Solid Biofuel Production from Meranti (Shorea Sp

Key Engineering Materials ISSN: 1662-9795, Vol. 789, pp 104-109 doi:10.4028/www.scientific.net/KEM.789.104 © 2018 Trans Tech Publications, Switzerland

Submitted: 2018-07-24 Revised: 2018-09-14 Accepted: 2018-10-05 Online: 2018-11-20

Solid Biofuel Production from Meranti (Shorea Sp.) Sawdust Using Hydrothermal Treatment Indah Astieningsih Mappapa1,a and Ahmad T. Yuliansyah1,b* 1

Department of Chemical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Indonesia a

[email protected], [email protected]

Keywords: Biomass, Hydrochar, Hydrothermal, Meranti sawdust

Abstract. In the context of industrialization, wood industry plays an important role as one of the pillar components in building Indonesia industry where 76.36% is supported by Meranti (Shorea Sp.). However, the increase of wood processing industries produces waste biomass in the form of large amount sawdust. Hydrothermal treatment is an environmentally clean technology of converting biomass into coal-like solid called hydrochar using subcritical water. The purpose of this research is to determine the effect of temperature and water to biomass (b/w) ratio in the formation of hydrochar from Meranti sawdust. This research was carried out using a 250 mL hydrothermal reactor where a mixture of Meranti sawdust and water heated at temperature variation of 240 and 300oC; b/w ratio 1:20, 2:20, 3:20; initial pressure of 1.0 Mpa and holding time for 30 minutes. Hydrochar were then characterized in terms of yield, caloric value, proximate and ultimate analysis. Based on experimental result, 39-78% raw materials were converted into hydrochar where the highest yield was found on temperature operation of 240oC and b/w ratio 2:20. Introduction Indonesia's forestry sector has succeeded in increasing industrial growth due to its role as a major raw material provider of downstream industry, investment value enhancement, export performance enhancer, business opportunity creator and employment increase. Behind it all, Meranti as one of typical tropics wood plays an important role in building that growth. Based on data from Indonesian Central Bureau of Statistic (2018) in 2016, Meranti contributed 4.312.013 m3 of 5.647.171 m3 logs production in Indonesia. Although the utilization of forest products in the form of wood continues to increase, but Indonesia's forest production only increased 9.8% annually which means that Indonesia's forest carrying capacity is no longer able to meet the demand for national timber (Ministry of Environment and Forestry,2012). Therefore, Setyawati [1] recommends the use of timber effectively and wisely through the application of the whole tree utilization concept, meaning that all tree components, including waste harvested and wood processing, must be utilized. In fact, 50.8% of the amount of processed timber ends up as waste, which 10.6% is from sawdust [2]. So, gaining the alternative technology of treating that waste biomass by using environmentally friendly methods are substantial. In fact, the application of technology of converting biomass into more valuable product has been widely applied both biochemical and thermochemical, for example through combustion, pyrolysis and gasification. These processes are proven to improve the quality of biomass but there are weaknesses that make these processes less effective, such as the biomass used must be dried in advance and high operating temperature (pyrolisis, 450-500oC and gasification, 900-1200oC) [3]. In the midst of these problems, there is a thermochemical process that can convert waste sawdust (biomass) with high water content (at least 30%) without the need to be dried first, so the overall energy required becomes low. Moreover, the operating temperature used is quite low (250-374oC with a pressure of 4-22 Mpa) compared to other thermochemical processes [4] making this process way more environmentally friendly, the process is known as hydrothermal treatment. Therefore, this paper aims to study the effect of temperature and biomass to water ratio on the solid product properties in the hydrothermal treatment.

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Experiment Waste biomass of Meranti in the form of sawdust was collected from PT. Cahaya Samtraco Utama Samarinda, Indonesia. Meranti sawdust used in the experiment was uniformed by using sieve size -24+32 mesh then characterized in terms of cellulose, hemicellulose, lignin content, and proximate analysis (water content, ash content, volatile matter and fixed carbon) showed in Table 1. Table 1. Proximate Analysis of Raw Material. Parameter (% wt d.b) Water content 10.84 Volatile matter 65.61 Fixed carbon 40.58 Ash content 0.32 This research was carried out at variation of temperature of 240 and 300oC with biomass to water ratio of 1:20, 2:20 and 3:20 using a 250 mL hydrothermal batch reactor equipped with stirrer, temperature control and pressure indicator. The experimental apparatus for hydrothermal treatment was the same equipment that was used by Octaviananda et al. [5]. Experiments were conducted with initial pressure at 1.0 Mpa and holding time for 30 minutes in each experiment. Meranti sawdust mixed with water in the reactor and then heated to reach the target temperature. After the reactor was cooled down to the ambient temperature, the slurry of product was filtered and dried in the oven at 105oC for 4 hours to obtain a solid product called hydrochar. Result and Discussion Hydrothermal, like other thermochemical conversion methods, based on thermal breakdown of biomass by applying elevated temperature in a suspension with water under saturated-pressure for a certain time. In the process of hydrothermal, long-chain polymer such as selulose, hemiselulose, and lignin broken into simpler molecular chains. Because of this, some solids dissolve in water to form a liquid product and some are degraded into gases. The solid product of hydrothermal turn into hydrochar which high in caloric value [6]. Hydrothermal is carried out with temperatures below the water critical point and high pressure (above 1 atm) to maintain the water remains liquid [7]. Under these conditions, the hydrogen intermolecular bond in the water is broken, causing the water polarity to decrease. As a result, water becomes more effective solvent for some organic compounds. Water has a very polar property, under room temperature the value of the dielectric constant of water is 80 so that water is known poorly in extract nonpolar/ organic components at room temperature. However, with increasing temperature, the dielectric constant value decreases followed by decreasing viscosity and water density but increasing diffusivity. So water in a given condition may have a dielectric constant approaching a nonpolar compound that can dissolve organic compounds in biomass [8]. Analysis of lignocellulosic content based on Fig. 1 showed that the highest content of red Meranti was 43.25% cellulose, followed by 33.77% lignin and 12.61% hemicellulose. According to Sjostrom [9] the sawdust will decompose gradually, hemicellulose will be degraded at 200-260°C, cellulose at 240-350oC, and lignin at 280-500oC. In addition, Bahri [10] claims that the heating value of sawdust can reach 4,046 kcal/kg and if sawdust is used as briquettes, the calorific value can be increased to 4,748.645 kcal / kg. The differences in the presentation of hemicellulose, cellulose and lignin will affect the products produced during the hydrothermal process because each of these compounds is degraded at different temperatures.

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Fig. 1. Lignocellulosic content of Meranti sawdust. During the process, the temperature rises and linear for 30-40 minutes to reach the operating temperature of 240 and 300oC at each biomass to water ratio (1:20, 2:20 and 3:20). An increase in temperature will cause an increase in vapor pressure and desorption thereby increasing the extraction efficiency [11]. Temperature and pressure profiles at any time during the hydrothermal process show that the temperature gives a significant effect while for each water-biomass ratio is coincident. This means that the water-biomass ratio has no significant effect on the temperature and pressure profiles of the hydrothermal treatment process. (a)

(b)

Fig. 2. (a) Percentages of dried solid yield in b/w ratio variation at 240oC and 300oC (b) Caloric value in b/w ratio variation at 240oC and 300oC. At the end of hydrothermal treatment processes, based on Fig. 2(a) can be concluded that by increasing temperature, the yield is getting low. It possible happen because the energy densification ratio is getting higher with the increasing of temperature [5, 12].


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Meanwhile, for larger water biomass variation will increase yield of hydrochar. The hydrochar yields were 65.33%, 73.11% and 78.27% for the 1:20, 2:20 and 3:20 variations at operation temperature of 240oC. At 300oC hydrochar yields were 43.6%; 49.7% and 54.8% for the 1:20, 2:20 and 3:20 variations respectively. This is because large amounts of biomass can not be degraded by the amount of water added. In addition, a smaller amount of water leads to limited solvolysis/ hydrolysis/ hydration of the lignocellulosic solid resulting in increased yield of hydrochar but decrease yield product of liquid product [13]. Hydrothermal treatment can improve the quality of biomass that is represented by an escalation of calorific value. Proximate analysis is performed to determine the quality based on important parameters such as moisture content, ash content, volatile matter and fixed carbon. The data in Table 2 shows that the temperature and biomass-water ratio have an effect on the property of hydrochar. Changes in some chemical properties in biomass tend to increase or decrease along with the increasing temperature. Table 2. Proximate Analysis Result. Properties Ash content (% db.) Water Content (% db.) Volatile Matter (% db.) Fixed Carbon (% db.)

1:20 0 9,90 73,8 16,2

240oC 2:20 0,18 7,89 74,84 17,09

3:20 0 7,90 74,8 17,3

300oC 1:20 2:20 0,16 0 7,24 8,01 64,22 58,06 28,38 23,93

3:20 0,56 5,93 62,3 31,2

Enhancement of temperature causes changes in moisture content in biomass. Table 2 shows the tendency that the higher the temperature the air content will decrease. Based on the theory of thermal decomposition of biomass, the increase in temperature will cause the fracture of the structure, where water will come out as the initial product of thermal decomposition. This cause with the increase of hydrothermal temperature, the water content in biomass will decrease Ash is the remain portion of the thermal decomposition which the main element is silica minerals and the effect is deficient to the caloric value of the product. So the higher the ash content produced then the product quality on the hydrothermal process will be lower. The ash contained in the product is a non combustible mineral after the thermal decomposition process and the accompanying reactions. High ash levels are affected by impurities contained in the raw material, so that the mineral content in the solid product is high enough and leave ash as the rest of the reaction process. The volatile matter content is a volatile agent as a decomposition of the compounds still present in the product of thermal decomposition other than water. The higher temperature, the lower volatile matter because of the thermal degradation process in biomass resulted in volatile substances will experience the cracking of the structure as a liquid product. In terms of fixed carbon content, an increase in temperature will increase the fixed carbon content. Moreover, the degradation process will cause the reduction of volatile matter and water content levels which result in increased carbon content. The highest fixed carbon gain was obtained at a temperature of 300oC and a water biomass ratio of 3:20. This is due to the higher temperatures that occur degradation of organic compounds that cause long-chain chemical bonds breaks into shorter chains causing a significant loss of carbon content. Decreasing water and ash content, together with increasing in heating value improve handling and storage properties of solid product of hydrothermal [5]. The calorific value determines the product quality of the hydrothermal treatment. The higher the caloric value the higher the quality of the solid product produced. The caloric value is the value of the combustion heat that a material can produce as fuel. The higher caloric value produced at higher temperatures influenced by the high fixed carbon content in the solid product of hydrothermal. In the process of thermal decomposition, the amount of water content will cause the loss of heat used for evaporation, thus it can be said that the lower the water content then the calorific value will increase. Hydrothermal treatment as a whole may increase the heating value (Fig. 2(b)) of a biomass by complex chemical reaction namely depolymerization of the biomass; degradation of monomers

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(cleavage, dehydration and decarboxylation reactions); and recombination of fragmented components [4]. The higher the temperature of the hydrothermal operation, the higher the heating value. This is influenced by the high carbon content bound to the solid product produced. In the thermal decomposition process, the amount of water content will cause the loss of heat used for evaporation, thus it can be said that the lower the water content, the heating value will increase. In the hydrothermal process, increasing temperature also affects to the chemical content contained in the molecular structure of biomass. Theoretically, the higher the temperature, the carbon content tends to be higher and the oxygen, hydrogen, nitrogen, and sulfur content tend to decrease (Tabel 3). The decrease in the oxygen, hydrogen, nitrogen and sulfur content of the hydrothermal product results from the breakdown of the bonds in the carboxyl, hydroxyl, amine, and sulfonic groups present in the molecular structure of the solid product due to an increase in temperature. This leads to an increase in carbon content in the solid product of hydrothermal treatment. Table 3. Ultimate Analysis Result. Properties C (% db.) H (% db.) N (% db.) S (% db.)

1:20 47,18 6,21 0,26 0,02

240oC 2:20 50,84 6,13 0,28 0,05

3:20 1:20 49,55 54,84 6,02 5,93 0,32 0,32 0,03 0,02

300oC 2:20 55,05 5,95 0,35 0,06

3:20 53,41 6,09 0,35 0,02

Summary By the hydrothermal treatment, approximately 39-78% wt. of the Meranti sawdust was turned into a solid product called hydrochar. After the reaction process, there are some of the content that drops down greatly such as oxygen, hydrogen, volatile matter, moisture content, and ash content. This is inversely proportional to the content of fixed carbon, carbon compounds and heat values. From the research results the highest caloric value obtained at temperature 300oC with b/w ratio 3:20. References [1] D. Setyawati, Komposit serbuk kayu plastik daur ulang: Teknologi alternatif pemanfaatan limbah kayu dan plastik, 2003 [2] D. Purwanto, Samet, Mahfuz, & Sakiman, Pemanfaatan limbah industri kayu lapis untuk papan partikel buatan secara Laminasi, DIP Proyek Penelitian dan Pengembangan Industri, 1994. [3] L. H. Zhang, C. B. Xu, and P. Champagne, Overview of recent advances in thermo-chemical conversion of biomass, Energy Conv. Manag. 51 (2010) 969-982. [4] K. Tekin, S. Karagӧz, and S. Bekta, A review of hydrothermal biomass processing, 40 (2014) 673-687. [5] C. Oktaviananda, R. F. Rahmawati, A. Prasetya, C. W. Purnomo, A. T. Yuliansyah, & R. B. Cahyono, Effect of temperature and biomass-water ratio to yield and product characteristics of hydrothermal treatment of biomass, Int. Conf. Chem. Chem. Proc. Eng. 2017. [6] A. T. Yuliansyah, T. Hirajima, S. Kumagai, and K. Sasaki, Production of solid biofuel from agricultural wastes of the palm oil industry by hydrothermal treatment production of solid biofuel from agricultural wastes of thr palm oil industry by hydrothermal treatment, Waste Biomass Valor, 1 (2010) 395-405. [7] Alaya, M. D. Rogelio Soto, L. de Castro, Continuous subcritical water xxtraction as a useful tool for isolation of edible essential oils, Food Chem. 75 (2001) 109-113.


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