3. Factors influencing properties of wood vinegar

Wood vinegar is a complex mixture of polar and non-polar compounds that varies widely in their property among samples that may be observed. These are primarily influenced by the type of carbonaceous feedstocks as well as production techniques.

#### 3.1. Feedstock

In general, cellulose (42–45%), hemicellulose (28–35%), and lignin (16–33%) are major constituents of the plant cell wall, which are primary components of wood, while water-soluble and organic-soluble compounds are the minor compounds [4]. The biopolymers and minor compounds are arranged in a complex structure as illustrated in Figure 2. It should be noted that

Figure 1. Wood vinegar from agricultural biomass waste.

Keywords: wood vinegar, carbonization, physicochemistry, tropical biomass, utilization

Pyroligneous acid also called wood vinegar is an aqueous liquid produced from pyrolysis of lignocellulose waste and biomass. They are formed by rapidly and simultaneously depolymerizing and fragmenting cellulose, hemicellulose, lignin and other constitutes of biomass. Those biopolymers were broken into smaller molecule with high temperature under air less atmospheres. The crude condensate smoke during pyrolysis was so called bio-oil. In order to prepare wood vinegar, this liquid is stand in a closed container for at least 3 months and decanted from sedimentation tar of bio-oil. The transparent solution in upper phase is practical wood vinegar. It has a special smoky odor and color is light yellow to brown depending on feedstock properties and pyrolysis system used for preparing it. The wood vinegar was very complex solution; the major proportion was water (80–90%) and minor proportion was more than 200 species of organic compounds. Recently, wood vinegar has been wildly applied for various proposes such as medicinal, smoky aroma, food and platelet aggregation and anti-dermatophyte activity in pharmaceuticals [1, 2]. In particular, in organic agriculture, a great number of toxic-chemicals were replaced by wood vinegar, a natural product, which has been used to combat disease and pests, stimulate plant growth, improve the quality of fruit, accelerate the speed of plant seed germination and serve as herbicides [3]. However, the physicochemistry and biological activity of wood vinegar are affected by many factors such as

The crude liquid obtained by condensation of an output, gas phase and smoke, during charcoal production process is called bio-oil. After standing the crude liquid in a closed container at ambient temperature for about 3 months, it will be separated into 2 phases. A clear solution of upper phase is wood vinegar or pyroligneous acid, while the lower phase is tar sediment. The

Wood vinegar is a complex mixture of polar and non-polar compounds that varies widely in their property among samples that may be observed. These are primarily influenced by the

In general, cellulose (42–45%), hemicellulose (28–35%), and lignin (16–33%) are major constituents of the plant cell wall, which are primary components of wood, while water-soluble and organic-soluble compounds are the minor compounds [4]. The biopolymers and minor compounds are arranged in a complex structure as illustrated in Figure 2. It should be noted that

acid has smoky odor, and color may vary from light yellow to dark brown (Figure 1).

chemical composition of biomass, pyrolysis system and refining method.

3. Factors influencing properties of wood vinegar

type of carbonaceous feedstocks as well as production techniques.

2. Definition of wood vinegar

3.1. Feedstock

1. Introduction

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variations in proportion of the constituents are not only depends on the plant species, but are also influenced by other factors such as habitat, age, part of the tree, etc. Hence, it could be deduced that variations in composition of feedstock used for the preparation of wood vinegar might give rise to different properties of the product.

Cellulose is a long-chain linear polymer of glucose that contains crystalline arrangements with smaller amorphous regions. There are arranged as micro-fibril which contributes to the structural component of the cell wall. In general, a similar content at approximately 43% wt is found in both hardwood and softwood [6].

Hemicellulose is shorter or branched amorphous polymer of five-or six-carbon sugars which naturally are associated with cellulose and lignin to from the matrix. The sub-units of hemicellulose in hardwoods and herbaceous plants such as wheat straw, cornstover and switch grass consist mainly of D-xylose, whereas D-mannose, D-xylose and D-galactose are the principal constituents in softwood [7].

Lignin, the third cell wall component, is a three-dimensional polymer formed from phenyl propane units with many different types of linkages between the building blocks. The main building blocks in the biosynthesis of hardwood and softwood lignin are different in structure. In softwoods, guaiacyl lignin is predominantly found resulting from polymerization of a higher fraction of conifer phenyl propane units. In hardwood, guaiacyl-syringyl lignin is present . It is a copolymer between coniferyl and sinapyl phenyl propane units where sinapyl unit fraction is higher than that in softwood lignin [8].

The water-soluble and organic-soluble compounds may be extracted from the lignocellulose biomass. For instance, the organic-soluble compounds in wood include terpenes, fats, waxes, phenolic compounds, hydrocarbons and sugars, while the water-soluble compounds are

liquid, char and gas at 75, 12 and 13% respectively [11]. The main objective of developing fast pyrolysis is to generate an enhanced fuel for generating heat and power. Fast pyrolysis technology has long been developed as a thermochemical conversion technology to produce

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

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

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Slow pyrolysis is a simple technology that has been practiced by the ancient Chinese. It has long been known as carbonization. The reaction is a thermal conversion process where wood or other biomass material is slowly heated in the absence of air or oxygen up to final temperature of about 500C. In slow pyrolysis, hemicelluloses are degraded in temperature range from 200 to 260C, cellulose at 240–350C and lignin at 280–500C [12]. Charcoal is most important product with about 30% of wood slow pyrolysis. It has long been used for heating, cooking, and

In Asia, slow pyrolysis was used to prepare charcoal. With the current increasing concern in regard to environment issues, the smoke from charcoal making could be called a pollutant. The wood vinegar produced by smoke from charcoal making has many benefits such as stimulating vegetables and plant growth, anti-harmful microorganisms [10]. Today, however, there is much diversity of charcoal wood including thinned wood, sawdust and backboard dust produced by sawmills, bark, windfall trees, dead trees, waste wood from agriculture and demolished buildings, bamboo, straw and rice husks. Different charcoal wood requires a different carbonization kiln but the principle of charcoal-making, i.e. baking charcoal wood by regulating the airflow, remains the same for all types of kilns. Similarly, the principle of recovering bio-oil has remained unchanged. To recover bio-oil, the chimney is placed above the smoke outlet of the charcoal kiln while a container is placed in the lower end of the

The color of the smoke produced in the carbonization of wood changes depending on the progress of this process. These are used as an impotent indicator to recover bio-oil. When carbonization starts, the white smoke first appears. This is wet smoke because the water

Figure 3. Fast pyrolysis kinetics of hemicellulose, cellulose, and lignin: TG = thermogravimetry; DTG = differential

industrial purposes. Bio-oil content was about 30% and gas content was about 35%.

high yields of bio-oil from biomass [4].

chimney to collect the dripping, condensed liquid.

thermogravimetry [10].

Figure 2. Composition of wood, illustrating the structure of lignocellulosic biomass [5].

sodium and potassium salts. In general, herbaceous biomass typically contains significant amounts of inorganic salts and organic-soluble compounds which may be found at approximately 15 and 20%wt, respectively. In contrast, in common woods, there are usually lower content which the inorganic salts and organic-soluble compounds may be found at approximately 0.3–0.4%wt and 2–3%wt, respectively [9].

#### 3.2. Pyrolysis processes and preparation of wood vinegars

Pyrolysis is mainly technology used to produce wood vinegar with thermal degradation of organic material. According to this system, the larger molecules were transformed to smaller with high temperature and air less condition. Pyrolysis technology has been continuously developed to support various purposes. In general, the pyrolysis types were classified based on heating rate mainly fast and slow pyrolysis.

Fast pyrolysis is an advance process in which biomass is rapidly heated to moderate temperature of around 500C and short residence time of typically less than 2 seconds. Fast pyrolysis kinetic of wood constituents determined the rate of thermal breakdown as presented in Figure 3. Hemicelluloses are fast decomposed in temperature range from 200 to 300C and cellulose is the least stable polymer decomposed from 300 to 400C. Lignin exhibits intermediate thermal degradation behavior from 250 to 500C. Thermal decomposition studies on separated lignin will not necessarily match the pyrolysis behavior of this component when it is present in the original biomass [10]. Typical product yields, dry wood basis, consisted of liquid, char and gas at 75, 12 and 13% respectively [11]. The main objective of developing fast pyrolysis is to generate an enhanced fuel for generating heat and power. Fast pyrolysis technology has long been developed as a thermochemical conversion technology to produce high yields of bio-oil from biomass [4].

Slow pyrolysis is a simple technology that has been practiced by the ancient Chinese. It has long been known as carbonization. The reaction is a thermal conversion process where wood or other biomass material is slowly heated in the absence of air or oxygen up to final temperature of about 500C. In slow pyrolysis, hemicelluloses are degraded in temperature range from 200 to 260C, cellulose at 240–350C and lignin at 280–500C [12]. Charcoal is most important product with about 30% of wood slow pyrolysis. It has long been used for heating, cooking, and industrial purposes. Bio-oil content was about 30% and gas content was about 35%.

In Asia, slow pyrolysis was used to prepare charcoal. With the current increasing concern in regard to environment issues, the smoke from charcoal making could be called a pollutant. The wood vinegar produced by smoke from charcoal making has many benefits such as stimulating vegetables and plant growth, anti-harmful microorganisms [10]. Today, however, there is much diversity of charcoal wood including thinned wood, sawdust and backboard dust produced by sawmills, bark, windfall trees, dead trees, waste wood from agriculture and demolished buildings, bamboo, straw and rice husks. Different charcoal wood requires a different carbonization kiln but the principle of charcoal-making, i.e. baking charcoal wood by regulating the airflow, remains the same for all types of kilns. Similarly, the principle of recovering bio-oil has remained unchanged. To recover bio-oil, the chimney is placed above the smoke outlet of the charcoal kiln while a container is placed in the lower end of the chimney to collect the dripping, condensed liquid.

The color of the smoke produced in the carbonization of wood changes depending on the progress of this process. These are used as an impotent indicator to recover bio-oil. When carbonization starts, the white smoke first appears. This is wet smoke because the water

sodium and potassium salts. In general, herbaceous biomass typically contains significant amounts of inorganic salts and organic-soluble compounds which may be found at approximately 15 and 20%wt, respectively. In contrast, in common woods, there are usually lower content which the inorganic salts and organic-soluble compounds may be found at approxi-

Pyrolysis is mainly technology used to produce wood vinegar with thermal degradation of organic material. According to this system, the larger molecules were transformed to smaller with high temperature and air less condition. Pyrolysis technology has been continuously developed to support various purposes. In general, the pyrolysis types were classified based

Fast pyrolysis is an advance process in which biomass is rapidly heated to moderate temperature of around 500C and short residence time of typically less than 2 seconds. Fast pyrolysis kinetic of wood constituents determined the rate of thermal breakdown as presented in Figure 3. Hemicelluloses are fast decomposed in temperature range from 200 to 300C and cellulose is the least stable polymer decomposed from 300 to 400C. Lignin exhibits intermediate thermal degradation behavior from 250 to 500C. Thermal decomposition studies on separated lignin will not necessarily match the pyrolysis behavior of this component when it is present in the original biomass [10]. Typical product yields, dry wood basis, consisted of

mately 0.3–0.4%wt and 2–3%wt, respectively [9].

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on heating rate mainly fast and slow pyrolysis.

3.2. Pyrolysis processes and preparation of wood vinegars

Figure 2. Composition of wood, illustrating the structure of lignocellulosic biomass [5].

Figure 3. Fast pyrolysis kinetics of hemicellulose, cellulose, and lignin: TG = thermogravimetry; DTG = differential thermogravimetry [10].

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 condition to recover bio-oil [13].

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 called tar sediment.
