Lignocellulosic biomass refers to plant biomass that is composed of cellulose,
hemicellulose and lignin. The two main lignocellulosic biomass sources in Malaysia
which are wood residues and oil palm trunks that removed during the oil palm
replanting activities. The oil palm trunks were not only underutilized but also
causes pollution as well (Ratnasingam et al., 2008).
These biomass can be derived into any chemicals with higher commercial values
using different method such as pyrolysis. Pyrolysis of biomass has received
special attention since it leads to useful products and simultaneously contributes
to diminish environmental pollution arising from wastes accumulation and/or
open field burning (Bonelli et al., 2001). Pyrolysis
is a process of high temperature carbonization of lignocellulosic biomass with
absent of oxygen. Pyroligneous acid which is one of the commercial sources for
acetic acid is one of the products from pyrolysis. Pyroligneous acid comprises
of water (10-20%), a mixture of carboxylic acids among which acetic acid is
the most prevalent, several aldehydes and alcohols and pyrolytic lignin (Ninomiya
et al., 2004). Acetic acid is an important chemical reagent and industrial
chemical. Acetic acid can be used as a spray-on preservative to discourage the
growth of fungal and molds. Jung (2007) stated the pyroligneous
acid inhibited the growth of pathogenic fungus, Alternaria mali, which
is known to be the agent of Alternaria blotch of apple plants. Pyroligneous
acid is also can be used as a fungicide for wood preservative. Bruce
and Highley (1991) stated that the pyroligneous acid useful for controlling
the wood decay Basidiomycetes by Trichoderma sp. Sameshima
et al. (2002) and Yatagai et al. (2002)
correlated the termiticidal activity with phenolic and acetic acid contents
in the pyroligneous acid produced from charcoal production. Nakai
et al. (2007) found that pyroligneous acid from pyrolysis of sugi
and acacia wood increased the resistance of wood against brown-rot fungi. Femi-Ola
et al. (2008) stated that many researchers are now focused towards
the alternative non toxic and biological methods of controlling termites.
As mentioned early, the pyroligneous acid produced from carbonization of wood
at temperature above 270°C without oxygen present. However, the content
of chemical compounds in pyroligneous acid depends on the biomass composition
mainly the three major components, i.e., cellulose, hemi-cellulose and lignin.
The interaction of the three major components during pyrolysis show different
reactivity depending on temperature that associated to thermal decomposition
of each component (Diem et al., 2005). The overall
pyroligneous acid conversion level related with interactions between the components
and minus amounts of mineral matter naturally present in whole biomass samples
that catalyze numerous reactions taking place during pyrolysis and affect the
final content of pyroligneous acid (Bonelli et al.,
2001; Liu et al., 2008).
This study focus on the efficacy of pyroligneous acid produced at different temperature from rubberwood and mixed hardwood sawdust and oil palm trunk against the white rot fungi, mold and termite under laboratory condition using rubberwood as test block. The rubberwood test blocks were immersed in pyroligneous acid extracted from the three lignocellulolic biomass respectively at three different pyrolysis temperatures. Fourier transform infrared (FT-IR) spectroscopy was employed to analyse the chemical compounds of the pyroligneous acid produced from three lignocellulolic biomass, respectively at three different pyrolysis temperatures.
MATERIALS AND METHODS
This project was carried out from year 2007 until 2009. Three lignocellulosic materials with the most abundant availability in Malaysia i.e., rubberwood, mixed hardwood sawdust and oil palm trunk were selected for this study. The rubberwood and mixed hardwood sawdust were collected from sawn milling factory in Klang, Selangor, Malaysia. Whereas, the oil palm trunk was felled in Ladang Pertanian UPM in Universiti Putra Malaysia, Malaysia.
Production of pyroligneous acids: The oil palm trunk was cut into small pieces before grinded into fines. The oil palm trunk fines, rubberwood and mix hardwood sawdust were sieved to obtain 40 mesh fines for further process. The fines was stored in the conditioning room at temperature 20°C with 65% relative humidity for one week prior to pyrolysis.
After one week, the fines were pyrolysed under temperature of 300, 400 and 500°C, respectively to produce pyroligneous acid. During the pyrolysis process, 80 g of fines were put in the flask and heated in the heating mantle to the require temperature. The pyroligneous acid was collected by condensing the gases from the pyrolysis process. The yields of pyroligneous acid collected were recorded.
Rubberwood test block: Forty five pieces of rubberwood (Hevea brasiliensis) block with size of 20 mm in width, 70 mm in length and 7 mm thick were prepared for molds test. Whereas, ninety pieces of rubberwood with the size of 25 mm in width, 25 mm in length and 9 mm in thick were prepared for decay fungi and termites tests. All the test samples were immersed in the pyroligneous acid at room temperature for 24 h in water bath. After 24 h, the rubberwood test blocks were taken out, the excess solution was wiped off and the test blocks were allowed to dry to constant weight under room temperature. The pyroligneous acid retention was calculated based on the gain in weight of the untreated wood.
Fourier transform infrared (FT-IR) spectroscopy test: In this study, the chemical components of pyroligneous acids obtained from different types and temperature of wood biomass were analyzed using Fourier transform infrared (FT-IR) spectroscopy. FT-IR spectroscopy has been used for determination of molecular structures, identification of compounds in biological samples and investigation of complex polymer. FT-IR spectra were recorded in the wavenumber range from 600-4000 cm-1 with PerkinElmer Spectrum. A resolution of 4 cm-1 and 4 scans/sample was used.
Biological durability evaluation test
Mold tests: Mold resistance test was tested according to standard ASTM D
4445: Standard Test Method for Fungicides for Controlling Sapstain and Mold
on Unseasoned lumber (Laboratory Method) (ASTM, 2003).
The rubberwood test block was placed on a U-shaped glass rod (3 mm in diameter)
together with control test block (no treatment). The glass rod was placed on
top of the wet papers inside the sterilized Petri dish. Mold (Penicillium
sp.) was applied onto the wet paper and the petri dish was sealed with cellophane
tape to prevent any contaminant with the contact of surrounding atmosphere and
incubated for 4 weeks in the incubator. At the end of the testing (after 4 weeks),
the number of days for the mold to visually observed (start to grow) on the
test block and coverage area by mold on test block were evaluated.
Decay fungi tests: Decay resistance test was tested according to ASTM
method D 2017-71 (ASTM, 1978) using cultures of common
white rot fungus Pycnoporous sanguineus (ASTM, 1978).
The rubberwood test blocks were condition to constant weight and steam-sterilized
at 100°C, weighed and exposed to Pycnoporous sanguineus. After 8
weeks of incubation at 27°C and 70% RH, the surface fungus mycelium was
removed, the specimens were dried at 60°C and weight losses were determined
as percentage of total rubberwood test block mass.
Termite tests: Termite resistance test on the rubberwood test blocks
were tested according to standard ASTM D3345-74 using the subterranean termites,
Coptotermes curvignathus (ASTM, 1980). Test blocks
were placed in the center of a cylindrical plastic container (50 mm in diameter
and 38 mm in height) with 1 g of subterranean termites. The test blocks were
set upon 1 g of washed sand and covered with a wet 42.5 mm Whatman filter paper
circle as a food source and to maintain humidity. The containers were maintained
at 25°C and 80% RH for 4 weeks. Termite activity in each bottle was observed
and rated after week 1 and week 4 of the testing period. At the end of the testing
period, the percentage of weight loss due to termite attack and termites mortality
rate were calculated.
RESULTS AND DISCUSSION
Yields of the pyroligneous acids: The yield of pyroligneous acid produced
from three lignocellulosic biomass at three different temperatures was shown
in Table 1, as shown in the table, an increase in the temperature
increases the pyroligneous acid yields. The highest pyroligneous acid yield
was obtained from pyrolysed oil palm trunk at the temperatures of 500°C.
The pyrolysis temperature has an important effect on the yield of pyrolysis
products from the various types of biomass. Encinar et
al. (2000) stated that the pyrolysis of Cynara cardunculus L.
carried out in a fixed-bed reactor at the temperature between 300 and 800°C
gave maximum pyroligneous acid yield at 500°C. In another study, the slow
pyrolysis of the straw and stalk of the rapeseed plant in a tubular reactor
under the conditions of static atmosphere was carried out in the temperature
range of 350-650°C and the maximum oil yield (about 18%) was obtained at
650°C (Onay et al., 2001). Demirbas
(2006) stated that the pyroligneous acid obtained from the shell pyrolysis
at lower temperatures (670-810 K) contain many highly oxygenated polar components
that help dissolve the phenolic fractions in water.
||Yield of pyroligneous acids from different lignocellulosic
biomass and different temperature (w/w)
At elevated carbonization temperatures, the amount of these oxygenated organic
components decreased which result in a greater heating value.
FT-IR analysis: Table 2 showed the possible chemical
compounds based on the functional group from FT-IR analysis. The broad band
of the hydroxyl stretching group with wave number of 3600-3200 cm-1
from FT-IR spectrum indicates that the present of water impurities and other
polymeric O-H in the pyroligneous acids (Islam et al.,
2003). The spectrum also showed that the band of C-H stretching with wave
number of 3000-2800 cm-1 indicates the present of alkanes groups
in the pyroligneous (Islam et al., 2003; Tsai
et al., 2007).
Cellulose and hemicelluloses decomposition products, such as carboxylic acids,
ketones, phenol, aldehydes and alcohol, were represented by C = O (A chemical
group consisting of carbon and oxygen) stretching group with the wave number
of 1750-1625 cm-1 by FT-IR spectrum. The C = C stretching vibrations
from the FT-IR spectrum indicates of alkenes and aromatics compounds present
in the pyroligneous acids (Beis et al., 2002;
Acikgoz et al., 2004). The wave number below
1500 cm-1, all the bands were very complex and had their origin in
a variety of vibrational modes. The pyroligneous acids were acidic as the oxygenated
functional groups of O-H; C = O; C-O and aromatic compounds shows in the FT-IR
results and had the potential as a chemical feedstock.
Weight gained rubberwood test blocks: Table 3 showed the weight gained of rubberwood test blocks immersed in pyroligneous acid for 24 h at room temperature, as shown in table, the gained in weight of all the treated blocks was range from 3.64-4.90%.
Mold tests: The result for the efficacy of pyroligneous acid as preservative chemical in rubberwood against mold Penicillium sp. is presented in Table 4. All the rubberwood test blocks treated with pyroligneous acid discourage the growth of the mold with the pyroligneous acid produced from oil palm trunk showed the most encouraging result against the mold.
|| FT-IR analysis for functional group in different types of
pyroligneous acid and temperature treated wood
|| Pyroligneous acids content in different types of pyroligneous
acid and temperature treated wood
|| Days of molds start to grow on different type of pyroligneous
acid and temperature
The result also shows that, as pyrolysis temperature increase, the pyroligneous
acid produced were effective against the mold. This may be caused by the different
chemical composition obtained between the types of pyroligneous acid pyrolysed
with different temperature. Nakai et al. (2007)
found that the temperature were an important factor in characterization of the
components and the effectiveness of the liquids in controlling wood-degrading
fungi was generally higher at higher temperature.
All the rubberwood test blocks treated with pyroligneous acid had less than
10% of block surface area were covered by mold after 4 week of testing period
except for control board that showed approximately 75% of block surface area
being covered with mycelium. The rubberwood blocks treated with pyroligneous
acid produced from oil palm trunk prevented mold growth effectively. Normally,
at moisture contents greater than 20%, mold establishment can occur on unseasoned
wood in 24-48 h if temperatures permit and rapid drying of the wood does not
|| Percentage of weight loss of rubberwood treated with temperature
in fungi test
Consequently, the mold will grow on the surface of wood and covered with more
surface area at the end of the testing period. This may explained why the control
blocks more susceptible to mold growth.
Decay fungi tests: After 8 weeks of being exposure to fungus Pycnoporous sanguineus, all untreated test blocks and blocks treated with pyroligneous acid showed fungus colonization visually on the surface of the blocks. The percentage of weight loss and resistance level of untreated test blocks and blocks treated with pyroligeneous acid from rubberwood, oil palm trunk and mixed hardwood pyroligneous acids, respectively were shown in Table 5.
The resistant classes were based on weight loss of test blocks as according
to Standard ASTM D-2017-71. Untreated test blocks showed moderate resistance
to fungus, meanwhile test blocks treated with Rubberwood pyroligneous acid pyrolysed
at temperature 300°C showed the highest resistant against the white rot
fungi. While, other treated blocks showed only resistant to white rot decay.
Phenolic components are expected to be primarily responsible for any antimicrobial
activity as stated by Suzuki et al. (1997). He
suggested that the phenolic compounds of 4-ethyl-2-methoxyphenol and 4-propyl-
2-methoxyphenol that contained inside pyroligneous acid might have some preservation
effects. Most phenolic compounds have disinfectant properties which may explain
why lignin-rich fractions are more effective preservatives than the whole bio-oil.
Termite tests: Mean percentage weight loss of treated and untreated rubberwood test blocks caused by subterranean termites, Coptotermes curvignathus was shown in Fig. 1 and the mortality and visual attack ratings were given in Table 6.
All the treated blocks have the weight loss approximately 10%. Whereas, untreated
blocks had higher amount of weight loss with value of 25%. According to Nakai
et al. (2007), the complex structure of pyrolysis liquid from carbonization
of wood biomass might be expected to protect wood from fungal and termite attack.
||Average termite attack and mortality rating for rubberwood
test blocks treated with different types of pyroligneous acids
|aTermite attack rating scale: 0, failure; 4, heavy;
7, moderate attack; 9, light attack and 10, sound. bMortality
rating: 0-33%, slight; 34-66%, moderate; 67-99%, heavy and 100%, complete
||Percentage of weight loss of rubberwood of different type
of pyroligneous acid and temperature in termite test
Previous studies by Sameshima et al. (2002)
and Yatagai et al. (2002) correlated the termiticidal
activity of wood vinegars with phenolic and acetic acid content from charcoal
production. In these studies, the low mean weight loss of treated blocks with
pyroligneous acid might caused by the present of phenolic and acetic acid content.
The summary of ANOVA shows that no significant different was observed on the
mean percentage weight loss for the variables used in this study. The pyoligneous
acid pyrolysed from any lignocellulosic biomass at different temperature equally
effective against termicidal activities except for treated block using mixed
hardwood pyroligneous acid that showed better resistance against termicidal
As shown in Table 6, Pyroligneous acids pyrolysed from different lignocellulosic biomass at different temperature were equally effective against subterranean termites where the entire termite in the testing bottles had 100% mortality compared to untreated wood where the termites mortality rate about 50%.
The highest pyroligneous acid yields were obtained at 500°C for all three types of lignocellulosic biomass. Temperature was an important factor in the yield production but not an important factor in the effectiveness of controlling wood biological attack. The pyroligneous acid from pyrolysis process of lignocellulosic biomass may have a potential source of a number of valuable chemicals. The FT-IR analysis revealed probable compounds such as ketone, aldehyde, phenols and carboxylic acids with water impurities. Some of those chemicals may have importance in developing new wood preservatives against biological degradation and also as a chemical feedstock.