Scholarly article on topic 'The Study of Optimization Hydrolysis Substrate Retention Time and Augmentation as an Effort to Increasing Biogas Productivity from Jatropha Curcas Linn. Capsule Husk at Two Stage Digestion'

The Study of Optimization Hydrolysis Substrate Retention Time and Augmentation as an Effort to Increasing Biogas Productivity from Jatropha Curcas Linn. Capsule Husk at Two Stage Digestion Academic research paper on "Agriculture, forestry, and fisheries"

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Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — S. Roy Hendroko, Satriyo K. Wahono, G.A. Praptiningsih, Salafudin, Agus S. Yudhanto, et al.

Abstract The biorefinery concept study for Jatropha curcas Linn (JCL) have been conducted by Bumimas Ekapersada team since 2010. This paper reports study of substrate hydrolysis retention time optimization and augmentation in two stage digestion from raw husk capsules (DH-JCL). It was conducted at the research farm of PT Bumimas Ekapersada, Bekasi, West Java, Indonesia. The augmentation treatment was comparation of 5% local commercial decomposer (EM-4) and arachea methanogens (GP-7) than digester slurry of DH-JCL. It concludes biogas production based on DH-JCL can be enhanced by retention time of hidrolysis substrate on 4 and/or 7 days, and using similar slurry starter.

Academic research paper on topic "The Study of Optimization Hydrolysis Substrate Retention Time and Augmentation as an Effort to Increasing Biogas Productivity from Jatropha Curcas Linn. Capsule Husk at Two Stage Digestion"

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Energy Procedía 47 (2014) 255 - 262

Conference and Exhibition Indonesia Renewable Energy & Energy Conservation [Indonesia EBTKE CONEX 2013]

The Study of Optimization Hydrolysis Substrate Retention Time and Augmentation as an Effort to Increasing Biogas Productivity from Jatropha curcas Linn. Capsule Husk at Two Stage Digestion

Roy Hendroko S.a*, Satriyo K. Wahonob, Praptiningsih G. A.c, Salafudind, Agus S. Yudhantoe, Imam Wahyudif, and Salundik Dohongg

aGraduate Student - Renewable Energy University of Darma Persada Jl. Raden Inten II, Jakarta 13450, Indonesia b Technical Implementation Unit for Development of Chemical Engineering Processes - Indonesian Institute of Sciences Jl. Jogja - Wonosari Km. 31,5 Desa Gading, Kec. Playen, Kab. Gunungkidul 55861, Indonesia cFaculty of Agrotechnology University of Merdeka, Jl. Serayu, PO. Box 12, Madiun 63131, Indonesia dDepartement of Chemical Engineering, ITENAS Jl. PHH Mustafa No.23, Bandung 40123, Indonesia ePTBumimas Ekapersada, Pasiranji, Cikarang Pusat, Bekasi 17812, Indonesia fFaculty of Agriculture and Animal Husbandry, University of Muhammadiyah Jl. Raya Tlogomas No. 246, Malang 65144, Indonesia gDepartement of Animal Production and Technology, Bogor Agricultural University, Darmaga Campus Bogor 16680, Indonesia

Abstract

The biorefinery concept study for Jatropha curcas Linn (JCL) have been conducted by Bumimas Ekapersada team since 2010. This paper reports study of substrate hydrolysis retention time optimization and augmentation in two stage digestion from raw husk capsules (DH-JCL). It was conducted at the research farm of PT Bumimas Ekapersada, Bekasi, West Java, Indonesia. The augmentation treatment was comparation of 5% local commercial decomposer (EM-4) and arachea methanogens (GP-7) than digester slurry of DH-JCL. It concludes biogas production based on DH-JCL can be enhanced by retention time of hidrolysis substrate on 4 and/or 7 days, and using similar slurry starter.

© 2014TheAuthors. Published by ElsevierLtd.

Selection and peer-review under responsibility of the Scientific Committee of Indonesia EBTKE Conex 2013

Keywords: biogas; two stage digestion; capsule husk; Jatropha curcas Linn; augmentation; hydrolysis retention time; biorefinery

* Corresponding author. Tel :+62-8159555028 E-mail : roy_hendroko@hotmail.com.

1876-6102 © 2014 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of the Scientific Committee of Indonesia EBTKE Conex 2013 doi: 10.1016/j.egypro.2014.01.222

Nomenclature

DH-JCL EM-4

Jatropha curcas Linn

Dried husk Jatropha curcas Linn

Effective Microorganism 4

1. Introduction

Biogas is a product of anaerobic degradation of organic substrates. Anaerobic digestion is described as a series of processes involving microorganisms to break down biodegradable material in the absence of oxygen. The overall result of anaerobic digestion is a nearly complete conversion of the biodegradable organic material into methane, carbon dioxide, hydrogen sulphide, ammonia and new bacterial biomass [1, 2]. Cheng Fang [3] concluded that biogas is one of the most efficient and effective options among the various other alternative sources of renewable energy currently available. This opinion is supported by a number of experts [4, 5, 6].

Biogas produces in an anaerobic vessel which called biogas plant. It is also commonly known as a bio-digester, bioreactor or anaerobic reactor / digester [7]. Multi-step biological reactions was happened in the bio-digester [8] which can be divided into three stages namely acid fermentation, acetogenensis, and methanogenensis; or four stages namely hydrolysis, acidogenensis, acetogenensis , and methanogenesis [9]. References [10, 11] shows three or four stages of anaerobic degradation can be grouped into two main stages. The first stage where hydrolysis, acidification and liquefaction take place and the second stage where acetate, hydrogen and carbon dioxide are converted into methane.

Two stage concept was initiated by Poland and Ghosh [12] and this technology has been improving until now. Roy et al. [13] have recapitulate the previous research results on two-stage digestion which reported that have some advantages than one stage. The studies are the water treatment, sewage dairy, sugar beet waste, residue waste processing, vegetable and fruit waste, potatoes, tomatoes, sweet sorghum, wine waste processing and municipal waste. Therefore, a series of research on two-stage biogas digester from capsules husk Jatropha curcas Linn (DH-JCL) has been conducted and reported by Bumimas Ekapersada Team [14-26].

DH-JCL was suggested to run in two stage digestion due to relatively small density, floating in the substrate solution with inlet digester clogging effects and incomplete hydrolysis reaction, relatively high C/N ratio, not ideal composition of N, P, K and S contents, high capacity buffer, high antinutrients, and bulky [15, 16, 17, 20, 22]. A series of previous research improve the efficiency biorefinery JCL cultivation as producing liquid biofuels -biodiesel. But the improvement technology of Bumimas Ekapersada was not optimal until now. Lack of consistency production was happened on biogas which made from DH-JCL in a two stage digestion. This paper reports a review for optimization liquid / substrate retention hydrolisis time and augmentation to enhance Bumimas Ekapersada technology, and recheck the data consistency of compared with the previous studies.

2. Material and Method

The research was conducted in the research farm laboratory of PT Bumimas Ekapersada, Bekasi, West Java, in October 2011 - November 2012. One litter glass digester was used as methanogenesis digester and two litters glass digester was used as hydrolysis digester was compiled CRD (completely randomized design) with three replications in a 32 oC water bath, as shown in Figure 1. 40 grams glass wool was used as immobilized growth which put into the metanogenesis digester. The materials research is DH-JCL cultivars JatroMas toxic category, semi-artificial inoculum (the slurry of DH-JCL digester) was used as starter [27] which is the DH-JCL slurry from the two stage digester capacity of 2 m3 on floating drum type.

The research consist of two studies. The first study is optimization hydrolysis retention time of liquid / substrate. The observation of retention time were 4, 7, 10, 14 days. DH-JCL was soaked with river water concentration of 1:8 in hydrolysis digester. The substrate on hydrolysis solution was transferred to the methanogenesis digester on day 4, 7, 10, 14 with draw and fill method [28].

The second study is the augmentation, microbial introduction [29], to increase the biogas production. The observations was conducted on the introduction 5% (v/v) of EM-4 (local commercial decomposer) as artificial stater

[28] in the digester. The hydrolysis, the introduction of 5% GP-7 (local commercial arachea methanogens), and as the controls were used slurry from the two stage DH-JCL digester capacity of 5 m3 on fixed dome type.

Digester hydraulic retention time of the two studies was set for 56 days. The observation variable are the volume of biogas production by water displacement method [28, 30], pH and temperature in the effluent with a pH meter and a digital thermometer, acetic acid levels with titration methods, and levels of methane with ceinhorn's saccharometer [31]. Statistical test use Duncan's Multiple Range Test (DMRT) on 5%.

Fig. 1. Schematic of two stage digester.

3. Result and discussion

3.1. Optimization hydrolysis retention time of liquid / substrate

All of four steps, the rate-limiting step (slowest reaction) in anaerobic fermentation with suspended organic matter [32], or if the substrate is in particulate form [33] is often considered to be the hydrolysis of the solids. This study tried to solve the problem by observation of hydrolysis digester retention time on influences of liquid / substrate hydrolysis for biogas production.

The previous research was conducted in the field scale at the methanogenesis digester floating drum system capacity of 2 m3, the hydrolysis digester capacity 50 liter HDPE (high density poly ethylene) with retention time treatment of 1, 3, 5, and 7 days. It concluded that optimum retention time is 5 and / or 7 days [13]. The advanced research was conducted in the field scale in the same digester, the methanogenesis digester on fixed dome system with capacity of 5 m3, HDPE hydrolysis digester capacity of 160 liters with the rentention time treatment of 4, 7, 10, 14 days. It concluded that optimum retention time is 4 days [16, 17, 24]. This previous research conclusions support Archana et al. [34] which suggested hydrolysis retention time of acidogenic digester was 4-5 days.

This study was conducted on the temperature of 31.05 - 31.42 oC in the hydrolysis digester and 31.75 - 32.10 oC in the methanogenesis digester. Some literature said the ideal temperature for mesophilic microbial growth is 30 - 35 oC [9] so that the first study took place in ideal conditions. The pH observations in the first study are listed in Figure 2 and Figure 3.

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 31 IS 37 39 41 43 45 47 49 51 53 55 г

1 > 5 7 9 11 1) 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 „

Fig. 2. pH curve in the hydrolysis digester.

Fig. 3. pH curve in the methanogenesis digester.

Figure 2 shows that the pH trend increased from the first day until the last day in the hydrolysis digester, especially in retention time treatment of 4, 7 and 10 days. pH values on the three retention time treatments (6.20 -8.10 with the average of 7.13 - 7.39) is not ideal conditions. The same problem of DH-JCL substrate has been proposed by Roy et al. [13] and Salafudin et al. [14]. Some literatures recommended an ideal pH in the hydrolysis digester is 5.0 - 7.0 [9].

In the retention time treatment of 14 days, the pH of 5.0 is achieved on 44th day. Although the average pH in retention time treatment of 14 days at the pH of 6.20, it can be concluded that it is also not ideal. This condition happened because in the hydrolysis digester formed NH3 which increase the solution pH [35], or the problem on the high buffer capacity which impacting on inaccuracy of pH values [21, 26]. The pH curve in the methanogenesis digester is shown in Figure 3.

The pH curve in the methanogenesis digester (5.30 - 7.80 with the average of 6.93 - 7.30) on the four treatments were categorized in ideal condition since some literatures suggest that the ideal pH value in methanogenesis digester is 6.00 - 8.50 [9]. The ideal condition in methanogenesis digester was also indicated by the increasing pH from acid condition on beginning toward alkaline conditions. Ginting [35] indicated the pH on the beginning generally occur in acid, then arachea methanogens use the acid as a substrate to raise the pH value. Ratnaningsih et al. [36] said arachea methanogens consume acid compounds which producing CO2. It dissolves in water to form bicarbonate ions (HCO3-) and produces more alkaline solution.

The pH value is not ideal in hydrolysis when associated with Figure 4a, 4b, 4c and 4d. However, acetic acid production was categorized in normal condition due to equivalent with the previous study [21] It support statement of Ken et al. [37] which indicated that low pH does not help the process of acidogenesis. On the other hand, there is a lack of pH sensitivity as a control in DH-JCL substrate [21, 26]. Refferences [38, 39] discovered pH is a very poor indicator in highly buffered substrates such as agricultural wastes. Its suggested that it is not recommended to use pH for indicating process imbalance in a well buffered system where the change of pH from VFA (volatile fatty acid) accumulation is often slow and too small. Acetic acid production, as the main precursor of methane [40] are listed in Figure 4 : (a), (b), (c), and (d).

Fig. 4. Acetic acid production curve in retention time treatment : (a) 4 days; (b) 7 days; (c) 10 days; (d) 14 days.

Figure 4 shows the average increase of acetic acid production in the hydrolytic digester are 1.38 g/l, 1.91 g/l, 1.97 g/l, 3.91 g/l at the retention time of 4, 7, 10, 14 days respectively. This is reasonable since the degradation process will be more perfect with increasing on retention time. However the average increase of acetic acid in the

methanogenensis digester of 1.26 g/l, 1.50 g/l, 1.85 g/l, 2.06 g/l showed the accumulation of acetic acid as indication of instability on acetic acid conversion to methane.

Figure 4 (a), (b), (c), and (d) show improvement levels of acetic acid in the methanogenesis digester on some periods. However, indication of acid accumulation do not appear at the Figure 3. Acetic acid accumulation in the final period increase rapidly with increasing retention time. It happens on day 52 in the retention time treatment of 4 days (Fig. 4 (a)). On the 14 days treatment, it happens on day 42 and there is accumulation acetic acid too (Fig. 4 (d)).

Fig. 5. Biogas production of methanogenesis digester in the four retention time treatment.

Figure 5 shows the highest biogas production was happened in the retention time treatment of 4 days, but not significantly different from the retention time treatment of 7 days at 5% DMRT. Retention time treatment of 14 days produced the lowest biogas, as a result of imbalance system (Fig. 4 (d)) which inhibits the activity of archaea as methane-producing [41].

Measurement of biogas quality with methane levels indicators showed four retention time treatments produce relatively similar levels, approximately 90% NH4. Based on this quality data and quantity (Fig. 5), it can be concluded DH-JCL optimum retention time was 4 days which is no significantly different on statistics with 7 days. These results support previous research [13, 16, 17, 24].

3.2. The augmentation for increase the biogas production

Dieter and Angelika [4] indicated the microbial work in the first stage is hydrolitic bacteria and acidogenic bacteria. On the other hand, in the second stage is acetogenic bacteria and methanogenic arachea. This opinion was supported by some researchers [11, 42]. Acidogenic bacteria takes 24-36 hours for growth, acetogenic bacteria takes 80-90 hours and methanogenic bacteria takes relatively slower on 5-16 days [4, 43] .

There is a possibility of imbalance process as the impact of slower growth in arachea methanogens with organic acids accumulation as the indicators which shown in Figure 4. The augmentation study, introduction of microbial [29] as a starter/innoculum namely EM-4 and GP-7, was conducted to solve these problem. Refference [44] suggested that starter is very important part which supporting the production of biogas. EM-4 (effective microorganism-4) is a local decomposer which reported contain 80 genus of microorganism such as fermentation bacteria of Lactobaccilus, fermentation fungi, Actinomycetes, bacteria of phosphate solvent and yeast [45]. GP-7 is a local comercial methanogens which reported by the manufacturer containing anaerobic bacteria Methanobacterium sp., Methanococcus sp., Bacillus sp, Lactobacillus sp. on a population of 106.

This study conducted on the average temperature of 33.80 oC (30.20 - 35.80 oC) in the hydrolysis digester and the average temperature of 33.85 oC (29.80 - 33.85 oC) in the methanogenesis digester. The average pH value observations in hydrolysis digester of 5.63 (5.00 - 5.68) and in the methanogenesis digester of 6.87 (6.00 - 7.30). Temperature and pH data shows that the research conducted in ideal conditions [9].

Table 1. Gas production of augmentation in the hydrolysis

digester.

Treatment Gas Production Notation *)

EM-4 0.0884 a

GP-7 0.9866 a

Slurry (control) 7.5393 b

Table 2. Biogas production of augmentation in the methanogenesis digester._

Treatment Biogas Production Notation *)

EM-4 10.6906 B

GP-7 7.9811 A

Slurry (control) 11.7950 C

Note : *) The same letter in the same column indicates no significantly difference based on DMRT 5%.

Fig. 6. Acetic acid production curve in the augmentation treatment.

Table 1 shows the gas production in hydrolysis digester. It shows that GP-7 produced gas higher than EM-4 although it was not significantly different on statistic. The highest gas production was happened in the slurry treatment of JCL digester. Biogas production in the methanogenesis digester shown in Table 2. Table 2 shows that the highest production was happened in slurry treatment and GP-7 treatment produced the lowest production which shown in Figure 6.

Figure 6 shows that the acetic acid production curve in the slurry treatment increased on day 7 to day 14. It was indicated imbalance growth of arachea methanogens with production / transfer of acetic acid in hydrolysis digester on this period. However, in the next period, production curve decrease and reach the lowest at the end than other treatments. It was suggested that acetic acid in the slurry treatment can be converted by arachea methanogens optimally. The slurry treatment produced the highest biogas production (Table 2). Starter effectiveness of similar material, the DH-JCL, has been reported by Salafudin et al. [14].

Biogas production of GP-7 treatment (Table 2) is the lowest due to acetic acid accumulation on day 7 to day 21 (Fig. 6). At the end of the study, the acetic acid in the treatment GP-7 on day 35 is the highest. The GP-7 augmentation was not able to solve the problems. Arachea methanogens in GP-7 grew slowly due to adaptation of arachea methanogens in GP-7 was not as fast as in the slurry ex digester DH-JCL although able to reduce acetic acid levels in day 21-35.

EM-4 as decomposers microbial was better than GP-7 which shown by the production in Table 2. The study of Figure 6 shows that the acetic acid curve of EM-4 treatment was decrease, but increased at day 21. Increasing levels of acetic acid need special caution since this does not seem on pH values indicator. EM-4 effectiveness in this study support previous studies [15, 21, 25], so the EM-4 can be used if DH-JCL slurry is not available.

4. Conclusion

The conclusions of two studies support the previous studies. Biogas production from DH-JCL can be improved by applying the retention time in the hydrolysis digester of 4-7 days. The best starter is slurry of DH-JCL. Acetic acid levels analysis should be used as a monitoring tool for DH-JCL degradation process in anaerobic digesters as a companion to the pH value which less sensitive relatively.

Acknowledgement

The authors would like to thank PT Sinarmas Agroresources and Technology (SMART) Jakarta, Indonesia for support in the research, especially Daud Dharsono and Tony Liwang for theirs useful comments. And also, special thanks to the research technicians, Ata Atmaja Wkd, Acam Are Hikman and Dewi Tiara Sagita.

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