Enhancement of Biogas Production from Capsule ...

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The 13 International Conference On QIR (Quality in Research), International Symposium on Chemical and Bioprocess Engineering, Yogyakarta 25-28 June 2013

Enhancement of Biogas Production from Capsule Husk Jatropha curcas Linn Substrates Using Urea and Crude Jatropha Oil as Additive Praptiningsih G.Aa, Ahmad Wahyudib, Satriyo K. Wahonoc, Roy Hendrokod, Salafudine, and Tony Liwangf a

Faculty of Agrotechnology University of Merdeka, Madiun 63131 Tel : (062)8155505260 E-mail : [email protected]

b

Faculty of Agriculture and Animal Husbandry University of Muhammadiyah, Malang 65144 Tel : (062)8113609227 E-mail : [email protected]

c

Technical Implementation Unit for Development of Chemical Engineering Processes – Indonesian Institute of Sciences, Yogyakarta 55861 Tel : (062)8157741020 E-mail : [email protected], [email protected] d

Graduate Student – Renewable Energy University of Darma Persada, Jakarta 13450 Tel : (062)8159555028 E-mail : [email protected] e

,

Faculty of Chemical Engineering, ITENAS, Bandung 40123 Telp (062) 81322326381 E-mail : [email protected] f

PT Sinarmas Agroresources and Technology Tbk., Jakarta 10350 Telp (062)8811230417 E-mail : [email protected] ABSTRACT

Processing of crude jatropha oil (CJO) for biodiesel produced waste, one of them was capsule husk about 30-80% weight of the Jatropha curcas Linn (JcL) fruit. Utilization of dried capsule husk (DH-JcL) for organic fertilizer directly was not recommended due to high C/N ratio value (40-69). Fermentation process could be solved these problems. This paper reports the study of culture enrichment to increase microbes present on JcL substrate with some additives. The study was conducted at the research garden of PT Bumimas Ekapersada, Bekasi, West Java in November - December 2012 using DH-JcL of JatroMas cultivars in toxic category as material. There were three variable, they were the control, 3% urea and 5% CJO as additive. Observation variables were biogas production volume, pH and temperature in the effluent. The results showed that effluent pH average about 5 and daily average biogas production showed that 56.64, 43.13 and 32.63 cc biogas/g VS for 3% urea, 5% CJO and the control respectively. The study concluded that urea and CJO was appropriate as additive for culture enrichment due to they could increase the biogas production of DH-JcL with the best result was achieved by 3% urea as additive. Key words : Biogas, capsule husk, Jatropha curcas Linn, urea, Crude Jatropha Oil (CJO)

1. INTRODUCTION Jatropha curcas Linn (JcL) was believed as biofuel crops renewable energy. In the other side, the facts show that the process of making Crude Jatropha Oil [CJO – Oil] (the biodiesel raw materials) were not environmental friendly. There are a number of waste, namely sludge CJO (S-CJO), seed cake (Jatropha curcas press cake, Jatropha curcas defatted waste), and capsule husk (jatropha fruit coat, fruit husk, hulls, shell, fruit shell, peel, fruit encapsulation) that were stacked in the field and / or thrown into the river. Stacking JcL waste on land would have negative impact on global warming due to greenhouse gases (GHG). Similarly with discharging to rivers would pollute the environment, one of them was negative impacts on fish life. As an agricultural waste for recycling soil nutrients and minerals, JcL seed cake (SC-JcL) was used as organic fertilizer [1, 2]. However capsule husk (DH-JcL) was not recommended as organic fertilizer with direct application (fresh). The quality

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The 13 International Conference On QIR (Quality in Research), International Symposium on Chemical and Bioprocess Engineering, Yogyakarta 25-28 June 2013 standards of organic fertilizer according to the Minister of Agriculture number 28/Permentan/OT.140/2/2009 said that C/N ratio for organic fertilizer was 15-25, whereas the DH-JcL C/N ratio was 40-69 [3]. Fermentation is one of the threatment to reduce the C/N ratio. Anaerobic fermentation is more efficient than aerobic, besides producing organic fertilizer (solid and liquid), it will produce gaseous bio-fuels, namely biogas. SC-JcL was also recommended as biogas substrate due to the biogas production was made from seed cake higher than cow dung [4, 5], but DH-JcL utilization as substrate having a number of constraints. DH-JcL float as biogas substrate due to its density is relatively low, so the fermentation process was imperfect. DH-JCL residual fibers fermentation also clogs at the inlet and outlet of biogas digester [6, 7]. DH-JcL does not suitable as biogas substrate due to slow degradation [8, 9]. DH-JcL volume is relatively large which is about 30-80% of the weight of fresh fruits [10, 11] or 8-15% of the dry weight [12]. In consideration to increase revenue of JcL farmer and to push JcL development as biodiesel feedstock, the series of study has been done which use DH-JcL as biogas substrate. The study was conducted in the laboratory and field scale with 6 m3 digester capacity [3, 13]. The series of studies were expected to push the development of two bio-fuels types, biogas and non-edible oilbased biodiesel. This paper reports one part of the series to increase the biogas production from DH-JcL with enrichment culture which conducted by increasing number of existed microbial at the waste by adding some of the required microbial nutrients for growth [14]. One of required biogas substrate is contains the C/N ratio of 16-25 [15] or 20-30 [16, 17] or 25-32 [18]. Based on these requirements, DH-JcL with the C/N ratio of 40-69 [3] was not suitable as a substrate. On the substrate with high C/N ratio (low nitrogen) will occur reduce biomass growth and reduce degradation [18], unstable pH and easy of pH decreasing [19], imperfect conversion of carbon to methane which indicated by high CO2 of biogas content [19, 20, 21], and insufficient microbial growth for methane production [22]. Urea was suggested as nitrogen source [23, 24]. Using 0.04-6% urea result positive impacts in single substrate cassava tubers, rice straw, cattle dung and / or substrate mixtures of meal waste, mixture of chicken feces and corn stalks, wood ash and poultry droppings, cattle slurry and pressed sugar cane stalk [25, 26, 27]. Another study proposed that 3% urea was better than 6% [28, 29]. Culture enrichment action is also called co-digestion technology which is different types of wastes are treated together [30, 31]. Because of urea is not waste and it is deliberately added to substrate for increasing the biogas production, it is called as additive [32, 33.34, 35] or supplement [36, 37] or amendment [38]. Mixtures substrate is identical with enrichment culture because it adds co-substrate for nutrient addition in the substrate. Some of study suggest a number of studies on the co-digestion positive impacts [36, 39]. The materials are rich in fat, can help to improve the quality and quantity of the biogas [40, 41, 42, 43, 44, 45]. Related JcL and CJO, a preliminary study reported that DH-JcL and 10% S-CJO as a co-digestion can increase biogas production [46].

2. METHODS The preliminary study was conducted at the research garden of PT Bumimas Ekapersada, Bekasi, West Java in November December 2012. On this laboratory scale, a liter glass laboratory digester was used as one-stage digester which was compiled completely randomized design (CRD) with three replications in water bath on 32 oC as in Figure 1. The materials are DH-JcL of JatroMas cultivars in toxic category as substrate which mixed with water in 1: 8 as the control treatment. The 1st treatment was using 3% urea (w/w) and the 2nd was using 5% CJO (w/w) as additives. As the starter was used semi-artificial innoculum [47] from the DH-JcL digester slurry. Hydraulic retention time was set for five weeks. Every day 4 g DH-JcL and 32 cc water as a feed was added and removed from the digester based on draw and fill method [48]. Observation variable were biogas production volume (water displacement method) [49], pH (pH meter) and temperature (digital thermometer) in the effluent.

Substrate Inlet-outlet Substrate Inlet-Outlet

Saluran Biogas

Biogas Outlet

Temperatur

Temperature Control Control

Reaktor Digester Water Bath

Water Bath

Figure 1. Schematic Research Digester

Biogas Storage (Gelas Ukur)

PE Plastic

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The 13 International Conference On QIR (Quality in Research), International Symposium on Chemical and Bioprocess Engineering, Yogyakarta 25-28 June 2013

3. RESULTS AND DISCUSSION Effluent pH of DH-JcL Digester

Ph 6,25 6 5,75 5,5 5,25 5 4,75 4,5 4,25 4 1

3

5

7

9

11

13

4 g DH-JcL + 32 ml water + CJO 5%

15

17

19

21

23

25

4 g DH-JcL + 32 ml water + Urea 3%

27

29

31

33

35 Day

4 g DH-JcL + 32 ml water

Figure 2. pH curves of DH-JcL digester effluent with three treatments Observations of 3rd pH treatment for 5 weeks were presented in Figure 2. Figure 2 shows that the average pH in the effluent with three treatments tended to decrease from 2nd week to 5th week. The average pH for five weeks, the treatment 1 (CJO as an additive), treatment 2 (urea as an additive), and controls were 5.32, 5.43 and 5.23 respectively. These data support previous studies which showed pH at one stage DH-JcL digester is not ideal conditions for biogas microbial growth, especially methanogenic bacteria [46]. Optimal pH for methanogenic bacteria is 6.7 to 7.5 [40], so pH conditions in Figure 2 was marginal category [50]. This is one issue on utilization DH-JcL substrate due to DH-JcL properties is very high buffering capacity such as another JcL waste (SC-JcL) [46]. The pH average of urea treatment was relatively higher than the others, especially in 5th – 17th day. It was similarly with the pH average of CJO treatment in 2nd – 5th day. These data indicate that urea and CJO able to provide better conditions than the controls. The daily production average of biogas on weekly recapitulated was shown in Table 1. Table 1. Daily biogas production (cc/g VS) of DH-JcL digester with three treatments Treatment 5% CJO 3% Urea Control

1st week 81.40 106.77 52.24

2nd week 29.53 46.19 21.96

3rd week 51.11 59.82 21,2

4th week 31.57 41.27 35.97

5th week 22.03 29.15 31.8

Average 43.13 56.64 32.63

Table 1 shows that the urea treatment produces the highest number of biogas production average at 56.64 cc/g VS. At weekly biogas production details, it appears that the urea treatment is always the highest except at 5th week. CJO treatment generate 2nd rank of production average at 43.13 cc/g VS. CJO additives were able to produce biogas in 2nd rank, especially in 1st – 3rd week. The data in Table 1 support the Figure 2, the urea treatment pH effect of biogas production is relatively higher than the others. The nitrogen addition through urea as enrichment culture action is useful to add nutrients for microbial growth which impacting for increase biogas production. The same conclusions were obtained at Sri Lanka in the urea treatment of rice straw which decrease C/N ratio from 80 to 30 [33]. The high C/N ratio has negative impact on the protein formation which needed for microbial growth due to the low nitrogen in the substrate [40]. Table 1 shows that the CJO treatment is the 2nd rank of the biogas average production, especially in the 3rd week which producing two times higher than the control. It has similarity with the addition of 5% fish oil which will double the biogas productions from manure or sewage sludge [45] and the addition of 5% oil bleaching earth (which has high lipids content) in hog manure substrate [44]. The correlation graph between biogas methane content and carbon chain length reveals that the higher C atoms in the substrate, then the higher the methane content of the biogas substrate [51]. Lipids C57H104O6 potentially CH4 yield on 1.014 l/g VS with CH4 levels at 70% was compared to the potentially CH4 of Carbohydrate C6H10O5 on 0.415 l/g VS with CH4 levels at 50% [43]. Fats will produce biogas on 1300 l/kg TS with CH4 levels at 72% was compared to the carbohydrate that produces 746 l/kg TS with CH4 levels at 50% [52]. Typical gas compositions for carbohydrate feeds are 55% methane and 45% carbon dioxide, while the gas contains as much as 75% methane for fats [53]. However, there are problems such as reduction in daily average biogas production. Daily biogas production is decrease from the 1st week to the 5th week with CJO, urea, and control treatment on 72.94%, 72.70%, and 39.15% respectively. Production decrease on additive treatment is greater than control. This is presumably due to the enrichment culture treatment impact to the accumulation of organic acids. The accumulation will form a weak acid buffer that will cause the pH became lower as shown

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The 13 International Conference On QIR (Quality in Research), International Symposium on Chemical and Bioprocess Engineering, Yogyakarta 25-28 June 2013 in Figure 2. It show that the additive urea and CJO are more stimulate the development of fermentative bacteria which not balanced by the rate of growth and development of methanogenic bacteria. With fats, the hydrolysis (the first stage of biogas fermentation) proceeds more rapidly with increasing emulsification (bioavailability), so that the acetogenesis (third stage of biogas fermentation) is limiting [40]. Addition of urea in cattle dung digesters at various organic loadings has been reported to be beneficial but has certain limitations, i.e. continuous addition of urea leads to decrease in biogas production and also ammonia toxicity [54]. pH decrease affects to the majority of methanogenic bacteria, are very sensitive with low pH, will die [55]. At pH < 6.5, only one genus of methanogenic bacteria (from 7 genus of methanogenic bacteria) is able to life namely Methanosarcina [40]. This affects the biogas production decreased from week to week as shown in Table 1. Further examination Figure 1 and Table 1 indicate other problems of DH-JcL substrate as shown on Table 2. Table 2. pH values and daily biogas production (cc/g VS) average of DH-JcL digester with three treatments in the 1st week Treatment 5% CJO 3% Urea Control

pH 5.71 5.73 5.63

Biogas Production 81.4 106.77 52.44

Table 2 shows that the observed pH and average daily production in the first week. pH values show flat at about 5, but the average biogas productions show relatively different. The urea treatment produces biogas at 2.03 times higher than the control in average. It show that, the pH value is not the appropriate properties for monitoring biogas fermentation especially for those containing highly buffered substrates such as agricultural wastes [50, 56.57, 58].

4. CONCLUSION This preliminary study concluded that 3% urea (w/w) and 5% CJO (w/w) was able to used as additives due to it could increase the biogas production of DH-JcL for each 132% and 173%. More research/study is needed to solve the decrease in the biogas production of DH-JcL as a result of the organic acids accumulation. At the other side, it was taken a cheap and easy way tool to monitor the biogas fermentation process as a replacement or companion of pH values.

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