Takuro Kobayashi

National Institute for Environmental Studies · Material Cycles Division

The microbial mats responsible for biological desulfurization from biogas in a full-scale anaerobic digester were characterized in terms of their structure, as well as their chemical and microbial properties. Filament-shaped elemental sulfur 100-500 μm in length was shown to cover the mats, which cover the entire headspace of the digester. This is...

This study investigated early stages of biofilm formation from sieved fine particles of anaerobic granules in the presence of various cationic substances using a quartz crystal sensor to improve biofilm formation in the anaerobic treatment of saline wastewater. The biomass attached on the sensor was greatly increased with Ca within the low range (8...

Engineered biochar production and utilization in anaerobic digestion (AD) potentially overcome its limited application to the treatment of slowly degradable or inhibitory substrates. Here an attempt was made to develop an optimized biochar production procedure for use in AD to stimulate palmitic acid biodegradation via direct interspecies electron...

Biomass-derived biochar is attracting growing interest as an effective additive for anaerobic digestion (AD). To improve energy yield and digestion performance through an integrated process of biochar production and AD, biochar upgrading using biomass fly ash leachate as a sustainable metal catalyst was investigated. The results indicate that the b...

Persistent concerns regarding environmental hazards arise from the difficulty in disposing of radioactive plant-based wastes originating from the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FNPP) in Japan in 2011. In this study, three anaerobic digestion (AD) strategies were proposed: Sole anaerobic wet fermentation, and wet ferm...

Anaerobic membrane bioreactors (AnMBRs) are formed through the combination of anaerobic digestion and membrane technology. The upgraded technology separates SRT from HRT in the anaerobic digester, shortening the treatment period, reducing the digester’s volume and improving effluent quality. Furthermore, AnMBRs have a strong tolerance for the exist...

Anaerobic biological treatment of high-salinity wastewater has attracted much attention due to its environmental and economic benefits. However, the granulation can be significantly inhibited by a certain concentration of high salinity, which leads to the poor reactor performance and process stability. The presence of high salinity can also alter t...

Kitchen waste has been confirmed as an appropriate substrate for anaerobic digestion, although means of alleviating the difficulties and time-consuming nature of the start-up phase need to be further explored. Based on the mechanism of anaerobic digestion, we discuss the factors influencing the anaerobic start-up phase of kitchen waste. By controll...

This study investigated oleate inhibition concentration on mesophilic and thermophilic sludge by utilizing acetate and H2/CO2 (80:20, v/v) as substrate, respectively. In addition, another batch experiment was carried out to explore the influence of oleate loads (mM-oleate/g-VS) on methane production. Generally, the mesophilic anaerobic system was m...

In this study, a newly established bench-scale thermophilic continuously stirred fluidized bed reactor (CSFBR) was applied for anaerobic co-digestion of food waste (FW) with grease trap waste (GTW). The performance of CSFBR regarding stability and treatment efficiency was inspected through a laboratory contrast experiment with two traditional conti...

Biomethane is biogas upgraded to natural gas quality, potentially contributing to decarbonation in the energy and transport sectors. Upgrading of biogas produced from anaerobic digestion of organic waste through separation of CO2 is the typical route for biomethane generation. Recently, conversion of CO2 in biogas to biomethane is attracting attent...

Tar generated as a by-product during biomass gasification contains a high concentration of refractory organic matters. In this study, a hybrid upflow anaerobic sludge-biochar bed reactor was established for tar treatment, and the methane yield was 120-154 NmL-CH4/g-CODinf, 20-30% higher than the control reactor. COD removal and methane production s...

In this pilot-scale study, an innovative mainstream treatment process that couples the anaerobic membrane reactor (AnMBR) with a one-stage PN/A system was proposed for advancing the concept of carbon neutrality in the municipal wastewater treatment plant. This work demonstrates the start-up procedure of a pilot-scale one-stage PN/A system for mains...

Anaerobic digestion of decabromodiphenyl ether was carried out and compared in two continuously stirred anaerobic bioreactors for 210 days under thermophilic and mesophilic conditions. Results show that the degradation of decabromodiphenyl ether followed the first-order reaction kinetics, which exhibited a higher removal rate in the thermophilic re...

The application of biofilm-based processes such as up-flow anaerobic sludge blanket (UASB) reactors for staline wastewater treatment faces the problems of low strength and stability of granules cause by high salt concentration. In this study, the effect of biochar/Fe addition on biofilm formation was examined in anaerobic treatment of high salinity...

Poor processing stability has been cited as the fatal shortcoming of the up-flow anaerobic sludge blanket (UASB) reactor treating starch wastewater (SW). In this study, the SW treatment performance in a one-stage UASB reactor and a pre-acidification equipped UASB process were evaluated together with the microbial dynamics. The results revealed that...

Highlights  Anaerobic digestion (AD) of radiocesium (RCs)-contaminated crops was investigated.  Anaerobic degradation of crops releases RCs into aqueous phase of digestate.  RCs-solubilization efficiency rose with increase in degradability of feedstocks.  Solid-liquid partition coefficient widely varied depending on the types of adsorbents.  9...

This study investigated the effects of the addition of micro- (Fe, Co, Ni, and Mo) and macro-(Sulfur) nutrients on mono-digestion of sorghum under mesophilic conditions. A continuous stirred-tank reactor was operated for more than 420 days under seven different experimental conditions. The experimental results showed poor performance for methane pr...

Biochar is a carbon rich product made from the biomass pyrolysis process. Recently, biochar addition in anaerobic digestion processes has attracted attention for its possible functions to act as pH stabilizing agent, microbial carrier, and interspecies electron transfer. In this study, the effects of rice husk biochar addition in sorghum anaerobic...

Oily organic waste is a promising feedstock for anaerobic co-digestion. Free long-chain fatty acids (LCFAs) produced from lipids can inhibit methanogenic consortia, so optimal control of LCFA concentration is the key to successful operation of co-digestion. Most LCFAs are present in the solid phase, making them difficult to detect and monitor. This...

In this study, an integrated system of siphon-driven self-agitated anaerobic reactor (SDSAR) and anaerobic fixed bed reactor (AFBR) was conducted for the treatment of wastewater from food waste disposer (FWD), and the effect of influent total solids (TS) concentration on the process performance was evaluated. When the influent TS concentration incr...

Ever‐growing demands for energy supplies in emerging countries has motivated the scientists of the world to search for renewable energy sources that could replace fossil fuels. Bioenergy technologies that use renewable sources for simultaneous biomass refinery and methane‐rich biogas production will play a role in energy security. Anaerobic digesti...

While anammox is a cost-effective nitrogen treatment process for wastewater with high nutrient strength, phosphorus remains untouched during this process and needs further treatment. In this study, the nitrogen removal and phosphorus recovery were achieved simultaneously at 25 °C using an anammox expanded bed. A stable high nitrogen removal efficie...

To enhance the reaction rate and yield during biodiesel synthesis with Novozym 435 (an immobilized lipase), a co-solvent method was applied, after which the relationships between reaction time and reaction yield during the single-phase enzymatic transesterification of triolein and methanol in the presence of co-solvents such as tetrahydrofuran, ace...

Anaerobic membrane bioreactor (AnMBR) holds great promise to treat a broad range of waste streams for concurrent pollutants transformation and biofuels harvest while producing less digestate residuals. In this review, recent research advances, new discoveries and commercial application status of AnMBR technique were summarized and reported. A compr...

During the transesterification of triglycerides with methanol catalyzed by immobilized lipase resin (Novozym 435 (N435)) in a glass vial, two types of aggregate of N435 particles were observed: a thin-layer aggregate on the glass surface inside the vial, and bulky aggregates. This prompted us to investigate the conditions under which only one type...

Given the aggravated greenhouse effect caused by CO2 and the current energy shortage, CO2 capture and reuse has been gaining ever-increasing concerns. Microbial Electrolysis Cells (MECs) has been considered to be a promising alternative to recycle CO2 bioelectrochemically to low-carbon electrofuels such as CH4 by combining electroactive microorgani...

In this study, a 200-day deca-brominated diphenyl ether (deca-BDE) degradation activity experiment was carried out, using consumer-use curtain material as the substrate. During the degradation process, polybrominated diphenyl ether (PBDE) products with fewer bromine atoms were gradually generated by the debromination of deca-BDE. The influences of...

It is becoming increasingly urgent to investigate the partition coefficients (expressed as log K DOC values) of polybrominated diphenyl ethers (PBDEs) in dissolved organic carbon (DOC) present in wastewater. In the current study, after 72 h of equilibration, the concentrations of four common PBDEs were measured in the presence of four DOC solutions...

This study investigated the effect of light intensity on three various microalga consortia collected from natural ecological water bodies (named A, B and C) towards their fatty acid profiling and fractions, carbohydrate and protein production at different light intensities of 100, 200 and 300 μmol m-2 s-1. The results indicating that increasing lig...

To investigate the influence of lipid concentration (of total solids, w/w) on anaerobic treatment of food waste under thermophilic condition, a siphon-driven self-agitated anaerobic reactor was operated for 220 days. The average lipid concentration was changed from 12.8% to 59.3% (w/w) step by step. The gas production rate increased from 1.97 to 2....

Each carbon-based material, due to the discrepancy in critical properties, has distinct capability to enrich electroactive microbes able to electrosynthesize methane from CO2. To optimize electromethanogenesis process, this study physically prepared and examined several carbon-based cathode materials: carbon stick (CS), CS twined by Ti wire (CS-Ti)...

The rapid growth of the biofuels sector address the key issues related with fossil fuels utilization, such as reducing the greenhouse gas emissions, and sustainable and renewable fuels production. Among various biofuels option, biohydrogen production is a novel biotechnological tool that can be converting the organic matter into a valuable energy w...

The effects of organic loading rate (OLR) and operating temperature on the performance of siphon-driven self-agitated anaerobic reactor (SDSAR) in an on-site food waste (FW) treatment system were investigated. Two reactors were operated in parallel for comparison between mesophilic condition (35 ± 1 °C) and thermophilic condition (55 ± 1 °C). With...

This study assessed the impact of swine manure (SM) dilution ratio on the microalgal biomass cultivation and further tested for biohydrogen production efficiency from the mixed microalgal biomass. At first, various solid/liquid (S/L) ratio of the SM ranged from 2.5 to 10 g/L was prepared as a nutrient medium for the algal biomass cultivation withou...

This study assessed the co-digestion of macro and microalgal biomass towards the improvement of hydrogen production. The red macroalgal biomass (Gelidium amansii) and green mixed microalgal biomass was mixed in a ratio of 8:2, with an initial substrate concentration of 10 g/L, and various amount of inoculum addition range from 3 to 15% (v/v) was ev...

Dewatering of waste activated sludge (WAS) is of major interest in its volume reduction, transportation and ultimate disposal. Persulfate-based oxidation process is a newly developed option for enhancing WAS dewaterability through the generation of powerful sulfate radicals (SO4-·). However, the enhancement in WAS dewaterability by persulfate diffe...

Low-quality waste oils and fats such as an oily content of trap grease offer an alternative to fossil fuel oil, but are not fully utilized since they contain saturated fatty acids (SFAs) and saturated triglycerides (STGs), which have relatively high melting points. For practical use of the oily content, it is necessary to remove the components that...

In order to boost the economics of biogas utilization in those small facilities for food waste (FW) digestion, proximate grease trap waste (GTW) was employed to co-digest with FW. A bench-scale continuous stirred tank reactor was set up and operated at mesophilic temperature to investigate the co-digestion limit and lipid/long chain fatty acid (LCF...

This study investigated the potential and possibility of three mixed microalgae consortia collected from various ecological niches towards bioenergy production of H2 and CH4 in batch experiments under mesophilic conditions. Three different consortia collected from wastewater treatment plant, in an open pond system and in the lake bed possess differ...

Biohydrogen production from lignocellulosic biomass (LCB) is an active research area. Several workers have tested a number of substrates under different operational conditions and brought forward the many positive process performance features and identified the main sources of inhibition. This review analyzes selected fermentative biohydrogen produ...

The dispersion of granules in upflow anaerobic sludge blanket (UASB) reactor represents a critical technical issue in methanolic wastewater treatment. In this study, the potentials of coupling a microbial electrolysis cell (MEC) into an UASB reactor for improving methanolic wastewater biodegradation, long-term process stability and biomethane recov...

This study investigated the effect of combination of pretreatment methods such as ultra-sonication and electrolysis for the minimum energy input to recover the maximal carbohydrate and solubilization (in terms of sCOD) from mixed microalgae biomass. The composition of the soluble chemical oxygen demand (COD), protein, carbohydrate revealed that the...

This research investigated the effects of various dilute acid (HCl, H2SO4, HNO3, H3PO4) pretreatment on the solubilization of marine macroalgal biomass Gelidium amansii and subsequent hydrogen fermentation in a batch vials. The dry grounded biomass was hydrolyzed at temperature of 121 °C, solid/liquid (S/L) ratio of 5% (w/v), dilute acid concentrat...

Long chain fatty acids (LCFAs) are the intermediates from anaerobic digestion of lipid-rich waste, and limit the digestion even at millimolar concentrations. The digestion characteristics of unsaturated and saturated LCFAs, represented by oleic and palmitic acids, are investigated. Consequently, palmitic acid was far less inhibitory than oleic acid...

Biological treatment of wastewater is a low-cost solution for remediation of wastewater. This book focuses on the bioremediation of wastewater, its management, monitoring, role of biofilms on wastewater treatment and energy recovery. It emphasizes on organic, inorganic and micropollutants entering into the environment after conventional wastewater...

In anaerobic digestion (AD), long-chain fatty acids (LCFAs) produced by hydrolysis of lipids, exhibit toxicity against microorganisms when their concentration exceeds several millimolar. An absorption detection system using a quartz crystal microbalance (QCM) was developed to monitor the LCFA concentration during an anaerobic digester’s operation t...

Solid-liquid equilibria (SLE) for the binary systems of C12-C18 saturated fatty acids or their triglycerides + hexadecane (systems of dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecarioic acid (stearic acid), 1,2,3-propanetriyl tridodecanoate (trilaurin), 1,2,3-propanetriyl tritetradecan...

The use of liquid fraction of pressed municipal solid waste (LPW) for hydrogen production was evaluated via electrohydrogenesis in a single-chamber microbial electrolysis cell (MEC). The highest hydrogen production (0.38 ± 0.09 m3 m−3 d−1 and 30.94 ± 7.03 mmol g−1 CODadded) was achieved at an applied voltage of 3.0 V and pH 5.5, increasing by 2.17-...

Hydrogen production from mixed microalgae biomass, predominantly containing Scendesmus and chlorella species, was investigated with a focus on enhancement strategies, in particular (i) pH control (at 5.5) and (ii) methanogenic inhibitor (BESA) addition along with pH control at 5.5. The results obtained showed that the later condition remarkably inc...

High-rate hydrogen production from galactose and rapid granule formation were achieved in a mesophilic (37 °C) upflow anaerobic sludge blank reactor (UASBr). Hybrid immobilized cells were seeded to a CSTR fed with galactose (15 g L-1) at a hydraulic retention time (HRT) of 12 h for 12 days, after which the mixed liquor from the CSTR was transferred...

This study investigated the effects of pretreatment methods (such as autoclave, ultrasonication and electrolysis) of mixed microalgae consortia (predominantly composed of _Scenedesmus_ followed by _Chlorella_ species) from natural ecological niche. In addition, the cultivated biomass (wet) was subsequently utilized for fermentative H2 production in...

Renewable energy recovery from submerged aquatic plants such as Egeria densa (E. densa) via continuous anaerobic digestion (AD) represents a bottleneck because of process instability. Here, a single-chamber membrane-free microbial electrolysis cell (MEC) equipped with a pair of Ti/RuO2 mesh electrodes (i.e. the combined MEC-AD system) was implement...

Hydrogen sulfide is major contaminants in biogas produced via anaerobic digestion of organic solid wastes and industrial wastewater, and has to be removed, as it is toxic and highly corrosive to materials. In recent years, as an alternative to the chemically based H2S removal technologies, biological processes using sulfide-oxidizing bacteria (SOB)...

Renewable energy recovery from submerged aquatic plants such asEgeria densa(E. densa) via continuousanaerobic digestion (AD) represents a bottleneck because of process instability. Here, a single-chambermembrane-free microbial electrolysis cell (MEC) equipped with a pair of Ti/RuO2mesh electrodes (i.e.the combined MEC-AD system) was implemented at...

Microbial electromethanogenesis, relying on electrochemically active biofilm on biocathode to convert carbon dioxide to methane, provides a novel approach for renewable energy storage. One key factor that governs electron exchange and methane formation efficiencies is the electrode material. To promote methane production, a biocathode via modifying...

Fermentative hydrogen production research grows rapidly around the globe to harness “clean energy” by the utilization of renewable feedstock, which can reduce climate change impacts as well as able to resolve concerns related to fossil fuel consumption. Biohydrogen production technologies have been carried out in various modes of operation among wh...

Fermentative hydrogen production research grows rapidly around the globe to harness "clean energy" by the utilization of renewable feedstock, which can reduce climate change impacts as well as able to resolve concerns related to fossil fuel consumption. Biohydrogen production technologies have been carried out in various modes of operation among wh...

Temperature-phased anaerobic digestion (TPAD) Two-stage Recycle Long-chain fatty acid (LCFA) a b s t r a c t Anaerobic digestion is an effective technology to recover energy from oily food waste. A single-stage system and temperature-phased two-stage systems with and without recycle for anaerobic digestion of oily food waste were constructed to com...

Dosage of nutrients for anaerobic digestion is essential to maintain their treatment performance. Kitchen waste generally contains low concentrations of nutrients, especially metals. However, for de-oiled grease trap waste (GTW), such a kitchen waste, little data are available in terms of nutrient supplementation to enhance anaerobic digestion. In...

This study investigated the effect of controlling pH (5.5) and heat pre-treatment of seed inoculum in dark fermentative hydrogen production. The results showed that only inoculum source plays an important role rather than pH and heat treatment. Seed source is vital factor despite, heat treatment and pH controlled at 5.5. Mesophilic fermentation res...

The effect of reduced form of sulfur compounds on granular sludge was investigated. Significant release of extracellular polymeric substance (EPS) from the granular sludge occurred in the presence of sulfide and methanethiol according to various concentrations. Granular sludge also showed a rapid increase in turbidity and decrease in diameter in ac...