
8
8.2
8.2
8.3
5.47
3.02
2.58
1.47
0.57
83
76
81
79
66
0.191
0.164
0.159
0.145
0.11
24
13
15
11
15
216
120
93
86
36
P3 (Borca)
A0 (12-23 cm)
Gr (23-52 cm)
R (52-80 cm)
7.9
7.8
7.9
1.48
1.18
1.85
66
66
71
0.166
0.117
0.145
13
15
19
65
44
48
Thus, it can be mentioned that the wood waste disposal influences significantly the
soil chemistry through increasing the pH value up to 7.8 – 8 (a typical brown soil has a pH
value of 4.8-5). A decrease for humus content is noticed, while the mineral elements content
variation is different: N and P decrease, K increases (for P1 –Bicaz and P2- Tasca). The
disposable P and K are present in a small quantity, a higher value of 24 ppm for P being
determined in the soil horizon A0 (8-31 cm) at P2 disposal site (Tasca). The determined
values for N, P, K are different as a function of wood waste disposal site.
Chemical investigation and thermogravimetry on wood sawdust specimens
The experimental data obtained on the wood sawdust chemical components are presented in
Table 3.
Table 3. Chemical analysis of wood sawdust specimens assayed from the wood waste disposal sites
Sawdust
specimen/
characteristic
P1
(0-18 cm)
P206
P1
(0-12 cm)
P209
P2
(0-4 cm)
P200
P3
(0-20 cm)
P213
P3
(20-60cm)
P214
P3
(60-80 cm)
P215
10.22
P2
(4-8 cm)
P200a
P200b
9.79
Humidity, %
Extractives with, %
Hot water
NaOH 1 %
Cellulose, %
Lignin, %
8.11
9.90
10.02
10.29
10.14
2.35
14.26
49.08
31.38
3.78
17.72
42.21
38.94
5.19
17.47
45.69
32.19
3.06
9.37
46.47
32.31
4.62
14.89
45.45
33.78
2.56
18.13
46.58
33.88
2.57
17.43
47.05
36.18
As it is shown in Table 3, a significant decrease of hot water extractives content is
noticed for P2 and P3 locations, at the bottom of wood waste dumps. The 1 % sodium
hydroxide solution extractives content decreases for wood sawdust specimens from P2
location. No significant variations are noticed both for cellulose and lignin contents.
2698
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
The wood sawdust specimens were also investigated by thermogravimetry analysis
[9, 10], exhibiting both a degradation process for different biopolymers, and a cleavage of
various bonds present in the lignocellulosic matrix. The literature data [11] evidenced that 1,
6-anhydro-glucopyranose represents the major component of solid waste resulted after
thermal decomposition of lignocellulosics and cellulose.
A slowly biodegradation process for the wood samples under study is evidenced
from the experimental data resulted from DTG analysis. In general, until 200 0C, the
combustion proceeds without significant differences, first occurring the dehydration of
reaction products. It follows a concurrence domain (200 – 300 0C) when the combustion
process for cellulose and lignin are quite different.
The carbohydrates exhibit significant weight losses of about 55 – 65 % at 350 0C.
Only lignin exhibits a different combustion process, a weight loss of 50 % being recorded at
450 – 500 0C. For carbohydrates, it can be observed a spontaneous cleavage of their catenes
through radicalic reactions in the temperature range of 300 – 400 0C, evidenced through the
considerable slope of the curves. Table 4 presents the parameters from thermogravimetry
data obtained for the wood sawdust specimens.
Table 4. Thermogravimetry data on wood sawdust specimens thermal decomposition (DTG curves)
Characteristic
T50, ºC
Ti, ºC
Tmax, ºC
WTmax, %
Tf, ºC
WTf, %
Ea, Kj/mol
n
P1 (Bicaz)
(0-18 cm)
360
218
350
36.3
387
49.3
111.06
1.1
Wood sawdust
P2 (Tasca)
(0-4) cm
(4-8) cm
358
350
230
217
340
345
32.7
36.0
380
380
47.6
49.5
113.9
108.9
1.2
1.1
(0-20) cm
365
213
336
34
375
50.5
102.26
1.1
specimens
P3 (Borca)
(20-60) cm
363
204
345
33.5
383
47.5
99.57
0.9
(60-80) cm
367
210
343
33.3
380
46.8
92.28
0.8
where: Ti – initial temperature; Tmax – maximum temperature; WTmax – weight loss at Tmax; Tf - final
temperature; WTf – final weight loss; T50 – temperature corresponding to a weight loss of 50 %; Ea – activation
energy; n – reaction order.
The activation energy calculated by using the Coats-Redfern method [8, 12] presents
lower values for the main thermal decomposition process of wood and cellulose, showing
differences as a function of structural changes extent for the analyzed wood sawdust
specimens. The activation energy values increase as the temperature increases.
In Table 5 are presented the values for endothermic peaks for cellulose thermal
decomposition process, for all wood waste dumps profiles.
Table 5. Thermogravimetry data for cellulose thermal decomposition process (DTG curves)
2699
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Characteristic
P1 (Bicaz)
(0-18 cm)
330
230
330
38
390
60
112.69
0
T50, ºC
Ti, ºC
Tmax, ºC
WTmax, %
Tf, ºC
WTf, %
Ea, Kj/mol
n
Cellulose
P2 (Tasca)
(0-4) cm
(4-8) cm
332
331
230
240
330
330
42
43.2
420
390
69
67
162.51
132.80
1.3
1.4
(0-20) cm
323
230
330
41.4
405
63
158.79
1.4
P3 (Borca)
(20-60) cm
325
250
330
39.1
410
63
154.20
1.3
(60-80) cm
333
230
330
45.2
410
64
151.30
1.2
Weight losses of 46.8-50.5 % are obtained at the end of the main thermal
decomposition process for wood specimens from P3 (Borca) location, decreasing to the
bottom of wood waste dump. For cellulose, weight loss WTmax presents values of 63-69 %.
The activation energy values for wood sawdust specimens vary in the 92.28-113.9 Kj/mol
range, while the reaction order values of 0.8-1.2 are noticed. For cellulose, significant
differences as a function of location and profile sections are observed.
The weight losses for wood and its biopolymers as main constituents (cellulose and
lignin) are presented in Fig. 1-3.
100
T, 0C
100
150
200
250
300
350
400
450
500
550
60
40
20
P215
P214
P213
P209
P206
P200b
P200a
0
P200
Weight loss, %
80
Fig.1. Weight loss for wood sawdust specimens
2700
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
100
T, 0C
100
150
200
250
300
350
400
450
500
550
Weight loss, %
80
60
40
20
P215
P214
P213
P209
P206
P200b
P200
P200a
0
Fig.2. Weight loss for cellulose isolated from wood sawdust specimens
100
T , 0C
100
150
200
250
300
350
400
450
500
550
Weight loss, %
80
60
40
20
P215
P214
P213
P209
P206
P200b
P200a
P200
0
Fig.3. Weight loss for lignin isolated from wood sawdust specimens
As it can be observed, the wood residues exhibit an intermediary evolution, giving a
mean weight loss situated between those for cellulose and lignin. The latter ones have a
different behavior depending on their specific thermal stability. Thus, the weight loss for
cellulose shows a significant decrease, more pregnant in the temperature range of 300-350
0
C, after that reaction occurring considerable slowly. Lignin is the most stable vegetal
component to the thermal destruction and shows significant weight loss in the temperature
range of 350-550 0C.
In Fig. 4-6 are presented the IR spectra for wood sawdust specimens and constitutive
biopolymers – cellulose and lignin. Depending on the chemical structure investigated, the
specific frequency bands cover a well-established domain in the IR spectra.
Figure 4 shows the IR spectra recorded for wood sawdust specimens, considering the
environmental biodegradation process occurred in a natural way. These spectra bring
together the specific vibrations for cellulose, hemicelluloses and lignin. A special mention
should be made on the P3 disposal site, at the top of wood waste dump (60-80 cm profile),
2701
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
where the IR band intensities decrease in the 1460-1730 cm
those for the other profiles.
–1
range, comparatively with
Fig.4. IR spectra for wood sawdust specimens
1) P200; 2) P200a; 3) P200b; 4) P209; 5) P206; 6) P213; 7) P214; 8) P215
IR spectra for celluloses isolated from wood waste specimens are represented in Fig.
5. The frequency shift to the left, at 1660 cm –1 band evidences possible interactions between
the chemical groups. In the 2900-3400 cm –1 frequency domain, a different vibration is
observed between the profile sections. For specimens from P3 location (60-80 cm profile), a
decreasing of frequency band from 2940 cm –1 (νCH2) is noticed. Some differences also
appear in the 1100-1500 cm –1 domain for all profile sections.
2702
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Fig.5. IR spectra for cellulose isolated from wood sawdust specimens
1) P200; 2) P200a; 3) P200b; 4) P209; 5) P206; 6) P213; 7) P214; 8) P215
The IR lignin spectra (Fig. 6) present the following specific bands: 3450 cm-1 (νOH),
2950 cm-1 (νCH3, νCH) , 1730 cm-1 (νC=O), 1600-1650 cm-1 (for aromatic chains), and 900 cm1
(νC − O − C). Besides other specific bands for lignin (at 1600, 1550, 1430, 1220, 1110, and
1040 cm-1), significant vibrations at 840 cm-1 and 1720 cm-1 (νC=O) are evidenced. Lignin
presents a reduced stiffness for this type of bonds.
Fig.6. IR spectra for lignin isolated from wood sawdust specimens
1) P200; 2) P200a; 3) P200b; 4) P209; 5) P206; 6) P213; 7) P214; 8) P215
2703
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
The typical absorbance ratios giving some indication of relative differences in
aliphatic to aromatic units ratio and the condensation level, calculated from IR spectra for
lignin, are presented in Table 6 [13].
Table 6. Absorbance ratios from IR lignin spectra
Absorbance ratio
P1 (Bicaz)
P2 (Tasca)
0-4 cm
4-8 cm
P3 (Borca)
0-20 cm
20-60 cm
60-80 cm
A2936/A1510
aliphatic / aromatic
0.3348
A1365/A1510
OH phenolic
0.2352
A1086/A1510
C-O groups
0.2787
A1330/A1269
syringyl/guaiacyl
0.5548
0.6250
0.5765
0.2102
0.2541
0.3785
0.2321
0.8618
1.7719
0.5733
0.6214
0.3943
0.2356
0.2571
0.2767
0.2707
0.4195
0.2933
0.8960
2.2682
0.7647
Peak height ratio A1330/A1269 representing the ratio of sum of syringyl (S) and
condensed guaiacyl (Gcond) to guaiacyl groups is lower for lignin from wood specimens at
P1 location (Bicaz). Ratios in Table 6 are orientative because carbonyl groups may affect
peaks on the mentioned wavenumbers. The absorbance ratio of aliphatic to aromatic CHx
groups varies with the wood waste disposal site (P2-Tasca > P3-Borca > P1-Bicaz).
Quantitative analysis of the IR spectra may evidence the structural peculiarities for wood
biopolymers during their isolation from wood sawdust waste, especially for the carbonyl
groups.
CONCLUSIONS
Soil dynamics presents differences as a function of wood waste disposal site. A slowly
increase for the soil pH values is noticed for all dumpsites.
Different extent of the wood biodegradation process is evidenced for wood waste
dumps considered here, the process being more intense at the bottom of these.
Extractives content decreases as a function of profile section from wood waste
dumps due to the rain water percolation.
Cellulose content exhibits an opposite evolution comparatively with the lignin
content, showing a significant decrease, fact evidenced for the oldest wood waste dump. It is
possible that the lignin biodegradation products are quickly involved in the humus formation
process.
The wood sawdust specimens were subjected to the thermal destruction exhibiting
both a degradation process for the biopolymers (cellulose and lignin), and a cleavage of
various bonds present in the lignocellulosic matrix.
REFERENCES
1.
S. Saka, Chemical composition and distribution, In Wood and Cellulosic Chemistry, (N.D.S. Hon, S.
Shiraishi, eds.), pp. 59-88. Marcel Dekker Inc. New York (1991).
2704
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
R.Pettersen, Chemical Composition of Wood. In The Chemistry of Solid Woods (R. M. Rowell, ed.).
Advances in Chemistry Series 207, pp. 57-126. American Chemical Society: Washington D.C.
(1984).
TAPPI (US Technical Association of Pulp and Paper Industry). Preparation of Wood for Chemical
Analysis. T 264 om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). Wood Extractives in Ethanol-Benzene
Mixture. T 204-om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). One Percent Sodium Hydroxide
Solubility of Wood and Pulp. T 212 om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). Water Solubility of Wood and Pulp. T
207 om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). Acid Insoluble Lignin in Wood and
Pulp. T 222 om-88, (1988).
A.W. Coats, J. P. Redfern. Kinetic parameters from thermogravimetric data. Nature 201, 68-69
(1964).
Gh. Rozmarin. Thermal analysis of wood and its components. Cellulose and Paper 34, 180-191
(1985).
Cr. I. Simionescu, M. Grigoras, A. Cernatescu – Asandei, Gh. Rozmarin. Chemistry of wood from
Romania, pp. 111-147. Romanian Academy Publishing House, Bucharest, Romania (1973).
B. Kaur, S. Gur, H. Bhatnagar. Studies on thermal degradation of cellulose and cellulose
phosphoramides. J. Appl. Polym.Sci. 31, 667-683 (1986).
T.R. Rao, A. Sharma. Pyrolysis rates of biomass materials. Energy 23, 973-978 (1998).
O. Faix, O. Beinhoff. FTIR spectra of milled wood lignins and lignin polymer models (DHP’s) with
enhanced resolution obtained by deconvolution. J. Wood Chem. Technol. 8, 505-522 (1988).
2705
EFFECT OF WOOD WASTE DISPOSAL ON DYNAMICS OF SOIL
CHEMISTRY
AND WOOD BIOPOLYMERS IN A FOREST AREA SITUATED ON
BISTRITA AND BICAZ VALLEY, NEAMT COUNTY, ROMANIA
1
Carmen – Alice Teaca1, Ruxanda Bodirlau1, Iuliana-Gabriela Breaban2
“Petru Poni” Institute of Macromolecular Chemistry, 41 A Gr. Ghica-Voda Alley, Iasi, RO-700487, Romania
2
“Al. I. Cuza” University, Department of Geography, 1Carol I Blv., Iasi, RO-700503, Romania
ABSTRACT
Wood waste represents a significant proportion of the waste stream. Forestry/saw mills and
the pulping industries produce wood waste, as well as the construction and demolition
activities. Wood waste, principally a relatively inert, but organic material becomes a priority
material, considering the rapidly evolving field of processing and end markets of this waste
material. Wood wastes (sawdust, wood chips, etc.) present disposal problems for industries
that generate such wastes. In our country, there are many districts that have significant
sawmilling and timber harvesting industries. One of them-Neamt district- generates a large
quantity of wood residue (especially, sawdust composed from 80 % softwood and 20 %
hardwood) that is now being landfilled as waste. Experimental data on wood biopolymers
for sawdust specimens assayed from wood waste dumpsites, located in different areas on the
Bistrita and Bicaz Valley, Neamt County, Romania, are presented here. Besides chemical
analysis, IR and DTG investigations were also performed in order to evidence the wood
biodegradation process. The study of soil dynamics from the wood waste disposal sites
included humus, mineral elements (N, P, K), pH, and total soluble salts content values
(CTSS) determination
KEYWORDS
wood waste disposal, soil dynamics, wood biopolymers, IR spectra, thermogravimetry
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
INTRODUCTION
Biodegradable natural materials are permanently exposed to degradation processes of an
environmental, chemical or microbial nature. The extent of the deterioration depends on the
environment in which these materials are usually found. Among biodegradable materials,
wood is considered to be a durable material that withstands weathering well without lossing
much of its structural properties (except for microbial attack). However, a number of
environmental (non-biological) parameters contribute significantly to the degradation of
wood, including humidity, temperature, solar light irradiation time, atmospheric ozone
content, and pollution. Another important aspect that may significantly affect the
degradation rate of wood is the kind of wood, i.e. softwood or hardwood. Hardwood and
softwood differ in several aspects, like fiber dimensions, chemical component composition
and lignin and cellulose content. The hardwood presents a vessel element and lignin with
both guaiacyl and syringyl units. Softwood does not contain vessel element, the lignin being
composed mostly of essentially only guaiacyl units [1]. In the present paper, data on a
chemical investigation of the softwood specimens (sawdust) assayed from wood waste
disposal sites (situated on Bistrita and Bicaz Valley, Neamt County, Romania), as different
profiles, are presented having mainly in view the biodegradation process. A dynamic
evolution of nutrients in the soil bed, including nitrogen, phosphorus, potassium contents, as
well as the humus, the extractives salts total content and pH values, was also approached.
MATERIALS AND METHODS
Study site
The wood waste disposal sites considered here are located in the Neamt County, northeastern Romania, in a mountain region (Bistrita and Bicaz Valley), being surrounded by
mixed coniferous and decidous forests. The soils are typical brown earths, with a structure of
siliceous sandstones and stones. The forests are mainly composed by coniferous tree species,
such as fir (Abies alba L.) and spruce (Picea abies L.), being also present some decidous
tree species, namely beech (Fagus sylvatica) and birch (Betula alba). The wood wastes
landfilled as dumps in this region are generated through forestry and sawmilling activities.
Soil dynamics analysis
Determination of pH, humus, mineral elements (N, P. K), and extractives salts total content
was performed for evaluating the soil dynamics at the wood waste disposal sites. Soil
samples preparation for analysis (drying, grounding) was achieved through the standard
method according to the SR ISO 11464-1997. Values for pH soil solution and salinity (total
concentration of soluble salts CTSS) were determined by using an InoLab Multilevel 1
(multiparameter- pH, conductivity, the dissolved oxygen) device according to the standard
SR ISO 10390-99. Humus content was determined by titration (standard method 7184 2185). An Inkjel automat Kjeldahl system was used to evaluate the total nitrogen content of
soil samples. A MOM Budapest device was used for determining the soluble potassium
content, while the phosphorous values were determined by using a Shimadzu 1601 PC
photocolorimeter.
2696
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Chemical investigation on the wood waste from disposal sites
In Table 1 are presented the wood sawdust specimens analyzed, the height of the wood
waste dumps ranging in the 1.5 – 2.0 m domain.
Table 1. Wood waste dump profile sections used for the sawdust specimens’assay
Wood waste dump
profile section
Bicaz (P1)
0-12 cm (P209)
0-18 cm (P206)
Geographical location (Neamt district)
Tasca (P2)
Borca (P3)
0-4 cm (P200)
0-20 cm (P213)
4-8 cm (P200a, P200b)
20-60 cm (P214)
60-80 cm (P215)
The wood sawdust specimens were preliminary washed and sieved for removing soil,
and further let air-dry thoroughly. The experimental methodology included the specific
techniques used by the wood chemistry [2]. To determine the wood biopolymers and
extractives content by the standard procedures, the fraction passed through the sieve having
0.40 mm mesh size has been used [3-7]. All the results are relative to the dry matter content
(%DM).
The wood sawdust specimens and their major chemical components (cellulose and
lignin) were further investigated through IR spectroscopy method and thermogravimetry
(DTG) in order to evaluate the biodegradation process. IR spectra were obtained by using a
SPECORD M-80 Carl Zeiss Jena spectrophotometer model, on samples in KBr pellets. A
MOM derivatograph (Paulik-Erdey type, Budapest, Hungary) was used in order to perform
the thermal analysis for wood sawdust specimens and cellulose component (sample weight
50 mg, under a dynamic air flow, at a constant heating rate of 12 0C/min up to the maximum
heating temperature of 600 0C). The device recorded simultaneously the following curves: T
– temperature curve for each moment, TG – weight of sample at each moment, and DTG –
rate of weight loss. The kinetic parameters for the main thermal decomposition reaction
were determined by the Coats-Redfern method [8].
RESULTS AND DISCUSSION
Soil analysis
The study of soil dynamics at wood waste disposal sites has evidenced some differences for
soil parameters, as it is shown in Table 2.
Table 2. Data on soil parameters for samples assayed from wood waste disposal sites
2697
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Soil horizon
pH
P1 (Bicaz)
A0m (18-28 cm)
A0 (28-62 cm)
humus, %
CTSS
N, %
P, ppm
K, ppm
7.94
3.36
106
83
0.18
0.27
15
13
242
82
7.7
8
P2 (Tasca)
A0 (8-31 cm)
A02 (31-48 cm)
G0 (48-52 cm)
Gr (52-62 cm)
R (63 cm)
8
8
8.2
8.2
8.3
5.47
3.02
2.58
1.47
0.57
83
76
81
79
66
0.191
0.164
0.159
0.145
0.11
24
13
15
11
15
216
120
93
86
36
P3 (Borca)
A0 (12-23 cm)
Gr (23-52 cm)
R (52-80 cm)
7.9
7.8
7.9
1.48
1.18
1.85
66
66
71
0.166
0.117
0.145
13
15
19
65
44
48
Thus, it can be mentioned that the wood waste disposal influences significantly the
soil chemistry through increasing the pH value up to 7.8 – 8 (a typical brown soil has a pH
value of 4.8-5). A decrease for humus content is noticed, while the mineral elements content
variation is different: N and P decrease, K increases (for P1 –Bicaz and P2- Tasca). The
disposable P and K are present in a small quantity, a higher value of 24 ppm for P being
determined in the soil horizon A0 (8-31 cm) at P2 disposal site (Tasca). The determined
values for N, P, K are different as a function of wood waste disposal site.
Chemical investigation and thermogravimetry on wood sawdust specimens
The experimental data obtained on the wood sawdust chemical components are presented in
Table 3.
Table 3. Chemical analysis of wood sawdust specimens assayed from the wood waste disposal sites
Sawdust
specimen/
characteristic
P1
(0-18 cm)
P206
P1
(0-12 cm)
P209
P2
(0-4 cm)
P200
P3
(0-20 cm)
P213
P3
(20-60cm)
P214
P3
(60-80 cm)
P215
10.22
P2
(4-8 cm)
P200a
P200b
9.79
Humidity, %
Extractives with, %
Hot water
NaOH 1 %
Cellulose, %
Lignin, %
8.11
9.90
10.02
10.29
10.14
2.35
14.26
49.08
31.38
3.78
17.72
42.21
38.94
5.19
17.47
45.69
32.19
3.06
9.37
46.47
32.31
4.62
14.89
45.45
33.78
2.56
18.13
46.58
33.88
2.57
17.43
47.05
36.18
As it is shown in Table 3, a significant decrease of hot water extractives content is
noticed for P2 and P3 locations, at the bottom of wood waste dumps. The 1 % sodium
hydroxide solution extractives content decreases for wood sawdust specimens from P2
location. No significant variations are noticed both for cellulose and lignin contents.
2698
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
The wood sawdust specimens were also investigated by thermogravimetry analysis
[9, 10], exhibiting both a degradation process for different biopolymers, and a cleavage of
various bonds present in the lignocellulosic matrix. The literature data [11] evidenced that 1,
6-anhydro-glucopyranose represents the major component of solid waste resulted after
thermal decomposition of lignocellulosics and cellulose.
A slowly biodegradation process for the wood samples under study is evidenced
from the experimental data resulted from DTG analysis. In general, until 200 0C, the
combustion proceeds without significant differences, first occurring the dehydration of
reaction products. It follows a concurrence domain (200 – 300 0C) when the combustion
process for cellulose and lignin are quite different.
The carbohydrates exhibit significant weight losses of about 55 – 65 % at 350 0C.
Only lignin exhibits a different combustion process, a weight loss of 50 % being recorded at
450 – 500 0C. For carbohydrates, it can be observed a spontaneous cleavage of their catenes
through radicalic reactions in the temperature range of 300 – 400 0C, evidenced through the
considerable slope of the curves. Table 4 presents the parameters from thermogravimetry
data obtained for the wood sawdust specimens.
Table 4. Thermogravimetry data on wood sawdust specimens thermal decomposition (DTG curves)
Characteristic
T50, ºC
Ti, ºC
Tmax, ºC
WTmax, %
Tf, ºC
WTf, %
Ea, Kj/mol
n
P1 (Bicaz)
(0-18 cm)
360
218
350
36.3
387
49.3
111.06
1.1
Wood sawdust
P2 (Tasca)
(0-4) cm
(4-8) cm
358
350
230
217
340
345
32.7
36.0
380
380
47.6
49.5
113.9
108.9
1.2
1.1
(0-20) cm
365
213
336
34
375
50.5
102.26
1.1
specimens
P3 (Borca)
(20-60) cm
363
204
345
33.5
383
47.5
99.57
0.9
(60-80) cm
367
210
343
33.3
380
46.8
92.28
0.8
where: Ti – initial temperature; Tmax – maximum temperature; WTmax – weight loss at Tmax; Tf - final
temperature; WTf – final weight loss; T50 – temperature corresponding to a weight loss of 50 %; Ea – activation
energy; n – reaction order.
The activation energy calculated by using the Coats-Redfern method [8, 12] presents
lower values for the main thermal decomposition process of wood and cellulose, showing
differences as a function of structural changes extent for the analyzed wood sawdust
specimens. The activation energy values increase as the temperature increases.
In Table 5 are presented the values for endothermic peaks for cellulose thermal
decomposition process, for all wood waste dumps profiles.
Table 5. Thermogravimetry data for cellulose thermal decomposition process (DTG curves)
2699
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Characteristic
P1 (Bicaz)
(0-18 cm)
330
230
330
38
390
60
112.69
0
T50, ºC
Ti, ºC
Tmax, ºC
WTmax, %
Tf, ºC
WTf, %
Ea, Kj/mol
n
Cellulose
P2 (Tasca)
(0-4) cm
(4-8) cm
332
331
230
240
330
330
42
43.2
420
390
69
67
162.51
132.80
1.3
1.4
(0-20) cm
323
230
330
41.4
405
63
158.79
1.4
P3 (Borca)
(20-60) cm
325
250
330
39.1
410
63
154.20
1.3
(60-80) cm
333
230
330
45.2
410
64
151.30
1.2
Weight losses of 46.8-50.5 % are obtained at the end of the main thermal
decomposition process for wood specimens from P3 (Borca) location, decreasing to the
bottom of wood waste dump. For cellulose, weight loss WTmax presents values of 63-69 %.
The activation energy values for wood sawdust specimens vary in the 92.28-113.9 Kj/mol
range, while the reaction order values of 0.8-1.2 are noticed. For cellulose, significant
differences as a function of location and profile sections are observed.
The weight losses for wood and its biopolymers as main constituents (cellulose and
lignin) are presented in Fig. 1-3.
100
T, 0C
100
150
200
250
300
350
400
450
500
550
60
40
20
P215
P214
P213
P209
P206
P200b
P200a
0
P200
Weight loss, %
80
Fig.1. Weight loss for wood sawdust specimens
2700
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
100
T, 0C
100
150
200
250
300
350
400
450
500
550
Weight loss, %
80
60
40
20
P215
P214
P213
P209
P206
P200b
P200
P200a
0
Fig.2. Weight loss for cellulose isolated from wood sawdust specimens
100
T , 0C
100
150
200
250
300
350
400
450
500
550
Weight loss, %
80
60
40
20
P215
P214
P213
P209
P206
P200b
P200a
P200
0
Fig.3. Weight loss for lignin isolated from wood sawdust specimens
As it can be observed, the wood residues exhibit an intermediary evolution, giving a
mean weight loss situated between those for cellulose and lignin. The latter ones have a
different behavior depending on their specific thermal stability. Thus, the weight loss for
cellulose shows a significant decrease, more pregnant in the temperature range of 300-350
0
C, after that reaction occurring considerable slowly. Lignin is the most stable vegetal
component to the thermal destruction and shows significant weight loss in the temperature
range of 350-550 0C.
In Fig. 4-6 are presented the IR spectra for wood sawdust specimens and constitutive
biopolymers – cellulose and lignin. Depending on the chemical structure investigated, the
specific frequency bands cover a well-established domain in the IR spectra.
Figure 4 shows the IR spectra recorded for wood sawdust specimens, considering the
environmental biodegradation process occurred in a natural way. These spectra bring
together the specific vibrations for cellulose, hemicelluloses and lignin. A special mention
should be made on the P3 disposal site, at the top of wood waste dump (60-80 cm profile),
2701
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
where the IR band intensities decrease in the 1460-1730 cm
those for the other profiles.
–1
range, comparatively with
Fig.4. IR spectra for wood sawdust specimens
1) P200; 2) P200a; 3) P200b; 4) P209; 5) P206; 6) P213; 7) P214; 8) P215
IR spectra for celluloses isolated from wood waste specimens are represented in Fig.
5. The frequency shift to the left, at 1660 cm –1 band evidences possible interactions between
the chemical groups. In the 2900-3400 cm –1 frequency domain, a different vibration is
observed between the profile sections. For specimens from P3 location (60-80 cm profile), a
decreasing of frequency band from 2940 cm –1 (νCH2) is noticed. Some differences also
appear in the 1100-1500 cm –1 domain for all profile sections.
2702
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
Fig.5. IR spectra for cellulose isolated from wood sawdust specimens
1) P200; 2) P200a; 3) P200b; 4) P209; 5) P206; 6) P213; 7) P214; 8) P215
The IR lignin spectra (Fig. 6) present the following specific bands: 3450 cm-1 (νOH),
2950 cm-1 (νCH3, νCH) , 1730 cm-1 (νC=O), 1600-1650 cm-1 (for aromatic chains), and 900 cm1
(νC − O − C). Besides other specific bands for lignin (at 1600, 1550, 1430, 1220, 1110, and
1040 cm-1), significant vibrations at 840 cm-1 and 1720 cm-1 (νC=O) are evidenced. Lignin
presents a reduced stiffness for this type of bonds.
Fig.6. IR spectra for lignin isolated from wood sawdust specimens
1) P200; 2) P200a; 3) P200b; 4) P209; 5) P206; 6) P213; 7) P214; 8) P215
2703
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
The typical absorbance ratios giving some indication of relative differences in
aliphatic to aromatic units ratio and the condensation level, calculated from IR spectra for
lignin, are presented in Table 6 [13].
Table 6. Absorbance ratios from IR lignin spectra
Absorbance ratio
P1 (Bicaz)
P2 (Tasca)
0-4 cm
4-8 cm
P3 (Borca)
0-20 cm
20-60 cm
60-80 cm
A2936/A1510
aliphatic / aromatic
0.3348
A1365/A1510
OH phenolic
0.2352
A1086/A1510
C-O groups
0.2787
A1330/A1269
syringyl/guaiacyl
0.5548
0.6250
0.5765
0.2102
0.2541
0.3785
0.2321
0.8618
1.7719
0.5733
0.6214
0.3943
0.2356
0.2571
0.2767
0.2707
0.4195
0.2933
0.8960
2.2682
0.7647
Peak height ratio A1330/A1269 representing the ratio of sum of syringyl (S) and
condensed guaiacyl (Gcond) to guaiacyl groups is lower for lignin from wood specimens at
P1 location (Bicaz). Ratios in Table 6 are orientative because carbonyl groups may affect
peaks on the mentioned wavenumbers. The absorbance ratio of aliphatic to aromatic CHx
groups varies with the wood waste disposal site (P2-Tasca > P3-Borca > P1-Bicaz).
Quantitative analysis of the IR spectra may evidence the structural peculiarities for wood
biopolymers during their isolation from wood sawdust waste, especially for the carbonyl
groups.
CONCLUSIONS
Soil dynamics presents differences as a function of wood waste disposal site. A slowly
increase for the soil pH values is noticed for all dumpsites.
Different extent of the wood biodegradation process is evidenced for wood waste
dumps considered here, the process being more intense at the bottom of these.
Extractives content decreases as a function of profile section from wood waste
dumps due to the rain water percolation.
Cellulose content exhibits an opposite evolution comparatively with the lignin
content, showing a significant decrease, fact evidenced for the oldest wood waste dump. It is
possible that the lignin biodegradation products are quickly involved in the humus formation
process.
The wood sawdust specimens were subjected to the thermal destruction exhibiting
both a degradation process for the biopolymers (cellulose and lignin), and a cleavage of
various bonds present in the lignocellulosic matrix.
REFERENCES
1.
S. Saka, Chemical composition and distribution, In Wood and Cellulosic Chemistry, (N.D.S. Hon, S.
Shiraishi, eds.), pp. 59-88. Marcel Dekker Inc. New York (1991).
2704
Teaca et al. EJEAFChe, 7 (13), 2008. [2695-2705]
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
R.Pettersen, Chemical Composition of Wood. In The Chemistry of Solid Woods (R. M. Rowell, ed.).
Advances in Chemistry Series 207, pp. 57-126. American Chemical Society: Washington D.C.
(1984).
TAPPI (US Technical Association of Pulp and Paper Industry). Preparation of Wood for Chemical
Analysis. T 264 om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). Wood Extractives in Ethanol-Benzene
Mixture. T 204-om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). One Percent Sodium Hydroxide
Solubility of Wood and Pulp. T 212 om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). Water Solubility of Wood and Pulp. T
207 om-88, (1988).
TAPPI (US Technical Association of Pulp and Paper Industry). Acid Insoluble Lignin in Wood and
Pulp. T 222 om-88, (1988).
A.W. Coats, J. P. Redfern. Kinetic parameters from thermogravimetric data. Nature 201, 68-69
(1964).
Gh. Rozmarin. Thermal analysis of wood and its components. Cellulose and Paper 34, 180-191
(1985).
Cr. I. Simionescu, M. Grigoras, A. Cernatescu – Asandei, Gh. Rozmarin. Chemistry of wood from
Romania, pp. 111-147. Romanian Academy Publishing House, Bucharest, Romania (1973).
B. Kaur, S. Gur, H. Bhatnagar. Studies on thermal degradation of cellulose and cellulose
phosphoramides. J. Appl. Polym.Sci. 31, 667-683 (1986).
T.R. Rao, A. Sharma. Pyrolysis rates of biomass materials. Energy 23, 973-978 (1998).
O. Faix, O. Beinhoff. FTIR spectra of milled wood lignins and lignin polymer models (DHP’s) with
enhanced resolution obtained by deconvolution. J. Wood Chem. Technol. 8, 505-522 (1988).
2705