Journal of Industrial and Engineering Chemistry 18 (2012) 2147–2150
Biogas production from moon jellyfish (Aurelia aurita) using of theanaerobic digestion
Ji-Youn Kim, Sung-Mok Lee, Jae-Hwa Lee *
Department of Bioscience and Biotechnology, Silla University, Busan 617-736, Republic of Korea
A R T I C L E I N F O
Article history:
Received 30 December 2011
Accepted 13 June 2012
Available online 21 June 2012
Key words:
Hydrogen gas
Methane gas
Jellyfish (Aurelia aurita)
Anaerobic digestion
A B S T R A C T
Jellyfish are a major problem to swimmers and a plague to fishermen. Presently, jellyfish are removed
from the sea using a separator system and the jellyfish waste is discarded. Thus, the objective of this work
was to produce bio-gas from Aurelia aurita using anaerobic digestion. Batch anaerobic studies were
conducted to examine the effect of pre-treating waste jellyfish and using the waste for anaerobic
hydrogen and methane gas production. Using this approach, jellyfish waste could be changed into
renewable energy. The effects of sludge heat, sonication and freeze treatment on hydrogen and methane
gas production in batch experiments were evaluated. The optimal treatment condition was determined
to be freeze treatment at �70 8C for 20 min. The total amounts of hydrogen and methane gas produced
from sludge that was heat treated for 20 min at 65 8C were 270 and 1640 mL/L, respectively. In addition,
the total amounts of hydrogen and methane gas produced from sludge that was sonicated for 20 min at
25 kHz were 275 and 1670 mL/L, respectively. The total amounts of hydrogen and methane gas produced
from sludge that was freeze treated for 20 min at �70 8C were 310 and 1800 mL/L, respectively.
� 2012 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.
Contents lists available at SciVerse ScienceDirect
Journal of Industrial and Engineering Chemistry
jou r n al h o mep ag e: w ww .e lsev ier . co m / loc ate / j iec
1. Introduction
Since global warming and environmental pollution is one of thegreatest environmental concerns, there has been an increase instudies dedicated to the generation of novel sources of bio-energy[1]. Several nations are trying to develop and use bio-energy,especially European countries, which are progressing toward thedevelopment of bio-energy policies and biomass production [2,3].Energy derived from wind, hydroelectric, geothermal, solarthermal and biomass sources are considered renewable [4].Because most forms of bio-energy are derived either directly orindirectly from the sun, there is an abundant supply of renewableenergy available, which is unlike fossil fuels [5]. Thus, the use ofbio-energy provides several environmental benefits. Althoughbiogas can be efficiently produced at the laboratory level, biogashas not yet been produced commercially from biomass productionfacilities [5,6].
Several types of biomass can be gasified, including waste, woodchips, straw, wood and more. In addition, renewable energygeneration and new and forthcoming environmental legislationhas gradually increased interest in anaerobic digestion technology.
* Corresponding author at: Department of Bioscience and Biotechnology,
Graduate School of Silla University, Busan 617-736, Republic of Korea.
Tel.: +82 51 999 5748; fax: +82 51 999 5636.
E-mail address: [email protected] (J.-H. Lee).
1226-086X/$ – see front matter � 2012 Published by Elsevier B.V. on behalf of The Ko
http://dx.doi.org/10.1016/j.jiec.2012.06.010
The optimum digester settings are important to both potentialbiogas yields and treatment. In addition, the cost for digesterheating comprises a large portion of the whole operating costs.Many previous studies have suggested that gas production duringanaerobic digestion is related to treatment and initial pH changes[7,8].
Biomass, such as jellyfish, can be degraded biologically. Sourcesof jellyfish mainly include Aurelia aurita, Nemopilema nomurai,Cyanea capillata, Dactylometra uinquecirrha, and Physalia [9,10]. A.
aurita is a very common worldwide scyphomedusa and is found incoastal waters. In addition, this is the most widely studied jellyfish.
The adult A. aurita body diameter ranges from 20 to 40 cm[11,12]. The removal of jellyfish has now become necessary in gulfareas, ports, industrial facilities, and power plants along the coasts.The yearly economic loss due to jellyfish ranges from $1521 to3048 hundred million in Korea [13,14]. Because of the largeamounts of removed jellyfish, jellyfish waste holds great promiseas a new source of biomass in Korea. However, jellyfish is currentlydiscarded using a separator system (JSS) in the sea area of Korea[15]. Despite this potential source of biomass, the potential of usingjellyfish for biofuel production has not yet been systematicallyevaluated.
The aim of the present study was to determine the optimumfermentation initial pH, temperature, initial substrate concentra-tion, heating [16–23], freezing and sonicating treatment [24] ofsludge derived from A. aurita for biogas production. Biogasproduced using A. aurita as a source of biomass consists of about
rean Society of Industrial and Engineering Chemistry.
Fig. 1. Effect of substrate concentration on hydrogen and methane gas yield. The
jellyfish were cultured without pH control and the seed sludge were cultured in
batch experiments using 300 mL flask mixed at 150 rpm and 35 8C under anaerobic
conditions. The concentration of the seed sludge was 1%. The total amounts of
evolved hydrogen and methane gas are shown. Values shown are averages of flask
run in duplicate.
J.-Y. Kim et al. / Journal of Industrial and Engineering Chemistry 18 (2012) 2147–21502148
2/3 methane (CH4), 1/3 carbon dioxide (CO2), a little hydrogensulfide (H2S) and a little hydrogen (H2). In addition, bio-gasproduction under the optimum conditions was examined in a 5 Lfermenter (working volume, 4 L). Thus, the primary objective ofthis work was to study the effect of sludge pretreatment and initialpH on hydrogen and methane gas production.
2. Materials and methods
2.1. Seeding sludge and feedstock
Seed sludge was obtained from an anaerobic digester at adomestic sewage treatment plant in Su-young, Korea. Thecollected sludge was centrifuged at 2000 rpm for 10 min and thenthe supernatant was used as inoculums [25]. 20% glycerol wasadded to the sludge and then stored in a freezer (SW-UF-120) at�70 8C. A. aurita were harvested from the southern sea in Koreaand washed with fresh water to remove salt. Washed seaweedsamples were finely chopped in a blender (HMF-1100, HANIL) andkept in freezer at �70 8C. Batch anaerobic studies were conductedas described in our previous work [25].
2.2. Pretreatment experiments
Experiments were designed to evaluate the effect of variouspretreatment methods on jellyfish (A. aurita) in regards to bio-gasproduction efficiency where wastewater sludge was used as theinoculum.
The sludge was subjected to heat treatment (XL-2020, HeatSystem-Ultrasonics), sonication treatment (Sonic Dismembrator,Model 500) and freeze treatment (freezer, SW-UF-120). For heattreatment, the samples were thermally treated in a heat System-Ultrasonics at 65 8C for 20 min. Sonication treatment wasperformed using a cell-breaker at a frequency of 25 kHz. Thesamples were placed in a 50 mL beaker with the ultrasonic probepositioned 2 cm above the bottom of the beaker. A sonication timeof 20 min was shown to be required for release of the insolubleorganic matter from the sample. Freeze treatment was conductedby adding glycerol to the sample and then placing the sample in afreezer (SW-UF-120) at �70 8C for 20 min.
2.3. Anaerobic digestion in 300 mL flask and 5 L fermentor
Bio-gas production experiments were carried out in a 300 mLflask or 5 L fermentor (KF 51, KoBiotech, Incheon, Korea). Theworking volume of the 300 mL flask was 100 mL. These flasks wereused to test the effects of substrate concentration, initial pH andsludge pretreatment on bio-gas production. Each flask was filledwith cooled jellyfish (A. aurita) samples (3 g), inoculums (1 mL)and deionized water (96 mL). The flasks were wrapped inaluminum foil to eliminate substrate photolysis, and nitrogengas was flushed for 10 min to remove oxygen within theheadspace.
The operational condition was 35 8C and 150 rpm without aninlet for gas. The accumulation of gas in the head-space of the flaskwas measured and sampled periodically for analysis of bio-gascontent. Following gas measurements, samples were discarded toprevent possible errors associated with the sampling procedure,such as a gas leakage. Before each sampling event, a tedlar bag wasused to equilibrate the pressure inside the flask to ambientpressure, and the volume in the tedlar bag was recorded and addedto the total volume measured in the headspace [26,27]. In addition,pH experiments were conducted to determine the optimal pH. Inthe pH-controlled experiments, bio-gas production under alloptimum conditions was investigated in a 5 L fermentor (workingvolume, 4 L).
2.4. Analysis of bio-gas
The composition of hydrogen and methane gas in the gaseousproduct was analyzed using a high-density hydrogen and methanegas detector (Electrochemical Sensor, Model No. XP-3140, ComosInc., Japan). The output signal displayed the % volumes of hydrogenand methane gas in the headspace of the fermentor, which wasconverted to mL/L. The sensor had a measuring range of 0–100%hydrogen or methane gas. The system was calibrated once everytwo days using the calibration cap provided with the instrument.Standard methods were used to evaluate pH.
3. Results and discussion
3.1. Bio-gas production from grinded jellyfish
In a previous study, the optimal conditions for culturingjellyfish were established and the jellyfish concentration, methodof treatment, and pH were selected based on these conditions. Toexamine the effects of fermenting jellyfish (A. aurita) on hydrogenand methane gas production, the seed sludge was cultured in batchexperiments using a 300 mL flask at 35 8C under anaerobicconditions. The jellyfish concentrations (A. aurita) used in thisstudy were 3 g, 5 g, 10 g and 20 g (Fig. 1). The total amount ofevolved hydrogen production at these concentrations was deter-mined to be 364.05, 402.1, 680.8 and 960.8 mL/L, respectively, andthe concentrations of produced methane gas were 2610.36, 2818.1,6315.4 and 7834.2 mL/L, respectively. However, the optimumhydrogen and methane gas production yield per substrate gramwas observed when 3 g of jellyfish (A. aurita) was used. The highesttotal hydrogen and methane gas production yields were121.35 mL/g and 870.12 mL/g, respectively, when the 3 g ofjellyfish was used. The hydrogen and methane gas productionunder these conditions was about seven times higher than theother conditions tested.
3.2. Effect of sludge treatment on biogas production
The effects of sludge heat treatment, sonication treatment,freeze treatment and no treatment on hydrogen and methane gasproduction in bath experiments are shown in Fig. 2. In addition,the total amount of hydrogen and methane gas produced fromnon-treated sludge was 185 and 1083 mL/L respectively. The
Fig. 3. Hydrogen and methane gas production in a 300 mL flask. The medium was
maintained at constant pH values (3.0, 3.5, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 9.5 and 10.0) for
3 days at 35 8C. The substrate was buffered with 6 N NaOH and 1 N HCl solutions at
pH values ranging from 3.0 to 10. The medium was cultured at constant pH values
between 3.0 and 10 for 3 days at 35 8C. Values shown are averages of flask run in
duplicate.
Fig. 4. Hydrogen and methane gas production in a 300 mL flask. Hydrogen and
methane gas from the substrate under controlled pH (4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0,
11.0) for 3 days at 35 8C. The residue of the substrate was buffered with 6 N NaOH
and 1 N HCl solutions at pH values ranging from 4.0 to 11. The medium was cultured
at constant pH values between 4.0 and 11 for 3 days at 35 8C. Values shown are
averages of flask run in duplicate.
Fig. 2. The effect of sludge heat, sonicate and freeze treatment on hydrogen and
methane gas production in batch experiments. The sludge was heat treated for
20 min at 65 8C, sonicate treated for 20 min at 25 kHz and freeze treated for 20 min
at �70 8C. Values shown are averages of flask run in duplicate.
J.-Y. Kim et al. / Journal of Industrial and Engineering Chemistry 18 (2012) 2147–2150 2149
total amount of hydrogen production remained relatively highover 10–20 min, where heat treatment for 20 min resulted in thehighest bio-gas production. The total amount of hydrogen andmethane gas produced from sludge that was heat treated for20 min at 65 8C was 279 and 1622 mL/L, respectively. In addition,the total amount of hydrogen and methane gas produced fromsludge that was sonicate treated for 20 min at 25 kHz was 290 and1665 mL/L, respectively. The total amounts of hydrogen andmethane gas produced from sludge that was freeze treated for20 min at �70 8C were 306 and 1803 mL/L, respectively. Therefore,the optimum freeze treatment condition for inactivation of bio-gasutilizing microorganisms was determined to be �70 8C for 20 min.Under this treatment condition, the production yield of hydrogenand methane gas was 165.41% and 166.18%, respectively, relativeto the non-treated sludge. Nath et al. [28] reported thatmicroorganisms predominantly produce acetic and butyric to-gether with hydrogen gas from carbohydrates. Due to the complexcomposition of jellyfish, complete degradation of the materialrequires the presence of microorganisms with a broad substraterange.
Many hydrogen and methane gas producing microorganismscan form endospores, which are considered ‘‘survival structures’’developed by these organisms when unfavorable environmentalconditions are encountered. But when favorable conditions return,the spores germinate [25,27,28].
3.3. Effect of initial pH on biogas production
Only grinded jellyfish (A. aurita), which was the optimalsubstrate, and freeze treated sludge were used for the pH studiesand the samples were cultured at 35 8C. To determine the optimalmedium pH for hydrogen and methane gas production, themedium pH was varied between 3.0 and 10.0. As shown in Fig. 3,the optimal pH for hydrogen and methane gas production wasabout pH 9.0. At this pH, the total amount of evolved hydrogen andmethane gas was 552.65 and 3947.50 mL/L, respectively. Incontrast, we observed a significant decrease in the amount ofhydrogen and methane gas produced between pH 3.0–3.5 and pH9.5–10.0. High production of bio-gas during fermentation de-creased when the pH was below 4.0, which may be due to adecrease in the activity of hydrogen-producing bacteria andmethanogen. Therefore, maintaining the medium pH at about 9.0may be necessary for practical hydrogen and methane gasproduction under cultured conditions at 35 8C.
3.4. Effect of secondary pH control with productivity of biogas
Hydrogen and methane gas production from 3 g of substratewas examined using secondary pH control for 3 day at 35 8C. Theprimary pH of the medium without pH control was shown togradually decrease to about 3.8–4.0 (Fig. 4). To determine whichmedium pH was optimal for bio-gas production, the residue of thesubstrate was buffered with 6 N NaOH and 1 N HCl solutions at pHvalues ranging from 4.0 to 11. The medium was cultured atconstant pH values between 4.0 and 11 for 3 days at 35 8C. Whenthe pH was maintained at 9.0, the total amount of evolvedhydrogen and methane gas was 222.3 and 1184.11 mL/L,respectively. In contrast, we observed a significant decrease inthe amount of bio-gas production at pH 4.0. Thus, the medium pHshould be maintained at around 9.0 for practical bio-gasproduction under cultured conditions at 35 8C. In addition,secondary pH adjustments may be needed to increase theefficiency of biogas production.
Fig. 5. Bio-gas production from Aurelia aurita in a 5 L bioreactor. The medium was
cultured at constant pH 9.0 for 6 days at 35 8C. Symbols: Hydrogen (*), Methane
gas (*), Time courses of pH changes at 5 L bioreactor (!). pH control; 6 N NaOH
solutions to maintain a pH of 9.0. Values shown are averages of 5 L bioreactor run in
duplicate.
J.-Y. Kim et al. / Journal of Industrial and Engineering Chemistry 18 (2012) 2147–21502150
3.5. Biogas production in a 5 L fermentor
Hydrogen and methane gas production under optimumconditions was investigated in a 5 L fermentor (working volume,4 L) (Fig. 5). The optimum fermentation substrate concentration,initial pH, pretreatment condition and sludge treatment weredetermined to be 3 g, 9.0 and freeze treatment at �70 8C for20 min, respectively, using the 300 mL reactions. Under theseoptimum conditions, the amount of bio-gas produced wasdetermined at the 4 L scale using 120 g/L of jellyfish (A. aurita)in a 4 L of culture fluid for 55 h. We observed a significant decreasein the amount of bio-gas produced at pH 3.8. The total amount ofevolved hydrogen and methane gas was 336.24 and 1357.16 mL/L,respectively. After inoculation, the residue of the substrate wasbuffered with 6 N NaOH solutions to maintain a pH of 9.0. The totalamount of evolved hydrogen and methane gas was 552.24 and2452.06 mL/L, respectively. In addition, if the initial pH was lowerthan 4, biogas production did not proceed in the flask experimentsand similar results were observed in the 5 L fermentor. Byadjusting the pH to 9.0, biogas production could be increased. Inthese experiments, pH was determined to be critical for bio-gasproduction, where no hydrogen and methane gas was produced atpH values between 6.0 and 9.0; however, during the same period,organic acid was produced. Bio-gas then evolved at pH valuesbetween 4.0 and 6.0, which were produced from the organic acid.Therefore, control over pH is needed for hydrogen and methane gasproduction.
4. Conclusions
The technical feasibility of using jellyfish (A. aurita) as a sourceof renewable energy was evaluated at the laboratory scale. Biogascan be produced from jellyfish quite simply through batch culturesmaintained within a given temperature range of sludge heat,sonication, freeze and non treatment conditions. Furthermore,when sludge was freeze treated at �70 8C for 20 min, the totalamount of evolved hydrogen and methane gas was the higher thanat any other conditions (310 mL/L, 1800 mL/L, respectively).
The initial optimum substrate concentration and optimum pHof milled jellyfish (A. aurita) were determined to be 3 g and pH 9.0,respectively, after freeze treatment. Under these conditions thetotal amount of evolved hydrogen and methane gas was
552.65 mL/L and 3947.50 mL/L, respectively. In addition, theproduction of hydrogen and methane gas while maintaining thepH at 9.0 was 222.3 mL/L and 1184.11 mL/L, respectively.Hydrogen and methane production were also evaluated underthe optimum conditions in a 5 L fermentor (working volume, 4 L).In the 5 L fermentor, the optimum fermentation substrateconcentration, initial pH, pretreatment condition and sludgetreatment were determined to be 3 g, 9.0, and freeze treatmentat �70 8C for 20 min. Under these conditions, the hydrogen andmethane gas production was 336.24 mL/L and 1357.16 mL/Lrespectively. In addition, when the substrate pH was initially9.0, the hydrogen and methane gas production was 552.24 mL/Land 2452.06 mL/L, respectively. However, no hydrogen andmethane gas was produced when the pH was maintained at 9.0.This occurred because when the pH dropped to 5.0, no change inbiogas production was observed. Thus, based on these combinedstudies, jellyfish hold great promise for use as biomass in biogasproduction.
Acknowledgments
This research was financially supported by the Ministry ofKnowledge Economy (MKE) and Korea Institute for Advancementof Technology (KIAT) through the Research and Development forRegional Industry.
References
[1] G. Berndes, M. Hoogwijk, R. Broek, Biomass & Bioenergy 25 (1) (2003) 1–28.[2] Commission of the European Communities, Communication from the Commis-
sion of 7 December 2005, Biomass Action Plan [SEC(2005) 1573], Brussels, COM(2005) 628 final.
[3] D. Hall, J. House, Journal of Power and Energy 209 (1995) 203–213.[4] V.T. Nejat, Energy Conversion and Management 49 (2008) 1820–1831.[5] I.M. Dincer, Rosen, Applied Energy 64 (1999) 231–239.[6] C.E. Wyman, B.J. Goodman, Applied Biochemistry and Biotechnology 39 (1933)
41–59.[7] K.J. Chae, S.K. Yim, K.H. Choi, S.K. Kim, W.K. Park, Water Science and Technology 49
(5–6) (2004) 427–434.[8] K.J. Chae, J. Am, S.K. Yim, I.S. Kim, Bioresource Technology (99) (2008) 1–6.[9] M. Kawahara, S. Uye, K. Ohtsu, H. Iizumi, Marine Ecology Progress Series (307)
(2006) 161–173.[10] E.Y. Kim, S.H. Lee, J.S. Kim, W.D. Yoon, D.H. Lim, A.J. Hart, W.C. Hodgson,
Toxicology Letters 167 (2006) 205–211.[11] H. Ishii, U. Bamstedt, Journal of Plankton Research 20 (5) (1998) 805–816.[12] W.T. Lo, I.L. Chen, Estuarine, Coastal and Shelf Science 76 (2008) 227–238.[13] M. Akiko, B. Takayuki, D. Naoshi, Y. Masahiro, W. Hiroo, U. Kiminori, Journal of
Natural Products 70 (2007) 1089–1092.[14] Y.H. Peggy Hsieh, J. Rudloe, Trends in Food Science & Technology 5 (1994)
225–229.[15] I.O. Kim, H.C. An, J.K. Shin, B.J. Cha, Journal of Korean Society Fish Technology 44
(2) (2008) 99–111.[16] F.Y. Chang, C.Y. Lin, International Journal of Hydrogen Energy 29 (2004) 33–39.[17] S. Van Ginkel, S. Sung, J.J. Lay, Environmental Science & Technology 35 (24) (2001)
4726–4730.[18] B.E. Logan, S.E. Oh, I.S. Kim, S.V. Ginkel, Environmental Science & Technology 36
(11) (2002) 2530–2535.[19] A. Cohen, B. Distel, A. van Deursen, J.G. van Andel, Journal of Microbiology 51
(1985) 179–192.[20] H.K. Han, H.S. Shin, Journal of the Air & Waste Management Association 54 (2004)
242–249.[21] Y.P. Guo, S.H. Kim, S.H. Sung, P.H. Lee, International Journal of Hydrogen Energy 35
(2010) 3450–3455.[22] J.J. Lay, K.S. Fan, J.K. Chang, International Journal of Hydrogen Energy 28 (2003)
1361–1367.[23] S.E. Oh, S.V. Ginkel, B.E. Logan, Environmental Science & Technology 37 (2003)
5186–5190.[24] E. Elsayed, H. Hisham, N. George, International Journal of Hydrogen Energy (2011)
1–5.[25] J.I. Park, J.W. Lee, S.J. Sim, J.H. Lee, Biotechnology and Engineering 14 (2009)
307–315.[26] W.F. Owen, D.C. Stuckey, J.B. Healy, L.Y. Young, P.L. McCarty, Water Research 13
(1979) 485–492.[27] J.H. Lee, D.G. Lee, J.l Park, J.Y. Kim, Korean Journal of Chemical Engineering 27 (1)
(2010) 187–192.[28] B. Xiao, J.J. Liu, Hazardous Materials 168 (2009) 163–167.
