Biogas production from moon jellyfish (Aurelia aurita) using of the anaerobic digestion

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    Journal of Industrial and Engineering Chemistry 18 (2012) 21472150

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    Journal of Industrial and

    jou r n al h o mep ag e: w ww .e1. 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 benets. Althoughbiogas can be efciently produced at the laboratory level, biogashas not yet been produced commercially from biomass productionfacilities [5,6].

    Several types of biomass can be gasied, including waste, woodchips, straw, wood and more. In addition, renewable energygeneration and new and forthcoming environmental legislationhas gradually increased interest in anaerobic digestion technology.

    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 jellysh, can be degraded biologically. Sourcesof jellysh 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 jellysh.

    The adult A. aurita body diameter ranges from 20 to 40 cm[11,12]. The removal of jellysh has now become necessary in gulfareas, ports, industrial facilities, and power plants along the coasts.The yearly economic loss due to jellysh ranges from $1521 to3048 hundred million in Korea [13,14]. Because of the largeamounts of removed jellysh, jellysh waste holds great promiseas a new source of biomass in Korea. However, jellysh is currentlydiscarded using a separator system (JSS) in the sea area of Korea[15]. Despite this potential source of biomass, the potential of usingjellysh 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 [1623], 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

    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.

    * 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: jhlee@silla.ac.kr (J.-H. Lee).

    1226-086X/$ see front matter 2012 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.http://dx.doi.org/10.1016/j.jiec.2012.06.010Biogas production from moon jellysh anaerobic digestion

    Ji-Youn Kim, Sung-Mok Lee, Jae-Hwa Lee *

    Department of Bioscience and Biotechnology, Silla University, Busan 617-736, Republic

    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

    Jellysh (Aurelia aurita)

    Anaerobic digestion

    A B S T R A C T

    Jellysh are a major probl

    from the sea using a separa

    was to produce bio-gas fr

    conducted to examine th

    hydrogen and methane g

    renewable energy. The effe

    gas production in batch ex

    to be freeze treatment at from sludge that was heat urelia aurita) using of the

    orea

    to swimmers and a plague to shermen. Presently, jellysh are removed

    system and the jellysh waste is discarded. Thus, the objective of this work

    Aurelia aurita using anaerobic digestion. Batch anaerobic studies were

    fect of pre-treating waste jellysh and using the waste for anaerobic

    roduction. Using this approach, jellysh waste could be changed into

    of sludge heat, sonication and freeze treatment on hydrogen and methane

    iments were evaluated. The optimal treatment condition was determined

    8C for 20 min. The total amounts of hydrogen and methane gas producedted for 20 min at 65 8C were 270 and 1640 mL/L, respectively. In addition,

    Engineering Chemistry

    l sev ier . co m / loc ate / j iec

  • 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 0100%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 jellysh

    In a previous study, the optimal conditions for culturingjellysh were established and the jellysh concentration, methodof treatment, and pH were selected based on these conditions. Toexamine the effects of fermenting jellysh (A. aurita) on hydrogenand methane gas production, the seed sludge was cultured in batchexperiments using a 300 mL ask at 35 8C under anaerobic

    J.-Y. Kim et al. / Journal of Industrial and Engineering Chemistry 18 (2012) 2147215021482/3 methane (CH4), 1/3 carbon dioxide (CO2), a little hydrogensulde (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) at70 8C. A. aurita were harvested from the southern sea in Koreaand washed with fresh water to remove salt. Washed seaweedsamples were nely 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 jellysh (A. aurita) in regards to bio-gasproduction efciency 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 ask and 5 L fermentor

    Bio-gas production experiments were carried out in a 300 mLask or 5 L fermentor (KF 51, KoBiotech, Incheon, Korea). Theworking volume of the 300 mL ask was 100 mL. These asks wereused to test the effects of substrate concentration, initial pH andsludge pretreatment on bio-gas production. Each ask was lledwith cooled jellysh (A. aurita) samples (3 g), inoculums (1 mL)and deionized water (96 mL). The asks were wrapped inaluminum foil to eliminate substrate photolysis, and nitrogengas was ushed 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 askwas 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 ask 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).conditions. The jellysh 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 jellysh (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 ofjellysh 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. 1. Effect of substrate concentration on hydrogen and methane gas yield. Thejellysh were cultured without pH control and the seed sludge were cultured in

    batch experiments using 300 mL ask mixed at 150 rpm and 35 8C under anaerobicconditions. The concentration of the seed sludge was 1%. The total amounts of

    evolved hydrogen and methane gas are shown. Values shown are averages of ask

    run in duplicate.

  • 3.4. Effect of secondary pH control with productivity of biogas

    Hydrogen and methane gas production from 3 g of substrate

    Fig. 3. Hydrogen and methane gas production in a 300 mL ask. The medium wasmaintained 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 atpH 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 ask run induplicate.

    J.-Y. Kim et al. / Journal of Industrial and Engineering Chemistry 18 (2012) 21472150 2149total amount of hydrogen production remained relatively highover 1020 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 jellysh, 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

    Fig. 2. The effect of sludge heat, sonicate and freeze treatment on hydrogen andmethane 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 minat 70 8C. Values shown are averages of ask run in duplicate.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 jellysh (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 signicant decrease in the amount ofhydrogen and methane gas produced between pH 3.03.5 and pH9.510.0. 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.was 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 3.84.0 (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, w...

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