This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights
Author's personal copy b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
Available online at www.sciencedirect.com
http://www.elsevier.com/locate/biombioe
Development of sap compressing systems from oil palm trunk Yoshinori Murata a,*, Ryohei Tanaka b, Kiyohiko Fujimoto b, Akihiko Kosugi a, Takamitsu Arai a, Eiji Togawa b, Tsutomu Takano b, Wan Asma Ibrahim c, Puad Elham c, Othman Sulaiman d, Rokiah Hashim d, Yutaka Mori a a
Japan International Research Center for Agricultural Sciences (JIRCAS), Biological Resource and Post-Harvest Technology Division, 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan b Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan c Forest Research Institute Malaysia (FRIM), 52109 Kepong, Selangor Darul Ehsan, Malaysia d Universiti Sains Malaysia (USM), 11800 USM, Penang, Malaysia
article info
abstract
Article history:
In an attempt to utilize felled palm trunks, we found that they contain a large quantity of
Received 24 September 2012
sap, and that abundant glucose and other fermentable sugars exist in the sap. In this study,
Received in revised form
we developed a prototype system for compressing the sap from oil palm trunks; it is
30 November 2012
composed of a rotary lathe, a shredder, and a compressing mill. A high compression effi-
Accepted 5 December 2012
ciency of the mill was maintained (a sap recovery of w80%) by properly preparing the
Available online 13 February 2013
trunks, which included peeling the bark and the outer layer of the trunks. In addition, a higher compression efficiency was obtained with a relatively slow rotation of the mill.
Keywords:
Consequently, the net energy ratio (NER) reached 4.8 when the sugar concentration in the
Elaeis guineensis
sap was 79 kg m3. This is the first paper about new developed systems for sap compressed
Oil palm trunk
from oil palm trunk. ª 2012 Elsevier Ltd. All rights reserved.
Compressing system Sap Ethanol NER
1.
Introduction
The oil palm (Elaeis guineensis) has become one of the most rapidly expanding equatorial crops in the world. The oil palm tree has an economic life, and the trees are replanted at an interval of 25 years due to decreased oil productivity [1]. In Malaysia, at least 120,000 ha of oil palm plantation was estimated to be replanted annually from 2006 to 2010 [2]. In Indonesia, 450,000 ha of oil palm plantation area is expected to be replanted annually during the next 25 years [3]. Palm
trunks are not appropriate as lumber due to their high moisture (70e80% on the basis of the total mass), which leads to large warping after drying [4]. There is no available method to practically utilize felled oil palm trunks, except in plywood factories [5]. A small percentage of the felled trunks are utilized as plywood, but nearly all of the old felled palm trunks are discarded and burned at the plantation site. The stems of the oil palm tree that are left on the floor of the plantation without further processing serve as a breeding ground for insect pests, such as rhinoceros beetles, and sources of
* Corresponding author. Tel./fax: þ81 29 838 6623. E-mail address:
[email protected] (Y. Murata). 0961-9534/$ e see front matter ª 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biombioe.2012.12.007
Author's personal copy b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
infection by Ganoderma sp., white rot fungus [6e11]. Therefore, the old felled palm trunks are a troublesome waste material, and a beneficial use for the felled trunks is strongly desired for environment preservation. In our previous studies, it was found that a felled trunk contains large amount of sugars in its sap such as glucose and sucrose. These sugars can be converted easily to ethanol and to lactic acid, so that the trunk was found to be a significant resource for the production of fuel ethanol, biochemical and bioplastics [3,12]. However, an efficient technology has not been established yet for obtaining a large amount of the sap from oil palm trunks. Therefore, a bench-scale equipment composed of a shredder and a compressing mill has been developed in this study, which is the first system for obtaining the sap from the trunk efficiently. In this paper, we showed the details of this system, the results of compressing trials in Malaysia, and the estimation of the net energy ratio (NER) for efficient ethanol production from palm sap.
2.
Material and methods
2.1.
Oil palm trunk and compressing sap system
Twenty-six oil palm (E. guinensis) trees that were 23e25 years old (height 12 m, diameter 30e45 cm) were felled, and their felled trunks were collected from some areas that located in Johor province (1 280 000 North, 103 450 000 East), Malaysia. Deli Dura x Yangambi, URTA or URTC as major cultivar, was used in this study. The palm trunk contains the sap; the end and top of the trunk, however are easily contaminated by fungi and bacteria. Therefore, approx. 50 cm of the butt and the top of the trunk were removed before peeling the outer layer, and the remaining wood was processed into smaller logs (1.2 m). The bark and outer layer of the trees were then peeled off using a rotary lathe. Consequently, the inner part of the palm trunk, or the palm trunk core (15e20 cm in diameter, 1.2 m in length), was prepared for pressing. The compressing system is composed of an existing rotary lathe, a new shredder, and new mills. The equipment (shredder and mills) in this study was designed and manufactured by MATSUO Inc. (Kagoshima, Japan) for testing purposes. The flow chart for compressing the sap from palm trunks was shown in Fig. 1AeC and the blueprints of shredder and mill were shown in Supplement Data (the blueprints in Supplementary Data). The bark and outer layer are peeled by the rotary lathe, the palm trunk core is ripped into small chips by the shredder. The chips are compressed by the mill in order to squeeze out the sap. The compressed residues are discharged from the mill via a chute. The processing capacities of the shredder and the mill in this system were approximately 550 kg of trunk per hour and 745 kg of shredded chips per hour, respectively. The power consumption was measured throughout the process, and the energy consumption was calculated on the basis of 1 h of through put trunk since these have a uniform mass of 30 kg.
2.2.
Shredder
The newly developed shredder for the palm trunk core is composed of two parts; a stage component and a cutting
9
component (Fig. 2-1A and B). The trunk core is laid on the ripping part of the shredder, and it is stably supported by the receiving roller and the rotary cutter. The palm trunk core is then shredded into small chips by the rotary cutter. Three types of rotary cutter blades were developed for shredding the palm trunk core for efficient compression of the sap from the shredded chips: cutters with 12 mm wide and 100 mm wide blades, and a polylayer blade (Fig. 2-2A).
2.3.
Compressing mills
The compressing mill comprises two mills (Fig. 3), and each mill is composed of three rotary hydraulic compressed rolls (Fig. 3A and Supplementary Fig.). The rate of turning of the rolls ranges from 0.22 rad s1 to 0.76 rad s1, and the pressure ranges from 2.9 MPa to 32.5 MPa for compression. The small chips from the shredder enter into a slot in the mill and are compressed in both the first and second mills. The compressed sap is collected in pans located under each mill, and the weight of the sap is determined immediately (Fig. 3B). We modified the roller press that is used sugar cane milling. As the fibers are both shorter and thicker than those of sugar cane, we changed the roll to increase the size of the groove, while reducing the angle of the chevron to reduce slippage of the chips and the loss of sap. Because the texture of fiber of oil palm trunk was quite different with ones of sugar cane, we needed to develop the systems for compression from oil palm trunk. The conditions (roll rotation and pressure) were optimized for the most efficient compression through trial runs.
2.4.
Sap yield and energy assessment
The weight of the shredded chips was determined immediately, and then the moisture of the shredded chips was measured using a moisture analyzer (MOC-120H, Shimazu). The sap yield was calculated on the basis of the mass of juice expressed relative to the moisture content of the trunk. The moisture in chips was estimated on basis of total mass. The water content of the trunk is surprisingly high at a mass fraction of 70e80% which is much higher than that of freshly harvested wood species that most frequently have around 50e60%. The major sugar in the sap from oil palm is glucose [3]. Therefore, the sugar concentration in the sap was estimated as glucose from the refractive index using the Brix scale (Refractometer Spittz; ATAGO CO LTD., Tokyo, Japan) and a standard glucose curve. The input energy was calculated from the consumed power during operation of the equipment, including the rotary lathe, the shredder, and the mill (Power: kWh, Supplementary Table 2). The power consumed from start to finish during the operation of each apparatus (i.e., the rotary lathe, shredder, and compressing mill) was determined using an electric power meter (Clamp on Power Hi Tester 3169-01, HIOKI E. E. CORPORATION) (Power, kWh in Supplementary Table 2). The input energy was then converted into thermal terms using the following equation:
Author's personal copy 10
b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
Fig. 1 e Flow chart of the compressing system for the palm trunks. The compressing system is composed of a rotary lathe (A), a shredder (B), and a compressing mill (C). In this study, we developed a new shredder and a new mill for efficient compression of the sap from oil palm trunks. The bark and outer layer are peeled by the rotary lathe (A), and the palm trunk core after peeling is ripped into chips by the shredder (B). The ripped chips are compressed and the sap is squeezed out by the mill (C).
Fig. 2 e 2-1 Shredder. A: The newly developed shredder is composed of a feeding stage for the trunk core and a ripping section for the trunk. B: The laid trunk core is stably supported by the receiving roller and the compressed roller in the ripping section, and is shredded into small chips by the rotary cutter. This shredder is able to rip the trunk at 500 kg hL1. 2-2 Blades. (A) The newly designed blades have widths of 12 mm and 100 mm or are polylayer blades (12 mm). (B) The shapes of the ripped chips produced using these blades.
Author's personal copy b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
11
Fig. 2 e (continued).
Input energy Jh
1
¼ Averaged power consumedðWhÞ 1
3600 sh
0:4 1
(1)
Units and factors: 0.4: the conversion coefficient in Japan for electric power produced from petroleum oil. The output energy was estimated based on the energy in the ethanol produced from the palm sap. The lower heat of combustion of ethanol is 21.2 MJ L1.
3.
Results and discussion
3.1.
Selection of the shredder blade
The palm trunk core (approx. 30 kg, 1.2 m in length 20 cm in diameter) was used after removing the bark and outer layer with a rotary lathe, because it was assumed that the material used for this process would be the waste trunks from the
Fig. 3 e Mill for compressing the sap. (A) This machine is composed of double mills. The sap is squeezed efficiently in the 1st mill and the 2nd mill. (B) The squeezed sap is collected into a pan located under each mill. The compression capacity is more than 500 kg hL1. The compressing residues are discharged from the mill via an eject shoot (C).
Author's personal copy 12
b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
plywood industry. (The blade of the rotary lathe used in these trials was 1.5 m in length). Three types of blades were developed for the shredder, including 12 mm and 100 mm blades and a polylayer blade (Fig. 2-2). The 12 mm blade consisted of 19 layers that had a width of 12 mm, while the 100 mm blade consisted of 5 tiers that had a width of 100 mm (Fig. 2-2A). The polylayer blade consisted of 19 tiers that were 12 mm in width and ripped the palm trunk into small chips with incisive cutting edges (Fig. 2-2A). The configurations of the chips that were ripped by the three types of blades are shown in Fig. 2-2B. The granule shape and size of the lipped particles are described as follows: 100 mm blade; plane shaving, approx. 10e15 cm in length, 12 mm blade; plane shaving, approx. 5e7 cm in length, polylayer blade; rectangle blocks, approx. 5e10 cm in length (Fig. 2-2B). Compressing trials were conducted using the ripped chips from these three blades in order to determine which blade provided the best performance. The compressing yield was calculated from the sap weight (kg) and the moisture mass fraction (%) of the shredded chips input. The electricity consumption was measured using a clamp-type power meter during the shredding trial (Supplementary Table 1-1). The compressing yield and the consumed power were compared for the three blades. The compressing yields from the chips that were ripped by the 12 mm blade and the polylayer blade were 77.7% and 71.6%, respectively (Table 1). However, while these blades showed good compression, the hourly energy consumption of the blades was quite high at 2.9 MJ and 5.0 MJ, respectively (Table 1). On the other hand, the 100 mm blade consumed less power than the 12 mm blade and the polylayer blade (1.3 MJ), although the compressing yield was slightly lower at 69.6% (Table 1). The 100 mm blade with the lower power consumption was selected for the next step.
3.2.
Optimization of the compressing conditions
Compressing trials were conducted on palm trunks with different diameters (Supplementary Table 1-2). Initially, the shredder was developed for trunks with a maximum core diameter of 200 mm, because that is the maximum size of palm trunks discharged as waste from veneer factories. Therefore, the diameters of the trunks used in the compressing trial were 150 mm and 200 mm. The mill conditions (revolution and pressure) were 0.33 rad s1 and 17.7 MPa for
Table 1 e The comparison of the performance among cutter types. Cuttersa 12 mm width 100 mm width Polylayer blade
Sap yieldb, %
Consumed powerc, MJ
77.7 5.7 69.6 8.8 71.6 9.7
2.9 0.5 1.3 0.2 5.0 1.7
a Oil palm trunk which be used for selection of blades: 1.2 m in length, 0.2 m in diameter, and approx. 30 kg. b The sap yield (%) was calculated as the mass fraction of the extracted sap from the initial trunk water content. (The extracted sap, kg)/(The moisture content in the shredded chips, kg) 100. c The consumed power (Mega Joule; MJ) was calculated according to Equation (1) in Materials and methods.
the 1st mill, and 0.36 rad s1 and 23.6 MPa for the 2nd mill, respectively. The sap yield was calculated from the moisture (%) in the shredded chips and the weight of the squeezed sap (kg), and was determined to be 71.9 8.6% for the 150 mm diameter trunks and 68.9 7.3% for the 200 mm diameter trunks (Table 2). The p-value was then calculated to determine whether there was any significant difference between the compressing yields for the 200 mm and 150 mm diameter trunks, and no significant difference ( p ¼ 0.47) was found. Next, the influence of the pressure and rotation of the compressing rolls on the sap yield was investigated. Compressing trials were conducted under eight different mill conditions (mill conditions 1e8), and the compressing yield was compared for different rotations (slow or fast) and different pressures (low or high). The raw data is shown in Supplementary Table 2, and the summarized data are shown in Table 3. When the rotation of the mills was slow (0.22 rad s1 in the 1st mill and 0.25 rad s1 in the 2nd mill), the compressing yield depended on the pressure of the mills; the highest compressing yield (79.6%) was achieved under high pressure conditions (29.5 MPa on the 1st mill and 32.5 MPa on the 2nd mill) (Table 3, condition 3). The compressing yield was then compared for runs with different rotations but the same pressure in the mills. When the rotation of the mills was fast under the same pressure, the compressing yield decreased from 72.5% to 63.5% (conditions 4 and 7 in Table 3). The calculated p-value ( p-value ¼ 0.03) indicated that there was significant difference in the sap yield for conditions 4 and 7. In addition, the compressing yield decreased from 79.6% to 60.9% under fast rotation even at high pressures (conditions 3 and 8 in Table 3). Furthermore, when the rotation of the mill (rad s1) changed from slow to fast (conditions 4 and 8) under high pressures, the compressing yield decreased at a faster rotation (Table 3). Therefore, it was concluded that the sap yield was dependent on the rotation (rad s1) of the mill. The configuration of the fiber in the oil palm trunk may be the reason for the dependence on the revolution rate. The oil palm trunk has short length fibers, and they slipped among the rolls during compressing, leading to low yields for the sap compressing. Therefore, the compressed mill was improved by adding a large groove and a low-cut chevron on the rolls of the mills in order to avoid this problem as much as possible (see Materials and methods). Increasing the sap yield was possible by optimizing the compressing conditions.
3.3. Life cycle assessment for ethanol production from oil palm trunks The energy consumption for ethanol production from oil palm trunks (1.2 m in length 20 cm in diameter) was then estimated beginning at the plantation. The palm tree planting density is assumed to be 142e148 ha1, yielding 19.2e22.2 t ha1 y1 of FFB, with a CPO yield of 3.5e4.0 t ha1 y1. This would correspond to a biodiesel fuel yield of 4.94 m3 h1 y1 [13e15]. The oil palm tree has an economical life span of approximately 20e25 years, and is replanted due to decreasing oil yield after 25 years [1]. We estimated all of the input energies related to (A) the fertilizer and transportation of the palm tree at the plantation, (B) the
Author's personal copy 13
b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
Table 2 e The compressing test in the log with different diameter 150 or 200 mm. Diameter of log
150 150 200 200
mm mm mm mm
Diameter of log, mm
av.a SDa av.b SDb
Shredded chips, kg
151.4 8.4 199.9 13.3
Moisture in chipsc, %
16.9 3.3 29.5 3.4
79.5 3.2 77.1 5.5
Sap yieldd, % 1st mill
2nd mill
Totale
44.8 4.5 48.6 6.7
27.1 11.6 20.3 9.8
71.9 8.6 68.9 7.3
The condition for squeezing was as follows: Mill 1 was set to 0.33 rad s1 in rotation and 17.7 MPa in pressure, and mill 2 was set to 0.36 rad s1 in rotation and 23.6 MPa in pressure. a The average and standard error were calculated from 7 times trials for squeezing in Supplement Tables 1 and 2. b The average and standard error were calculated from 10 times trials for squeezing in Supplement Tables 1 and 2. c The moisture was calculated on the mass fraction basis of the total mass. d Sap yield, mass fraction % ¼ (sap weight/moisture in chips) 100. e Total ¼ 1st mill þ 2nd mill.
processing of the palm trunk (debarking, shredding, and compressing), and (C) the energy for ethanol production from the sap of the oil palm trunk via fermentation.
3.4.
Input energy from plantation to compressing mill
3.4.1. Energy for nutrition and for transportation of the oil palm tree on the plantation The energy for cultivation of the oil palm trees includes the energy consumed in the production of the fertilizer and pesticides used on the plantation [16]. The input energy for transportation consists of the fuel to carry the felled trunks from the plantation to the factory. These input energies were estimated using the data in Supplementary Table 3 (Fertilizer). The fertilizer input is 10.9 GJ ha1 y1 (Supplementary Table 3), which on the basis of a single trunk is equivalent to 73.7 MJ y1. The transportation energy equivalent for each tree is 47.2 MJ for the assumed 8 km transportation distance from the plantation to the mill [16].
3.4.2.
Processing of the palm trunk
The electric power consumption per trunk core (20 cm 1.2) was measured while processing the trunk and compressing the sap (Table 4 and Supplementary Table 2). The power for rotary lathe processing averaged 0.24 kWh, and the power
for ripping the trunk into chips and compressing the sap was 0.17 kWh and 0.23 kWh, respectively. The sum of the processing energies was thus 0.64 kWh based on the compressing trials (Table 4). When converted from Wh to MJ (: 640Wh 3600 s h1), the sum of energy for processing was 2.3 MJ. Finally, the total energy for processing was 5.8 MJ from calculation according to Equation (1) (Table 4).
3.4.3.
Energy for ethanol production
Estimation of the input energy for ethanol production from the oil palm sap was based on published data for ethanol production from sugar cane in Brazil [17] (Supplementary Table 4). The input energy related to the electricity, chemicals, and lubricants for ethanol production from sugar cane is summarized in Supplementary Table 4. In Brazil, the power consumption in the mill on one tonne of canes (TC) was estimated to be 12.9 kWh as outside electric power [17]. The electricity for ethanol production from 1 t of sugar cane was estimated to be 46.4 MJ, and the energy associated with the chemicals and lubricants for ethanol production from 1 tonne of sugar cane was 49.4 MJ (Supplementary Table 4, Ethanol Production). In this study, the energy (electricity plus chemicals and lubricants) for ethanol production was estimated from palm sap based on the data for sugar cane juice. The electrical energy to process one trunk core (20 cm diameter, 1.2 m length) is 0.41 MJ,
Table 3 e The compressing condition on mill. Mill 1
Condition 1 Condition 2 Condition 3 Condition 4 Condition 5 Condition 6 Condition 7 Condition 8
Mill 2
Rotation, rad s1
Pressure, MPa
Rotation rad, s1
Pressure, MPa
0.22 0.22 0.22 0.33 0.33 0.33 0.76 0.76
14.7 17.7 29.5 14.7 17.7 23.6 14.7 29.5
0.25 0.25 0.25 0.36 0.36 0.36 0.83 0.83
17.7 23.6 32.5 17.7 23.6 29.5 17.7 32.5
Shredded chips, kg
Moisture in chipsa, %
31.2 26.0 31.7 27.4 29.0 26.6 33.2 31.5
81.4 80.1 84.3 82.2 78.1 81.5 82.1 84.6
Sap yield, % 1st mill
2nd mill
Total
40.1 51.1 50.8 51.3 46.7 51.1 33.7 40.0
31.2 19.3 28.8 21.2 20.9 25.1 29.7 20.9
71.3 70.4 79.6 72.5 67.6 76.2 63.5 60.9
Logs with 200 mm in diameter were used for squeezing trials. The rotation and the pressure of roll on mill mean the processing condition for compression on Mill 1 and Mill 2. a Moisture in chips was calculated on basis of total mass.
Author's personal copy 14
b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
Table 4 e Input energy during processing a palm trunk.a
Trunk core (20 cm 1.2 m)
Rotally lathe, kWh
Shredder, kWh
Mill, kWh
Sum of energy, kWh
Sum of enrgyb, MJ
Total energy, MJc
0.24
0.17
0.23
0.64
2.30
5.8
Total energy, MJ ¼ (Sum of energy: 2.3 MJ) (100/40). a Powers for rotary lathe, shredder, and mill were used average values from Supplement Table 2. b Energy conversion from Wh to MJ: Wh 3600 s h1. c Power generation efficiency is assumed as 40%.
while the energy used in the fermentation chemicals is about 0.44 MJ (Supplementary Table 4, Ethanol production).
3.5. Energy output from the ethanol and compressing residues The palm trunk core (20 cm in diameter 1.2 m in length) after peeling the bark using a rotary lathe was used for producing the sap. All of the data related to the compressing conditions in the mill are shown in Table 5. Approximately 29.6 kg of ripped chips were obtained from each palm trunk core after shredding, and an average 16.9 kg of squeezed sap was obtained after milling of the chips (Table 5). The glucose content in the sap was estimated to be 79 kg m3 from the glucose standard using the Brix scale (Table 5). The weight of the glucose was thus calculated to be 1.34 kg in the sap, the ethanol produced from the glucose was estimated to be 0.79 L, and the energy from the ethanol was estimated to be 16.7 MJ. There were some residues (approx. 10 kg) from the ripped chips after compressing the sap. The compressed residues had a moisture content of 40e50%, and the effective heat value of the oil palm residue was revealed as a low heating value (LHV) of 7.5 MJ kg1. Thus, the potential of the heat value in the palm residues was calculated as 76.1 MJ. Assuming the
effective heat is 20% of the potential heat of the residues, the effective heat corresponds to 15.2 MJ (Table 5). Consequently, the total energy output was estimated to be 32.0 MJ from sum of the ethanol and the residues (Table 5).
3.6. Net energy ratio (NER) for ethanol production from oil palm trunks The input energy (cultivation, transportation from plantation to mill, processing of the trunk, and ethanol production) per palm trunk core is shown in (Table 4 and Supplementary Tables 3 and 4). All of the input and output energies are also shown and compared in Fig. 4. Note that the energy for fertilizer at the plantation, which was estimated above, is actually used for palm oil production, and not for palm trunk cultivation. Therefore, it was estimated at zero for the palm trunk cores used for ethanol production (Fig. 4). We estimated the transportation fuel between the oil palm plantation and the palm oil mill from data reported by Kamahara et al. The distance between the plantation and the palm oil mill was assumed to be 8 km. A whole trunk was estimated to be 40 cm in diameter 10 m in length, with a weight of approx. 1,140 kg. The energy for transportation of one entire trunk was estimated to be 47.2 MJ (Supplementary Table 3). In the case of the
Table 5 e Output energy from ethanol and compressing residues. Ripped Sap Glucoseb, Glucoseb, EtOH Energy from Residue Potential Effective Total Mill a kg production EtOH, MJd after sq, heatf, MJ heat, MJg Energyh, condition chips, collected, kg m3 MJ kg kg (calc.), Lc kg (estimated)e 1 2 3 4 5 6 7 8 Ave. SD
31.2 26.0 31.7 27.4 29.0 26.6 33.2 31.5 29.6 2.7
18.1 14.2 21.2 16.5 15.2 16.4 17.3 16.3 16.9 2.1
77 90 73 72 85 78 79 74 79 6
1.42 1.30 1.57 1.21 1.31 1.30 1.39 1.23 1.3 0.1
0.83 0.77 0.93 0.71 0.77 0.77 0.82 0.72 0.79 0.07
17.7 16.2 19.6 15.1 16.4 16.2 17.3 15.3 16.7 1.5
10.5 9.4 8.4 8.7 11.0 8.2 12.7 12.2 10.1 1.7
78.6 70.8 63.0 65.4 82.8 61.2 95.4 91.2 76.1 13.0
15.7 14.2 12.6 13.1 16.6 12.2 19.1 18.2 15.2 2.6
33.4 30.4 32.2 28.2 33.0 28.5 36.4 33.5 32.0 2.8
a Mill condition is same with ones of Table 3. b Sap sugar was measured with brix meter, and was converted to glucose using the calibration curve of a standard glucose solution. Glucose in sap was calculated as follows; Glucose in sap kg ¼ (gravity of sap; 1.0167 g mL1) (sap collected, kg) (glucose conc./1000, kg m3). c Ethanol yield from 1 mol of glucose ¼ 0.511, ethanol fermentation efficiency ¼ 91.1%, ethanol density; 0.789 g/mL. Ethanol (kg) was calculated as follows; EtOH, kg ¼ [(glucose, kg) 0.911 0.51]/0.789. d Carolies of ethanol; 21.2 MJ L1. e The efficiency of residue collection was estimated at 80%. Residue after squeezing, kg ¼ [(shredded chips, kg) (sap collected, kg)] 0.8. f Low heat value (LHV) of residues with 50% moisture was estimated as 7.5 MJ kg1. Potential heat, MJ ¼ (Residues after sq., kg) 7.5. g Effective heat was estimated at 20% of potential heat of residues. h Total energy ¼ (Energy from EtOH, MJ) þ (Effective heat, MJ).
Author's personal copy b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
15
Output Input
1.0 4.8 In plantation Fertilizer: 0 MJ Transportation : 0 MJ For processing Compressing sap: 5.8 MJ For ethanol production Electricity: 0.41 MJ Chemicals & lubricants: 0.44 MJ
Produced ethanol: 16.8 MJ Electricity: 15.2 MJ
Total input energy: 6.65 MJ
Total output energy: 32.0 MJ
Fig. 4 e Net energy ratio (NER) for ethanol production from oil palm trunks. Input and output energies were calculated on the base of one trunk core (20 cm diameter 3 1.2 m length). Input energy (6.65 MJ): Fertilizer and transportation at the plantation (0 MJ), processing for compression (5.8 MJ), and fermentation to produce ethanol (0.85 MJ). Output energy (32.0 MJ): produced ethanol (16.8 MJ) and the electricity from the compressed residues (15.2 MJ).
palm trunk cores, which are waste from plywood factories, the energy for transportation was estimated to be zero. The energy for processing was estimated to be 5.8 MJ (Table 4), and the energies for ethanol production (electricity, the chemicals and lubricants) used in that process were estimated to be 0.41 MJ and 0.44 MJ, respectively (see the section “Energy for ethanol production”). The total input energy (sum of the fertilizer, transportation, processing, electricity, chemicals, and lubricants) was therefore 0 MJ þ 0 MJ þ 5.8 MJ þ 0.41 MJ þ 0.44 MJ ¼ 6.65 MJ. On the other hand, the output energy was the sum of the energy from ethanol and the effective heat of the residues (Table 5). Therefore, the output energy was 32.0 MJ. Thus, when ethanol is produced from palm oil sap (as produced in this study), the net energy ratio (NER) of the output to input energies is 4.8 (Fig. 4). Initially, because plywood factories produce veneer from felled trunks, it would be good to use the waste palm trunks from these factories. However, nearly all of the palm trunks are left at the oil palm plantation and encourage contamination by Ganoderma SP and Rhinoceros beetle due to the damage on the stems of the trees [6,8e11,18]. There is currently no major industrial use for the palm trunk, and thus the palm trunk has actually become a problem for plantations. If the whole trunk could be used for ethanol production, this troublesome issue could be resolved. A whole trunk contains 33.3 folds of palm trunk core, and, thus, if 33.3 times the volume of sap can be obtained from a whole trunk, the sugar concentration in all of the sap is 79 kg m3, and the ethanol efficiency is the same as that used in the analysis for the palm trunk core, the volume of ethanol produced would be 26.3 L. There are 142e148 oil palm trees per hectare [14] (Supplementary Table 3). If the sap was collected from all of the old trunks that were logged, a large volume of ethanol (3892.4 L ha1) could be produced.
When ethanol was produced from 1 tonne of sugar cane, and the power was self-sufficiently generated from bagasse combustion, the NER was 8.3 [17]. The weight of a whole trunk of an oil palm tree was estimated to be 1.14 t (Supplementary Table 3, Transportation). In the case of the palm trunk core, the NER was estimated to be 4.8. The difference in the NER for the oil palm core and sugar cane is due to the lower sugar concentration in the palm oil sap. Sugar cane juice contains 16% sucrose, while the sap from the oil palm cores in this study contained 8% glucose (Table 5 and Supplementary Table 2). However, we have found that the sugar content in the trunk increases after cutting [12]. Specifically, the sugar content increased to 16% via maturation of the palm trunk after cutting. When the whole trunk is used for ethanol production, then the energy for transportation of the whole trunk must be considered (47.2 MJ). If this energy is counted as input energy, the NER is 6.2 (data not shown). This value is lower than that of ethanol from sugar cane. However, the energy for processing of the trunk was high in this trial (5.8 MJ in Fig. 4). If the processing and compressing operation is systemized and optimized for commercial scale, the process would be more efficient and the input energy would decrease while the output energy would be improved, and consequently, the NER would be enhanced. Therefore, the sap from the oil palm trunk might be a promising non-food-source raw material for ethanol or bioplastic production, leading to an effective contribution to resolving the environmental issues for sustainable palm oil industries.
4.
Conclusions
We developed a processing and compressing system for the squeezing of the sap from oil palm trunks in order to increase
Author's personal copy 16
b i o m a s s a n d b i o e n e r g y 5 1 ( 2 0 1 3 ) 8 e1 6
the utilization of the rich sugar inside the palm trunk. This system is composed of a rotary lathe, a shredder, and a compressing mill. The compressing yield was approx. 80% under slow rotation conditions on the mill, and the sap yield was dependent on the rotation (rad s1). Ethanol production from palm trunks has a positive NER and would contribute to the increased utilization of the palm trunk and the sustainability of biofuel production from a non-food resource. This is the first report about the systems for sap compressed from oil palm trunk.
[5]
[6]
[7]
[8]
Acknowledgments This study was supported by the New Energy and Industrial Technology Department Organization (NEDO), Japan, as an international collaborative research project. We appreciate the Sojitz Machinery Corporation as a collaborator in this study. We also appreciate MATSUO Inc. as the developer of the equipment (shredder and mills) that was used in this study.
[9]
[10]
[11]
Appendix A. Supplementary data
[12]
Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.biombioe.2012.12.007.
[13]
references
[14]
[1] Ismail A, Mamat MN. The optimal age of oil palm replanting. Malaysia Palm Oil Board (MPOD). Oil Palm Ind Econ J 2002; 2(1):11e8. [2] Basiron Y, Weng CK. Oil palm: the agricultural producer of food, fiber, and fuel for global economy. Oil Palm Ind Econ J 2006;8(1):1e17. [3] Kosugi A, Tanaka R, Magara K, Murata Y, Arai T, Sulaiman O, et al. Ethanol and lactic acid production using sap squeezed from old oil palm trunks felled for replanting. J Biosci Bioeng 2010;110:322e5. [4] Sahri MH, H’ng PS, Baker ES. Anatomical characteristics and utilization of oil palm wood. In: Nobuchi T, Sahri MH, editors. The formation of wood in tropical forest trees e a challenge
[15] [16]
[17]
[18]
from the perspective of functional wood anatomy. Serdang MY: Penerbit Universiti Putra Malaysia; 2008. p. 161e78. Sulaiman O, Hashim R, Wahab R, Samsi HW, Mohamed AH. Evaluation on some finishing properties of oil palm plywood. HolzRohWerkst 2008;66:5e10. Huger AM. The Oryctes virus: its detection, identification, and implementation in biological control of the coconut palm rhinoceros beetle, Oryctes rhinoceros (Coleoptera: Scarabaeidae). J Invertebr Pathol 2005;89:78e84. Paterson RRM. Ganodermadesease of oil palm e a white rot perspective necessary for integrated control. Crop Prot 2007; 26:1369e76. Pilotti CA. Stem rots of oil palm caused by Ganoderma boninense: pathogen biology and epidemiology. Mycopathologia 2005;159:129e37. Ramle M, Wahid MB, Norman K, Glare TR, Jackson TA. The incidence and use of Oryctes virus for control of rhinoceros beetle in oil palm plantations in Malaysia. J Invertebr Pathol 2005;89:85e90. Susanto A, Sudharto PS, Purba RY. Enhancing biological control of basal stem rot disease (Ganoderma boninense) in oil palm plantations. Mycopathologia 2005;159(1):153e7. Utomo C, Werner S, Niepold F, Deising HB. Identification of Ganoderma, the causal agent of basal stem rot disease in oil palm using a molecular method. Mycopathologia 2005;159: 159e70. Yamada H, Tanaka R, Sulaiman O, Hashim R, Hamid ZAA, Yahya MKA, et al. Old oil palm trunk: a promising source of sugars for bioethanol production. Biomass Bioenerg 2010; 34(11):1608e13. Latif J, Noor MM, Dolmat MT, Din AK. Economics of higher planting density in palm plantations. Oil Palm Ind Econ J 2003;3(2):32e9. Persson UM, Azar C. Preserving the world’s tropical forestsea price on carbon may not do. Environ Sci Technol 2010;44: 210e5. Yusoff S. Renewable energy from oil palm e innovation on effective utilization of waste. J Clean Prod 2006;14:87e93. Kamahara H, Hasanudin U, Widiyanto A, Tachibana R, Atsuta Y, Goto N, et al. Improvement potential for net energy balance of biodiesel derived from palm oil: a case study from Indonesian practice. Biomass Bioenerg 2010;34:1818e24. Goldemberg J, Macedo IdC, Leal MRLV, Silva JEARd. Assessment of greenhouse gas emissions in the production and use of fuel ethanol in Brazil. p. 3e37, http://www. wilsoncenter.org/sites/default/files/brazil.unicamp.macedo. greenhousegas.pdf; 2004. Sanderson FR. An insight into spore dispersal of Ganoderma boninense on oil palm. Mycopathologia 2005;159:139e41.
