The Effects of Pyrolysis Temperature and Time to The Quality of Coconut (Cocos Nucifera) Midrib
Liquid Smoke
Ruka Yulia1*, Wahyu Ana Pria1, Lukmanul Hakim1, Teuku Makmur2
1Faculty of Agriculture Technology, Universitas Serambi Mekkah, Aceh, Indonesia
2Faculty of Agriculture, Universitas Syiah Kuala, Aceh, Indonesia
*Corresponding Author: Ruka Yulia, [email protected]
Abstract
The aim of this study was to determine the effect of pyrolysis temperature and pyrolysis time on the quality of liquid smoke of coconut midribs waste such as yield, pH, acetic acid, phenol. The method of this research was the descriptive method. The variables of this study were pyrolysis time of 2 hours and 3 hours and pyrolysis temperature of 200, 250, 300, 350, 400 oC with two repetitions. The result showed that the best condition of coconut midrib liquid smoke was on the pyrolysis temperature of 400 oC, for 3 hours pyrolysis time resulted in yield, pH, acetic acid and phenol of liquid smoke were 24%, 2.53, 6,45 ppm, 3,76 ppm. The increase in pyrolysis time and temperature was also found to increase the yield, phenol, acetic acid, and pH.
Keywords: Pyrolysis, liquid smoke, coconut midribs
1. Introduction
Coconut midrib is a leaf stalk of a coconut plant often used as a material for making biomass. Coconut midribs waste (CMW) is frequently left to rot despite still containing dry matter nutrients equivalent to natural grass. Old and fallen midribs are generally rich in hemicellulose, lignin, and cellulose.
Research on coconut midribs has been carried out by several researchers. The research has been focused on several aspects, such as on the use of coconut midribs as an ingredient in animal feed processing (Suprapto & Nurhajati, 2013), organic fertilizers (Nur & Lay, 2014), and mackerel preservative (Agustina, Sunartaty, Makmur & Yulia, 2020). Organic components in coconut midribs, such as lignin, hemicellulose, and cellulose content, make them still worth to be processed into a high-value and multi-functional product, such as liquid smoke.
Liquid smoke is the result of the pyrolysis process of a material containing cellulose, hemicellulose, and lignin. Research on liquid smoke has been carried out by Agustina, et al.
(2020). The best quality of liquid smoke from betel nut waste was at a pyrolysis temperature of 400 ° C for 3 hours with a yield of 25.2%, 32.4 ppm of acetic acid, 0.630 phenol, and pH. 1.23.
Suhanda (2016) reported that the best quality of liquid smoke from cashew nut shells is obtained from the pyrolysis temperature of 400oC and identifies the components of the compounds contained in liquid smoke from cashew nut shells consisting of phenol, benzenediol, pyro line, heptine, and pyran components. Some researchers had made liquid smoke from rubber shells (Fadillah & Alfiarty, 2015), wood dust (Ermaya & Shintawati, 2020; Sarwendah, Feriadi, Wahyuni & Arisanti, 2019), and leather waste durian (Zultinar, 2014; Rahmalinda, Amri &
Zutiniar, 2014).
Pyrolysis temperature and pyrolysis time greatly affect the quality of the liquid smoke produced. The variables affect the decomposition of hemicellulose, cellulose, and lignin polymers into simpler components, such as phenol, carbonyl, formaldehyde, and acetic acid. In addition, the differences in the amount of hemicellulose, cellulose, and lignin composition in each organic material also affect the time and temperature of pyrolysis. The composition of smoke is influenced by several factors, including the type of wood and moisture content. A high level of moisture content in wood will reduce the phenol content, increase the carbonyl compound, and make the product flavor more acidic. Based on the description above, this study attempted to determine the effects of pyrolysis temperature and pyrolysis time on the quality of liquid smoke from coconut midrib waste (CMW), namely yield, pH, acetic acid, and phenol.
2. Method
The instruments used in this research were the reactor (burning place for coconut midribs) and the condenser unit. The analysis used a titration instrument, beaker glass, erlenmeyer, measuring cup, analytical balance, spectrophotometer, stove and digital thermocouple. This study used coconut midribs obtained from the Samahani area, Aceh Besar. The materials used for the analysis were cooling media, PP indicators, 0.1 M NaOH, aquadest, H3PO4, NH4Cl, NH4OH, amino antipirin, potassium ferricyanide, chloroform (CHCl3), sodium sulfate anhydra and copper sulfate (CuSO4).
The design used in this was descriptive research. This study consisted of 2 levels of treatments that 10 experimental units obtained. The arrangement of treatment combinations between temperature and time of coconut midribs into liquid smoke can be seen in Table 1.
Table 1. Research design of pyrolysis temperature and pyrolysis time of coconut midrib liquid smoke
Pyrolysis Time
Pyrolysis Temperature
Acetic Acid pH Yield Liquid Smoke Volume 2 hours 200ºC
250ºC 300ºC 350ºC 400ºC 3 hours 200ºC 250ºC 300ºC 350ºC 400ºC
Preparation of Coconut Midribs
Coconut midribs were taken from coconut groves in the Samahani area, Aceh Besar. The coconut midrib was cleaned from dirt attached on them. The wet and moist coconut midribs were dried first under the sunlight for 3 days before being cut into smaller pieces for easier burning and ready to use.
Procedure for Making Liquid Smoke from Coconut Midribs (modified from Prasetyo wati et al, 2014)
Prepare 1 condenser unit which functions to condense or change the high-pressure gas to turn into high-pressure liquid which will then flow to the receiver dryer and proceed to the expansion valve. The coconut midrib that had been cut into small pieces and weighed as much as 1 kg then put into the reactor. Connected the flue to the condenser using a hose and connected the thermocouple to the reactor of pyrolysis which was a place for burning liquid smoke. The stove was turned on and waited until the temperature was 250 °C, 300 °C and 450 °C. Burning the coconut midribs in the condenser for 2 hours, 3 hours according to the research design. The temperature was constant during combustion. After condensing into the Erlenmeyer, cool the liquid smoke at room temperature and pack it in a bottle. Recorded the volume of liquid smoke obtained.
Liquid smoke was ready for analysis.
Analysis Methods Yield
The yield was measured based on the volume of condensate produced (ml) from each unit weight of material burned. The yield is then calculated by a formula:
x 100%
pH
Measuring the pH of liquid smoke using a pH meter, before measuring the pH meter, it was calibrated with a buffer solution.
Phenol Content
Took a few ml of liquid smoke then added aquadest until the volume was 100 ml. Added 1 ml of H3PO4 and 1 ml of CuSO4. Distillation until you can distillate about 80 ml. Add 30 ml of aquadest water. Continue distillation until the distillate amount was 100 ml. The distillate was added with 2 ml of NH4Cl, and 1 ml of NH4OH. Add 0.5 ml of the amino antipyrine solution and shake. Then add 0.5 ml of the potassium ferricyanide solution, shake it and let it stand. Then extracted with 5 ml chloroform. The extract that had been obtained was filtered through filter paper which is given 1 gram of sodium sulfate anhydridate. Then the filter results were immediately measured with a spectrophotometer at a wavelength of 480 nm.
Acid content
Take some 0.2 mL of the liquid smoke that you get then added distilled water until the volume is 100 mL. Added 3 drops of phenolphthalein indicator. Titrated with 0.1 N NaOH.
Recorded the volume of NaOH used for titration. Calculated the acetic acid content in liquid smoke using the formula
3. Results and Discussions
Coconut midribs used in this study were collected from coconut groves in Samahani Village. The dried coconut midribs that had been dried by the sun used as the material to be pyrolysis. The Pyrolysis process was conducted by a unit condenser equipped with a thermocouple.
From the pyrolysis process, coconut midribs liquid smoke was obtained. The characteristics of the coconut midrib liquid smoke could be seen at Table 2 below.
Table 2. Characteristics of coconut midrib liquid smoke Pirolysis
Time
Pirolysis temperature
Coconut midrib liquid smoke
Yield (%) pH Acetic Acid
(ppm)
Phenol (ppm)
2 hours
200°C 5 2,68 4,05 2,16
250°C 9,5 2,63 4,20 2,35
300°C 15 2,62 4,80 2,59
350°C 7,5 2,62 5,25 3,01
400°C 16,5 2,57 6,30 3,57
3 hours
200°C 7,5 2,65 3,90 2,07
250°C 15 2,62 4,35 2,45
300°C 19 2,62 4,61 2,63
350°C 22,5 2,61 5,40 3,29
400°C 24 2,53 6,45 3,76
Yield
Yield is an indicator to determine the effectiveness of a process. The higher the yield obtained, the more successful the process or research is carried out. The yield produced in the pyrolysis process of coconut midrib liquid smoke can be seen in Table 2. It showed the yield of liquid smoke obtained between 5- 24%. The yield obtained at 3 hours of pyrolysis time and pyrolysis temperature of 400 oC is 24% (w/w). Meanwhile, the lowest yield of liquid smoke was obtained when the pyrolysis was 2 hours and the pyrolysis temperature was 200 oC, which was 5% (w / w).
The effect of pyrolysis time and pyrolysis temperature on yield (%) of liquid smoke from coconut midrib can be seen in Figure 1.
Figure 1. Effect of pyrolysis time and pyrolysis temperature on yield (%) of liquid smoke from coconut midribs
Figure 1 showed that the yield of liquid smoke tends to increase with increasing pyrolysis time and pyrolysis temperature. The yield obtained was higher at the pyrolysis time of 3 hours. In the range of 1-2 hours, the pyrolysis process that occurs is the release of water, CO gas and CO2
gas. During that time period, the water content in CMW experienced evaporation first and the decomposition that occurred was still not perfect or not all of it was decomposed. Over time, more water and gas compounds have been evaporated so that there is more time left to decompose the
components in coconut midribs (hemicellulose, cellulose and lignin) into new compounds. This is indicated by the amount of smoke that comes out of the reactor is more shown at 3 hours than when the pyrolysis time is 2 hours. The condensed smoke produces a volume of liquid smoke a greater time at 3 hours. The components that were decomposed were tetradecanoic acid, methyl hexadecanoic acid and hexadecanoic acid (Ratnawati & Singgih, 2010).
Increasing the pyrolysis temperature caused an increase in the volume of liquid smoke produced. Whereas at the lowest pyrolysis temperature, which is 200 °C, it produces a low yield of liquid smoke because the CMW charring process is not optimal. The charring process occurs faster at high temperatures which causes the component decomposition process in the LKP to be more perfect. The yield will increase at high temperatures. At 400 °C, the yield is higher due to the amount of lignin that is decomposed. Conversely, at a temperature of 200 °C, the yield decreases due to the slow heating speed. The speed of the heating process and the amount of heat used affect the yield of liquid smoke.
The optimum yield produced in this study was lower than the pyrolysis of betel nut skin waste with a pyrolysis temperature at 450 oC and a pyrolysis time at 3 hours was 25.2% (Yulia, Arifandi, Lamona, Makmur & Yuslinaini, 2020), pyrolysis of rubber fruit shells with a temperature a 400 °C and time Pyrolysis at 2 hours was 39.53% (Fadillah & Alfiarty, 2015), liquid smoke from durian skin waste, the highest smoke yield is obtained from pyrolysis temperature 350 °C and pyrolysis time 150 minutes which produces a yield of 26.52% (Zultinar, 2014).
The low yield in CMW pyrolysis is because this waste has a low lignin content or is classified as softwood where the percentage of softwood cellulose is 54-58% and the lignin component in softwood is 18-24% (Fadillah & Alfiarty, 2015). In addition, weight loss also affects the low yield of LKP liquid smoke because of the components that are not converted into condensate. The weight lost can be caused by the presence of volatile gases such as CO2, CO, H2 and CH4 which cannot be condensed with water as a cooling medium (Rahmalinda et al., 2014).
pH
Measuring the pH value in liquid smoke aims to determine the level of the decomposition of raw materials to produce organic acids in liquid smoke (Fadillah & Alfiarty, 2015). Following are the results of the pH analysis of LKP liquid smoke produced in the pyrolysis process can be seen in Table 2. The results showed that the highest pH of CMW liquid smoke was obtained at 200
°C pyrolysis temperature and 2 hours of pyrolysis time at 2.68 and the lowest was obtained at 400
°C and the pyrolysis time for 3 hours was 2.53. The pH value of the liquid smoke produced is in the range from 2.53 to 2.68. This acidic nature comes from the acidic compounds contained in liquid smoke, especially acetic acid and also other acids. This indicates that the CMW liquid smoke produced is acidic. The effect of pyrolysis time and pyrolysis temperature on the pH of liquid smoke from CMW can be shown in Figure 2.
Figure 2. Effect of pyrolysis time and pyrolysis temperature on the pH of liquid smoke from coconut midribs
Figure 2 showed that an increase in pyrolysis time and pyrolysis temperature caused the pH value of CMW liquid smoke to decrease. The pH value will decrease with increasing temperature until it reaches 400 °C. This is because the relatively high temperature will cause the components in CMW to be decomposed to produce acetic acid, phenol, propionic and other compounds.
According to Rahmalinda et al., (2014) the tendency to decrease the pH of liquid smoke is due to the increased content of acetic acid and phenol compounds after distillation. The higher the total phenol content in liquid smoke, the lower the pH value or more acidic.
The pH of CMW liquid smoke was slightly higher than the liquid smoke of rubber fruit shells which ranged from 2.440 to 2.497 (Fadillah & Alfiarty, 2014) and the liquid smoke from the areca nut peel, namely 1.23 - 1.70 (Yulia et al, 2020). The pH of the results of this study was lower than the liquid smoke from sawdust, namely 3.34 (Sarwendah, et al., 2019) and the water smoke of durian skin and palm midribs, namely 4 and 3.4 (Rahmalinda et al., 2014). The results of this study prove that the liquid smoke from coconut midribs has good antibacterial properties due to its low pH. A low pH value indicates that the quality of the liquid smoke produced has a high quality, because it affects storage capacity (Ermaya & Shintawati, 2020).
Acetic Acid
Acetic acid produced in the pyrolysis process from liquid smoke from coconut midrib can be seen in Table 2. It could be seen that the highest liquid smoke acetic acid content from coconut midrib was obtained at 400 °C pyrolysis temperature and 3 hours pyrolysis time of 6.45 mg / mL.
While the lowest acetic acid was obtained at a temperature of 200 °C and a pyrolysis time of 3 hours at 3.90 mg/mL. The effect of pyrolysis time and pyrolysis temperature on the results of acetic acid levels of liquid smoke from coconut midribs can be seen in Figure 3.
Figure 3. The effect of pyrolysis time and pyrolysis temperature on the yield of liquid smoke acetic acid from coconut midrib
Figure 3 showed that the longer time and temperature used in the pyrolysis process of liquid smoke from coconut midribs, the higher the acetic acid content in liquid smoke. This is due to high temperatures which cause hemicellulose, cellulose and lignin to decompose into simpler organic acid components such as carboxylic acids and acetic acids (Zultinar, 2014). It can be seen that every gram of coconut midrib can produce acetic acid in the range of 3.90 - 6.45 mg/mL.
Acetic acid in liquid smoke is the result of the second stage of pyrolysis, namely hemicellulose pyrolysis. Hemicellulose contained in liquid smoke from coconut midribs is a polymer formed from several monosaccharides, namely pentosan (C5H8O4) and hexosan (C6H10O5). Pyrolysis of pentosan produces furfural, furans and their derivatives along with a long series of carboxylic acids. The pyrolysis of hexosan mainly produces acetic acid (Kasim et al., 2015). So, when the pyrolysis time was 3 hours and the pyrolysis temperature was 400 °C, more hexosan was decomposed to produce acetic acid. The low levels of acetic acid in CMW liquid smoke due to a small amount of the hexosan component had decomposed into acetic acid.
The acetic acid levels in this study were lower than the liquid smoke of betel nut peel by 32.4 ppm (Yulia et al., 2020), coconut shell and corncob liquid smoke were 81 and 84.45 ppm (Jenita et al., 2019), and liquid smoke of rubber fruit shells of 13.71 ppm (Fadillah & Alfiarty, 2015).
Phenol Content
Phenol is one of the smoke components which is an indicator of quality parameters in determining smoke quality. Phenol is an active substance that can provide antibacterial and antimicrobial effects on liquid smoke (Fadillah & Alfiarty, 2015). The phenol content produced in the pyrolysis process from liquid smoke from coconut midrib can be seen in Table 2. From the results, the highest value was obtained at 400 °C pyrolysis temperature and 3 hours pyrolysis time of 3.76 ppm and the lowest was obtained at 200 °C and the pyrolysis time for 3 hours was 2.07 ppm. The effect of pyrolysis time and pyrolysis temperature on the results of phenol levels of liquid smoke from coconut midribs can be seen in Figure 4.
Figure 4. The effect of pyrolysis time and pyrolysis temperature on the results of phenol content of liquid smoke from coconut midribs
In Figure 4 it can be seen that the phenol content of liquid smoke tends to increase with increasing pyrolysis time and pyrolysis temperature. In pyrolysis, phenol is produced from the decomposition of lignin compounds. Lignin is a complex polymer consisting of large molecular weight phenyl propane monomers. The compounds obtained from the pyrolysis of the basic structure of lignin play an important role in giving the smoke aroma of the smoke products. These compounds are phenols, phenolic ethers such as guaikol, siringol and homologs and their derivatives (Girard, 1992). Lignin begins to decompose at temperatures of 300-350 °C and ends at 400-450 °C so that the phenol content in CMW liquid smoke is more at higher heating temperatures because lignin has a complex structure, stable, and difficult to decompose. A lot of heat is required to produce phenol.
4.Conclusions
Based on the results of the research, the best conditions of the pyrolysis process of coconut midrib liquid smoke waste were at 400 °C and 3 hours with a yield of 24%, pH was 2.53, acetic acid levels were 6.45 ppm, phenol content was 3.76 ppm. The increasing temperature and time of pyrolysis affected yield, pH, phenol, and acetic acid in coconut midrib liquid smoke.
References
Agustina, R., Sunartaty, R., Makmur, T., Yulia, R., (2020). Inovasi pengawetan alami ikan kembung (rastrelliger kanagurta) menggunakan abu pelepah kelapa dengan variasi lama pengeringan terhadap hedonik. Serambi Journal of Agricultural Technology (SJAT), 2(2), 82- 90.
Ermaya, D., & Shintawati. (2020). Karakterisasi limbah menjadi asap cair dari serbuk kayu dan tempurung kelapa (cocos nucifera). Serambi Journal of Agricultural Technology (SJAT), 2 (2): 60 – 63.
Girard, J.P. (1992). Technology of meat and meat products. New York: Ellias Howard Ltd.
Jenita J., Anggraini S.P.A, Yuniningsih, S. (2019). Pembuatan asap cair dari tempurung kelapa, tongkol jagung, dan bambu menggunakan proses slow pyrolysis. eUREKA : Jurnal Penelitian Mahasiswa Teknik Sipil dan Teknik Kimia, 3(1) : 42-49.
Kasim, F, Arum, N dan Erliza, H. (2015). Aplikasi asap cair pada lateks. Skripsi. Program Studi Teknologi Industri Pertanian. Fakultas Teknologi Pertanian. Universitas Andalas, Padang.
Nur M., dan A. Lay (2014). Limbah kelapa sebagai pupuk organik pada bibit kelapa (cocos nucifera). Buletin Palma, 15 (1): 1-7.
Rahmalinda, Amri, Zutiniar. (2014). Studi komparasi karakteristik asap cair hasil pirolisis dari kulit durian, pelepah dan tandan kosong sawit dengan pemurnian secara distilasi. Jurnal Online Mahasiswa (JOM) Bidang Teknik dan Sains, 1(1): 1 -9.
Ratnawati dan H. Singgih. (2010). Pengaruh suhu pirolisis cangkang sawit terhadap kuantitas dan kualitas asap cair. Jurnal Sains Materi Indonesia. 12(1): 7-11.
Sarwendah M., Feriadi, Wahyuni T., Arisanti, T.F. (2019). Pemanfaatan limbah komoditas perkebunan untuk pembuatan asap cair. Jurnal Littri, 25(1): 22 – 30.
Suprapto, T. dan Nurhajati T. (2013). Penurunan serat kasar dan peningkatan protein kasar sabut kelapa (cocos nucifera linn) secara amofer dengan bakteri selulolitik (actinobacillus ml-08) dalam pemanfaatan limbah pasar sebagai sumber bahan pakan. Jurnal Agro Veteriner, 2(1): 60 - 70.
Sunartaty, R. dan Yulia R. (2017). Pembuatan abu dan karakteristik kadar air dan kadar abu dari abu pelepah kelapa. Prosiding Seminar Nasional II USM 2017.
Eksplorasi Kekayaan Maritim Aceh di Era Globalisasi dalam Mewujudkan Indonesia sebagai Poros Maritim Dunia, Vol. 1: 560-562.
Yulia, R., Arifandi, W., Lamona, A., Makmur, T., Yuslinaini. (2020). Karakteristik asap cair dari limbah kulit buah pinang (areca catechu l.) dengan berbagai variasi suhu dan waktu pirolisis. Jurnal Teknologi Agro-Industri. 7 (1): 32- 46.
Zultinar. (2014). Pengaruh variasi temperatur dan waktu terhadap rendemen pirolisis limbah kulit durian menjadi asap cair. Skripsi. Jurusan Teknik Kimia Universitas Riau, Pekan Baru
