Energy production from different organic wastes by anaerobic co-digestion: Maximizing methane yield versus maximizing synergistic effect

Kim, Jinsu,Baek, Gahyun,Kim, Jaai,Lee, Changsoo Elsevier 2019 RENEWABLE ENERGY Vol.136 No.-

<P><B>Abstract</B></P> <P>The anaerobic co-digestion of spent coffee grounds (SCG) and <I>Ulva</I> biomass, which are problematic wastes and unsuitable for mono-digestion, with food waste (FW) was investigated to widen the scope of feedstocks for biogas production. The effect of the feedstock mixing ratio on the methane yield and synergistic effect of co-digestion was analyzed by response surface analysis. The models for the methane yield and synergistic effect indicated different response patterns and predicted the maximum responses at different mixing ratios. As maximizing the conversion of individual feedstocks to methane is the primary focus in this study, the mixing ratio required for maximizing the synergy index is perceived to be more desirable than that for maximizing methane yield of the mixture. The experimental and modeling results demonstrated that FW, SCG, and <I>Ulva</I> biomass can be effectively co-digested with little antagonistic effect, regardless of their mixing ratio, and a synergistic effect in most cases. It is expected that co-digestion could be flexibly applied when managing the waste feedstocks to enhance their energy recovery potential. The findings of this study can help promote the valorization of underused waste feedstocks through co-digestion and increase the deployment of renewable energy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Anaerobic co-digestion of FW, SCG, and <I>Ulva</I> at different mixing ratios was studied. </LI> <LI> Co-digestion effect on biogas production was assessed by response surface analysis. </LI> <LI> Effects on the methane yield and synergistic effect of co-digestion were analyzed. </LI> <LI> Co-digestion exerts additive/synergistic effects regardless of the mixing ratio. </LI> <LI> Synergy in co-digestion of waste feedstocks was modeled by RSA for the first time. </LI> </UL> </P>

<i>Ulva</i> biomass as a co-substrate for stable anaerobic digestion of spent coffee grounds in continuous mode

Kim, Jaai,Kim, Hakchan,Lee, Changsoo Elsevier Applied Science 2017 Bioresource Technology Vol.241 No.-

<P><B>Abstract</B></P> <P> <I>Ulva</I> biomass was evaluated as a co-substrate for anaerobic digestion of spent coffee grounds at varying organic loads (0.7–1.6g chemical oxygen demand (COD)/Ld) and substrate compositions. Co-digestion with <I>Ulva</I> (25%, COD basis) proved beneficial for SCG biomethanation in both terms of process performance and stability. The beneficial effect is much more pronounced at higher organic and hydraulic loads, with the highest COD removal and methane yield being 51.8% and 0.19L/g COD fed, respectively. The reactor microbial community structure changed dynamically during the experiment, and a dominance shift from hydrogenotrophic to aceticlastic methanogens occurred with increase in organic loading rate. Network analysis provides a comprehensive view of the microbial interactions involved in the system and confirms a direct positive correlation between <I>Ulva</I> input and methane productivity. A group of populations, including <I>Methanobacterium</I>- and <I>Methanoculleus</I>-related methanogens, was identified as a possible indicator for monitoring the biomethanation performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Ulva</I> was examined as co-substrate for anaerobic digestion of spent coffee grounds. </LI> <LI> Co-digestion with <I>Ulva</I> proved beneficial for continuous SCG biomethanation. </LI> <LI> Beneficial effect is more pronounced at higher organic and hydraulic loads. </LI> <LI> Reactor microbial community structure changed dynamically during the experiment. </LI> <LI> Network analysis provides a comprehensive view of microbial interactions. </LI> </UL> </P>

Anaerobic co-digestion of spent coffee grounds with different waste feedstocks for biogas production

Kim, Jaai,Kim, Hakchan,Baek, Gahyun,Lee, Changsoo Elsevier 2017 Waste management Vol.60 No.-

<P><B>Abstract</B></P> <P>Proper management of spent coffee grounds has become a challenging problem as the production of this waste residue has increased rapidly worldwide. This study investigated the feasibility of the anaerobic co-digestion of spent coffee ground with various organic wastes, i.e., food waste, <I>Ulva</I>, waste activated sludge, and whey, for biomethanation. The effect of co-digestion was evaluated for each tested co-substrate in batch biochemical methane potential tests by varying the substrate mixing ratio. Co-digestion with waste activated sludge had an apparent negative effect on both the yield and production rate of methane. Meanwhile, the other co-substrates enhanced the reaction rate while maintaining methane production at a comparable or higher level to that of the mono-digestion of spent coffee ground. The reaction rate increased with the proportion of co-substrates without a significant loss in methanation potential. These results suggest the potential to reduce the reaction time and thus the reactor capacity without compromising methane production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The feasibility of the co-digestion of SCG with various organic wastes was studied. </LI> <LI> FW, <I>Ulva</I>, and whey enhanced the reaction rate without a significant loss in BMP. </LI> <LI> Co-digestion with WAS had an apparent antagonistic effect on methane production. </LI> <LI> The microbial community structure varied little with different substrate mixtures. </LI> </UL> </P>

16S rDNA Detection and Quantification of Aceticlastic Methanogens Using Real-time Quantitative PCR with Group-specific Primer and Probe Sets

Jaai Kim(김자애),Youngseob Yu(유영섭),Seokhwan Hwang(황석환) 한국생물공학회 2004 한국생물공학회 학술대회 Vol.2004 No.10

Co-feeding spent coffee grounds in anaerobic food waste digesters: Effects of co-substrate and stabilization strategy

Kim, Danbee,Kim, Hakchan,Kim, Jaai,Lee, Changsoo Elsevier 2019 Bioresource technology Vol.288 No.-

<P><B>Abstract</B></P> <P>Anaerobic digestion of spent coffee grounds (SCG) is considered disadvantageous, particularly under mono-digestion conditions, owing to slow degradation and nutrient imbalance. This study investigated the effect of co-feeding of SCG at a low ratio into food waste (FW) digesters, with the aim to determine whether SCG can be effectively treated and valorized using the spare capacity of existing digesters. Duplicate reactors showed stable performance under FW mono-digestion conditions but manifested severe deterioration in three volume turnovers after co-feeding of SCG (FW:SCG at 10:1 on a volatile solids basis). The reactors failed to recover despite repeated interrupted feeding and stabilization, and <I>Ulva</I> was added (FW:SCG:<I>Ulva</I> at 20:2:1) for nutrient supplementation. The two reactors subjected to different stabilization strategies (i.e., timing and intervals of interrupted feeding) responded differently to <I>Ulva</I> co-feeding: one recovered and maintained stable albeit suboptimal performance, whereas the other failed. Furthermore, the microbial communities developed differently in the reactors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SCG was anaerobically treated as a co-substrate in continuous food waste digesters. </LI> <LI> SCG co-feeding at 10% of food waste (VS basis) led to major process disturbances. </LI> <LI> Stable performance was restored with added <I>Ulva</I> (5% of food waste) in one reactor. </LI> <LI> Stabilization strategies significantly influenced process resilience and stability. </LI> <LI> Both archaeal and bacterial community structures changed greatly after adding SCG. </LI> </UL> </P>

Use of real-time PCR for group-specific quantification of aceticlastic methanogens in anaerobic processes: Population dynamics and community structures

Yu, Youngseob,Kim, Jaai,Hwang, Seokhwan John Wiley & Sons 2006 Biotechnology and bioengineering Vol.93 No.3

<P>The TaqMan quantitative PCR (QPCR) method was used to detect and quantify the 16S rRNA genes of aceticlastic methanogens at different taxonomic levels. Three different sets of primers coupled with a TaqMan probe for QPCR assays to detect the 16S rRNA genes of the order Methanosarcinales, as well as the families Methanosarcinaceae and Methanosaetaceae, were separately used. Using these primer and probe sets, the 16S rRNA genes of aceticlastic methanogens in samples from various anaerobic processes (i.e., nine pure cultures, batch experiment, and three different continuous processes including a full-scale digester), were monitored and quantified by QPCR assays. A batch experiment cultivating a mixture of aceticlastic methanogens, was conducted to monitor their population dynamics. Using this group-specific quantification method, the dynamics of a competition between two aceticlastic populations, as modulated by the acetate concentration, could well be described. The target 16S rRNA genes in environmental samples, collected from three different anaerobic processes treating sludge, cheese whey, and synthetic wastewaters, were additionally quantified. The quantified 16S rRNA gene concentrations for all samples successfully represented the community structures of the target methanogens, which were correlated accurately with the operational parameters of the anaerobic processes. It was also successful to demonstrate probe nesting of aceticlastic methanogens at the levels of order and family. © 2005 Wiley Periodicals, Inc.</P>

Absolute and relative QPCR quantification of plasmid copy number in <i>Escherichia coli</i>

Lee, Changsoo,Kim, Jaai,Shin, Seung Gu,Hwang, Seokhwan Elsevier 2006 Journal of biotechnology Vol.123 No.3

<P><B>Abstract</B></P><P>Real-time QPCR based methods for determination of plasmid copy number in recombinant <I>Escherichia coli</I> cultures are presented. Two compatible methods based on absolute and relative analyses were tested with recombinant <I>E. coli</I> DH5α harboring pBR322, which is a common bacterial cloning vector. The separate detection of the plasmid and the host chromosomal DNA was achieved using two separate primer sets, specific for the plasmid β-lactamase gene (<I>bla</I>) and for the chromosomal <SMALL>D</SMALL>-1-deoxyxylulose 5-phosphate synthase gene (<I>dxs</I>), respectively. Since both <I>bla</I> and <I>dxs</I> are single-copy genes of pBR322 and <I>E. coli</I> chromosomal DNA, respectively, the plasmid copy number can be determined as the copy ratio of <I>bla</I> to <I>dxs</I>.</P><P>These methods were successfully applied to determine the plasmid copy number of pBR322 of <I>E. coli</I> host cells. The results of the absolute and relative analyses were identical and highly reproducible with coefficient of variation (CV) values of 2.8–3.9% and 4.7–5.4%, respectively. The results corresponded to the previously reported values of pBR322 copy number within <I>E. coli</I> host cells, 15–20.</P><P>The methods introduced in this study are convenient to perform and cost-effective compared to the traditionally used Southern blot method. The primer sets designed in this study can be used to determine plasmid copy number of any recombinant <I>E. coli</I> with a plasmid vector having <I>bla</I> gene.</P>

Unusual bacterial populations observed in a full-scale municipal sludge digester affected by intermittent seawater inputs

Lee, Changsoo,Kim, Jaai,Chinalia, Fabio Alexandre,Shin, Seung Gu,Hwang, Seokhwan Springer-Verlag 2009 Journal of industrial microbiology & biotechnology Vol.36 No.5

Fermentation and growth kinetic study of Aeromonas caviae under anaerobic conditions

Lee, Changsoo,Kim, Jaai,Hwang, Kwanghyun,Hwang, Seokhwan Springer-Verlag 2009 Applied microbiology and biotechnology Vol.83 No.4

Thermo-acid and thermo-alkaline solubilization of Ulva biomass under mild-temperature conditions

( Heejung Jung ),( Jaai Kim ),( Changsoo Lee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 심포지움 Vol.2014 No.2

The worldwide attention to biomass as a renewable energy resource is gradually increasing in recent years. Seaweeds are considered a promising next-generation biomass feedstock for biofuel production due to their high content of readily biodegradable carbohydrates. However, the rigid cellular structure hinders efficient utilization of seaweed biomass, and various pretreatment methods have been applied to enhance the hydrolysis rate. This study investigated the effects of thermo-acid and thermo-alkaline pretreatment methods on Ulva solubilization. Ulva, a green macroalgal genus, is known to often cause serious marine green tides, posing environmental concerns, worldwide. Ulva biomass collected from a local beach was thermo-chemically pretreated using HCl or NaOH under mild-temperature conditions (<100℃). Response surface analysis (RSA) was used to statistically examine and compare the effects of the pretreatment methods tested, with the explored chemical dose and temperature ranges of 0 - 200 mM and 50 - 90℃, respectively. Solubilization of Ulva biomass was demonstrated by increases in both soluble chemical oxygen demand (SCOD) and dissolved total nitrogen (DTN) levels. Up to 130% and 790% increases respectively in SCOD and DTN were observed in alkali-treated trials while up to 81% and 395% increases respectively in SCOD and DTN were in acid-treated trials. The response surface models constructed for each pretreatment method showed that thermo-alkaline pretreatment was more effective than thermo-acid treatment on the solubilization of Ulva biomass under the mild-temperature conditions used in this study. It was statistically shown by RSA that NaOH concentration had a much greater effect on the solubilization rate than did temperature within the explored experimental region.