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Anaerobic digestion (AD) of organic waste to produce biogas is a mature biotechnology commercialised for decades. However, the relatively recent discovery of direct interspecies electron transfer (DIET) brings a new opportunity to improve the efficiency of biogas technology. DIET may replace mediated interspecies electron transfer (MIET) by efficient electron transfer between exoelectrogens and electrotrophic methanogens, thereby enhancing yields and rates of biogas production. Ethanol, as the initial electron donor in the discovery of the DIET pathway, is now a “hot topic” in the literature. Recent studies have indicated that ethanol in AD functions not only as the substrate, but also as the precursor to stimulate DIET by enriching exoelectrogens and electrotrophic methanogens for co-digesting complex organic wastes. This review aims to highlight the state of the art and recent advances in ethanol-based DIET in AD. The DIET associated reactions of ethanol oxidation and carbon dioxide reduction are assessed by thermodynamic analysis to reveal the extent of the potential for improvement of the AD processes that utilizes DIET pathways. Three ethanol-based DIET strategies are discussed: (1) ethanol as the sole substrate supplemented with conductive materials in AD, (2) ethanol co-digestion with complex substrates and (3) ethanol-type fermentation prior to AD. This review aims to chart the pathways for improved AD performance by utilizing ethanol-based DIET in specific treatments of biological wastes.
Dong Feng; Xiaobo Guo; Richen Lin; Ao Xia; Yun Huang; Qiang Liao; Xianqing Zhu; Xun Zhu; Jerry D. Murphy. How can ethanol enhance direct interspecies electron transfer in anaerobic digestion? Biotechnology Advances 2021, 52, 107812 .
AMA StyleDong Feng, Xiaobo Guo, Richen Lin, Ao Xia, Yun Huang, Qiang Liao, Xianqing Zhu, Xun Zhu, Jerry D. Murphy. How can ethanol enhance direct interspecies electron transfer in anaerobic digestion? Biotechnology Advances. 2021; 52 ():107812.
Chicago/Turabian StyleDong Feng; Xiaobo Guo; Richen Lin; Ao Xia; Yun Huang; Qiang Liao; Xianqing Zhu; Xun Zhu; Jerry D. Murphy. 2021. "How can ethanol enhance direct interspecies electron transfer in anaerobic digestion?" Biotechnology Advances 52, no. : 107812.
Editorial on the Research Topic Innovative Technology and System Integration for Gaseous Biofuels Production Primary energy demand in the world is expected to continue to grow over the next few decades with population and economy (Sarkodie et al., 2019; Sharma et al., 2020). Excessive exploitation and utilization of fossil fuels have led to energy shortage and environmental pollution (Cheng et al., 2020). To date, many countries have the ambition to achieve carbon neutrality between 2050 and 2060. It is urgent to explore advanced and clean fuel sources for the future sustainable development and decarbonization of the society (Chiaramonti et al., 2021). Biomass resources, such as straws, food wastes, algae, and manures, are underutilized in most parts of the world (Chew et al., 2017; Qin et al., 2018). Converting biomass feedstock to green gaseous biofuels has a great potential for the reduction of pollutant emissions and may play a significant role in future energy system (Khoo et al., 2020; Murphy and Thamsiriroj, 2011). There are a number of existing pathways capable of producing gaseous biofuels; however, the optimal pathway is difficult to define due to technology challenges and maturity, variations in available feedstock, and the wider contexts within which a solution is implemented. For example, biogas rich in methane can be produced through anaerobic digestion (AD), which is a mature technology and has been applied worldwide in recent years. Nevertheless, the biogas production rate, the process stability, and the feedstock utilization efficiency are still not satisfactory and need to be further improved. Additionally, the treatment of liquid digestate from full-scale biogas systems may require significant energy inputs and raise environmental risks (Xia and Murphy, 2016). To achieve an efficient AD process, it is crucial to fully understand the mechanisms of the microbial conversion to propose effective enhancement strategies. An energy-efficient and environment-friendly biomass feedstock pre-treatment and hydrolysis processes would be advantageous for the access and utilization by microbes to improve biofuel production (Deng et al., 2019). Furthermore, the biomass pre-treatment, biofuel production and upgrading, as well as byproducts production should be integrated and optimized to maximize the efficiency and minimize the cost of such a system. The research topic includes three original research articles and two review articles, which combine and cover various aspects of the innovation in gaseous biofuels production technologies and systems. Lin et al. investigated the impact of hydrothermal dilute acid pre-treatment on the hydrolysis performance of grass silage. An optimal hydrothermal condition at the temperature of 140°C and time of 20 min was identified, with a maximum sugar yield of 0.29 g/g volatile solid (VS). A first-order reaction model combining grass silage hydrolysis and degradation was established to successfully predict the production and consumption of sugars. The authors indicated that heat recovery could significantly reduce the energy requirement of hydrothermal pre-treatment process. Uddin et al. reviewed the innovative technologies and key factors for AD process. The challenges and the future perspective associated with AD process were highlighted. The authors identified appropriate temperature and pH, a strong inoculum to substrate ratio, good mixing, and small particle sizes are crucial to ensure an efficient AD process, which can provide some guidelines for the renewable gaseous biofuels production by using organic wastes as substrates. The work of Te et al. was dedicated to the optimization of pyrolysis parameters for biochar production from banana peels. The optimal pyrolysis parameters were identified at a temperature of 356.1°C, a residence time of 180 min, and a heating rate of 14.7°C min−1, achieving a biochar yield of 58.8 and a O/C ratio of 0.289. Subsequently, the optimum biochar was selected for the growth of Ipomoea aquatica. The results suggested that the highest final plant height could be achieved at a biochar dosage of 1%. Wang et al. assessed the potential of microalgae as substrates for the production of clean gaseous biofuels. The hydrogen-producing enzymes in microalgae and the hydrogen production pathways have been summarized and compared. Various bioprocess engineering and genetic engineering were reviewed for the enhancement of biohydrogen production. Also, the recent progresses in integrated biorefinery systems for hydrogen and methane co-production were discussed in detail. The study also highlighted the future trends and challenges associated with hydrogen and methane production from microalgae. A study by Khamtib et al. used expanded clay as a supporting material for hydrogen co-fermentation of oil palm trunk hydrolysate and slaughterhouse wastewater by Thermoanaerobacterium thermosaccharolyticum KKU19 in a fixed-bed reactor under a non-sterile condition. Long-term results demonstrated that expanded clay can effectively immobilize the microbial cells, while converting organic substrates into hydrogen. An optimal hydrogen production rate of 6.82 L/L and a hydrogen yield of 231.99 ml H2/g-COD were achieved at a hydraulic retention time of 6 h. Meanwhile, the dominant soluble metabolite products were butyric and acetic acids, suggesting an efficient hydrogen fermentation process. Collectively, these studies demonstrated a high level of scholarship and addressed a wide range of technical issues that constrain progress towards realizing gaseous biofuels in full-scale integrated production plants. We sincerely thank all authors and reviewers for their valuable contribution to the research topic. We also thank the Frontiers in Energy Research team for their support and assistance. AX wrote the Editorial with contributions from PS, AR, and TW. All authors contributed to the Editorial and approved the final version....
Ao Xia; Pau-Loke Show; Alissara Reungsang; Timothy Walmsley. Editorial: Innovative Technology and System Integration for Gaseous Biofuels Production. Frontiers in Energy Research 2021, 9, 1 .
AMA StyleAo Xia, Pau-Loke Show, Alissara Reungsang, Timothy Walmsley. Editorial: Innovative Technology and System Integration for Gaseous Biofuels Production. Frontiers in Energy Research. 2021; 9 ():1.
Chicago/Turabian StyleAo Xia; Pau-Loke Show; Alissara Reungsang; Timothy Walmsley. 2021. "Editorial: Innovative Technology and System Integration for Gaseous Biofuels Production." Frontiers in Energy Research 9, no. : 1.
Facilitating the direct interspecies electron transfer with supplying versatile conductive materials to accelerate methane production in anaerobic digestion has received considerable attention, while the stimulatory mechanism of conductive materials on the direct interspecies electrons transfer still remains unclear. Herein, the thermodynamic characteristics of syntrophic methanogenesis induced by different conductive materials in various fermentation conditions were investigated to explore the stimulatory mechanism. The results showed that the supplementation of conductive materials significantly affected the Gibbs free energy changes of both propionate oxidation and electrotrophic methanogenesis. Activated carbon contributed to propionate oxidation as a thermodynamically favorable reaction with Gibbs free energy changes in the range of −310.9 and −399.4 kJ mol−1 and the available energy of propionate oxidation was 4.4 times higher than that with c-type cytochrome at a CO2 partial pressure of 0.4 bar. Conductive material with a low redox potential facilitated electrotrophic methanogenesis as a thermodynamically favorable reaction. The Gibbs free energy change of propionate oxidation increased after elevating CO2 partial pressure or electrons concentration but decreased with an increase in pH, temperature, or the propionate concentration.
Xiaobo Guo; Huize Chen; Xianqing Zhu; Ao Xia; Qiang Liao; Yun Huang; Xun Zhu. Revealing the role of conductive materials on facilitating direct interspecies electron transfer in syntrophic methanogenesis: A thermodynamic analysis. Energy 2021, 229, 120747 .
AMA StyleXiaobo Guo, Huize Chen, Xianqing Zhu, Ao Xia, Qiang Liao, Yun Huang, Xun Zhu. Revealing the role of conductive materials on facilitating direct interspecies electron transfer in syntrophic methanogenesis: A thermodynamic analysis. Energy. 2021; 229 ():120747.
Chicago/Turabian StyleXiaobo Guo; Huize Chen; Xianqing Zhu; Ao Xia; Qiang Liao; Yun Huang; Xun Zhu. 2021. "Revealing the role of conductive materials on facilitating direct interspecies electron transfer in syntrophic methanogenesis: A thermodynamic analysis." Energy 229, no. : 120747.
Microalgae is a promising candidate for reducing greenhouse gas and producing renewable biofuels. For microalgae biofilm cultivation, a strong adhesion ability of microalgae cells onto the surface is a prerequisite to resist the fluid shear stress, while strong adhesion is not of benefit to the biofilm harvesting process. To solve this dilemma, a thermoresponsive surface (TMRS) with lower critical solution temperature of 33 °C was made by grafting N-isopropylacrylamide onto a silicate glass slide. The wettability of the TMRS changed from hydrophilic (contact angle of 59.4°) to hydrophobic (contact angle of 91.6°) when the temperature rose from 15 to 35 °C, resulting in the increase of adhesion energy of the TMRS to Chlorella vulgaris cells by 135.6%. The experiments showed that the cells were more likely to attach onto the TMRS at the higher temperature of 35 °C owing to the surface microstructures generated by the hydrogel layer shrinkage, which is similar in size to the microalgae cells. And the cell coverage rate on TMRS increased by 32% compared to the original glass surface. Conversely, the cells separate easily from the TMRS at a lower temperature of 15 °C, and the cell adhesion density was reduced by 19% due to hydrogel layer swelling to a relatively flat surface.
Weida Zeng; Yun Huang; Ao Xia; Qiang Liao; Keming Chen; Xun Zhu; Xianqing Zhu. Thermoresponsive Surfaces Grafted by Shrinkable Hydrogel Poly(N-isopropylacrylamide) for Controlling Microalgae Cells Adhesion during Biofilm Cultivation. Environmental Science & Technology 2021, 55, 1178 -1189.
AMA StyleWeida Zeng, Yun Huang, Ao Xia, Qiang Liao, Keming Chen, Xun Zhu, Xianqing Zhu. Thermoresponsive Surfaces Grafted by Shrinkable Hydrogel Poly(N-isopropylacrylamide) for Controlling Microalgae Cells Adhesion during Biofilm Cultivation. Environmental Science & Technology. 2021; 55 (2):1178-1189.
Chicago/Turabian StyleWeida Zeng; Yun Huang; Ao Xia; Qiang Liao; Keming Chen; Xun Zhu; Xianqing Zhu. 2021. "Thermoresponsive Surfaces Grafted by Shrinkable Hydrogel Poly(N-isopropylacrylamide) for Controlling Microalgae Cells Adhesion during Biofilm Cultivation." Environmental Science & Technology 55, no. 2: 1178-1189.
The anaerobic digestion of wastewater rich in volatile fatty acids (VFAs) provides a sustainable approach for methane production whilst reducing environmental pollution. However, the anaerobic digestion of VFAs may not be stable during long-term operation under a short hydraulic retention time. In this study, conductive carbon cloth was supplemented to investigate the impacts on the anaerobic digestion of VFAs in wastewater sourced from dark fermentation. The results demonstrated that the failure of anaerobic digestion could be avoided when carbon cloth was supplemented. In the stable stage, the methane production rate with carbon cloth supplementation was improved by 200–260%, and the chemical oxygen demand (COD) removal efficiency was significantly enhanced compared with that in the control without carbon cloth. The relative abundance of potential exoelectrogens on the carbon cloth was increased by up to 8-fold compared with that in the suspension. Electrotrophic methanogens on the carbon cloth were enriched by 4.2–17.2% compared with those in the suspension. The genera Ercella and Petrimonas along with the methanogenic archaea Methanosaeta and Methanosarcina on the carbon cloth may facilitate direct interspecies electron transfer, thereby enhancing methane production.
Dong Feng; Ao Xia; Qiang Liao; Abdul-Sattar Nizami; Chihe Sun; Yun Huang; Xianqing Zhu; Xun Zhu. Carbon cloth facilitates semi-continuous anaerobic digestion of organic wastewater rich in volatile fatty acids from dark fermentation. Environmental Pollution 2020, 272, 116030 .
AMA StyleDong Feng, Ao Xia, Qiang Liao, Abdul-Sattar Nizami, Chihe Sun, Yun Huang, Xianqing Zhu, Xun Zhu. Carbon cloth facilitates semi-continuous anaerobic digestion of organic wastewater rich in volatile fatty acids from dark fermentation. Environmental Pollution. 2020; 272 ():116030.
Chicago/Turabian StyleDong Feng; Ao Xia; Qiang Liao; Abdul-Sattar Nizami; Chihe Sun; Yun Huang; Xianqing Zhu; Xun Zhu. 2020. "Carbon cloth facilitates semi-continuous anaerobic digestion of organic wastewater rich in volatile fatty acids from dark fermentation." Environmental Pollution 272, no. : 116030.
Dark fermentation of organic wastes, such as food waste and algae, via mixed hydrogen-producing bacteria (HPB) is considered a sustainable approach for hydrogen production. The biofilm system protects microorganisms from the harmful environment and avoids the excessive loss of bacteria caused by washout, which ensures that the dark fermentation process remains stable. In this study, a downflow anaerobic packed-bed reactor was commissioned to investigate the biofilm formation process of mixed HPB under various operational parameters. Scanning electron microscopy indicated changes in surface morphology during the biofilm formation period. Proteins and polysaccharides in extracellular polymeric substances were identified by confocal laser scanning microscopy to reveal their distribution characteristics. A hydraulic retention time of 0.5 d, a substrate concentration of 15 g/L and an HPB inoculum ratio of 30% were identified as the optimal operational parameters for biofilm formation. Meanwhile, the biofilm dry weight reached 81.2 g/m2, and the extracellular proteins and polysaccharides achieved 1.6 and 5.2 g/m2, respectively. The diversity of bacteria between suspension and biofilm showed significantly different distributions; Clostridiales and Lactobacillales were identified as the dominant orders in the biofilm formation process. The abundances of Clostridiales and Lactobacillales were 15.1% and 56.2% in the biofilm, respectively.
Jie Mei; Huize Chen; Qiang Liao; Abdul-Sattar Nizami; Ao Xia; Yun Huang; Xianqing Zhu; Xun Zhu. Effects of Operational Parameters on Biofilm Formation of Mixed Bacteria for Hydrogen Fermentation. Sustainability 2020, 12, 8863 .
AMA StyleJie Mei, Huize Chen, Qiang Liao, Abdul-Sattar Nizami, Ao Xia, Yun Huang, Xianqing Zhu, Xun Zhu. Effects of Operational Parameters on Biofilm Formation of Mixed Bacteria for Hydrogen Fermentation. Sustainability. 2020; 12 (21):8863.
Chicago/Turabian StyleJie Mei; Huize Chen; Qiang Liao; Abdul-Sattar Nizami; Ao Xia; Yun Huang; Xianqing Zhu; Xun Zhu. 2020. "Effects of Operational Parameters on Biofilm Formation of Mixed Bacteria for Hydrogen Fermentation." Sustainability 12, no. 21: 8863.
Hydrothermal treatment can facilitate hydrolysis of biomass wastes such as algae and livestock manures, by converting high-molecular weight carbohydrates and proteins to monosaccharides and amino acids. However, further decomposition and reciprocal reaction of monosaccharides and amino acids are usually accompanied with hydrothermal treatment, which have negative impacts on microbial fermentation performance. In this study, glucose and glycine were used as model substrates during hydrothermal treatment coupled with semi-continuous hydrogen and methane fermentation. The results showed that thermal decomposition of glucose was stronger than glycine, due to the binary interactions between carbonyl group and amino group. Acidic condition could suppress conversion of intermediate compounds to polymers, thereby improving 5-HMF concentration to 7.59 g/L. Hydrothermal by-products had adverse impacts on hydrogen fermentation stability, resulting in a wide fluctuation of hydrogen production rate of around 0.55 L/L/d. Adding sulfuric acid for treatment would increase the competition of sulphate reducing bacteria, and cause a stuck methane fermentation. Additionally, by-products degradation promoted the growth of hydrogenotrophic and mixotrophic methanogens.
Qiang Liao; Chihe Sun; Ao Xia; Qian Fu; Yun Huang; Xun Zhu; Dong Feng. How can hydrothermal treatment impact the performance of continuous two-stage fermentation for hydrogen and methane co-generation? International Journal of Hydrogen Energy 2020, 46, 14045 -14062.
AMA StyleQiang Liao, Chihe Sun, Ao Xia, Qian Fu, Yun Huang, Xun Zhu, Dong Feng. How can hydrothermal treatment impact the performance of continuous two-stage fermentation for hydrogen and methane co-generation? International Journal of Hydrogen Energy. 2020; 46 (27):14045-14062.
Chicago/Turabian StyleQiang Liao; Chihe Sun; Ao Xia; Qian Fu; Yun Huang; Xun Zhu; Dong Feng. 2020. "How can hydrothermal treatment impact the performance of continuous two-stage fermentation for hydrogen and methane co-generation?" International Journal of Hydrogen Energy 46, no. 27: 14045-14062.
White-rot fungi is capable of producing extracellular enzymes that degrade lignin structure and facilitate biofuel production from lignocellulosic biomass wastes. However, fungal monocultures are constrained by low activities of the lignin-degrading enzyme system, leading to poor treatment efficiency and a long duration, which are not advantageous for large-scale applications. To improve enzyme production and enhance lignin degradation, a novel coculture system was proposed using the white-rot fungi Phanerochaete chrysosporium and Irpex lacteus CD2. The degradation efficiency of the alkali lignin by the fungal coculture was 26.4%, which was higher than that of the fungal monocultures. It was due to the production of lignin degrading enzymes was promoted in the liquid medium. Scanning electron microscopy, Fourier transform infrared, thermogravimetric and mercury porosimeter analyses results revealed that the alkali lignin treated with the fungal coculture had the largest porosity, and the degree of destruction of the alkali lignin structure by the fungal coculture was higher than that of the fungal monocultures. Meanwhile, the nonproductive adsorption of enzymes on alkali lignin was significantly reduced by 61.0% when the biomass was treated with the fungal coculture. As a result, the nonproductive adsorption was remarkably reduced, while it significantly improved the cellulase catalysis efficiency. These results demonstrated the synergistic effects of the fungal coculture for biomass treatment and provided a new approach for increasing lignin degradation while improving enzymatic catalysis and biofuel production through fungal coculture.
Ruhong Luo; Qiang Liao; Ao Xia; Zhichao Deng; Yun Huang; Xianqing Zhu; Xun Zhu. Synergistic Treatment of Alkali Lignin via Fungal Coculture for Biofuel Production: Comparison of Physicochemical Properties and Adsorption of Enzymes Used As Catalysts. Frontiers in Energy Research 2020, 8, 1 .
AMA StyleRuhong Luo, Qiang Liao, Ao Xia, Zhichao Deng, Yun Huang, Xianqing Zhu, Xun Zhu. Synergistic Treatment of Alkali Lignin via Fungal Coculture for Biofuel Production: Comparison of Physicochemical Properties and Adsorption of Enzymes Used As Catalysts. Frontiers in Energy Research. 2020; 8 ():1.
Chicago/Turabian StyleRuhong Luo; Qiang Liao; Ao Xia; Zhichao Deng; Yun Huang; Xianqing Zhu; Xun Zhu. 2020. "Synergistic Treatment of Alkali Lignin via Fungal Coculture for Biofuel Production: Comparison of Physicochemical Properties and Adsorption of Enzymes Used As Catalysts." Frontiers in Energy Research 8, no. : 1.
For microalgae flocculation, the main drawback is high time consumption caused by low flocs settling velocity, thus, enhancing the sedimentation performance is an urgent problem in need of a solution. To enhance the settling velocity of microalgae flocs, montmorillonite clay was applied to microalgae flocculation in the form of flocculant carrier in this study. With clay, the effective density of microalgae flocs was enhanced remarkably. When the dry weight ratio of clay to cationic starch was 2, the effective density of microalgae flocs was 3.15-fold of that without clay. As a result, the settling velocity of microalgae flocs was enhanced 2.34 times. Additionally, owing to the tear effect of clay and well distribution of cationic starch, the mean diameter of generated flocs was slightly reduced and microalgae harvesting efficiency was improved. All these results suggested that the montmorillonite clay promises to be an ideal candidate for microalgae flocculation that can both enhance the microalgae sedimentation and adsorption performance.
Chaoyang Wei; Qiang Liao; Yun Huang; Xun Zhu; Ao Xia; Xianqing Zhu. Simultaneous enhancing the sedimentation and adsorption performance of Chlorella vulgaris with montmorillonite modified cationic starch. Biochemical Engineering Journal 2020, 164, 107785 .
AMA StyleChaoyang Wei, Qiang Liao, Yun Huang, Xun Zhu, Ao Xia, Xianqing Zhu. Simultaneous enhancing the sedimentation and adsorption performance of Chlorella vulgaris with montmorillonite modified cationic starch. Biochemical Engineering Journal. 2020; 164 ():107785.
Chicago/Turabian StyleChaoyang Wei; Qiang Liao; Yun Huang; Xun Zhu; Ao Xia; Xianqing Zhu. 2020. "Simultaneous enhancing the sedimentation and adsorption performance of Chlorella vulgaris with montmorillonite modified cationic starch." Biochemical Engineering Journal 164, no. : 107785.
The two-step photosynthetic biogas upgrading process, which combines CO2 capture by carbonate solution and carbonate regeneration by using aquatic microbial oxygenic photoautotrophs (i.e., cyanobacteria, algae, and diatoms), may provide a potential alternative to the commercial routes used for gaseous biofuel upgrading. Such a process not only provides a green and low energy intensive biogas upgrading pathway but also converts CO2 in biogas into high value biomass. To improve the upgrading performance, the effects of light intensity and NaHCO3 concentration on the growth and the HCO3- transformation characteristics of halophilic and alkaliphilic Spirulina platensis were investigated in this study. Experimental results showed that the light attenuation of S. platensis culture was significant. Increasing light intensity up to 210 μmol m-2 s-1 effectively improved the S. platensis growth and photosynthetic pigment accumulation. S. platensis could grow in the range of 0.05 to 0.6 M NaHCO3, and a maximum biomass concentration of 1.46 g L-1 was achieved under an optimal growth condition of 0.1 M NaHCO3, which was 65.9% higher than at 0.05 M NaHCO3. Moreover, the bicarbonate utilization efficiency reached 42.0%. Finally, in a case study, a biogas stream at a flow rate of 800 m3 h-1 could generate biomass up to 344 kg h-1, corresponding an energy value of 5591 MJ h-1.
Wenfan Ye; Ao Xia; Cheng Chen; Qiang Liao; Yun Huang; Xianqing Zhu; Xun Zhu. Sustainable carbon capture via halophilic and alkaliphilic cyanobacteria: the role of light and bicarbonate. Biofuel Research Journal 2020, 7, 1195 -1204.
AMA StyleWenfan Ye, Ao Xia, Cheng Chen, Qiang Liao, Yun Huang, Xianqing Zhu, Xun Zhu. Sustainable carbon capture via halophilic and alkaliphilic cyanobacteria: the role of light and bicarbonate. Biofuel Research Journal. 2020; 7 (3):1195-1204.
Chicago/Turabian StyleWenfan Ye; Ao Xia; Cheng Chen; Qiang Liao; Yun Huang; Xianqing Zhu; Xun Zhu. 2020. "Sustainable carbon capture via halophilic and alkaliphilic cyanobacteria: the role of light and bicarbonate." Biofuel Research Journal 7, no. 3: 1195-1204.
Production of biomethane from distillery by-products (such as stillage) in a circular economy system may facilitate a climate neutral alcohol industry. Anaerobic digestion (AD) of easily degradable substrates can lead to rapid acidification and accumulation of intermediate volatile fatty acids, reducing microbial activity and biomethane production. Carbonaceous materials may function as an abiotic conductive conduit to stimulate microbial electron transfer and resist adverse impacts on AD. Herein, nanomaterial graphene and more cost-effective pyrochar were comparatively assessed in their ability to recover AD performance after acidic shock (pH 5.5). Results showed that graphene addition (1.0 g/L) could lead to a biomethane yield of 250 mL/g chemical oxygen demand; this is an 11.0% increase compared to that of the control. The recovered process was accompanied by faster propionate degradation (CH3CH2COO¬– + 2H2O → CH3COO¬– + CO2 + 6H+ + 6e–). The enhanced performance was possibly ascribed to the high electrical conductivity of graphene. In comparison, pyrochar addition (1.0 and 10.0 g/L) did not enhance biomethane yield, though it reduced digestion lag-phase time by 18.1% and 12.2% compared to the control, respectively. Microbial taxonomy analysis suggested that Methanosarcina (81.5% in abundance) with diverse metabolic pathways and OTU in the order DTU014 (6.4% in abundance) might participate in direct interspecies electron transfer contributing to an effective recovery from acidic shock.
Benteng Wu; Richen Lin; Xihui Kang; Chen Deng; Ao Xia; Alan D. W. Dobson; Jerry D Murphy. Graphene addition to digestion of thin stillage can alleviate acidic shock and improve biomethane production. ACS Sustainable Chemistry & Engineering 2020, 8, 1 .
AMA StyleBenteng Wu, Richen Lin, Xihui Kang, Chen Deng, Ao Xia, Alan D. W. Dobson, Jerry D Murphy. Graphene addition to digestion of thin stillage can alleviate acidic shock and improve biomethane production. ACS Sustainable Chemistry & Engineering. 2020; 8 (35):1.
Chicago/Turabian StyleBenteng Wu; Richen Lin; Xihui Kang; Chen Deng; Ao Xia; Alan D. W. Dobson; Jerry D Murphy. 2020. "Graphene addition to digestion of thin stillage can alleviate acidic shock and improve biomethane production." ACS Sustainable Chemistry & Engineering 8, no. 35: 1.
Three main pretreatment methods (torrefaction, hydrothermal carbonization and degradative solvent extraction) have been developed to deoxygenate and upgrade biomass into biochar, hydrochar and extract, respectively, which have a variety of high-value applications. However, the influence of the three pretreatment methods on the moisture absorption and self-ignition characteristics of biomass still remains unclear, which greatly affects the subsequent storage, transportation and utilization process of the biochar, hydrochar and extract. Therefore, the effects of torrefaction, hydrothermal carbonization and degradative solvent extraction on the moisture absorption and self-ignition characteristics of biomass were investigated and compared in this study. The results showed that the moisture absorption ratios of the pretreated products (biochar, hydrochar and extract) were as low as 3.8%, 1% and 0.8%, respectively, which was obviously lower than that of RS (8%), indicating that the moisture absorption propensities of biochar, hydrochar and extract were all obviously inhibited compared to RS. These results were caused by the dramatic removal of oxygen functional groups during the three pretreatment processes. The heat release of biochar (6950 kJ/kg) and hydrochar (7134 kJ/kg) below 300 °C were obviously higher than that of RS (5950 kJ/kg), while the heat release of extract (5063 kJ/kg) below 300 °C was much lower than that of RS. Compared with RS, biochar and hydrochar had higher specific surface areas and higher contents of inorganic metallic elements, which contributed to their higher self-ignition susceptibilities than those of RS. In contrast, the extract had a dense structure and extremely low oxygen functional groups contents as well as low inorganic metallic elements contents, which jointly led to its lower self-ignition susceptibility than that of RS. This research is expected to provide a comprehensive understanding of the influence mechanism of pretreatment on the moisture absorption and self-ignition characteristics of biomass.
Man Liu; Xianqing Zhu; Rong Chen; Qiang Liao; Ao Xia; Yun Huang. Influence of torrefaction, hydrothermal carbonization and degradative solvent extraction pretreatments on moisture absorption and self-ignition characteristics of biomass. Fuel 2020, 282, 118843 .
AMA StyleMan Liu, Xianqing Zhu, Rong Chen, Qiang Liao, Ao Xia, Yun Huang. Influence of torrefaction, hydrothermal carbonization and degradative solvent extraction pretreatments on moisture absorption and self-ignition characteristics of biomass. Fuel. 2020; 282 ():118843.
Chicago/Turabian StyleMan Liu; Xianqing Zhu; Rong Chen; Qiang Liao; Ao Xia; Yun Huang. 2020. "Influence of torrefaction, hydrothermal carbonization and degradative solvent extraction pretreatments on moisture absorption and self-ignition characteristics of biomass." Fuel 282, no. : 118843.
The inhibitory effects of typical intermediate degradation products of furfural including furfuralcohol and furoic acid, as well as the transformation characteristics and the corresponding rate-limiting step, were analysed during hydrogen fermentation in this study. The results showed that furfural inhibition on hydrogen production were much higher than its derivatives, resulting in a maximum inhibition coefficient in the range of 7.1%–99.8%. Furfural at the concentrations ranging from 1 to 4 g/L was completely degraded after 48 h of fermentation, whereas 49%–70% of furfuralcohol remained unconverted after 96 h of fermentation. The degradation of furfural was actually an aldehyde-alcohol transformation process. Although adding furfuralcohol prolonged the lag-phase time and reduced the hydrogen production peak rate, it had slightly negative impacts on the accumulative hydrogen yield. Additionally, furoic acid exhibited a higher degradation rate than that of furfural and furfuralcohol, which was completely degraded after 24 h of fermentation. The typical metabolic product was acetic acid, and this process may simultaneously produce hydrogen. However, the transformation of furfuralcohol to furoic acid was still a rate-limiting step. Compared with the control group, the energy conversion efficiencies with the addition of furfural derivatives could decrease by 12.7%–91.7%. A high concentration (above than 2 g/L) of furfural and its derivatives would also significantly decrease the species richness and diversity.
Chihe Sun; Qiang Liao; Ao Xia; Qian Fu; Yun Huang; Xianqing Zhu; Xun Zhu; Zhengxin Wang. Degradation and transformation of furfural derivatives from hydrothermal pre-treated algae and lignocellulosic biomass during hydrogen fermentation. Renewable and Sustainable Energy Reviews 2020, 131, 109983 .
AMA StyleChihe Sun, Qiang Liao, Ao Xia, Qian Fu, Yun Huang, Xianqing Zhu, Xun Zhu, Zhengxin Wang. Degradation and transformation of furfural derivatives from hydrothermal pre-treated algae and lignocellulosic biomass during hydrogen fermentation. Renewable and Sustainable Energy Reviews. 2020; 131 ():109983.
Chicago/Turabian StyleChihe Sun; Qiang Liao; Ao Xia; Qian Fu; Yun Huang; Xianqing Zhu; Xun Zhu; Zhengxin Wang. 2020. "Degradation and transformation of furfural derivatives from hydrothermal pre-treated algae and lignocellulosic biomass during hydrogen fermentation." Renewable and Sustainable Energy Reviews 131, no. : 109983.
Stimulating direct interspecies electron transfer with conductive materials is a promising strategy to overcome the limitation of electron transfer efficiency in syntrophic methanogenesis of industrial wastewater. This paper assessed the impact of conductive foam nickel (FN) supplementation on syntrophic methanogenesis and found that addition of 2.45 g/L FN in anaerobic digestion increased the maximum methane production rate by 27.4 % (on day 3) while decreasing the peak production time by 33 % as compared to the control with no FN. Cumulative methane production from day 2 to 6 was 14.5 % higher with addition of 2.45 g/L FN than in the control. Levels of FN in excess of 2.45 g/L did not show benefits. Cyclic voltammetry results indicated that the biofilm formed on the FN could generate electrons. The dominant bacterial genera in suspended sludge were Dechlorobacter and Rikenellaceae DMER64, whereas that in the FN biofilm was Clostridium sensu stricto 11. The dominant archaea Methanosaeta in the FN biofilm was enriched by 14.1 % as compared to the control.
Xiaobo Guo; Chihe Sun; Richen Lin; Ao Xia; Yun Huang; Xianqing Zhu; Pau-Loke Show; Jerry D. Murphy. Effects of foam nickel supplementation on anaerobic digestion: Direct interspecies electron transfer. Journal of Hazardous Materials 2020, 399, 122830 .
AMA StyleXiaobo Guo, Chihe Sun, Richen Lin, Ao Xia, Yun Huang, Xianqing Zhu, Pau-Loke Show, Jerry D. Murphy. Effects of foam nickel supplementation on anaerobic digestion: Direct interspecies electron transfer. Journal of Hazardous Materials. 2020; 399 ():122830.
Chicago/Turabian StyleXiaobo Guo; Chihe Sun; Richen Lin; Ao Xia; Yun Huang; Xianqing Zhu; Pau-Loke Show; Jerry D. Murphy. 2020. "Effects of foam nickel supplementation on anaerobic digestion: Direct interspecies electron transfer." Journal of Hazardous Materials 399, no. : 122830.
Aiming at enhancing the microalgae biomass concentration to produce methane, electrolytic bubble carrying was introduced to Chlorella vulgaris flocculation. With the help of electrolytic microbubbles, instead of settling down, the microalgae flocs rise up. During this flocculation-rising process, the microalgae was concentrated to 63.6 g L−1 which was 5.5-fold of that concentrated in flocculation-settling process. Additionally, the mean floc rising velocity of 29.3 mm s−1 was 22.5-fold of the settling velocity of 1.3 mm s−1. The harvested biomass can be directly used as the substrates of methane fermentation and the fermentation period was shortened by 22.1% with a high C/N (28.0) of cationic starch. Furthermore, the additional cost for these improvements was only 0.09 kWh for per kilogram microalgae (kWh kg−1), and it was less than a quarter of the energy required for mixing. Therefore, based on the high biomass concentration and low additional energy consumption, the combination of electrolytic bubble carrying and cationic starch can be an ideal microalgae-harvesting method for biofuel production.
Chaoyang Wei; Yun Huang; Qiang Liao; Xun Zhu; Ao Xia; Xianqing Zhu. Application of bubble carrying to Chlorella vulgaris flocculation with branched cationic starch: An efficient and economical harvesting method for biofuel production. Energy Conversion and Management 2020, 213, 112833 .
AMA StyleChaoyang Wei, Yun Huang, Qiang Liao, Xun Zhu, Ao Xia, Xianqing Zhu. Application of bubble carrying to Chlorella vulgaris flocculation with branched cationic starch: An efficient and economical harvesting method for biofuel production. Energy Conversion and Management. 2020; 213 ():112833.
Chicago/Turabian StyleChaoyang Wei; Yun Huang; Qiang Liao; Xun Zhu; Ao Xia; Xianqing Zhu. 2020. "Application of bubble carrying to Chlorella vulgaris flocculation with branched cationic starch: An efficient and economical harvesting method for biofuel production." Energy Conversion and Management 213, no. : 112833.
Algal bloom biomass, sourced from a freshwater lake in Chongqing, was pre-treated by hydrothermal pre-treatments with or without acid/alkali catalysts, and subsequently used as a substrate for sustainable biohythane production via fermentation. Fourier transform infrared (FTIR) spectroscopy analyses suggested hydrothermal acid/alkali pre-treatments significantly changed peak intensities of chemical compositions in algal bloom biomass. Derivative thermogravimetric (DTG) analyses showed more macromolecular substances hydrolysed after hydrothermal acid/alkali pre-treatments. When bloom algae were pre-treated with 1% HCl at 140 °C for 10 min, an optimal specific hydrogen yield (SHY) of 39.4 mL/g volatile solid (VS) was obtained, which is 38.2% higher than raw biomass. However, a 34.4% decrease in SHY occurred under hydrothermal pre-treatment with 1% NaOH due to the enhancement of Maillard reaction. When using the effluents in methane fermentation, specific methane yields (SMYs) were 177.1–276.8 mL/g VS. Two-stage process effectively reduced the total fermentation time by 22.7% compared with single-stage fermentation.
Cheng Chen; Chihe Sun; Ao Xia; Qiang Liao; Xiaobo Guo; Yun Huang; Qian Fu; Xianqing Zhu; Xun Zhu. Sustainable biohythane production from algal bloom biomass through two-stage fermentation: Impacts of the physicochemical characteristics and fermentation performance. International Journal of Hydrogen Energy 2020, 45, 34461 -34472.
AMA StyleCheng Chen, Chihe Sun, Ao Xia, Qiang Liao, Xiaobo Guo, Yun Huang, Qian Fu, Xianqing Zhu, Xun Zhu. Sustainable biohythane production from algal bloom biomass through two-stage fermentation: Impacts of the physicochemical characteristics and fermentation performance. International Journal of Hydrogen Energy. 2020; 45 (59):34461-34472.
Chicago/Turabian StyleCheng Chen; Chihe Sun; Ao Xia; Qiang Liao; Xiaobo Guo; Yun Huang; Qian Fu; Xianqing Zhu; Xun Zhu. 2020. "Sustainable biohythane production from algal bloom biomass through two-stage fermentation: Impacts of the physicochemical characteristics and fermentation performance." International Journal of Hydrogen Energy 45, no. 59: 34461-34472.
The inherent disadvantages such as high oxygen content, low energy density, high moisture adsorption propensity and high spontaneous combustion tendency, have limited the widespread utilization of lignocellulosic biomass. A novel degradative solvent extraction (DSE) method has been recently developed to deoxygenate and upgrade biomass into two high-quality extracts (Soluble and Deposit) with various high-value applications. However, the moisture adsorption and spontaneous combustion characteristics of Soluble and Deposit still remain unclear, which are important for the safe storage, transportation and subsequent application of Soluble and Deposit. Therefore, in this study, the moisture adsorption and spontaneous combustion characteristics of Soluble, Deposit as well as raw biomass were investigated and compared. The moisture adsorption ratios of Soluble and Deposit were lower than 1.5% and 2.5% respectively, which were significantly lower than that of raw biomass, indicating that degradative solvent extraction greatly inhibited the moisture adsorption propensity of biomass. The ignition temperatures of Soluble and Deposit were at least 110 °C higher than that of raw biomass, and the activation energy of low temperature oxidation of Soluble and Deposit were 1.2–2.0 times higher than that of raw biomass. Soluble and Deposit had much higher weight loss temperature, heat release temperature, ignition temperature and higher activation energy of low temperature oxidation, revealing that the spontaneous combustion tendency of Soluble or Deposit was also significantly suppressed in comparison with raw biomass. The physicochemical properties of raw biomass, Soluble and Deposit were detailedly characterized, and it can be concluded that the low content of oxygen-containing functional groups, poor pore structure and dense surface structure jointly suppressed the moisture adsorption propensity and spontaneous combustion tendency of biomass after degradative solvent extraction. This research proves that degradative solvent extraction could not only achieve the upgrading of biomass but also inhibit the moisture adsorption propensity and spontaneous combustion tendency of biomass.
Xianqing Zhu; Weixiang Qian; Xian Li; Shan Tong; Zhenzhong Hu; Yun Huang; Ao Xia; Hong Yao. Moisture adsorption and spontaneous combustion characteristics of biomass wastes after degradative solvent extraction. Fuel 2020, 266, 117109 .
AMA StyleXianqing Zhu, Weixiang Qian, Xian Li, Shan Tong, Zhenzhong Hu, Yun Huang, Ao Xia, Hong Yao. Moisture adsorption and spontaneous combustion characteristics of biomass wastes after degradative solvent extraction. Fuel. 2020; 266 ():117109.
Chicago/Turabian StyleXianqing Zhu; Weixiang Qian; Xian Li; Shan Tong; Zhenzhong Hu; Yun Huang; Ao Xia; Hong Yao. 2020. "Moisture adsorption and spontaneous combustion characteristics of biomass wastes after degradative solvent extraction." Fuel 266, no. : 117109.
Photobioreactor (PBR) is the most critical equipment for microalgal photosynthetic fixation of CO2. It provides suitable environmental conditions, such as CO2, light and nutrients, for microalgal growth. As the major carbon source for microalgae, CO2 gas is pumped into PBR with the formation of bubbles and formed gas-liquid flow. The gas-liquid flow affects CO2 and nutrients transmission as well as microalgae cells distribution in PBR, thereby affecting the biochemical reaction of microalgae. While the migration and transport of biochemical reaction products affect the two-phase flow, phase distribution and flow resistance in the PBR in return, thus affecting the transport of light and nutrients. Therefore, microalgal photosynthetic rate is determined synthetically by two-phase flow and the transport of CO2, light and nutrients in PBR. Deep understanding of gas-liquid two-phase flow, energy and mass transfer coupling with microalgal growth in PBR is the cornerstone for the design of an efficient microalgae PBR.
Jingwei Fu; Yun Huang; Qiang Liao; Ao Xia; Qian Fu; Xun Zhu. Photo-bioreactor design for microalgae: A review from the aspect of CO2 transfer and conversion. Bioresource Technology 2019, 292, 121947 .
AMA StyleJingwei Fu, Yun Huang, Qiang Liao, Ao Xia, Qian Fu, Xun Zhu. Photo-bioreactor design for microalgae: A review from the aspect of CO2 transfer and conversion. Bioresource Technology. 2019; 292 ():121947.
Chicago/Turabian StyleJingwei Fu; Yun Huang; Qiang Liao; Ao Xia; Qian Fu; Xun Zhu. 2019. "Photo-bioreactor design for microalgae: A review from the aspect of CO2 transfer and conversion." Bioresource Technology 292, no. : 121947.
Biogas production from microalgae biomass via anaerobic digestion can be enhanced by hydrothermal pretreatment. The process of hydrothermal pretreatment has a significant impact on the energy gain, greenhouse gas emissions, and levelized cost of energy in biogas production from microalgae biomass, which has not been reported until now. In this study, life cycle and economic assessments of biogas production from microalgae biomass with hydrothermal pretreatment and with solar-driven hydrothermal pretreatment were conducted. The results showed that both types of pretreatment methods improved the biogas yield, promoted the energy gain, and reduced the levelized cost of energy. In biogas production through hydrothermal pretreatment, the net energy ratio (Energy input/Energy output), greenhouse gas emissions, and levelized cost of energy were 0.54, −129.94 g CO2-eq/(kWh biogas), and 0.22 $/m3, respectively, whereas in biogas production through solar-driven hydrothermal pretreatment, the corresponding values were 0.69, −166.13 g CO2-eq/(kWh biogas), and 0.17 $/m3, respectively. The biogas yield had the maximum effect on the net energy ratio and economic benefit. The efficiency in nitrogen recovery from the biogas residual had the maximum effect on greenhouse gas emissions. This work provides a theoretical guide to promote the environmental and economic benefits of biogas production from microalgae biomass.
Chao Xiao; Qian Fu; Qiang Liao; Yun Huang; Ao Xia; Hao Chen; Xun Zhu. Life cycle and economic assessments of biogas production from microalgae biomass with hydrothermal pretreatment via anaerobic digestion. Renewable Energy 2019, 151, 70 -78.
AMA StyleChao Xiao, Qian Fu, Qiang Liao, Yun Huang, Ao Xia, Hao Chen, Xun Zhu. Life cycle and economic assessments of biogas production from microalgae biomass with hydrothermal pretreatment via anaerobic digestion. Renewable Energy. 2019; 151 ():70-78.
Chicago/Turabian StyleChao Xiao; Qian Fu; Qiang Liao; Yun Huang; Ao Xia; Hao Chen; Xun Zhu. 2019. "Life cycle and economic assessments of biogas production from microalgae biomass with hydrothermal pretreatment via anaerobic digestion." Renewable Energy 151, no. : 70-78.
Solar-driven hydrothermal pretreatment is an efficient approach for the pretreatment of microalgae biomass for biofuel production. The flow and heat transfer characteristics of microalgae slurries in a solar-driven hydrothermal pretreatment system, which are not clear yet due to the complex thermo-physical properties and non-uniform heat flux, significantly affect the performance of hydrothermal pretreatment. Herein, a flow and heat transfer model of microalgae slurries with non-uniform heat flux was established, and the effects of direct normal irradiation and volume fraction of microalgae biomass on the flow and heat transfer characteristics were investigated. The results showed that secondary flow occurred on the cross section of absorber tube. With the increasing direct normal irradiation, the local Nu firstly decreased and following increased on axial, while the average wall shear stress firstly increased and then decreased on axial. With the increasing volume fraction, the local Nu decreased, while the wall shear stress increased. The average viscosity of microalgae slurry near wall had a significant effect on local Nu and average wall shear stress. The understanding of flow and heat transfer characteristics of microalgae slurry in non-uniform heat flux will be beneficial to the design and optimization of the solar-driven hydrothermal pretreatment system.
Qian Fu; Chao Xiao; Yun Huang; Qiang Liao; Ao Xia; Hao Chen; Xun Zhu. Numerical study of flow and heat transfer characteristics of microalgae slurry in a solar-driven hydrothermal pretreatment system. Applied Thermal Engineering 2019, 164, 114476 .
AMA StyleQian Fu, Chao Xiao, Yun Huang, Qiang Liao, Ao Xia, Hao Chen, Xun Zhu. Numerical study of flow and heat transfer characteristics of microalgae slurry in a solar-driven hydrothermal pretreatment system. Applied Thermal Engineering. 2019; 164 ():114476.
Chicago/Turabian StyleQian Fu; Chao Xiao; Yun Huang; Qiang Liao; Ao Xia; Hao Chen; Xun Zhu. 2019. "Numerical study of flow and heat transfer characteristics of microalgae slurry in a solar-driven hydrothermal pretreatment system." Applied Thermal Engineering 164, no. : 114476.