Biohydrogen Production System Research Articles

Biological fermentation pilot-scale systems and evaluation for commercial viability towards sustainable biohydrogen production

Featuring high caloric value, clean-burning, and renewability, hydrogen is a fuel believed to be able to change energy structure worldwide. Biohydrogen production technologies effectively utilize waste biomass resources and produce high-purity hydrogen. Improvements have been made in the biohydrogen production process in recent years. However, there is a lack of operational data and sustainability analysis from pilot plants to provide a reference for commercial operations. In this report, based on spectrum coupling, thermal effect, and multiphase flow properties of hydrogen production, continuous pilot-scale biohydrogen production systems (dark and photo-fermentation) are established as a research subject. Then, pilot-scale hydrogen production systems are assessed in terms of sustainability. The system being evaluated, consumes 171,530 MJ of energy and emits 9.37 t of CO2 eq when producing 1 t H2, and has a payback period of 6.86 years. Our analysis also suggests future pathways towards effective biohydrogen production technology development and real-world implementation.

Sodium alginate based artificial biofilms polymerized by electrophoretic deposition for microbial hydrogen generation

This study developed an artificial biofilm of Rhodospirillum rubrum bacteria immobilized within an alginate matrix using electrophoretic deposition (EPD) on an electrode. The resulting biofilm immobilized bacteria effectively and maintained a high survival rate, facilitating stable and high-efficiency hydrogen generation for longer periods compared to biofilms produced using free bacteria. Hydrogen production efficiency remained constant when the substrate was periodically replaced, indicating that the bacteria could survive within the biofilm for long-term hydrogen production. EPD produced mechanically stable large-scale biofilms economically and rapidly, which effectively overcame operational limitations such as culture medium temperature, pH, and flow rate. Therefore, this proposed method has the potential to accelerate the commercialization of biohydrogen production systems through large-scale biofilm production to facilitate continuous hydrogen generation. The technique can be utilized in various hydrogel-based applications, providing a cost-effective and efficient manufacturing process with customized biological and mechanical properties. The developed biofilms have implications beyond biohydrogen production and could be applied to hydrogel-based medical, cosmetic, and food applications. This study highlights the importance of immobilizing bacteria for stable and efficient hydrogen generation and demonstrates the potential of EPD in fabricating mechanically stable biofilms for large-scale production.

Enhanced biohydrogen yield and light conversion efficiency during photo-fermentation using immobilized photo-catalytic nano-particles

Bacterial immobilization is a common method in anaerobic fermentation, since of the maintenance of high bacterial activity, insurance of high density microbial during continuous fermentation, and quick adaptability to the environment. While, the bio-hydrogen production capacity of immobilized photosynthetic bacteria (I-PSB) is seriously affected by the low light transfer efficiency. Hence, in this study, photo-catalytic nano-particles (PNPs) was added into the photo-fermentative bio-hydrogen production (PFHP) system, and its enhancement effects of bio-hydrogen production performance were investigated. Results showed that the maximum cumulative hydrogen yield (CHY) of I-PSB with 100 mg/L nano-SnO2 (154.33 ± 7.33 mL) addition was 18.54% and 33.06% higher than those of I-PSB without nano-SnO2 addition and control group (free cells), and the lag time was the shortest indicating a shorter cell arrest time, more cells and faster response. Maximum energy recovery efficiency and light conversion efficiency were also found to be increased by 18.5% and 12.4%, respectively.

A System Analysis of a Bio-Hydrogen Production System Using Granulated Mine Residue as a H2S Adsorbent

An energy production system that combines biomass and fuel cells produces much energy with minimal environmental impact. However, the hydrogen sulfide (H2S) contained in gasified biomass degrades fuel cell performance, thus negating the advantages of this combination. In this study, the removal of H2S by adsorption after biomass gasification was investigated. Metal oxides with high adsorption performance are common H2S adsorbents. However, they have a significant environmental impact in terms of metal depletion, which is an environmental impact indicator. Therefore, neutralized sediment materials from mine drainage treatments can be used as H2S adsorbents. A previous study found that the adsorption performance of H2S adsorbents is equivalent to that of metal oxides, especially in the high-temperature zone (300 °C), and the environmental impact is considerably lower than that of metal oxides. However, because the neutralized sediment is a powder (Φ 4.5 μm on average), there is a possibility that the gas will not flow due to the pressure drop when it is used in a large adsorption column. Therefore, in this study, we propose the use of granulated neutralized sediments for practical plant operations. No studies have investigated the adsorption performance of granulated neutralized sediment through experiments or quantitatively investigated the effect of using waste material as a H2S adsorbent to reduce the environmental impact of hydrogen production. Based on these data, the sulfur capture capacity of the granulated neutralized sediment was experimentally investigated. The extent to which the environmental impact of the hydrogen production system could be reduced when granulated neutralized sediment was used as the H2S adsorbent was assessed. Note that the granulated neutralized sediment is formed with about a Φ 0.56–1.25 mm diameter. The granulated neutralized sediment exhibited approximately 76.8% of the adsorption performance of zinc oxide (ZnO) on a conventional adsorbent. In terms of the LCA, the global warming potential (GWP) and the abiotic depletion potential (ADP) were improved by approximately 0.89% (GWP) and 55.3% (ADP) in the entire hydrogen production process. This study demonstrated that the use of waste materials can significantly reduce the environmental impact on the entire system.

Machine learning technology in biohydrogen production from agriculture waste: Recent advances and future perspectives

Agricultural waste biomass has shown great potential to deliver green energy produced by biochemical and thermochemical conversion processes to mitigate future energy crises. Biohydrogen has become more interested in carbon-free and high-energy dense fuels among different biofuels. However, it is challenging to develop models based on experience or theory for precise predictions due to the complexity of biohydrogen production systems and the limitations of human perception. Recent advancements in machine learning (ML) may open up new possibilities. For this reason, this critical study offers a thorough understanding of ML’s use in biohydrogen production. The most recent developments in ML-assisted biohydrogen technologies, including biochemical and thermochemical processes, are examined in depth. This review paper also discusses the prediction of biohydrogen production from agricultural waste. Finally, the techno-economic and scientific obstacles to ML application in agriculture waste biomass-based biohydrogen production are summarized.

Thermal Design of a Biohydrogen Production System Driven by Integrated Gasification Combined Cycle Waste Heat Using Dynamic Simulation

Utilizing biological processes for hydrogen production via gasification is a promising alternative method to coal gasification. The present study proposes a dynamic simulation model that uses a one-dimensional heat-transfer analysis method to simulate a biohydrogen production system. The proposed model is based on an existing experimental design setup. It is used to simulate a biohydrogen production system driven by the waste heat from an integrated gasification combined cycle (IGCC) power plant equipped with carbon capture and storage technologies. The data from the simulated results are compared with the experimental measurement data to validate the developed model’s reliability. The results show good agreement between the experimental data and the developed model. The relative root-mean-square error for the heat storage, feed-mixing, and bioreactor tanks is 1.26%, 3.59%, and 1.78%, respectively. After the developed model’s reliability is confirmed, it is used to simulate and optimize the biohydrogen production system inside the IGCC power plant. The bioreactor tank’s time constant can be improved when reducing the operating volume of the feed-mixing tank by the scale factors of 0.75 and 0.50, leading to a 15.76% and 31.54% faster time constant, respectively, when compared with the existing design.

Tolerance of photo-fermentative biohydrogen production system amended with biochar and nanoscale zero-valent iron to acidic environment

Anaerobic fermentation system is easy to become acidic due to the generation of small molecular acids, which will affect the metabolism of bacteria. Therefore, it is necessary to improve the acid resistance of system. In this work, the tolerance of photo-fermentative biohydrogen production system amended with biochar, nanoscale zero-valent iron (nZVI) and biochar + nZVI to acidic environment was studied. Results showed that additives improved the stability and performance of the photo fermentation. The best increment of biohydrogen from 0 to 286.83 ± 2.77 mL was obtained by adding biochar and nZVI together at the original pH of 4.5. The additive reduced the oxidation–reduction potential and promoted the consumption of acetate and butyrate. At initial pH of 5, 6 and 7, the highest biohydrogen yield of 361.02 ± 10.11, 419.36 ± 10.70 and 382.67 ± 25.08 mL was obtained by adding nZVI, respectively, representing 42%–44.45% increase compared with the control group under the same conditions.

Role of surfactant in affecting photo-fermentative bio-hydrogen production performance from corncob

Surfactant addition can cause a significant change in the interface state of the solution system, which is helpful to avoid agglomeration and sedimentation of solid state, and improve the mass transfer capacity. Hence, the performance of high-solid photo-fermentative bio-hydrogen production system with bio-surfactant addition was evaluated in this work. Corncob was selected as raw material, and cumulative hydrogen yield (CHY) was taken as reference. The effect of Rhamnolipids (RLs) and Tea Saponin (TSn) addition on hydrogen yield capacity was investigated. The results showed that CHY was effectively increased by the addition of RLs and TSn, the highest CHY of 356.42 ± 16.5 mL and 265.38 ± 7.5 mL appeared when the concentrations of surfactant addition were 0.08 g/L RLs and 1.5 g/L TSn, which were 67.85% and 24.97% higher than control group, respectively. The maximum energy conversion efficiency reached 5.47% and 4.08% with an increase of 67.8% and 25.2%.

Influence of laser photoactivated graphitic carbon nitride nanosheets and nickel nanoparticles on purple non-sulfur bacteria for biohydrogen production from biomass

The objective of this study is to increase biohydrogen production from biomass using laser photoactivated nanomaterials. Light saturation of photo-fermentation is a vital factor that influences fermentation effectiveness and hydrogen yield. In this study, it is hypothesized that the bio-stimulation of hydrogen-producing purple non-sulfur (PNS) bacteria using laser photoactivated nanomaterials can enhance the endurance ability of such bacteria to unsteady light irradiation, where this leads to overcome the challenge of light saturation. Furthermore, the addition of nanomaterials leads to bio-stimulate the bacterial cells and enhance their activity and growth rate and, therefore, increase biohydrogen production from biomass. A biohydrogen production system and a model of photobioreactor were manufactured and installed. Food wastes were collected from kitchen leftovers of different fast-food suppliers and were used in this study as feedstocks for biohydrogen production. The production process was conducted as following: exposing 16.5 mg/l of graphitic carbon nitride nanosheets on the one hand and 50 mg/l of nickel nanoparticles on the other hand to a helium-neon green laser radiation source with a wavelength of 543 nm for 1 h, then adding them to the bacterial inoculum and then mixing them with biomass and water by a ratio of 0.5:1:2 which were then kept in the photobioreactor exposed to white light emitting diodes (LEDs) with a luminous flux of 3600 lumen and at 30 °C for 26 days with mixing for 5 min every 30 min to produce biohydrogen. By this method, it is possible to improve the bioenvironmental conditions and the bio-responses of bacteria which results in increasing the biohydrogen yield by 287% over the conventional method.

Potential for biohydrogen production from organic wastes with focus on sequential dark- and photofermentation: the Philippine setting

Fossil fuel remains the world’s main source of energy, but its massive use leads to the exhaustion of natural energy resources as well as climate change. With this, the interest in developing alternative energy sources has emerged globally—among these is hydrogen. Among the hydrogen production approaches, biological fermentation has been attracting global attention because of its environmental and economic merits. This process utilizes diverse feedstocks including complex organic waste materials. The Philippines has a great potential to produce hydrogen from biomass primarily because it is an agricultural country. The country is abundant in various agricultural wastes such as livestock manure, and plant residues of rice, corn, sugarcane, and coconut, as well as agro-industrial and municipal organic wastes with millions of tons generated per year. A number of studies have explored the use of technologies such as the dark fermentation (DF), photofermentation (PF), and the integration of DF and PF to utilize organic wastes for biohydrogen production. This review paper provides an overview of the organic waste scenario in the Philippines including approaches to utilize different wastes for fermentative biohydrogen production. An initial estimate conducted on the biohydrogen production suggested that the Philippines can yield 0.34–2.24 × 106 t/year from agricultural residues alone using the proposed two stage DF-PF hybrid system, with a positive net energy conversion, hence validating the possibility of establishing a biohydrogen production system from organic wastes generated in the country.

Preparation of active hydrogen-producing cultures from palm oil mill sludge for biohydrogen production system

Methods are investigated to prepare active hydrogen (H2)-producing cultures originating from palm oil mill sludge using dark fermentation. The first successful method that produces potent H2-producing cultures and avoids growing H2-consuming methanogens involves heat pretreatment of the sludge at 100 °C for 2 h and then the sludge sample is shocked in an ice bath for 15 min. Subsequently, a glucose solution rich in nutrients (glucose-based substrate) of 14.80 g chemical oxygen demand (COD)/L is fed in to enrich the H2-producing cultures. The H2 production reaches 78.63% on day 31. The second method involves acid pretreatment of sludge with 10 M hydrochloric acid at pH 3 for 48 h. Glucose-based substrate of 25.47 g COD/L is fed into the system. The H2 production is 69.41% on day 27. For both methods, the H2 production is stable after the H2 content reached its maximum. The operation is performed semi-continuously using a hydraulic retention time of 1 day and at 30 °C. The optimum bacterial cells-to-COD level of substrate is approximately 0.60 in the start-up medium. The fermentation medium has an optimum initial pH of 5 and a final pH of 5.2–5.3. These two methods are recommended to produce active H2-producing cultures for plant start-up in bio-H2 production.

Analysis of carbon footprint and energy performance of biohydrogen production through gasification of different waste agricultural biomass from the Philippines

Agricultural crop residues are available in abundance in Asian countries such as the Philippines. These residues have high potential as feedstock to produce clean and high-value energy products, to mitigate global warming and reduce dependence on fossil fuels. This study investigated the carbon footprint and energy performance of biohydrogen production system through gasification of different waste agricultural biomass. The proposed system includes biomass transport and pre-processing, gasification process, and biohydrogen enrichment and purification technologies. Calculation of the syngas composition was performed using a stoichiometric-thermodynamic equilibrium model using python script. Generation of energy from fossil fuel to support the system operations produced the highest greenhouse gas emission. The production system using sugarcane leaves as feedstocks exhibited the lowest carbon footprint, highest gasification efficiency, and best energy performance based on the computed energy ratio. Biophysical allocation was used to determine the burden associated with the biomass during its growth phase. Incorporation of the carbon uptake during biomass growth phase reduced the carbon footprint of the system. Sensitivity analysis showed that increasing C/O and H/O ratio improves the quality of the syngas produced, while increasing C/H ratio results to lower biohydrogen yield. In selection of feedstock mix, it is preferred to maximize C/O and H/O ratio while reducing C/H ratio of the feedstock composition.

Predictive functional profiling of microbial communities in fermentative hydrogen production system using PICRUSt

PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states) is based on 16S rRNA sequencing data, which can analyze the microbial functions in fermentation system. In this study, PICRUSt was adopted to figure out the direct evidence of functions of the microbial community in biohydrogen production system. PICRUSt analysis demonstrated that metabolic flux shifted from acid-producing pathway to hydrogen-producing pathway, and the hydrogen-consuming homoacetogenic pathway was eliminated by ionizing radiation pretreatment at 5 kGy. KEGG (Kyoto Encyclopedia of Genes and Genomes) based functional genes analysis showed enriched energy metabolism and diminished homoaceto gene, which enhanced the hydrogen production. However, the diminished carbohydrate metabolism indicated that the pretreatment reduced the activity of microbial consortia to degrade various substrates. This study suggested that PICRUSt is an effective approach to analyze the functional profiling of microbial community in fermentative hydrogen production system.

Ameliorated hydrogen production through integrated dark-photo fermentation in a flat plate photobioreactor: Mathematical modelling and optimization of energy efficiency

Biohydrogen production through ‘one-pot’ integration of the dark fermentative and photofermentative routes has become one of the most researched versions of the bioprocess. Present investigation experimentally and mathematically assessed the performance of a single stage integrated dark-photo (SSIDP) biohydrogen production system focusing on amelioration of hydrogen yield and energy conversion efficiency (ECE) through optimization. Dark fermentative C. acetobutylicum and photofermentative Rhodopseudomonas sp. were combined in a flat plate photobioreactor (FPPBR) and operated adopting a ‘batch – repeated batch cycle’ strategy for biohydrogen production for the first time. Hydrogen yield and ECE were optimized with respect to the ratio of the photo- to dark- fermentative bacteria (P:D), the fraction of medium removed and refilled during operation (γ) and intensity of light (I) by using the statistical tool response surface methodology (RSM). Maximum cumulative hydrogen of 4.44 mol H2/mol glucose was produced from the operation of the SSIDP FPPBR under optimal condition (P:D (2:1), γ (0.1), I (90 W/m2)). The optimum yield was almost 2.24 times higher than the yield (1.98 mol H2/mol glucose) obtained from batch operation of the FPPBR using same quantity of glucose and optimum values of P:D and I. ECE of the optimally operated FPPBR in batch - repeated batch cycle mode (45.31%) was also enhanced by the same factor (2.24) in comparison to that (20.20%) obtained from the batch operation. Switch over to the batch – repeated batch cycle strategy from the batch mode operation led to attainment of 2.96 fold (196.75%) increment on overall energy conversion efficiency. A deterministic mathematical model has been developed for a priori prediction of the profiles of the substrate and products of the SSIDP FPPBR system. Reasonably high degree of agreement between the predicted and experimental data confirmed the validity and adequacy of the evaluative power of the developed model.

제강공정의 배열 및 부생가스를 활용한 바이오수소 생산 시스템의 동적 시뮬레이션

본 논문에서는 제철소의 배열과 부생가스를 이용한 바이오수소 시스템을 제안하고 간헐적으로 발생하는 skirt의 냉각수를 활용하는 경우에 대하여 동적 시뮬레이션을 수행하고 시스템 구성요소의 시간에 따른 온도 변화를 실험과 비교하였다. 1톤급 반응기 시뮬레이터와 시뮬레이션을 비교한 결과 각 구성요소에서의 온도변화폭과 경향이 잘 예측되는 것을 확인하였다. 실험과 시뮬레이션은 설계조건 뿐 아니라 2가지 탈설계 조건에서도 잘 일치하였다. 신뢰성을 확인한 후 시뮬레이션을 이용하여 실제 현장에 설치될 10톤급 반응기의 설계를 수행하였다. 시뮬레이션을 수행한 결과 축열조의 열원 유효성 및 반응기의 최소 온도 편차를 보장하는 시스템의 최소 체적을 발견하였다.

Progress in microbiology for fermentative hydrogen production from organic wastes

Dark fermentative hydrogen production from organic wastes can achieve dual benefits of clean energy generation and waste utilization, which offers the best prospects for a biohydrogen production process with high environmental benefits. Biohydrogen production system is a complex biological process, which is affected by many factors, including operational conditions (e.g. temperature, pH), substrate type, reactor design etc., and depends on the microbial type, retention time, activity, productivity and end products. Among these influencing factors the hydrogen-producing microorganisms play a vital role. Great efforts have been made to enhance the hydrogen production efficiency from the perspective of microbiology. In this review, the microbiology, biochemistry and enzymology for biological hydrogen production were briefly summarized and analyzed. The recent progress in microbiology for hydrogen production through dark fermentation was reviewed, including microorganisms, biochemistry, enzymology, microbial modification and the identification of the microbial community structure. Metabolic pathways can be modified by metabolic engineering, thus enhancing the biological hydrogen production through overcoming limiting factors for hydrogen production in various systems by increasing the flow of electrons to hydrogen-producing pathways, increasing substrate utilization, and engineering more efficient and/or oxygen-resistant hydrogen-evolving enzymes. Finally, concluding remarks and perspectives are given.

설비공학회 분야의 최근 연구 동향 : 2017년 학회지 논문에 대한 종합적 고찰

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2017. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) In building mechanical system research fields, twenty studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (2) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to the ventilated cavity of curtain-wall system for enhancing insulation and preventing condensation, the improvement plans of condensation defect examples in apartment building and the calculation method for the transmitted solar irradiance using the total horizontal irradiance. The subjects of building energy are worked on the energy consumption characteristics in office buildings, energy performance analysis for energy saving potentials in a hospital building, outdoor air cooling system operated with load prediction, building energy efficiency rating changes by enhanced building envelope standards, energy saving effect for the external insulation construction, energy reduction of a heating network through the application of an absorption heat pump, analysis of thermal load profile according to the window retrofit in an old school building, calculating regional balance point temperature for heating degree-days in korea, short-term load prediction using artificial neural network models, the simple window model applied to EnergyPlus, possibility of building energy saving through the building data, optimal cooling operation of a single family house model equipped with renewable energy facility by linear programming. The remained studies are related to the comparison between korea and china evacuation laws in office building, the effect of cold air stimulation during the driver’s drowsiness, the calculation of the attachedpiping-material rate for the building mechanical-service system in office buildings, the development of a modularlightweight steel ceiling system and the evaluation of local loss coefficients for different waveguide-below-cutoff (wbc) arrays of electromagnetic pulse. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, research subjects include the improvement of Type II and double-effect absorption heat pumps, the seasonal performance of compression heat pumps, a vertical receiver in a compression heat pump, the performance of a domestic built-in ice maker and the performance characteristics of a surface water heat pump system. In the alternative refrigeration/energy system category, subjects include a membrane dehumidification system, a CO₂-hydrate circulation system, a Zeolite 13x chemical thermal energy storage system and the performance criteria for heat pumps as a renewable energy device. In the system control category, subjects include a defrosting control system using photoelectric sensors and the control method for an organic thermal storage-chiller system. (4) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for prediction of stratification model for diffusers in underfloor air distribution system using the CFD, transport properties for transportation of captured CO₂, dynamic thermal design of a 1-ton class bio-hydrogen production system simulator, cylindrical premixed burner, heat transfer enhancement in a divergent passage with 30° inclined ribs, the development of regulatory guideline on the applicability of CFD software, a staggered fin, single phase thermal stratification in both cold legs and downcomer. In the area of pool boiling and condensing, effects of tube diameter and surface sub-cooling temperature on R1234ze(E) and R1233zd(E) film condensation heat transfer characteristics in smooth horizontal laboratory tubes, surface energy variations and condensate behaviors on nitrogen ion implanted aluminum surfaces were studied. In the area of industrial heat exchangers, plate type enthalpy exchanger through CFD analysis of elements, fluidized bed heat exchanger for heat recovery from multi-heat sources, paper enthalpy exchange element by impregnation of the spacer, the effect of the air temperature on the air-side heat-transfer coefficient and the friction factor of a fin-and-tube heat exchanger, cooling of telecommunication cabinet, effects of seawater fouling on a plate-frame heat exchanger, carbon dioxide during heating process in the near-critical region for single channel, a heat exchanger for an air-compressor of a railway vehicle were studied.

Potential use and the energy conversion efficiency analysis of fermentation effluents from photo and dark fermentative bio-hydrogen production

Effluent of bio-hydrogen production system also can be adopted to produce methane for further fermentation, cogeneration of hydrogen and methane will significantly improve the energy conversion efficiency. Platanus Orientalis leaves were taken as the raw material for photo- and dark-fermentation bio-hydrogen production. The resulting concentrations of acetic, butyric, and propionic acids and ethanol in the photo- and dark-fermentation effluents were 2966mg/L and 624mg/L, 422mg/L and 1624mg/L, 1365mg/L and 558mg/L, and 866mg/L and 1352mg/L, respectively. Subsequently, we calculated the energy conversion efficiency according to the organic contents of the effluents and their energy output when used as raw material for methane production. The overall energy conversion efficiencies increased by 15.17% and 22.28%, respectively, when using the effluents of photo and dark fermentation. This two-step bio-hydrogen and methane production system can significantly improve the energy conversion efficiency of anaerobic biological treatment plants.

Continuous hydrogen production by dark fermentation in a foam SiC ceramic packed up‐flow anaerobic sludge blanket reactor

AbstractBiohydrogen generation using anaerobic sludge from a sewage treatment plant is a promising strategy for converting waste into renewable energy. The porous foam SiC ceramic structured packing was used as a support in the up‐flow anaerobic sludge blanket (UASB) reactor to enhance the biohydrogen yield. Using glucose as the major carbon source, the SiC‐UASB reactor was continuously operated under the organic loading rates (OLR) between 30 and 90 gglucose/L · d at a hydraulic retention time (HRT) of 4 h. The maximum hydrogen production rate (5.24 L/L · d) and hydrogen content (50 %) were obtained at 60 gglucose/L · d OLR. It demonstrated that the reaction of fermentation was predominated by the butyric acid pathway. The employment of SiC packings resulted in quick startup (∼5 days) and high efficiency of hydrogen production. The buffering capacity and the cell culture immobilization ability of the UASB reactor were obviously improved by the application of SiC packings, which increased the feasibility of scale‐up of the continuous biohydrogen production system.

Life-cycle performance of hydrogen production via indirect biomass gasification with CO2 capture

The implementation of CO2 capture into biohydrogen-production systems is seen as a potential solution for greening the energy sector. However, the performance of biocapture strategies needs to be assessed thoroughly in order to guarantee their suitability. In this work, the Life Cycle Assessment methodology is used to evaluate an energy system producing hydrogen from short-rotation poplar biomass through gasification coupled with carbon dioxide capture. The biomass feedstock is dried and milled before being fed to a low-pressure char-indirect gasifier. The syngas produced is conditioned and undergoes a water gas shift process. Biohydrogen is separated from the rest of compounds in a pressure swing adsorption (PSA) unit. The PSA off-gas is burnt for electricity production and the exhaust gas from this power-generation section goes through a two-stage gas separation membrane process for CO2 capture. The results show that the system succeeds in obtaining a negative (i.e., favourable) global warming impact with a low cumulative non-renewable energy demand. Direct emissions to the air, external electricity production and biomass production are the key processes contributing to the evaluated impacts. When it comes to replacing conventional (fossil-based) hydrogen, the biohydrogen product is found to be a better alternative than biohydrogen without CO2 capture only under global warming aspects.