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Effect of the accuracy of pH control on hydrogen fermentation
Moon, Chungman,Jang, Sujin,Yun, Yeo-Myeong,Lee, Mo-Kwon,Kim, Dong-Hoon,Kang, Won-Seok,Kwak, Seung-Shin,Kim, Mi-Sun Elsevier 2015 Bioresource technology Vol.179 No.-
<P><B>Abstract</B></P> <P>pH, known as the most important parameter in H<SUB>2</SUB> fermentation, cannot be precisely controlled in a scaled-up fermenter as in a lab fermenter. In the preset work, to assess the effect of pH control accuracy on H<SUB>2</SUB> fermentation, the pH was controlled at 6.0±0.1, 6.0±0.3, 6.0±0.5, 6.0±0.7, and 6.0±0.9 during batch fermentation of food waste. Up to deviation of ±0.3, a high H<SUB>2</SUB> yield of 1.67–1.73molH<SUB>2</SUB>/mol hexose<SUB>added</SUB> was attained with producing butyrate as a major metabolite (>70% of total organic acids produced). A huge drop of H<SUB>2</SUB> production, however, was observed at deviation >±0.5 with lowered substrate utilization and increased production of lactate. Next generation sequencing results showed that <I>Clostridium</I> was found to be the dominant genus (76.4% of total number of sequences) at deviation of ±0.1, whereas the dominant genus was changed to lactic acid bacteria such as <I>Streptococcus</I> and <I>Lactobacillus</I> with increase of deviation value.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A significant effect of pH control accuracy on H<SUB>2</SUB> fermentation performance. </LI> <LI> High H<SUB>2</SUB> yield and substrate utilization at deviation of ±0.1 and ±0.3. </LI> <LI> Low H<SUB>2</SUB> production with lowered substrate utilization at deviation >±0.5. </LI> <LI> Lactic acid bacteria became dominant with increase of deviation value. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
문충만(Chungman Moon),이은재(Eun-Jae Lee ),이재근(Jaekune Lee ) 유기성자원학회 2019 유기성자원학회 학술발표대회논문집 Vol.2019 No.춘계
가축분뇨는 오폐수 발생량에 비하면 적은 수준이지만 유기물, 질소/인과 같은 영양염류 함량이 높아 배출유량에 비해 높은 오염부하량을 가지고 있으며 공공수역 수질악화에 영향을 미치기 때문에 지자체에서는 관리 방안이 반드시 필요한 배출원중의 하나이다. 본 연구에서는 대전광역시의 가축분뇨 발생 현황 및 처리 현황에대해서 파악하고 지자체의 효율적인 관리 방안을 제시하는 것이 목적이다. 대전광역시에서는 총 351호의 농가에서 92,780두의 가축을 사육하고 있는데, 이 중 소나말을 사육하는 농가는 204호에서 총 4,309두이며 닭을 사육하는 농가는 총 102호로 총 83,425두를 사육하고 있다. 대전광역시의 축종별 가축분뇨 발생량은 총80,115L/d이며 이 중 소나 말이 59,033 L/d로 전체의 약 73.7%를 차지하고 있으며두수가 가장 많은 닭은 8,760 L/일로 약 10.9%를 차지하고 있다. 또한 발생되는가축분뇨의 대부분은 퇴비화로 처리(79,241 L/d)로 처리되고 있으며 퇴비화 이외에처리는 현재 파악되고 있지 않은 실정이다. 현재 대전광역시 내에 분포하는 농지에 필요한 질소, 인산, 칼륨의 요구량은 각각 4,405,137 kg/y, 430,465 kg/y, 552,660 kg/y으로 대전시에서 발생하는 가축분뇨를 100% 비료 화하였을 때 생성되는 질소, 인산, 칼륨의 양은 각각 163,506 kg/y, 196,184 kg/y, 120,093 kg/y으로 가축분뇨를 비료화 하였을 때 대전시에서 100% 수용 가능하므로 대전광역시에서는 가축분뇨를 비료화 하여 농지살포를 우선 고려한 정책을 추진하고 있다. 다만 현재 예측되지 않는 가축분뇨의 급증 또는 지역적 여건변화를 만족하기 위해 공공처리시설의 설치가 요구될 경우, 지자체 차원에서 그에 따른 계획과 필요한 재원을 마련할 필요가 있으나 대전시의 가축분뇨 발생은 넓은 지역에서 소량 발생하기 때문에가축분뇨 운송에 대한 문제가 발생하기 때문에 공공처리시설 설치는 현실적으로어렵다. 현재 자체 정화처리시설은 시설관리 및 유지 등의 기술적인 어려움이 있어 운영이 거의 되고 있지 않지만 앞으로 자체 정화처리시설의 확대를 위해 제도적 또는 기술적으로 지원할 수 있는 방안 마련이 필요하다.
Continuous performance of hydrogenotrophic methanogenic mixed cultures: Kinetic and SMP analysis
Kim, Mi-Sun,Moon, Chungman,Kang, Seoktae,Kim, Dong-Hoon Elsevier 2017 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.42 No.45
<P><B>Abstract</B></P> <P>To investigate the characteristics of hydrogenotrophic methanogenic (HM, 4H<SUB>2</SUB> + CO<SUB>2</SUB> → CH<SUB>4</SUB> + 2H<SUB>2</SUB>O) mixed cultures, continuous stirred-tank reactors (CSTRs) were operated at various H<SUB>2</SUB> loading rates (HLR, 2.8–14.0 m<SUP>3</SUP> H<SUB>2</SUB>/m<SUP>3</SUP>/d) and hydraulic retention times (HRTs, 5–30 d). The feeding gas was composed of H<SUB>2</SUB>/CO<SUB>2</SUB> (80:20 on volume basis), and HRT was controlled by the continuous pumping of a nutrient medium. At a fixed HLR of 4 kg COD/m<SUP>3</SUP>/d (1 kg COD = 1.4 m<SUP>3</SUP> H<SUB>2</SUB>), complete H<SUB>2</SUB> conversion to CH<SUB>4</SUB> (> 98% on a COD basis) was observed up to the HRT decrease to 6 d. However, at HRT 5 d, the H<SUB>2</SUB> conversion gradually decreased, reaching 30% within 30 d, and the H<SUB>2</SUB> content in the head space increased to 70%, which triggered the production of acetate with an increased concentration to 3 g COD/L. When the HLR was increased at a fixed HRT of 10 d, the maximum CH<SUB>4</SUB> production rate of 2.75 m<SUP>3</SUP> CH<SUB>4</SUB>/m<SUP>3</SUP>/d was achieved at 8 kg COD/m<SUP>3</SUP>/d. A kinetic analysis conducted using the Monod equation showed that HM cultures had a maximum specific growth rate of 0.18 d<SUP>−1</SUP> and a half-saturation coefficient of 1.73 g COD/L. Though, successful hydrogenotrophic CH<SUB>4</SUB> conversion was achieved, the broth contained soluble microbial products (SMPs) at a concentration of 80–250 mg/L, which exceeded the effluent regulation standard. Most of the organic matters in SMPs consisted of humic-like and fulvic-like organic matters with a low molecular weight (<1 kDa).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Investigate the characteristics of hydrogenotrophic methanogens. </LI> <LI> CSTR operation at various H<SUB>2</SUB> loading rates and HRTs. </LI> <LI> Complete H<SUB>2</SUB> conversion to CH<SUB>4</SUB> up to the HRT decrease to 6 d. </LI> <LI> Maximum CH<SUB>4</SUB> production rate of 2.75 m<SUP>3</SUP> CH<SUB>4</SUB>/m<SUP>3</SUP>/d at 8 kg COD/m<SUP>3</SUP>/d. </LI> <LI> Maximum specific growth rate = 0.18 d<SUP>−1</SUP>, half-saturation coefficient = 1.73 g COD/L. </LI> </UL> </P>
Elucidating acetogenic H<sub>2</sub> consumption in dark fermentation using flux balance analysis
Lalman, Jerald A.,Chaganti, Subba Rao,Moon, Chungman,Kim, Dong-Hoon Elsevier 2013 Bioresource technology Vol.146 No.-
<P><B>Abstract</B></P> <P>In this study, a flux balance analysis (FBA) was adopted to estimate the activity of acetogenic H<SUB>2</SUB>-consuming reaction. Experimental data at different substrate concentrations of 10, 20, and 30g COD/L showing the lowest, medium, and highest H<SUB>2</SUB> yields, respectively, were used in the FBA to calculate the fluxes. It was interesting to note that the hydrogenase activity based on R12 (2Fd<SUP>+</SUP> +2H<SUP>+</SUP> →2Fd<SUP>2+</SUP> +H<SUB>2</SUB>, ferredoxin (Fd)) flux was most active at 10g COD/L. The flux of R17 (4H<SUB>2</SUB> +2CO<SUB>2</SUB> →CH<SUB>3</SUB>COOH), a mechanism for reutilizing produced H<SUB>2</SUB>, increased in steps of 0.030, 0.119, and 0.467 as the substrate concentration decreased. Contradictory to our general understanding, acetate production found to have a negligible or even negative effect on the final H<SUB>2</SUB> yield in dark fermentation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Revealing the acetogenic H<SUB>2</SUB>-consuming reaction using FBA in dark fermentation. </LI> <LI> Reutilization of produced H<SUB>2</SUB> by acetogenic H<SUB>2</SUB>-consuming reaction was crucial. </LI> <LI> Acetate production has a negligible or even negative effect on the final H<SUB>2</SUB> yield. </LI> </UL> </P>