Enrichment of hydrogenotrophic methanogens by means of gas recycle and its application in biogas upgrading

Yun, Yeo-Myeong,Sung, Shihwu,Kang, Seoktae,Kim, Mi-Sun,Kim, Dong-Hoon Elsevier 2017 ENERGY Vol.135 No.-

<P><B>Abstract</B></P> <P>Biomethanation by hydrogenotrophic methanogens has been proven as a potential process for managing renewable power intermittency and upgrading biogas. The present work aimed to enrich hydrogenotrophic methanogens under different mixing conditions (gas recycle <I>vs.</I> mechanical mixing) and temperatures (mesophilic <I>vs.</I> thermophilic conditions) for biogas upgrading. The synthetic gas (H<SUB>2</SUB>:CO<SUB>2</SUB> = 4:1) was fed to the reactor bottom at a hydrogen injection rate (HIR) of 1.6 L H<SUB>2</SUB> L<SUP>−1</SUP> d<SUP>−1</SUP>. The gas recycle (100 L L<SUP>−1</SUP> d<SUP>−1</SUP>) under thermophilic condition was found to be the most effective, reaching over 96% H<SUB>2</SUB> conversion to CH<SUB>4</SUB> within 15 d of operation. Archaea community analysis performed by 454 pyrosequencing showed that the sequence of <I>Methanosaeta</I> sp. decreased while obligate-hydrogenotrophic methanogens increased: <I>Methanoculleus chikugoensis</I> (19.5%) and <I>Methanothermococcus thermolithotrophicus</I> (28.1%) under mesophilic and thermophilic condition, respectively. To the thermophilic enriched culture, the biogas produced from an up-flow anaerobic sludge blanket reactor with additional hydrogen (four times of CO<SUB>2</SUB>) was fed at various HIRs for 200 d. As HIR increased, H<SUB>2</SUB> consumption rate also increased with CO<SUB>2</SUB> removal contained in the biogas. Up to an HIR increase to 19.2 L H<SUB>2</SUB> L<SUP>−1</SUP> d<SUP>−1</SUP>, the high calorific biomethane (96% of CH<SUB>4</SUB>) could be obtained at gas recycle rate of 200 L L<SUP>−1</SUP> d<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biomethanation by hydrogenotrophs for upgrading biogas by applying gas recycle. </LI> <LI> Highest performance achieved by applying gas recycle under thermophilic condition. </LI> <LI> A gradual increase in obligate-hydrogenotrophic methanogens after enrichment. </LI> <LI> Almost complete conversion of H<SUB>2</SUB> to CH<SUB>4</SUB> at 19.2 L H<SUB>2</SUB> L<SUP>−1</SUP> d<SUP>−1</SUP>. </LI> <LI> Achievement of high calorific biomethane (96% CH<SUB>4</SUB>) during long term operation. </LI> </UL> </P>

Increased biodegradability of low-grade coal wastewater in anaerobic membrane bioreactor by adding yeast wastes

Yun, Yeo-Myeong,Kim, Myungchan,Kim, Hyojeon,Kim, Dong-Hoon,Kwon, Eilhann E.,Kang, Seoktae Elsevier 2019 Journal of environmental management Vol.234 No.-

<P><B>Abstract</B></P> <P>Demineralization is required in upgrading low-grade coal to serve as an alternative energy resource for the production of fuel and valuable chemicals but generates a large amount of low-grade coal wastewater (LCWW). The objective of this study was to investigate the effects of a co-substrate on an anaerobic membrane bioreactor (AnMBR) treating LCWW. CH<SUB>4</SUB> was not produced during the operation fed by LCWW alone. When yeast wastes (YW) were supplemented, there was a gradual increase in the biodegradability of LCWW, achieving 182 CH<SUB>4</SUB> mL/g COD with 58% COD removal efficiency. The analysis of physicochemical characteristics in the effluent of AnMBR, done by excitation-emission matrix (EEM) and size exclusion chromatography (SEC), showed that the proportion of soluble microbial products (SMPs) and aromatic group with high-molecular weight (>1 kDa) increased. Microbial analysis revealed that the increased dominance of bacteria <I>Comamonas</I>, <I>Methanococcus,</I> and <I>Methanosarcina</I> facilitated biodegradation of LCWW in the presence of YW.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Enhanced biodegradation of low-grade coal wastewater by adding yeast extract. </LI> <LI> Increased soluble microbial products and aromatic groups with high molecular weight. </LI> <LI> Increased dominance of bacteria <I>Comamonas</I>, <I>Methanococcus,</I> and <I>Methanosarcina</I>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electrodialytic separation of volatile fatty acids from hydrogen fermented food wastes

Bak, Changhyeon,Yun, Yeo-Myeong,Kim, Jeong-Hoon,Kang, Seoktae Elsevier 2019 International journal of hydrogen energy Vol.44 No.6

<P><B>Abstract</B></P> <P>In this study, we investigated the electrodialysis (ED) process for the economic and efficient recovery of volatile fatty acids (VFAs) from the hydrogen fermentation broth of food wastes. Among tested operational variables, the volumetric ratio of the feed to the concentrate (V<SUB>F</SUB>:V<SUB>C</SUB>) was found to be the most critical for the fast and economic recovery of VFAs. Meanwhile, the increase in the applied voltage did not result any significant impact in the enhancement of VFA recovery due to the intrinsic resistance of anionic exchange membrane against to VFAs. The maximum VFAs purity of 96.2% was successfully achieved at the operational condition of V<SUB>F</SUB>:V<SUB>C</SUB> of 1:2 and 8 V with energy consumption of 0.395 kWh/kg-VFAs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrodialysis was feasible for recovery of VFAs. </LI> <LI> The maximum purity of 96.2% was achieved from food waste fermentates. </LI> <LI> The recovery of VFAs was impacted by applied voltages and volume of the concentrate. </LI> </UL> </P>

Statistical optimization of chemical cleaning conditions of reverse osmosis membrane process in forward osmosis testing set-up

Fagkaew, Pattarasiri,Yun, Yeo-Myeong,Kim, Hyojeon,Kang, Seoktae Balaban Publishers 2018 Desalination and Water Treatment Vol.103 No.-

Usability Tests with a Virtual Arthroscopic Surgery Simulator

Hyukjin Kwon,Einjeong Hwang,Seoktae Yun,Myeungcheol Shin,Jaegyun Lim 대한전자공학회 2020 IEIE Transactions on Smart Processing & Computing Vol.9 No.1

Arthroscopic surgery is one of the most difficult surgeries, so even if an orthopedic resident trains a lot, it is difficult to perform surgery well. In addition, a resident does not have many opportunities to perform surgery before becoming a licensed orthopedist. In order to help train residents, we created a virtual arthroscopic surgery simulator. Our goal is to improve the residents’ surgical proficiency in repairing rotator cuff tears and Bankart lesions. We carried out nine usability tests with an orthopedist, and are improving the simulator based on the results.

Changes in microbial community associated with dechlorination of leftover chloroform in two-stage anaerobic Co-fermentation (H₂+CH₄) of lipid-extracted microalgae waste with food waste leachate

Kim, Dong-Hoon,Kang, Seoktae,Yun, Yeo-Myeong Elsevier 2019 International journal of hydrogen energy Vol.44 No.4

<P><B>Abstract</B></P> <P>In our previous research, two-stage anaerobic co-fermentation (TSAC) treating lipid-extracted microalgae waste (LEMW) mixed with food waste leachate (FWL) was successfully designed to recover the additional energy (H<SUB>2</SUB> and CH<SUB>4</SUB>) while mitigating the inhibition of leftover chloroform (CF). This study aimed to elucidate the change in the microbial community and their association with the CF degradation in the TSAC. 90% of CF was dechlorinated in the acidogenic reactor of TSAC when LEMW was fed with FWL at a ratio of 40:60. The results of microbial analysis clearly showed that <I>Dehalobacter</I> (5.3%) played the role in dehalorespiration while <I>Clostridium</I> (8.9%) and <I>Enterobacter</I> (3.6%) promoted cometabolic dechlorination. In contrast, the microbial consortia were completely inhibited by CF when LEMW was fed without FWL. In the methanogenic reactor of TSAC, increased <I>Methanosarcina</I> (57.8%), <I>Methanobacterium</I> (10.4%), and <I>Methanosaeta</I> (8.6%) were observed. Those were involved in successful conversion of acetate and H<SUB>2</SUB> into CH<SUB>4</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Changes of microbial consortia associated with dechlorination of leftover CF. </LI> <LI> 90% of CF was dechlorinated in the acidogenic stage fed by LEWM: FWL (40:60). </LI> <LI> CF removal by <I>Dehalobacter</I>, <I>Clostridium</I>, and <I>Enterobacter</I> in the acidogenic stage. </LI> <LI> High abundance of <I>Methanosarcina</I> in the methanogenic stage. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

탄소나노튜브를 이용한 유기성 폐기물의 혐기성 소화에 대한 메탄 생성 속도 증대

양성민(Seongmin Yang),윤여명(Yeo-Myeong Yun),정구륜(Guryun Jung),강석태(Seoktae Kang) 유기성자원학회 2019 유기성자원학회 학술발표대회논문집 Vol.2019 No.춘계

혐기성 소화 공정은 폐기물들을 재사용하여 에너지원으로 사용할 수 있다는 점에서 널리 사용되고 있다. 하지만 반응조의 소화 속도가 느리다는 문제점을 가지고있으며 늘어나는 폐기물 양을 감당하기 위해 반응조를 확장하기 위한 추가 비용이요구되고 있다. 따라서 미생물의 소화 속도를 증가시켜 혐기성 소화조의 경제성을높이는 연구들이 활발히 진행되고 있다. 그 중 산 생성 미생물과 메탄생성 미생물상호간의 전자 전달 속도를 증가시킴으로써 공생관계를 향상시키는 DIET(Direct interspecies electron transfer) 기술은 공정의 변화가 아닌 미생물 사이에 전자 전달 속도를 증가시켜 소화 속도가 증가된다는 장점을 가지고 있어 많이 연구되고 있다. 그럼에도 불구하고 아직 혐기성 소화과정 각 단계에 미치는 영향에 관한 연구가 부족한 상태이기 때문에 본 연구에서는 전도성 물질인 탄소 나노튜브를 이용하여 혐기성 소화과정에 대한 영향성을 확인해 보고자 한다.…

전도성 물질 주입을 통한 혐기성소화 및 페놀 분해율 향상

김희진 ( Huijin Kim ),김효전 ( Hyojeon Kim ),강석태 ( Seoktae Kang ),윤여명 ( Yeo-myeong Yun ) 한국폐기물자원순환학회 2021 한국폐기물자원순환학회 추계학술발표논문집 Vol.2021 No.-

High-calorific bio-hydrogen production under self-generated high-pressure condition

Lee, Mo-Kwon,Sivagurunathan, Periyasamy,Yun, Yeo-Myeong,Kang, Seoktae,Na, Jeong-Geol,Kim, Dong-Hoon Elsevier 2018 Bioresource technology Vol.264 No.-

<P><B>Abstract</B></P> <P>For the use of biologically produced H<SUB>2</SUB>, removal of CO<SUB>2</SUB> is an indispensable process. Unlike conventional CO<SUB>2</SUB> removal methods, this study proposed a self-generated high-pressure dark fermentation (HPDF) process as a novel strategy for directly producing high-calorific bio-H<SUB>2</SUB>. The pressure was automatically increased by self-generated gas, while the maximum pressure inside fermenter was restricted to 1, 3, 5, 7, and 10 bar in a batch operation. As the pressure increased from 1 to 10 bar, the H<SUB>2</SUB> content increased from 55% to 80%, whereas the H<SUB>2</SUB> yield decreased from 1.5 to 0.9 mol H<SUB>2</SUB>/mol hexose<SUB>added</SUB>. The highest H<SUB>2</SUB> content of 80% was obtained at both of 7 and 10 bars. Increased lactate production with increased abundance of lactic acid bacteria was observed at high-pressure. Despite the lower H<SUB>2</SUB> yields at high-pressure conditions, HPDF was found to be economically beneficial for obtaining high-calorific bio-H<SUB>2</SUB> owing to the low CO<SUB>2</SUB> removal cost.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel approach for bio-H<SUB>2</SUB> upgrading under high-pressure dark fermentation. </LI> <LI> High H<SUB>2</SUB> content up to 80% was achieved at 7 and 10 bar. </LI> <LI> H<SUB>2</SUB> yield was decreased as pressure increased. </LI> <LI> Increased abundance of lactate producers but decreased abundance of <I>Clostridium</I> sp. </LI> <LI> The benefit for obtaining high-calorific bio-H<SUB>2</SUB> was increased by high-pressure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Growth of Wrinkle-Free Graphene on Texture-Controlled Platinum Films and Thermal-Assisted Transfer of Large-Scale Patterned Graphene

Choi, Jae-Kyung,Kwak, Jinsung,Park, Soon-Dong,Yun, Hyung Duk,Kim, Se-Yang,Jung, Minbok,Kim, Sung Youb,Park, Kibog,Kang, Seoktae,Kim, Sung-Dae,Park, Dong-Yeon,Lee, Dong-Su,Hong, Suk-Kyoung,Shin, Hyung- American Chemical Society 2015 ACS NANO Vol.9 No.1

<P>Growth of large-scale patterned, wrinkle-free graphene and the gentle transfer technique without further damage are most important requirements for the practical use of graphene. Here we report the growth of wrinkle-free, strictly uniform monolayer graphene films by chemical vapor deposition on a platinum (Pt) substrate with texture-controlled giant grains and the thermal-assisted transfer of large-scale patterned graphene onto arbitrary substrates. The designed Pt surfaces with limited numbers of grain boundaries and improved surface perfectness as well as small thermal expansion coefficient difference to graphene provide a venue for uniform growth of monolayer graphene with wrinkle-free characteristic. The thermal-assisted transfer technique allows the complete transfer of large-scale patterned graphene films onto arbitrary substrates without any ripples, tears, or folds. The transferred graphene shows high crystalline quality with an average carrier mobility of ∼5500 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP> at room temperature. Furthermore, this transfer technique shows a high tolerance to variations in types and morphologies of underlying substrates.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-1/nn5060909/production/images/medium/nn-2014-060909_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5060909'>ACS Electronic Supporting Info</A></P>