Production of Bioethanol from Tropical Woody Biomass

OPEN JOURNAL OF RENEWABLE ENERGY AND SUSTAINABLE DEVELOPMENT Volume 1, Number 2, July 2014

OPEN JOURNAL OF RENEWABLE ENERGY AND SUSTAINABLE DEVELOPMENT

Production of Bioethanol from Tropical Woody Biomass Abu Saleh Ahmed1 , Md. Saiful Islam2 *, Md. Ashraful Hoque2,3 and Yogeswaran Doraisingam1 1

Department Mechanical and Manufacturing Engineering, Universiti Malaysia Sarawak 94300 Kota Samarahan, Sarawak, Malaysia. 2 Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Selangor, Malaysia. 3 Department of Biochemistry and Molecular Biology, Faculty of Science, University of Rajshahi, Rajshahi-6205, Bangladesh. *Corresponding author: [email protected]

Abstract: In this study, we used the hydrolysis fermentation method to convert woody biomass, corn stove, sawdust and oil palm empty fruit bunch (OPEFB) to bioethanol. The samples were first pretreated and hydrolyzed to obtain sugar. The sugar content were measured and recorded. Upon the addition of the yeast peptone dextrose (YPD) medium, the biomass solutions were fermented using conventional yeast and the ethanol obtained were measured and analyzed. The result shows that the OPEFB has the highest sugar content followed by the corn stove waste and finally the sawdust waste. The amount of ethanol obtained in the fermentation process was in line with the amount of mixed sugar content in the hydrolyzed solutions. The OPEFB exhibits the highest ethanol yield, followed by the corn stove waste, and finally the sawdust waste. Keywords: Woody Biomass; Hydrolysis Fermentation; Bioethanol

1. INTRODUCTION Global warming is of everyone’s concern nowadays. Depleting fossil resources due to excessive use of fossil fuels is also a worrying issue needed to be addressed. With so many energy issues and controversies in the world, biomass becomes an attractive and serious topic for many. There are many definitions for biomass. Biomass can be defined as a renewable energy source, biological material derived from living or recently living organisms [1, 2]. Biomass is usually a plant matter grown to produce heat or generate electricity [3]. In order to promote biodiversity and sustainable and healthy forest and ecosystem management and to meet local and regional bioenergy needs, woody biomass will be a critical part of biomass supply mix in the future bio-economy [4–6]. Biomass for energy can include a wide range of materials. High value material for which there is an alternative market, such as good quality, large timber, are very unlikely to become available for energy applications. However there are huge resources of co-products, residues and waste that exist. Such wastes could potentially become available in quantity at relatively low cost or even negative cost where there is currently a requirement to pay for disposal. There are five basic categories of material which could be mentioned. The first would be the virgin wood 1


from forestry, arboricultural activities or from wood processing, energy crops which are high yield crops grown specifically for energy applications, and agricultural residues which are residues from agriculture harvesting or processing. Furthermore there are food waste, from food and drink manufacture, preparation and processing, and post-consumer waste, and industrial wastes co-products from manufacturing and industrial processes [7]. All the fossil fuels used today maybe in the form of coal, oil and natural gas. These are simply ancient biomass. The earth had buried ages-old plant material over millions of years and converted it into these valuable fuels. But fossil fuels are not considered renewable because they take such a long time to create. The different between biomass and fossil fuels can also be seen by its effect on the environment. A plant releases most of its chemical matter back into the atmosphere when it decays, but fossil fuels are locked away deep in the ground and do not affect the earth’s atmosphere until they are dug up and burned [7]. Biomass is actually carbon based and is also composed of a mixture of organic molecules containing hydrogen, usually including atoms of oxygen, and often nitrogen as well. It also has small quantities of other atoms, which includes alkali, heavy metal, and alkaline earth metal [3]. Wood, waste, and alcohol fuels are three distinct energy sources of biomass energy. Wood energy is derived both from wood waste streams and direct use of harvested wood. Waste energy is the second-largest source of biomass energy in general. Municipal solid waste (MSW), manufacturing waste, and landfill gas are main contributors of waste energy which can be found [8]. Biomass can be converted to other usable forms of energy. Examples of such energies are methane gas which is the main ingredient of natural gas or transportation fuels like ethanol and biodiesel. Ethanol can be produced by fermenting crops like corn and sugar cane. Another transportation fuel, biodiesel can be produced from left-over food products such as vegetable oils and animal fats [9]. There are many conversion technologies which may be used to convert biomass energy into other useful energies. Some conversion technologies may release the energy directly, in the form of heat or electricity. Certain conversion technologies convert it to another form, such as liquid biofuel or combustible biogas. Some classes of biomass resource may have a number of usage options, whereas others may only have one appropriate technology [3]. There are many research have been carried on production of bioethanol from various woody biomass, however very few research carried out on bioethanol production from tropical woody biomass i.e. corn stove, sawdust and oil palm empty fruit bunch [2, 3]. Therefore, the aim of this study is to produce bioethanol from tropical woody biomass and their characteristic analysis.

2. EXPERIMENTAL 2.1 materials In this study, three types of biomass namely wood waste (sawdust), corn-waste and oil palm empty fruit bunch(OPEFB)were used. The objective of this pretreatment method will be to increase the contact surface area for microorganism, catalysts, or steam. This process is carried out in order to convert all the bulky materials to a suitable form which is the powder form. The recommended major diameter of the particle for hydrolysis purpose ranges from 1 mm to a few centimeters [10]. The first specimen for example the sawdust was dried under the sun in order to force out any moisture in it. Subsequently it was converted into smaller particle in the form of powder using the conventional blender. The same was carried out for the oil palm empty fruit bunch fiber and the corn-waste. Instant yeast was purchased from the local store in Kota Samarahan. Instruments used for this study were autoclaved (BENZ, model number- E SA20L), magnetic stirrer, 2

Production of Bioethanol from Tropical Woody Biomass

glucose refractometer (PLA-15S, ATAGO-Japan).

2.2 Methods Approximately 25g of each sample was dissolved in 500ml of 20% (V/V) Sulfuric Acid (H2 SO4 ) solution for hydrolysis. This mixture was then stirred with the mixing rod until the biomass waste was thoroughly blended with the solution. After that, the biker was covered with the aluminum foil. Next, the sample was autoclaved 3.5 hours. After that, the biker containing the hydrolyzed solution was removed and cooled. Then the solution was filtered through a 12mm of Whatman filter paper into a conical flask with the help of the glass funnel. After the filtration process, the solution was covered with an aluminum foil in order to protect the solution from any contaminations. The next process would be analyzing the sugar content in the hydrolyzed solution. The above method was applied to all the remaining biomass samples as well. The glucose refractometer was used for analyzing the sugar content in the hydrolyzed solutions. The sample was analyzed by carefully injecting 30 micro liter of the solution into the analyzer quickly. The respecting reading was taken and recorded for analysis later. Due to the inoperable condition of the A 2-L Biotron Fermenter (LiFluxGx), an alternative approach was used. This was done by using a magnetic stirrer. In order to hydrolyze of extracted solution and to measure the sugar content, the yeast peptone dextrose or simply the YPD medium was prepared by adding 10g of yeast extract, 20g of peptone, and 20g of glucose to 1 liter of water in a biker. The solution was mixed well using the mixing rod and it was then autoclaved for about 2 hours. After that, the solution was left to cool before stored for later use in the experiment. Before the fermentation process, all the mediums were sterilized. This includes the YPD medium and all the biomass solutions. The entire medium was autoclaved for around 3 hours. All the solutions were left to be cooled at room temperature. Soon after that, 100ml of each sample was mixed with 100ml of the YPD medium. The ratio was maintained at 1:1 ratio (YPD to biomass solution). This mixed solution had now been prepared for the fermentation purpose. In the alternative method, the magnetic stirrer was used in order to produce a constant stirring. The solutions were transferred into a 300ml conical flask each. About one and half tea spoon of instant yeast was added to each of the solution. The solution was then stirred using the magnetic stirrer upon adding the magnetic capsule. The speed was maintained to about 150 rpm. The temperature knob was adjusted until a constant temperature about 30 degrees Celsius was obtained. The temperature was measured from time to time using the thermometer in order to obtain a suitable heater magnitude in the machine. The fermentation was done for three consecutive days or about 72 hours. Samples were collected using a syringe in an interval of 3 hours for 9 hours in a day. Before collecting the sample, the stirring speed was reduced and the aluminum foil was uncovered. A small amount of the solution was taken out carefully using the syringe and inserted into the 10ml fusion tube. The samples were transferred and kept in the freezer. The other samples were also fermented using the similar method mentioned above. The B5 Glucose analyzer was again used to determine the amount of ethanol in each sample for each respecting biomass sample. A total of 27 samples from all the 3 types of biomass solution were measured and recorded for analysis purpose. 3


Table 1. Mixed sugar content of all the hydrolyzed biomass solution Mixed Sugar content Sample

Amount (g/l) Percentage (%)

Sawdust

18.20

36.40

OPEFB

21.27

42.54

Corn-waste

19.24

38.48

Table 2. Ethanol content of all the hydrolyzed biomass solution Ethanol content Sample

Amount (g/l) Percentage (%)

Sawdust

8.51

OPEFB

9.95

17.02 19.9

Corn-waste

8.99

17.98

3. RESULTS AND DISCUSSIONS 3.1 Sugar and Ethanol Analysis The mixed sugar content of all the hydrolyzed biomass solution was measured by using glucose refractometers.The mixed sugar content, measured from the glucose refractometer was summarized in Table 1. The amount of ethanol yield was measured according to the maximum yield of ethanol obtained. The result was shown in Table 2. The percentage of the ethanol yield was measured from the total amount of sample used in terms of weight.

3.2 Fermentation of Different Biomass Solution The entire three graphs show a similar pattern or trend. The mixed sugar content decreases with time. The ethanol content depends on the amount of sugar in the solution. The carbon source from the glucose is actually the nutrient needed by the yeast for the fermentation process. The simplified fermentation reaction for glucose can be written as: C6 H 12 O6 ! 2CH 3CH 2 OH + 2CO2 Glucose

Ethanol

CarbonDioxide

Large fraction of substrate carbon is converted to ethanol in the anaerobic fermentation process [11]. However the ethanol content increases with time. Important information which could be derived from the graphs is that the ethanol content is always lower than the total mixed sugar content in the beginning of the fermentation. This is due to the conversion efficiency. It is impossible to gain 100% efficiency in the conversion process. Akinori Matsushika mentioned that the percentage of ethanol efficiency to be approximately 47% to 49% [2]. So it is logical to anticipate the yield of ethanol to be approximately half 4


Figure 1. Mixed Sugar Fermentation of Sawdust Solution

the amount of sugar content in the solution. The yeast contains enzyme which is known as invertase. This acts as a catalyst and helps to convert the sucrose sugars into simple sugar (C6 H12 O6 ) [12]. Another important trend that can be retrieved from the graphs is that the mixed sugar content decreases rapidly to approximately the value of 0 within the first 12 hours of the fermentation. So in accordance, the ethanol production shows a sharp gradient increase of its content to its maximum value within the first 12 hours as well. This is possibly due to the non-existence of any inhibitory effect of the component of lignocellulosichydrolysate on the growth of S. Cerevisiae [2]. The maximum amount of ethanol obtained from the fermentation process of Sawdust Solution was about 8.51 g/l (Table 2). The maximum amount of sugar at the beginning of the fermentation process was 18.2 g/l (Table 1). The maximum amount of ethanol obtained from the fermentation of OPEFB was about 9.95g/l (Table 2).. The maximum amount of sugar at the beginning of the fermentation process was about 21.27 g/l (Table 1). The maximum amount of ethanol obtained from the fermentation of corn stove waste solution was about 8.99 g/l (Table 2). The maximum amount of sugar at the beginning of the fermentation process was about 19.24 g/l (Table 1).

3.3 Comparison In comparison the amount of sugar content in OPEFB was the highest which was about 21.27 g/l. The lowest amount of sugar content was from the sawdust specimen with the value of 18.2 g/l. The corn stove waste displayed a sugar content of 19.24 g/l which was in between both of the specimens mentioned. The ethanol content actually depends on the amount of sugar contained in the specimen itself. So the OPEFB displayed the highest value of ethanol content with 9.95 g/l, followed by the corn stove waste with 8.99 g/l, and finally the sawdust with 8.51 g/l. The result obtained was absolutely logically according to the total sugar content which naturally exists in those specimens. In nature, the OPEFB fiber contains 22.1% 5


Figure 2. Mixed Sugar Fermentation of OPEFB Solution

Figure 3. Mixed Sugar Fermentation of Corn Stove Solution

of hemicellulose and 59.97% of cellulose which makes the total sugar content to be approximately 82.1% which is the highest among the entire specimen under consideration [12]. The corn has the second highest total sugar content which is about 74 %. The corn specimen is composed of 43% of hemicellulose and 31% of cellulose [13]. The wood is the specimen with the least amount of sugar content among the entire specimen in this experiment which is about 70%. This actually consists of 30% of hemicellulose and 40% cellulose [? ].

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4. CONCLUSION The main objective of this experiment would be to convert the waste biomass product into bioethanol through a suitable conversion method. The fermentation hydrolysis was the chosen method in this experiment. The samples used were oil palm empty fruit bunch; corn stove waste, and sawdust. The biomass samples were collected from different areas and were pretreated before the experiment. Samples were dried to remove any moisture in it and were grinded in order to reduce its size. The samples were hydrolyzed through diluted Sulfuric acid in order to break down the molecular structures in the attempt to obtain sugar. The hydrolyzed solutions were then fermented with conventional yeast after adding the YPD medium with the ratio of 1:1 with the hydrolyzed solution. During the fermentation process, the mixed sugar content decreases with time. The ethanol content depends on the amount of sugar content in the solution. The oil palm empty fruit bunch contained the highest amount of sugar with 21.27 g/l which was about 42.54 % by weight. It was followed by the corn stove waste with 19.24 g/l which was approximately about 38.48 % by weight. The biomass with the least amount of sugar was the sawdust with 18.20 g/l which was about 36.40 % by weight. The ethanol measurement result was in line with the sugar content in those samples. The oil palm empty fruit bunch produced the highest ethanol content from the fermentation process which was about 9.95 g/l which was equivalent to 19.9 % by weight. It was followed by the corn stove waste which produced about 8.99 g/l or 17.98 % of ethanol by weight. The least amount of ethanol was produced by the sawdust sample with 8.51 g/l which amounts to 17.02 % by weight. The result complies with the sugar content which naturally exists in those specimens. The OPEFB contains 82.1 % of sugar content in nature followed by corn with 74 % and finally sawdust with 70 %.

ACKNOWLEDGEMENTS This work was supported by the Faculty of Engineering, Universiti Malaysia Sarawak.

References [1] A. S. Ahmed, New Approach of Highly Efficient Fermentation Process for Bio-ethanol from Woody Biomas. PhD thesis, 2007. [2] A. Matsushika, S. Watanabe, T. Kodaki, K. Makino, and S. Sawayama, “Expression of protein engineered NADP+ -dependent xylitol dehyrogenase increases ethanol production from xylose in recombinant,” Saccharomyces cerevisiae, 2008. [3] B. E. Centre, “Biomass,” 2009. [4] V. Balan, L. da Costa Sousa, S. Chundawat, L. Marshall, D adn Sharma, C. Chambliss, and B. Dale, “Enzymatic digestibility and pretreatment degradation products of FEX-treated hardwoods,” Biotechnology Progress, vol. 25, pp. 365–375, 2009. [5] I. Ballesteros, A. Oliva, JM adn Navarro, J. Gonzalez, A adn Carrasco, and M. Ballesteros, “Effect of chip size on steam explosion pretreatment of softwood,” pp. 84–86 and 97–110, 2000. [6] J. Zhu and X. Pan, “Woody biomass pretreatment for cellulosic ethanol production: Technology and energy consumption evaluation,” vol. 101, pp. 4992–5002, 2010. [7] C. Cheng, H. H. Hani, and K. S. K. Ismail, “Production of Bioethanol from Oil Palm Empty Fruit Bunch,” pp. 69–71, 2007. 7


[8] [9] [10] [11]

eia, “Renewables and Alternate Fuels,” 2009. E. kids, “BIOMASS–Renewable Energy from Plants and Animals,” 2009. InfinitePower.org, “Biomass: Natures Most Flexible Energy Resource,” 2010. L. Wei, L. O. Pordesimo, C. Igathinathane, and W. D. Batchelor, “Process engineering evaluation of ethanol production from wood through bioprocessing and chemical catalysis,” Biomass and bioenergy, vol. 33, no. 2, pp. 255–266, 2009. [12] M. F. Ruth and S. R. Thomas, “The Effect of Corn Stover Composition on Ethanol Process Economics,” 2003. [13] N. Abdullahand and H. Gerhauser, “Bio-oil derived from empty fruit bunches,” 2008.

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