Production and characterization of palm fruit shell bio-oil for wood preservation.
Subject:
Oils and fats industry (Production management)
Oils and fats industry (Production processes)
Palm oil (Production processes)
Waxes industry (Production management)
Waxes industry (Production processes)
Oils and fats industry (Production processes)
Palm oil (Production processes)
Waxes industry (Production management)
Waxes industry (Production processes)
Authors:
Sunarta, Sigit
Darmadji, Purnama
Uehara, Tohru
Katoh, Sadanobu
Darmadji, Purnama
Uehara, Tohru
Katoh, Sadanobu
Pub Date:
02/01/2011
Publication:
Name: Forest Products Journal Publisher: Forest Products Society Audience: Trade Format: Magazine/Journal Subject: Business; Forest products industry Copyright: COPYRIGHT 2011 Forest Products Society ISSN: 0015-7473
Issue:
Date: Feb, 2011 Source Volume: 61 Source Issue: 2
Topic:
Event Code: 230 Production management; 320 Manufacturing processes
Product:
Product Code: 2076272 Palm Oil NAICS Code: 311223 Other Oilseed Processing SIC Code: 2074 Cottonseed oil mills; 2075 Soybean oil mills; 2076 Vegetable oil mills, not elsewhere classified; 2077 Animal and marine fats and oils; 2079 Edible fats and oils, not elsewhere classified
Geographic:
Geographic Scope: New York Geographic Code: 1U2NY New York
Accession Number:
265021866
Full Text:
Abstract
Pyrolytic liquid (bio-oil), produced by pyrolyzing the shell of the palm fruit, was characterized, and its preservative properties were examined using drywood termites (Cryptotermes spp.) and blue stain fungi (Ceratocystis spp.). The yield from shell bio-oil production ranged from 35 to 37 percent relative to the mass of the raw material. The shell bio-oil had the following properties: specific gravity (ranging from 1.0365 to 1.0431), refractive index (ranging from 1.3594 to 1.3613), wood absorption level (ranging from 0.0088 to 0.0625 g/[cm.sup.3]), and retention (ranging from 0.0022 to 0.0141g/[cm.sup.3]). The shell bio-oil also had termicidal activity as shown by drywood termite mortalities: 25 percent between days 3 and 6, 50 percent between days 3 and 20, and 100 percent between days 5 and 49 in termite resilience tests. Using a fluorescence microscope, we demonstrated that the shell bio-oil- treated wood completely inhibited the growth of blue stain fungi on both pine (Pinus merkusii) and Sengon (Paraserianthes falcataria) wood.
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The annual worldwide demand for palm oil products and derivatives has recently significantly increased. The US Department of Agriculture (USDA) reported that global palm oil consumption reached a record 37.3 million metric tons in 2006 and 2007, representing an increase of 13.2 million metric tons since 2001. This trend of strong increases in palm oil consumption is likely to continue in the coming decade (USDA 2006).
Although palm oil production provides economic advantages in some countries, it also produces problems, especially in developing countries. Production waste, such as fronds, fibers, mesocarps, kernel cakes, palm shells, and liquid waste require proper handling to avoid polluting the environment (Saono and Sastrapradja 1983).
Technology for recycling this biomass using pyrolysis could address such environmental problems and ensure the efficient use of natural resources. Pyrolysis appears to be the most promising technology because of its ease and low cost. Pyrolysis also results in at least two beneficial products: pyrolytic liquid (liquid smoke, vinegar, bio-oil, or tar) and charcoal, both obtained from one operation.
Liquid smoke or wood bio-oil, a product of pyrolysis, has been long used as a food preservative because of its antibacterial and antioxidant characteristics, its color, and its flavor (Gorbatov et al. 1971, Hollenbeck 1979). Wood bio oil contains a large amount of acetic acid, formic acid, methanol, acetone, phenol, and neutral compounds required for wood preservation. Future uses of pyrolytic liquid are diverse, including as additives for combustion, and as adhesives, fuel enhancers, and specialty chemicals for fertilizers or preservatives (Girard 1992, Vasile and Brebu 2006). Freel and Graham (2002) found that bio-oil derived from wood exhibits properties required of a preservative.
This study focused on identifying and characterizing the physical properties of raw pyrolytic liquid (shell bio-oil) produced from the shell of the oil palm fruit. These properties can be used to address the need for environmental wood preservatives and for identifying the properties of pyrolytic liquid obtained from different sources. The shell bio-oil produced from oil palm fruit shells was tested for its usefulness as a wood preservative, and especially for preventing the termite and fungal attacks common in tropical countries. The effects of the preservative in preventing termite attack on wood destined for indoor use and in preventing blue stain fungal attack on freshly cut wood prior to being milled were assessed.
Materials and Methods
Materials
Air-dried shells of oil palm fruit were purchased from Sumatra Plantation (Indonesia). To control moisture content, the shells were stored for approximately 6 months at constant temperature (20[degrees]C) and relative humidity (50%) before testing; air-dried shells had a moisture content of 12 percent.
Pine (Pinus merkusii) and Sengon (Paraserianthes falcataria) logs were obtained from a community forest at Cangkringan village (Yogyakarta, Indonesia). The logs varied in diameter from 25 to 30 cm, and were 2 to 3 m in length. All logs were processed on the same day and were protected from fungal infection.
Termite (Cryptotermes spp.) cultures were provided by the Laboratory of Wood Preservation in the Department of Forest Products Technology (Gadjah Mada University, Indonesia).
Methods
Fungi culture preparation.--Blue stain infected sapwood was used as the fungal culture source. To isolate pure cultures, colonies were removed with a razor blade and washed by vortexing in tap water. This process was repeated three times. The fungal suspension was plated onto potato dextrose agar (PDA) medium and incubated at constant temperature (20[degrees]C) and humidity (80%) for several days. The resulting colonies were removed and replated onto fresh PDA medium. This process was repeated until a pure culture was obtained; the culture was maintained in an incubator. All specimens were examined microscopically to determine their condition and were used in the experiments below.
Pyrolysis of oil palm fruit shells and the physical properties of the product.--The fruit shells were pyrolyzed in a laboratory furnace at 300[degrees]C, 350[degrees]C, or 400[degrees]C. The temperature was ramped at various rates to reach the final temperature, which was maintained for 4 hours. An ice-cold water condenser trapped the condensate of the released gases. The collected pyrolytic liquid, commonly known as shell biooil or liquid smoke, was cooled overnight at room temperature (20[degrees]C). The specific gravity of the shell bio-oil was measured by following ASTM Standard D369-84 (ASTM International 2002), and an Atago hand-held refractometer was used to measure the refractive index of the solutions.
Wood sample treatment.--Wood samples were obtained from unseasoned sapwood of pine and Sengon wood. The following sample sizes were used for the different tests: 1 by 1 by 2 cm (absorption and retention under equilibrium conditions), 5 by 5 by 3 cm (resilience against drywood termite attack under equilibrium conditions), and 3 by 3 by 1 cm (resilience against fungal stain under fresh conditions). Wood was sampled randomly as required to provide the needed samples. All wood samples were treated with shell bio-oil either by soaking or dipping and then kept wet for a period of time sufficient to allow the preservative solution to penetrate and diffuse through the cell walls of the wood. The samples of wood for the termite resilience test were then dried, but the samples for the fungicidal test were kept wet. Further testing was conducted to determine preservation properties such as absorption and retention, which are important in determining the quality of a preservative treatment (Hunt and Garrat 1953, Fengel and Wegener 1984).
The absorption value of the pyrolytic oil preserver was calculated by
A = (fww - iw) / v (1)
where
A = absorption,
fww = final wet weight (g),
iw = initial weight (g), and
v = sample volume ([cm.sup.3]).
This study required knowledge of the absorption value in order to identify the amount and depth of active compound penetrating the wood.
The retention value of the pyrolytic oil preserver was calculated by
R = (adw -iw) / v (2)
where
R = retention,
adw = air-dried weight (g),
iw = initial weight (g), and
v sample volume ([cm.sup.3]).
Termite attack resilience test.--Wood resilience tests against termites (Cryptotermes spp.) followed the American Wood Protection Association (AWPA) standards, with some modifications (AWPA 1997, Nakai et al. 2007). Fifty termites were confined with a glass barrier attached to a treated wood sample. For 3 months, termite mortality was calculated daily. The effectiveness of preservation was determined based on termite mortality percentages (25%, 50%, or 100%).
Stain fungi resilience test.--Isolates of fungi were inoculated on fresh wood samples (five replicates) maintained in an incubator at 20[degrees]C, and the samples were observed daily under an Olympus BX 41 microscope for 2 weeks to observe the growth and spread of the fungus on the fresh wood. Data obtained were subjected to one-way analysis of variance with completely randomized design and Tukey's multiple range test at a significance level of P = 0.05. Factorial design was chosen to examine the effect of each factor (temperature of pyrolysis, type of wood, and method of preservation) to the response variable (result of each type of experiments).
Results and Discussion
Shell bio-oil characteristics
The pyrolytic liquids were heterogeneous and separated into a lower heavy oil phase and an upper aqueous phase; these phases were not isolated and were studied together as bio-oil. The raw material, palm fruit shell with 12 percent moisture content, yielded between 35.98 and 38.95 percent shell bio-oil (ratio of the weight of bio-oil to the weight of the raw material) following pyrolysis, similar to other recent reports (Phan et al. 2008, Carrier et al. 2010). Carrier et al. (2010) reported that slow pyrolysis at around 450[degrees]C, achieved at a heating rate of 15[degrees]C [min.sup.-1], provided good yields, superior quality of the char product (>30%, wt/wt), and optimum yields of bio-oil.
Statistical analysis indicated no significant differences in the yield and specific gravity of shell bio-oil produced at the three temperatures tested for pyrolysis (Table 1) and significant effect on refractive index of the bio-oil (Table 2).
The specific gravity of shell bio-oil ranged from 1.0365 to 1.0431, fulfilling the AWPA Standard P1 for wood preservatives, which requires a specific gravity of not more than 1.025. The refractive index of the shell bio-oil ranged from 1.3598 to 1.3610, fulfilling the Acceptance Criteria for Organic Wood Preservatives Systems (Annex A) of International Code Council-Evaluation Service (ICC-ES) 2007, which is applied in the United States (ICC-ES 2009). Thus, palm shell bio-oil offers promising prospects as a wood preservative.
Application of shell bio-oil for wood preservation
Absorption and retention of shell bio-oil.--The shell bio-oil penetrated and diffused into the two types of wood differently (Table 3). Generally, pine (softwood) showed higher absorption than Sengon (hardwood). Water-soluble and water-based preservatives quickly and easily penetrate the vessels of hardwood by diffusing through cell walls. The penetration of preservatives through softwood cells is limited by the presence of a dotted boundary, which results in decreased permeability of preservatives. Thus, the preservative requires more time to penetrate pine wood. Longer soaking times will allow more preservative to be absorbed by the wood. The tracheid valve structure of pine wood resulted in the preservative residing longer in pine than in Sengon wood. The difficulty of water-soluble preservatives to impregnate resin channels will limit their value for treating pine wood (Freeman et al. 2002) but likely explains why pine wood absorbed more shell bio-oil than Sengon wood in the dipping experiments.
Long-term effective wood preservation requires adequate retention, so various chemical preservatives and treatment methods are used in accordance with the properties of each type of wood. Based on the test result, although only intended for short-term preservation, this bio-oil has shown good retention value, especially for specific types of wood (pine and Sengon) and uses (AWPA 1997). In this study, the average retention value of both preserved pine and Sengon wood was 0.005917 g/[cm.sup.3], although that of Sengon wood (0.006126 g/[cm.sup.3]) was overall higher than that of pine wood (0.005707 g/[cm.sup.3]). Statistically, the absorption value was influenced by type of wood, and the retention values were only influenced by the temperature of pyrolysis used in preparing the preservatives (Table 4).
We found that shell bio-oil retention on yellow pine is comparable to that of other waterborne preservatives such as copper naphthenate 1 percent (5.278 kg/[m.sup.3]), chromated copper arsenate 1 percent (5.626 kg/[m.sup.3]), or ammoniacal copper quat type C 1 percent (8.439 kg/[m.sup.3]) (Freeman et al. 2002). Generally, retention level varies depending on the species, assay zones, climatic conditions, and exposure conditions. The retention levels obtained in this study are average for preservative retention levels issued by AWPA Commodity Standards (AWPA 1997).
Termiticidal effect of shell bio-oil.--The termiticidal test indicates wood resilience, reflected by the mortality of drywood termites. In this study, the wood protection properties of shell bio-oil were determined by dipping or soaking the entire wood sample in shell bio-oil. All three shell bio-oil samples exhibited clear and similar termiticidal activity (Table 5). The observed drywood termite mortalities were approximately 25 percent between days 3 and 6, 50 percent between days 3 and 20, and 100 percent between days 5 and 49. Statistically, there was no significant difference in the results between/within the temperature of pyrolysis, type of wood, and method of preservation observed in this study.
It was previously reported that bio-oil (wood bio-oil) has little to no termiticidal activity and that it is weak compared with synthetic termiticides (Yamanoi 1993). In contrast, the results of our study strongly suggest that shell bio-oil has the potential to be a low-cost and environmentally low-impact wood preservative. Yatagai et al. (2002) also showed that acetic acid, which is the largest component of the wood bio-oil from carbonization of wood, exhibited high termiticidal activity against Reticulitermes speratus.
Fungicidal activity of shell bio-oil.--The preservation of wood by shell bio-oil against attack by blue stain fungi (Ceratocystis spp.) was measured. Using a fluorescence microscope, we demonstrated that wood treated with shell bio-oil completely inhibited the growth of blue stain fungi on both pine wood and Sengon wood (Table 6). Fungi only grew well at the neutral pH of the control samples. Therefore, fungi cannot thrive and may die if the timber has an extreme (e.g., acidic) pH. Rather than merely stopping fungal growth, shell bio-oil appears to act as a fungicide and kills spores and hyphae.
To develop a shell bio-oil useful against fungi, it is also essential to conduct wood resilience tests against decay fungi. It has been noted that wood bio-oil exhibits significant activity against white rot, brown rot, and several decay fungi (Freel and Graham 2002, Mazela 2007, Mohan et al. 2008). Freel and Graham (2002) found that bio-oil from wood is more effective against white rot fungi than against brown rot decay fungi. However, bio-oil affords nearly total protection against decay fungi at retentions in excess of 13 lb/[ft.sup.3] (Freel and Graham 2002, Mazela 2007).
The development of an effective and safe wood preservative generally requires extensive laboratory and field tests, including leaching studies. Determining the amount of leaching of a biocide preservative is important for predicting the long-term efficacy of treated wood and for determining potential environmental contamination. It is also the first step in finding additives or modifications to reduce preservative leaching (Mourant et al. 2009). Leaching studies should demonstrate the amount of leaching that may occur under field conditions. Information about leaching must be evaluated with respect to exposure conditions and product type. Previous scientists have highlighted the need for further research to address the effects of exposure to different environments, such as fresh water, seawater, and highly organic environments, and the need to monitor the overall environmental fate of leached wood preservative components (Lebow 1993, Hingston et al. 2001, Obanda et al. 2008).
Conclusions
The yield of shell bio-oil produced from palm shell oil ranged between 35 and 37 percent of the raw material. The following properties of shell bio-oil were determined: specific gravity (ranged from 1.0365 to 1.0431), refractive index (ranged from 1.3594 to 1.3613), wood absorption level (ranged from 0.0088 to 0.0625 g/[cm.sup.3]), and retention (ranged from 0.0022 to 0.0141 g/[cm.sup.3]). Shell bio-oil has potential as a wood preservative for preventing attacks by drywood termites and blue stain fungi. The following drywood termite mortalities were achieved: 25 percent between days 3 and 6, 50 percent between days 3 and 20, and 100 percent between days 5 and 49. Blue stain fungi did not grow on shell bio-oil--treated wood.
Literature Cited
American Wood Protection Association (AWPA). 1997. Standard method for laboratory evaluation to determine resistance to subterranean termites. Standard E1-97. AWPA, Birmingham, Alabama. pp. 279-282.
ASTM International. 2002. Standard test method for specific gravity of creosote fractions and residue. D369-84. ASTM International, Philadelphia.
Carrier, M., T. Hugo, J. Gorgens, and H. Knoetze. 2010. Comparison of slow and vacuum pyrolysis of sugar cane bagasse. J. Anal. Appl. Pyrolysis 90:18-26.
Fengel, D. and G. Wegener. 1984. Wood: Chemistry, Ultrastructure, Reactions. Walter de Gruyter, Berlin.
Freel, B. and R. G. Graham. 2002. Bio oil preservatives. US patent 6485841 BI.
Freeman, M. H., D. P. Kamdem, E. L. Schmidt, and P. Nzokou. 2002. Water-borne copper naphthenate: A potential new preservative for softwoods, hardwoods, and composites. Presented at the Proceedings of the Forest Products Society: Enhancing the Durability of Lumber and Engineered Wood Products, February 11-13, 2002, Kissimmee, Florida. 27 pp.
Girard, J. P. 1992. Smoking in Technology of Meat and Meat Products. Ellis Horwood Press, New York.
Gorbatov, V. M., N. N. Kpylova, V. P. Volovinskaya, Y. N. Lyaskovskaya, K. L. Bazarova, R. I. Khlamova, and G. Y. Yakovleva. 1971. Liquid smokes for use in cured meats. Food Technol. 25:71.
Hingston, J. A., C. D. Collins, R. J. Murphy, and J. N. Lester. 2001. Leaching of chromated copper arsenate wood preservatives: A review. Environ. Pollut. J. 111:53-66.
Hollenbeck, C. M. 1979. Liquid smoke flavors, status of development. Food Technol. 33(5):88-89.
Hunt, G. M. and G. A. Garrat. 1953. Wood Preservation. 2nd ed. McGraw-Hill Book Co., Inc., New York.
International Code Council-Evaluation Service (ICC-ES). 2009. Acceptance criteria for proprietary wood preservative system--Common requirements for treatment process, test methods and performance. AC-326. ICC-ES, Birmingham, Alabama.
Lebow, S. 1993. Leaching of wood preservative components and their mobility in the environment: Summary of pertinent literature. General Technical Report FPL-GTR-93. USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin.
Mazela, B. 2007. Fungicidal value of wood tar from pyrolysis of treated wood. Waste Manag. J. 27:461-465.
Mohan, D., J. Shi, D. D. Nicholas, C. U. Pittman, Jr., P. H. Steele, and J. E. Cooper. 2008. Fungicidal values of bio-oils and their lignin-rich fractions obtained from wood/bark fast pyrolysis. Chemosphere J. 71: 456-465.
Mourant, D., D. Q. Yang, X. Lu, B. Riedl, and C. Roy. 2009. Copper and boron fixation in wood by pyrolytic resins. Bioresour. Technol. J. 100(3): 1442-1449.
Nakai, T., S. N. Kartal, T. Hata, and Y. Imamura. 2007. Chemical characterization of pyrolysis liquids of wood-based composites and evaluation of their bio-efficiency. Build. Environ. J. 42:1236-1241.
Obanda, D. N., T. F. Shupe, and H. M. Barnes. 2008. Reducing leaching of boron-based wood preservatives: A review of research. Bioresour. Technol. J. 99:7312-7322.
Phan, A. N., C. Ryu, V. N. Sharift, and J. Swithenbank. 2008. Characterisation of slow pyrolysis product from segregated wastes for energy. J. Anal. Appl. Pyrolysis 81:65-71.
Saono, S. and D. Sastrapradja. 1983. Major agricultural crop residues in Indonesia and their potential as raw materials for bioconversion. In: The Use of Organic Residues in Rural Communities. C. A. Shacklady (Ed.). United Nations University, Tokyo. pp. 11-23.
US Department of Agriculture (USDA). 2006. Oilseeds: World markets and trade. Circular Series FOP 6. US Department of Agriculture, Washington, D.C.
Vasile, C. and M. A. Brebu. 2006. Thermal valorization of biomass and synthetic polymer waste: Upgrading of pyrolysis oils. J. Cell. Chem. Technol. 40(7):489-512.
Yamanoi, K. 1993. Anti-termite of wood vinegar. Siroari 94:28-31. (In Japanese.)
Yatagai, M., M. Nishimoto, K. Hori, T. Ohira, and A. Shibata. 2002. Termiticidal activity of wood vinegar, its components and their homologues. J. Wood Sci. 48:338-42.
The authors are, respectively, PhD student, Dept. of Natural Resources Process Engineering, Interdisciplinary Faculty of Sci. and Engineering, Shimane Univ., Matsue, Shimane, Japan (sigit_nonwood@yahoo.com); Professor, Dept. of Plant Crops Product Technol., Faculty of Agric. Technol., Gadjah Mada Univ., Bulaksumur, Yogyakarta, Indonesia (pdarmadji@ugm.ac.id); and Professor and Associate Professor, Dept. of Natural Resources Process Engineering, interdisciplinary Faculty of Sci. and Engineering, Shimane Univ., Matsue, Shimane, Japan (uehara@riko. shimane-u.ac.jp, sadanobu@riko.shimane-u.ac.jp). This paper was received for publication in February 2011. Article no. 11-00017.
Pyrolytic liquid (bio-oil), produced by pyrolyzing the shell of the palm fruit, was characterized, and its preservative properties were examined using drywood termites (Cryptotermes spp.) and blue stain fungi (Ceratocystis spp.). The yield from shell bio-oil production ranged from 35 to 37 percent relative to the mass of the raw material. The shell bio-oil had the following properties: specific gravity (ranging from 1.0365 to 1.0431), refractive index (ranging from 1.3594 to 1.3613), wood absorption level (ranging from 0.0088 to 0.0625 g/[cm.sup.3]), and retention (ranging from 0.0022 to 0.0141g/[cm.sup.3]). The shell bio-oil also had termicidal activity as shown by drywood termite mortalities: 25 percent between days 3 and 6, 50 percent between days 3 and 20, and 100 percent between days 5 and 49 in termite resilience tests. Using a fluorescence microscope, we demonstrated that the shell bio-oil- treated wood completely inhibited the growth of blue stain fungi on both pine (Pinus merkusii) and Sengon (Paraserianthes falcataria) wood.
**********
The annual worldwide demand for palm oil products and derivatives has recently significantly increased. The US Department of Agriculture (USDA) reported that global palm oil consumption reached a record 37.3 million metric tons in 2006 and 2007, representing an increase of 13.2 million metric tons since 2001. This trend of strong increases in palm oil consumption is likely to continue in the coming decade (USDA 2006).
Although palm oil production provides economic advantages in some countries, it also produces problems, especially in developing countries. Production waste, such as fronds, fibers, mesocarps, kernel cakes, palm shells, and liquid waste require proper handling to avoid polluting the environment (Saono and Sastrapradja 1983).
Technology for recycling this biomass using pyrolysis could address such environmental problems and ensure the efficient use of natural resources. Pyrolysis appears to be the most promising technology because of its ease and low cost. Pyrolysis also results in at least two beneficial products: pyrolytic liquid (liquid smoke, vinegar, bio-oil, or tar) and charcoal, both obtained from one operation.
Liquid smoke or wood bio-oil, a product of pyrolysis, has been long used as a food preservative because of its antibacterial and antioxidant characteristics, its color, and its flavor (Gorbatov et al. 1971, Hollenbeck 1979). Wood bio oil contains a large amount of acetic acid, formic acid, methanol, acetone, phenol, and neutral compounds required for wood preservation. Future uses of pyrolytic liquid are diverse, including as additives for combustion, and as adhesives, fuel enhancers, and specialty chemicals for fertilizers or preservatives (Girard 1992, Vasile and Brebu 2006). Freel and Graham (2002) found that bio-oil derived from wood exhibits properties required of a preservative.
This study focused on identifying and characterizing the physical properties of raw pyrolytic liquid (shell bio-oil) produced from the shell of the oil palm fruit. These properties can be used to address the need for environmental wood preservatives and for identifying the properties of pyrolytic liquid obtained from different sources. The shell bio-oil produced from oil palm fruit shells was tested for its usefulness as a wood preservative, and especially for preventing the termite and fungal attacks common in tropical countries. The effects of the preservative in preventing termite attack on wood destined for indoor use and in preventing blue stain fungal attack on freshly cut wood prior to being milled were assessed.
Materials and Methods
Materials
Air-dried shells of oil palm fruit were purchased from Sumatra Plantation (Indonesia). To control moisture content, the shells were stored for approximately 6 months at constant temperature (20[degrees]C) and relative humidity (50%) before testing; air-dried shells had a moisture content of 12 percent.
Pine (Pinus merkusii) and Sengon (Paraserianthes falcataria) logs were obtained from a community forest at Cangkringan village (Yogyakarta, Indonesia). The logs varied in diameter from 25 to 30 cm, and were 2 to 3 m in length. All logs were processed on the same day and were protected from fungal infection.
Termite (Cryptotermes spp.) cultures were provided by the Laboratory of Wood Preservation in the Department of Forest Products Technology (Gadjah Mada University, Indonesia).
Methods
Fungi culture preparation.--Blue stain infected sapwood was used as the fungal culture source. To isolate pure cultures, colonies were removed with a razor blade and washed by vortexing in tap water. This process was repeated three times. The fungal suspension was plated onto potato dextrose agar (PDA) medium and incubated at constant temperature (20[degrees]C) and humidity (80%) for several days. The resulting colonies were removed and replated onto fresh PDA medium. This process was repeated until a pure culture was obtained; the culture was maintained in an incubator. All specimens were examined microscopically to determine their condition and were used in the experiments below.
Pyrolysis of oil palm fruit shells and the physical properties of the product.--The fruit shells were pyrolyzed in a laboratory furnace at 300[degrees]C, 350[degrees]C, or 400[degrees]C. The temperature was ramped at various rates to reach the final temperature, which was maintained for 4 hours. An ice-cold water condenser trapped the condensate of the released gases. The collected pyrolytic liquid, commonly known as shell biooil or liquid smoke, was cooled overnight at room temperature (20[degrees]C). The specific gravity of the shell bio-oil was measured by following ASTM Standard D369-84 (ASTM International 2002), and an Atago hand-held refractometer was used to measure the refractive index of the solutions.
Wood sample treatment.--Wood samples were obtained from unseasoned sapwood of pine and Sengon wood. The following sample sizes were used for the different tests: 1 by 1 by 2 cm (absorption and retention under equilibrium conditions), 5 by 5 by 3 cm (resilience against drywood termite attack under equilibrium conditions), and 3 by 3 by 1 cm (resilience against fungal stain under fresh conditions). Wood was sampled randomly as required to provide the needed samples. All wood samples were treated with shell bio-oil either by soaking or dipping and then kept wet for a period of time sufficient to allow the preservative solution to penetrate and diffuse through the cell walls of the wood. The samples of wood for the termite resilience test were then dried, but the samples for the fungicidal test were kept wet. Further testing was conducted to determine preservation properties such as absorption and retention, which are important in determining the quality of a preservative treatment (Hunt and Garrat 1953, Fengel and Wegener 1984).
The absorption value of the pyrolytic oil preserver was calculated by
A = (fww - iw) / v (1)
where
A = absorption,
fww = final wet weight (g),
iw = initial weight (g), and
v = sample volume ([cm.sup.3]).
This study required knowledge of the absorption value in order to identify the amount and depth of active compound penetrating the wood.
The retention value of the pyrolytic oil preserver was calculated by
R = (adw -iw) / v (2)
where
R = retention,
adw = air-dried weight (g),
iw = initial weight (g), and
v sample volume ([cm.sup.3]).
Termite attack resilience test.--Wood resilience tests against termites (Cryptotermes spp.) followed the American Wood Protection Association (AWPA) standards, with some modifications (AWPA 1997, Nakai et al. 2007). Fifty termites were confined with a glass barrier attached to a treated wood sample. For 3 months, termite mortality was calculated daily. The effectiveness of preservation was determined based on termite mortality percentages (25%, 50%, or 100%).
Stain fungi resilience test.--Isolates of fungi were inoculated on fresh wood samples (five replicates) maintained in an incubator at 20[degrees]C, and the samples were observed daily under an Olympus BX 41 microscope for 2 weeks to observe the growth and spread of the fungus on the fresh wood. Data obtained were subjected to one-way analysis of variance with completely randomized design and Tukey's multiple range test at a significance level of P = 0.05. Factorial design was chosen to examine the effect of each factor (temperature of pyrolysis, type of wood, and method of preservation) to the response variable (result of each type of experiments).
Results and Discussion
Shell bio-oil characteristics
The pyrolytic liquids were heterogeneous and separated into a lower heavy oil phase and an upper aqueous phase; these phases were not isolated and were studied together as bio-oil. The raw material, palm fruit shell with 12 percent moisture content, yielded between 35.98 and 38.95 percent shell bio-oil (ratio of the weight of bio-oil to the weight of the raw material) following pyrolysis, similar to other recent reports (Phan et al. 2008, Carrier et al. 2010). Carrier et al. (2010) reported that slow pyrolysis at around 450[degrees]C, achieved at a heating rate of 15[degrees]C [min.sup.-1], provided good yields, superior quality of the char product (>30%, wt/wt), and optimum yields of bio-oil.
Statistical analysis indicated no significant differences in the yield and specific gravity of shell bio-oil produced at the three temperatures tested for pyrolysis (Table 1) and significant effect on refractive index of the bio-oil (Table 2).
The specific gravity of shell bio-oil ranged from 1.0365 to 1.0431, fulfilling the AWPA Standard P1 for wood preservatives, which requires a specific gravity of not more than 1.025. The refractive index of the shell bio-oil ranged from 1.3598 to 1.3610, fulfilling the Acceptance Criteria for Organic Wood Preservatives Systems (Annex A) of International Code Council-Evaluation Service (ICC-ES) 2007, which is applied in the United States (ICC-ES 2009). Thus, palm shell bio-oil offers promising prospects as a wood preservative.
Application of shell bio-oil for wood preservation
Absorption and retention of shell bio-oil.--The shell bio-oil penetrated and diffused into the two types of wood differently (Table 3). Generally, pine (softwood) showed higher absorption than Sengon (hardwood). Water-soluble and water-based preservatives quickly and easily penetrate the vessels of hardwood by diffusing through cell walls. The penetration of preservatives through softwood cells is limited by the presence of a dotted boundary, which results in decreased permeability of preservatives. Thus, the preservative requires more time to penetrate pine wood. Longer soaking times will allow more preservative to be absorbed by the wood. The tracheid valve structure of pine wood resulted in the preservative residing longer in pine than in Sengon wood. The difficulty of water-soluble preservatives to impregnate resin channels will limit their value for treating pine wood (Freeman et al. 2002) but likely explains why pine wood absorbed more shell bio-oil than Sengon wood in the dipping experiments.
Long-term effective wood preservation requires adequate retention, so various chemical preservatives and treatment methods are used in accordance with the properties of each type of wood. Based on the test result, although only intended for short-term preservation, this bio-oil has shown good retention value, especially for specific types of wood (pine and Sengon) and uses (AWPA 1997). In this study, the average retention value of both preserved pine and Sengon wood was 0.005917 g/[cm.sup.3], although that of Sengon wood (0.006126 g/[cm.sup.3]) was overall higher than that of pine wood (0.005707 g/[cm.sup.3]). Statistically, the absorption value was influenced by type of wood, and the retention values were only influenced by the temperature of pyrolysis used in preparing the preservatives (Table 4).
We found that shell bio-oil retention on yellow pine is comparable to that of other waterborne preservatives such as copper naphthenate 1 percent (5.278 kg/[m.sup.3]), chromated copper arsenate 1 percent (5.626 kg/[m.sup.3]), or ammoniacal copper quat type C 1 percent (8.439 kg/[m.sup.3]) (Freeman et al. 2002). Generally, retention level varies depending on the species, assay zones, climatic conditions, and exposure conditions. The retention levels obtained in this study are average for preservative retention levels issued by AWPA Commodity Standards (AWPA 1997).
Termiticidal effect of shell bio-oil.--The termiticidal test indicates wood resilience, reflected by the mortality of drywood termites. In this study, the wood protection properties of shell bio-oil were determined by dipping or soaking the entire wood sample in shell bio-oil. All three shell bio-oil samples exhibited clear and similar termiticidal activity (Table 5). The observed drywood termite mortalities were approximately 25 percent between days 3 and 6, 50 percent between days 3 and 20, and 100 percent between days 5 and 49. Statistically, there was no significant difference in the results between/within the temperature of pyrolysis, type of wood, and method of preservation observed in this study.
It was previously reported that bio-oil (wood bio-oil) has little to no termiticidal activity and that it is weak compared with synthetic termiticides (Yamanoi 1993). In contrast, the results of our study strongly suggest that shell bio-oil has the potential to be a low-cost and environmentally low-impact wood preservative. Yatagai et al. (2002) also showed that acetic acid, which is the largest component of the wood bio-oil from carbonization of wood, exhibited high termiticidal activity against Reticulitermes speratus.
Fungicidal activity of shell bio-oil.--The preservation of wood by shell bio-oil against attack by blue stain fungi (Ceratocystis spp.) was measured. Using a fluorescence microscope, we demonstrated that wood treated with shell bio-oil completely inhibited the growth of blue stain fungi on both pine wood and Sengon wood (Table 6). Fungi only grew well at the neutral pH of the control samples. Therefore, fungi cannot thrive and may die if the timber has an extreme (e.g., acidic) pH. Rather than merely stopping fungal growth, shell bio-oil appears to act as a fungicide and kills spores and hyphae.
To develop a shell bio-oil useful against fungi, it is also essential to conduct wood resilience tests against decay fungi. It has been noted that wood bio-oil exhibits significant activity against white rot, brown rot, and several decay fungi (Freel and Graham 2002, Mazela 2007, Mohan et al. 2008). Freel and Graham (2002) found that bio-oil from wood is more effective against white rot fungi than against brown rot decay fungi. However, bio-oil affords nearly total protection against decay fungi at retentions in excess of 13 lb/[ft.sup.3] (Freel and Graham 2002, Mazela 2007).
The development of an effective and safe wood preservative generally requires extensive laboratory and field tests, including leaching studies. Determining the amount of leaching of a biocide preservative is important for predicting the long-term efficacy of treated wood and for determining potential environmental contamination. It is also the first step in finding additives or modifications to reduce preservative leaching (Mourant et al. 2009). Leaching studies should demonstrate the amount of leaching that may occur under field conditions. Information about leaching must be evaluated with respect to exposure conditions and product type. Previous scientists have highlighted the need for further research to address the effects of exposure to different environments, such as fresh water, seawater, and highly organic environments, and the need to monitor the overall environmental fate of leached wood preservative components (Lebow 1993, Hingston et al. 2001, Obanda et al. 2008).
Conclusions
The yield of shell bio-oil produced from palm shell oil ranged between 35 and 37 percent of the raw material. The following properties of shell bio-oil were determined: specific gravity (ranged from 1.0365 to 1.0431), refractive index (ranged from 1.3594 to 1.3613), wood absorption level (ranged from 0.0088 to 0.0625 g/[cm.sup.3]), and retention (ranged from 0.0022 to 0.0141 g/[cm.sup.3]). Shell bio-oil has potential as a wood preservative for preventing attacks by drywood termites and blue stain fungi. The following drywood termite mortalities were achieved: 25 percent between days 3 and 6, 50 percent between days 3 and 20, and 100 percent between days 5 and 49. Blue stain fungi did not grow on shell bio-oil--treated wood.
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The authors are, respectively, PhD student, Dept. of Natural Resources Process Engineering, Interdisciplinary Faculty of Sci. and Engineering, Shimane Univ., Matsue, Shimane, Japan (sigit_nonwood@yahoo.com); Professor, Dept. of Plant Crops Product Technol., Faculty of Agric. Technol., Gadjah Mada Univ., Bulaksumur, Yogyakarta, Indonesia (pdarmadji@ugm.ac.id); and Professor and Associate Professor, Dept. of Natural Resources Process Engineering, interdisciplinary Faculty of Sci. and Engineering, Shimane Univ., Matsue, Shimane, Japan (uehara@riko. shimane-u.ac.jp, sadanobu@riko.shimane-u.ac.jp). This paper was received for publication in February 2011. Article no. 11-00017.
Table 1.--Mean and standard deviation of yield, specific gravity,
and refractive index of shell bio-oil. (a)
Pyrolysis temp Yield Specific gravity
([degrees]C) (b)
300 0.3750 (2.950E-02) 1.043117 (2.80638E-02)
350 0.3500 (2.828E-02) 1.041967 (2.88972E-02)
400 0.3578 (3.545E-02) 1.036467 (2.51339E-02)
Pyrolysis temp Refractive index
([degrees]C) (b)
300 1.359750 (2.25832E-04) A
350 1.360133 (3.20416E-04) A
400 1.361067 (5.85377E-04) B
(a) In the same column, means followed by different letters are
significantly different (Tukey's test, 0.05 a level). Means
followed by no letters are not significantly different
(statistically similar).
(b) Pyrolysis temperature caused significant differences in
refractive index of bio-oil.
Table 2.--Comparisons of refractive index means at different
temperatures of pyrolysis.
Pyrolysis Mean
temp ([degrees]C) difference SE P
300 and 400 -0.0013167 (a) 0.0002 0.000
350 and 400 -0.0009333 (a) 0.0002 0.003
Pyrolysis
temp ([degrees]C) 95% CI
300 and 400 -0.00193 to -0.00071
350 and 400 -0.00154 to -0.00032
(a) The mean difference is significant at the 0.05 level.
Table 3. Average absorption and retention properties of shell
bio-oil.
Absorption Retention
Pyrolysis Soaking (g/[cm.sup.3]) (g/[cm.sup.3])
Wood [degrees]C) time (h) (a) (b)
P. merkusii 300 Dipped 0.0097 0.0039
24 0.0359 0.0066
48 0.0625 0.0080
350 Dipped 0.0088 0.0037
24 0.0540 0.0066
48 0.0701 0.0110
400 Dipped 0.0103 0.0045
24 0.0487 0.0035
48 0.0465 0.0034
P. falcataria 300 Dipped 0.0119 0.0058
24 0.0244 0.0069
48 0.0271 0.0022
350 Dipped 0.0102 0.0048
24 0.0247 0.0064
48 0.0295 0.0141
400 Dipped 0.0103 0.0061
24 0.0235 0.0049
48 0.0232 0.0038
(a) Absorption was influenced by type of wood. Mean (standard
deviation) = 0.0295 (0.0203).
(b) Retention was influenced by pyrolysis temperature: pyrolysis
at 350[degrees]C provided significantly different results
compared with pyrolysis at 400[degrees]C. Mean (standard
deviation) = 0.0059 (0.0040).
Table 4.-Comparison of retention means at different
temperatures of pyrolysis. (a)
Mean
Pyrolysis difference
temp ([degrees]C) (b) SE P 95% CI
350 and 400 34056 0.0011149 0.011 0.00068-0.006131
(a) Tukey's test for absorption was not performed because type of
wood only contained two parameters.
(b) The mean difference is significant at the 0.05 level.
Table 5.--Average mortality of drywood termites on shell
bio-oil--treated wood. (a)
Achieving mortality (d) (b)
Pyrolysis
temp Soaking
Wood ([degrees]C) time (h) 25% 50% 100%
P. merkusii 300 Dipped 4.33 12 41.67
24 3.33 4.67 12.67
48 3 3.33 15
350 Dipped 5.33 13 41.67
24 3.67 4.67 26.33
48 2.67 3.67 5.67
400 Dipped 4.33 13 41.67
24 3.33 4 7.67
48 2 2.33 4.33
Control 52.33 69.33 88.67
P. falcataria 300 Dipped 3.67 5 17.67
24 3 4.33 22.67
48 3.33 6.33 26.67
350 Dipped 7.33 19.67 49
24 3.33 5 30.33
48 3.33 6 22
400 Dipped 4 10.67 41.67
24 3.33 5.33 19.33
48 3.33 3.67 18.33
Control 56 68 92
(a) No factors (temperature of pyrolysis, type of wood, and method of
preservation) significantly influenced termite mortality. Tukey's
tests were not performed because there were no significant
differences between factors.
(b) Means (standard deviations) = 5.83 (3.35) for 25 percent
mortality, 15.56 (11.43) for 50 percent mortality, and 32.67
(11.18) for 100 percent mortality.
Table 6.--Average of fungal (Ceratocystis spp.) growth on shell
bio-oil-treated wood. (a)
Pyrolysis Soaking
Wood temp ([degrees]C) time (h) Fungal growth
P. merkusii No preservative Control 1 Growth
treatment Control 2 Growth
Control 3 Growth
300 Dipped No growth (died)
24 No growth (died)
48 No growth (died)
350 Dipped No growth (died)
24 No growth (died)
48 No growth (died)
400 Dipped No growth (died)
24 No growth (died)
48 No growth (died)
P. falcataria No preservative Control 1 Growth
treatment Control 2 Growth
Control 3 Growth
300 Dipped No growth (died)
24 No growth (died)
48 No growth (died)
350 Dipped No growth (died)
24 No growth (died)
48 No growth (died)
400 Dipped No growth (died)
24 No growth (died)
48 No growth (died)
(a) No factors (temperature of pyrolysis, type of wood, and method of
preservation) significantly influenced fungal growth.
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