4. Physicochemical properties of wood vinegars

Wood vinegar is a complex mixture of polar and non-polar chemicals with varying molecular weights and compositions, which depends upon feedstock and processing condition. Some physical properties such as pH, specific gravity, color, odor, dissolved tar content, ignition residue and transparency have been reported. Due to the presence of organic acids such as acetic acid, formic acid and propionic acid, the acidity of wood vinegar is often in the range of pH 2–4. Total soluble tar contents were found within a range of 0.23–0.89% wt. The specific gravity and o Brix was reported within a range of 1.005–1.016 g/mL and 1.7–6.6, respectively [3, 14].

The major proportion in wood vinegar is water (80–90%) that is a result of feedstock dehydration. Water is usually miscible with the oligomeric lignin-derivative components because of the solubilizing effect of other polar hydrophilic compounds, low-molecular-weight acids,


Compound Organic acidic

Acetic acid Alcohol derivatives

Methanol n-Propanol

n-Butanol

∑

Alcohol derivatives Furfural and furan derivatives

2-Furfuraldehyde

Methyl-2-furoate

2-Methylfuran

∑ Phenol derivative

Phenol 2-Methylphenol

3-Methylphenol

4-Methylphenol

2-Ethylphenol

2,6-Dimethylphenol

2,5-Dimethylphenol

2,4-Dimethylphenol

2,3-Dimethylphenol

∑ Phenol derivatives

Methoxyphenol

 derivatives

0.06

6.92

5.23

4.43

 3.26

 3.30

 0.00

 0.04

 0.00

 ND

 0.03

 0.00 ND

ND

0.26

 0.22

 ND

 0.21

 0.01 ND

0.29

 0.01

 0.10

 0.00

 0.17

 0.01 0.07

 0.00 0.13

 0.01

 0.24 ND 0.04

5.98

 0.00

 0.05 3.70

 5.03 169

 0.00 ND

 0.00

 0.20

ND

 ND

 0.00 0.12

 0.00

http://dx.doi.org/10.5772/intechopen.77380

ND

0.03

 0.00

 ND

 ND

 ND

0.94

3.82

1.67

0.11

0.03

 0.00

 0.03

 0.00

 ND

 0.02

 0.00 ND

 0.00

 0.19

 0.01

 0.07

 0.00 0.13

 0.01 0.04

 0.00

 0.16 0.03

0.05

 0.00

 0.42

 0.00 ND

 0.00

 0.06

 0.00 0.03

 0.00

 0.00

 0.09

 0.00 0.04

 0.00

 0.01

 0.78

 0.68

 0.68

 0.00 0.69

 0.01 0.61

 0.00

 1.28

 0.05

 0.05

 0.00 0.32

 0.0

 0.02

 2.85

 0.01

 2.76

 0.01 1.57

 0.01 2.07

 0.01

 3.17

 0.01

 2.16

 0.11 4.06

 0.06

 0.01

 0.95

 0.01

 0.75

 0.01 0.54

 0.02 0.45

 0.01

 1.01

 0.01

 0.67

 0.01 0.46

 0.02

Physicochemistry and Utilization of Wood Vinegar from Carbonization of Tropical Biomass Waste

Furfural and furan derivatives

0.45

0.18

0.23

 0.86

 0.01

 0.54 4.34

0.95

 4.74

 3.04

 0.01

 0.27

 0.00 0.31

 0.01 0.39

 0.01

 0.34 6.44

 0.00

 0.79 4.10

 1.35

 0.02 0.55

 0.03

 0.01

 0.74

 0.01

 0.08

 0.00 0.37

 0.01 0.41

 0.01

 0.87

 0.01

 0.62

 0.02 0.13

 0.01

 0.00

 3.06

 0.01

 0.60

 0.02 4.06

 0.02 2.24

 0.01

 5.23

 0.01

 2.69

 0.03 0.67

 0.01

3.92

ND ND 3.92

8.12

3.85

 3.80

 3.62

ND

ND

 ND

 ND

ND

ND

 ND

 ND

 0.04

 8.12

 0.27

 3.85

 0.66 3.80

 0.07 3.62

 0.03

 6.13 0.02

ND 6.15

4.43

 4.52

 0.00

 ND ND

 ND

 ND

 0.14

 4.43

 0.09 4.52

 0.05

40.26

 1.02

 55.98

 1.22

 37.38

 0.04 35.26

 0.15 65.29

 0.02

 32.49

 0.08

 69.34

 0.17 70.60

 0.20

Concentration

L.

leucocephala

 1 L.

leucocephala 2 A. indica 1 A. indica 2 E.

camaldulensis

 1 E.

camaldulensis

 2 D. asper

 H. brasiliensis

 (mg.mL1

)

Table 1. Physicochemical property of eight wood vinegars from five wood species [15].


contained in charcoal wood comes out as steam. At this stage, temperature inside kiln and the smoke out of the chimney are about 300 and 80C, respectively. After that the color of the smoke changes to a mixture of white and yellowish brown with an irritating burning smell then the color changes back to white within a short time. The white smoke reappears and the smell changes to a sweet smell. The temperature inside kiln and the smoke out of the chimney is lower than 300C and range from 80 to 150C. This stage recommends as the optimal

On wood vinegar preparation, the crude bio-oil solution is kept in a closed container and stands at ambient temperature for about 3 months. The solution then will be separated into 2 phases; the clear upper phase that is wood vinegar is drained off, while the lower phase is

Wood vinegar is a complex mixture of polar and non-polar chemicals with varying molecular weights and compositions, which depends upon feedstock and processing condition. Some physical properties such as pH, specific gravity, color, odor, dissolved tar content, ignition residue and transparency have been reported. Due to the presence of organic acids such as acetic acid, formic acid and propionic acid, the acidity of wood vinegar is often in the range of pH 2–4. Total soluble tar contents were found within a range of 0.23–0.89% wt. The specific gravity and

The major proportion in wood vinegar is water (80–90%) that is a result of feedstock dehydration. Water is usually miscible with the oligomeric lignin-derivative components because of the solubilizing effect of other polar hydrophilic compounds, low-molecular-weight acids,

pKa Total

L. leucocephala 1 3.40 1.006 0.000 4.47 0.01 4.70 0.37 0.02 3.80 0.10 274.50 154.00 5.00 91.13 0.27 L. leucocephala 2 3.10 1.007 0.000 4.61 0.02 4.70 0.57 0.01 4.60 0.10 270.80 375.50 6.20 84.54 0.02 A. indica 1 3.40 1.004 0.000 3.28 0.03 4.70 0.37 0.02 3.00 0.10 273.40 150.50 5.00 91.50 0.06 A. indica 2 3.20 1.005 0.000 3.16 0.04 4.70 0.58 0.03 3.40 0.10 271.00 298.00 6.50 93.48 0.15 E. camaldulensis 1 3.10 1.006 0.000 4.62 0.04 4.70 0.57 0.02 4.60 0.10 272.60 221.00 5.00 89.44 0.25 E. camaldulensis 2 3.50 1.008 0.000 3.62 0.03 4.70 0.49 0.02 3.40 0.10 270.80 393.00 8.00 90.37 0.20 H. brasiliensis 2.90 1.012 0.000 4.92 0.02 4.70 0.96 0.03 6.00 0.20 268.00 467.00 7.00 85.30 0.50 D. asper 2.90 1.010 0.000 4.92 0.02 4.70 0.71 0.01 5.60 0.20 269.20 470.00 6.00 81.44 0.26

soluble tar (% by weight)

Degree Brix

λmax (nm) Amax Water

content (% by weight)

Brix was reported within a range of 1.005–1.016 g/mL and 1.7–6.6, respectively [3, 14].

condition to recover bio-oil [13].

4. Physicochemical properties of wood vinegars

TAC<sup>b</sup> (% by weight)

Table 1. Physicochemical property of eight wood vinegars from five wood species [15].

Sample Physical and chemical parameters pH SG (g.mL<sup>1</sup> )

called tar sediment.

168 Tropical Forests - New Edition

o


Table 2. Chemical compositions of eight wood vinegars from five wood species [15].

alcohols, hydroxyaldehydes, and ketones, mostly originating from the decomposition of car-

acids, alcohols, aldehydes, ketones and sugars. It appears that acetic acid is the highest proportion [14] in this fraction. The other components are also found, for instance, phenols and monolignols (quaiacol and syringol) which are degradation products from lignin. Levoglucosan, levoglucosenone, furfural, substituted furan, are derived from cellulose. The simpler organic molecules are converted from fats, mucilage, wax, alkaloids, and terpenoids. For inorganic salts

The physicochemical characteristics of eight wood vinegars from the carbonization of five wood

—Leucaena leucocephala (Katin), Azadirachta indica (Sadao), Eucalyptus camaldulensis

brasiliensis (rubber wood) and Dendrocalamus asper (bamboo), which were produced by heating

C in a Thai-Iwate kiln showed the pH of 2.9

Chemical compositions of wood vinegars consisted of acetic acid as the largest component

However, it has been showed that wood vinegar is unstable during prolong storage or aging process. The viscosity of the mixture gradually increases and phase separation is slowly occurs. Apart from sedimentation of a high-density particle and colloidal matter, this might be a result from the series of chemical reaction such as an aldol condensation reaction between aldehydes and alcohols, and self-aggregation of aldehydes with those of reactive oligomers. In addition, the metallic components may also play important role as reaction

As mentioned earlier, there are wide variations in the property of wood vinegar due to its mixture of many compounds with different concentrations. However, Japan Pyroligneous Liquor Association, an industrial body for pyroligneous liquor trader sets 7 parameters in order to standardize a good quality of the product. These are included pH value of around

or reddish brown, has a marked smoky odor, the dissolved tar content should not more than 3%, ignition residue should not more than 0.2%, and exhibit transparency without suspended solid matter [13]. However, Fagernäs et al. [12] stated that the commercialized wood vinegar in European Unions (EU) has not been accepted because quality is widely varies. Accordingly, attention should be paid to obtain knowledge base on the preparation processes and quality

–0.963% by weight and total soluble tar not more than 3%. The values of the specific

–20% wt are water-soluble organic compounds. These comprise of

Physicochemistry and Utilization of Wood Vinegar from Carbonization of Tropical Biomass Waste

 1

). A high number of phenol derivatives (16 compounds) were found and

, Hevea

171

 1 )

) followed by

–3.5, total soluble tar of

's standards, Table 1 [15].

) and bamboo (1.010 g mL

http://dx.doi.org/10.5772/intechopen.77380

 1

–11 mg mL

–1.050, color should be a pale yellow, bright brown

bohydrates.

species

0.325

(30.45

The minor proportions of 10

wood samples up to 400

–70.60 mg mL

2-methylphenol (2

catalysis [16].

 1

5. Quality of wood vinegars

3.0, standard specific gravity around 1.010

control using a practical and cheap procedure.

–4 mg mL

and metallic complex are commonly reduced to ash.

gravity of only two products, from rubber wood (1.012 g mL

were within the acceptance criteria of quality assessments of Japan

those in higher concentrations were 4-propyl-2-methoxyphenol (5

), Table 2

.

 1 alcohols, hydroxyaldehydes, and ketones, mostly originating from the decomposition of carbohydrates.

The minor proportions of 10–20% wt are water-soluble organic compounds. These comprise of acids, alcohols, aldehydes, ketones and sugars. It appears that acetic acid is the highest proportion [14] in this fraction. The other components are also found, for instance, phenols and monolignols (quaiacol and syringol) which are degradation products from lignin. Levoglucosan, levoglucosenone, furfural, substituted furan, are derived from cellulose. The simpler organic molecules are converted from fats, mucilage, wax, alkaloids, and terpenoids. For inorganic salts and metallic complex are commonly reduced to ash.

The physicochemical characteristics of eight wood vinegars from the carbonization of five wood species—Leucaena leucocephala (Katin), Azadirachta indica (Sadao), Eucalyptus camaldulensis, Hevea brasiliensis (rubber wood) and Dendrocalamus asper (bamboo), which were produced by heating wood samples up to 400C in a Thai-Iwate kiln showed the pH of 2.9–3.5, total soluble tar of 0.325–0.963% by weight and total soluble tar not more than 3%. The values of the specific gravity of only two products, from rubber wood (1.012 g mL<sup>1</sup> ) and bamboo (1.010 g mL<sup>1</sup> ) were within the acceptance criteria of quality assessments of Japan's standards, Table 1 [15]. Chemical compositions of wood vinegars consisted of acetic acid as the largest component (30.45–70.60 mg mL<sup>1</sup> ). A high number of phenol derivatives (16 compounds) were found and those in higher concentrations were 4-propyl-2-methoxyphenol (5–11 mg mL<sup>1</sup> ) followed by 2-methylphenol (2–4 mg mL<sup>1</sup> ), Table 2.

However, it has been showed that wood vinegar is unstable during prolong storage or aging process. The viscosity of the mixture gradually increases and phase separation is slowly occurs. Apart from sedimentation of a high-density particle and colloidal matter, this might be a result from the series of chemical reaction such as an aldol condensation reaction between aldehydes and alcohols, and self-aggregation of aldehydes with those of reactive oligomers. In addition, the metallic components may also play important role as reaction catalysis [16].
