Scholarly article on topic 'Biological Purification System: Integrated Biogas from Small Anaerobic Digestion and Natural Microalgae'

Biological Purification System: Integrated Biogas from Small Anaerobic Digestion and Natural Microalgae Academic research paper on "Agriculture, forestry, and fisheries"

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{"Biological purification" / bio-methane / bio-refinery / "CO2 levels" / microalgae.}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Salafudin, Roy Hendroko Setyobudi, Satriyo Krido Wahono, Anggi Nindita, Praptiningsih G. Adinurani, et al.

Abstract Photosynthetic pigments, including chlorophyll, have an important role since they provide the oxygen and the source of energy for all living things. Plant and algae growth is affected by the photosynthesis speed which depends on the availability of carbon dioxide (CO2). This paper reports on the pilot plant scale study of the impact of 20% to 50% CO2 on biogas into the growing medium of microalgae which obtained bio-methane purification results as gaseous bio-fuels. Research material was produced from the Jatropha curcas Linn. husk biogas digester and a 0.15 m3 HDPE drum was used as a purification. The purification tank was filled with Catfish (Clarias gariepinus) farm water which grew “wild” microalgae naturally. The water was fed from the top with continuous flow of (16 to 31) L· min–1 and the biogas was fed from the bottom at (18 to 29) L · min–1. CO2 level data of biogas was measured by orsat apparatus and processed with t test. The results achieved average efficiency reduction levels of CO2 on 50% in two cycles (24% in the first and 26% in the second).

Academic research paper on topic "Biological Purification System: Integrated Biogas from Small Anaerobic Digestion and Natural Microalgae"

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Procedia Chemistry 14 (2015) 387 - 393

2nd Humboldt Kolleg in conjunction with International Conference on Natural Sciences,

HK-ICONS 2014

Biological Purification System : Integrated Biogas from Small Anaerobic Digestion and Natural Microalgae

Salafudina, Roy Hendroko Setyobudib,c*, Satriyo Krido Wahonode, Anggi Ninditaf, Praptiningsih G. Adinuranig, Yogo Adhi Nugrohoh, Andi Sasmitoh, Tony Liwangh

aDepartement of Chemical Engineering, ITENAS Jl. PHH Mustafa No.23, Bandung 40123, Indonesia bMa Chung Research Center for Photosynthetic Pigments, Villa Puncak Tidar N-01 Malang 65151, East Java, Indonesia cIndonesian Association of Bioenergy Scientist and Technologist. BPPT Building II, 22nd floor Jl. MH. Thamrin No. 8 Jakarta 10340 dIndonesian Institute of Sciences. Jl. Jogja - Wonosari Km. 31,5 Desa Gading, Kec. Playen, Kab. Gunungkidul 55861, Indonesia eMawson Institute and School of Engineering, University of South Australia, Mawson Lakes SA 5095, Adelaide, Australia fDepartment of Agronomy and Horticulture, Bogor Agricultural University, Jl. Meranti, Kampus IPB Darmaga, Bogor 16680, Indonesia gFaculty of Agrotechnology,University of Merdeka, Jl. Serayu, PO. Box 12, Madiun 63131, Indonesia hPT Sinar Mas Agroresources and Technology Tbk. Sinar Mas Land Plaza, 2nd Tower, Jl. Thamrin, Jakarta 10350, Indonesia

Abstract

Photosynthetic pigments, including chlorophyll, have an important role since they provide the oxygen and the source of energy for all living things. Plant and algae growth is affected by the photosynthesis speed which depends on the availability of carbon dioxide (CO2). This paper reports on the pilot plant scale study of the impact of 20 % to 50 % CO2 on biogas into the growing medium of microalgae which obtained bio-methane purification results as gaseous bio-fuels. Research material was produced from the Jatropha curcas Linn. husk biogas digester and a 0.15 m3 HDPE drum was used as a purification. The purification tank was filled with Catfish (Clarias gariepinus) farm water which grew "wild" microalgae naturally. The water was fed from the top with continuous flow of (16 to 31) L- min-1 and the biogas was fed from the bottom at (18 to 29) L • min-1. CO2 level data of biogas was measured by orsat apparatus and processed with t test. The results achieved average efficiency reduction levels of CO2 on 50 % in two cycles (24 % in the first and 26 % in the second).

© 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the Scientific Committee of HK-ICONS 2014 Keywords: Biological purification; bio-methane; bio-refinery; CO2 levels; microalgae.

* Corresponding author. Tel.: +062 8159 555 028 E-mail address: roy_hendroko@hotmail.com

1876-6196 © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the Scientific Committee of HK-ICONS 2014 doi: 10.1016/j.proche.2015.03.069

Nomenclature

LPG liquefied petroleum gas IDR Indonesian Rupiah

JcL Jatropha curcas Linn. trillion 1012, Tera (T)

HDPE high-density polyethylene

1. Introduction

Kompas Daily, February 28, 2013 reported that since 2006 Pertamina suffered a loss of IDR 16 trillion as a result of 12 kg LPG selling under economic price1. Based on 2012 financial report audit, the Pertamina business of 12 kg LPG recorded losses of IDR 5 trillion2. Kerosene conversion has made Indonesia dependent on the import of LPG about 60.6 %3. Dependence on imports is harmful in energy security because of the LPG availability in the world is not big, it is only produced from approximately 8 % from natural gas and 8 % from petroleum refineries4. Related to the limited availability, Aep Saepudin, an Indonesian Institute of Sciences expert suggested to use biogas as LPG substitution4. The consideration for this case are: biogas is categorized as modern cooking oil5; efficient biomass conversion processes6,7; minimizing global warming and not competing do with food crops8,9; Indonesia is rich in biomass as feedstock biogas and gaseous biofuels usage is relatively broad10; relatively simple technology, household appliances can be made in Indonesia, and the tropical climate in Indonesia supports the anaerobic process with low cost11; minimizing the contamination of ground water12, producing fertilizer with rich organic nutrients13,14 and repairing material of soil fertility.

On the other hand, biogas has weaknesses, among them is biogas heat generating effectiveness (2 830 kcal) is lower than LPG (6 530 kcal)15. Biogas effective heat can be increased by removing some impurities, mainly CO2 which in biogas composition level constitutes 20 % to 50 %16,17, by performing purification (upgrading, enrichment, scrubbing, stripping, capture, cleaning-up). There are a number of purification methods that have been applied in some countries, namely: absorption of liquids into the physics/chemical; adsorption on the surface of a solid adsorbent; membranes separation; cryogenic separation; and chemical change18. However, these technologies are only efficient for large-scale biogas (industrial)7. Reference19 shows that the cost to purify biomethane for household scale is three times higher biomethane for than biogas production cost.

Biological purification technology is worth examining because it has double impact. Microalgae, Scenedesmus sp., in laboratory experiments using biogas slurry as growing medium and biogas are given periodically generating 21 % of CO2 compared with 24 % of control20. Arthrospira sp., Chololera vulgaris SAG 211 -11b, Chlorella sp. MM-2, Chlorella sp. MB-9, Chlorella vulgaris ARC 1, Chlamydomonas sp. and Scenedesmus sp. were reported as a positive synergy with biogas21-27. Gemstone Team, the University of Maryland studies on the efficiency of biogas purification with microalgae, Chlorococcum littorale and Phaeodactylum tricornutum28. However, previous studies20-27 used pure cultures of microalgae even mutant which might not be applied to small-scale digester households, especially in rural areas of Indonesia.

Biological purification applied biorefinery concept29, namely the integration of microalgae and biogas. Growth of microalgae needs water, air, nutrients, and CO2 for photosynthesis process. CO2 is the limiting factor in the cultivation of algae because the level of CO2 in the air is approximately 0.0300 % to 0.0387 %30-34. Reference32 showed that partial CO2 pressure in the air is not sufficient (0.032 kPa) to achieve high growth rates, since the optimal value is 0.1 kPa. CO2 is the dominant nutrient in algae growth. Stoichiometrically the CO2 demand in algae varies between 1.65 up to 2 CO2 kg-1 dry biomass32. Reference29 showed that 1 kg of micro-algae requires about 1.8 kg to 2 kg CO2. This data was supported by some research33-35, 1 t algae biomass production requires about 1.8 t CO2. Biogas contains CO2 levels of 20 % to 50 %, as well as biogas digesters which produce nutrient-rich slurry. The integration was expected to have positive synergy that spurs the growth of microalgae as an available alternative of other biofuel feedstocks as well as purification of biogas into biomethane at low cost.

2. Material and methods

2.1. Materials

The preliminary study was conducted at the research garden of PT Bumimas Ekapersada, Bekasi, West Java, from July to October 2012. The biogas was produced from the two-phase digester used capsule husk Jatropha curcas Linn. (JcL) as feedstock11,36. The Catfishes (Clarias gariepinus) were maintained in the pond with an area of 2 m x 1.5 m x 1 m. The pond was filled with 50 % river water and 50 % biogas digester slurry outlet. The Catfishes were fed with a mix of JcL seed cake which has been detoxified37,38 in the synergy of food and energy systems. Algae grow naturally / wildly in the catfish ponds and Algae identification was performed in Microalgae Laboratory of Surfactant Bioenergy Research Centre (SBRC), Bogor Agricultural University, IPB-Bogor, West Java.

2.2 Instrumentation

HDPE drum was used as a purification tank with working volume of 0.15 m3. Schema and diagram of purification tank are shown in Figure 1 and Figure 2. CO2 levels were measured by biogas orsat apparatus, in accordance with standard two holder procedures. Biogas was accommodated in a HDPE plastic holder of 2 m3 capacity. The biogas was transferred to bottom of purification tank and released from the top of purification tank. An electric pump of 50 L ■ min-1 capacity was used for catfish pond water recirculation.

Purified Gas Outlet

Top View

Fig. 1. Schema of purification tank.

Purification Tank

Gas Flow meter

Fig. 2. Diagram of purification tank.

2.3 Procedure

In the first step, the CO2 levels of the biogas sample in the A holder were measured. The biogas from the A holder with 2 m3 of capacity was pressed continuously by ballast for entry into the bottom of purification tank. Purification tank was filled with 0.15 m3 water from the catfish pond which was overgrown with algae. Catfish pond water was pumped continuously into the purification tank from the top and exited through the hole in the bottom to get back into the pond. The Pump capacity was set equal to the biogas discharge income. Biogas bubbles from the bottom of the tank will be contacted with water pond overgrown with algae and further out of the hole in the top into the B holder head with 2 m3 capacity. The CO2 levels in the B holder were measured by orsat apparatus. This procedure was referred to The First Cycle. The Second Cycle procedure performed the same as the first cycle, namely biogas in the B holder was pressed into purification tank and was accepted by the A holder. CO2 levels in the second cycle in the A holder were measured by orsat apparatus. The research was conducted six times at intervals of two days. T test was performed to analyze the first cycle and the second cycle. CO2 capture efficiency (%) was calculated with the following Equation 122 :

Influent of CO2 - Effluent of CO2 x 100% (1)

Influent of CO2

3. Results and discussion

Identification of catfish pond water showed that overgrown microalgae in the pond such as Scenedesmus sp., Nitzchia sp., Tetraspora sp., and Selenastrum sp. showed the number of (178 to 315) cells ■ mL-1. Biogas flow measurement showed the number of (18 to 29) L ■ min-1 and discharge measurements showed the number of pond water recirculation of (16 to 31) L ■ min-1. Measurement of CO2 capture efficiency (%) according to the Equation 1 is shown in Figure 3. Figure 3 shows that the "natural /wild algae" was able to reduce the levels of CO2 in the biogas with the 1st treatment cycle number of 24 %, the 2nd treatment cycle number of 26 %, so with two times circulation of CO2 reduction of 50 % was gained then there was no significant difference on the result of the t test administered to the first cycle and then to the second cycle was gained CO2 reduction of 50 %. T test on the 1st cycle than 2nd cycle was no real different. It can be concluded that biogas entry can be offset by the discharge pool water recirculation (algae).

Fig. 3. The average CO2 capture efficiency (%) in the1st cycle, 2n cycle, and total cycle.

The percent efficiency rate of 50 % as the number of performance "natural /wild algae" is lower than the previous study21 which is mutant strain of microalga Chlorella sp. MM-2 was reportedable to approximate 70 % on cloudy days and 80 % on sunny days. Similarly, it is lower than Chlorella vulgaris, SAG211-11b which was reported to be able to reduce the amount of 97.07 % CO226. However, 50 % percent efficiency in this preliminary study was higher than the performance of micro algae Arthrospira sp.which was reported be able to reduce the levels of CO2 by 2.5 % to 11.5 %22.This study is ongoing, particularly improving purification tank, for improving CO2 capture efficiency that will impact directly on elevated levels of methane. The benefit of this improvement is time reduction of biogas stove in the kitchen as shown in previous studies39,40. Similarly, observation of H2S reduction levels being made to minimize corrosion, which in previous studies it was reported that micro algae Arthrospira sp. and Chlorella vulgaris, SAG211-11b produce24,26.

4. Conclusion

This preliminary study concludes that "natural / wild algae" growing in catfish ponds can be used as a biological purification of biogas. 1st treatment cycle was able to reduce the levels of CO2 in the biogas in the amount of 24 %, in the 2nd treatment cycle the number is 26 %, so with the circulation conducted twice, CO2 reduction of 50 % was gained. In view of the results of this study, integration technology of catfish ponds and biogas digesters in rural areas can be recommended to get energy and sustainable food.

Acknowledgements

The authors would like to thank PT Sinar Mas Agro Resources and Technology (PT SMART Tbk.) Jakarta, Indonesia for supporting this study. Special thanks to the research technicians, Ata Atmaja WKD, Acam Are Hikman and Dewi Tiara Sagita for their daily measurement contribution.

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