光合细菌产氢研究进展与问题

化石能源的日益枯竭及其长期使用造成了严重的环境污染,寻找清洁的可再生能源成为当前亟待解决的世界性重大课题。光合细菌产氢以其较高的底物转化效率、较高的光能利用率以及能够灵活利用多种小分子有机酸等特点而成为大规模生物产氢的研究热点。文章从光合细菌产氢机理(主要针对光合单位、固氮酶和氢酶的联合产氢机理)、影响光合细菌产氢的各种物理因素和如何提高光合细菌的产氢量等方面,系统介绍了当前国内外光合细菌产氢的最新研究结果及进展,并对该领域研究存在的主要问题及发展趋势进行了简要评述。     

A novel nutrient control method to deprive green algae of sulphur and initiate spontaneous hydrogen production

The green alga Chlamydomonas reinhardtii has the ability to produce clean and renewable molecular hydrogen through the biophotolysis of water. Hydrogen production takes place under anaerobic conditions, which may be imposed metabolically by depriving the algae of sulphur. Sulphur-deprivation typically requires the spatial and temporal separation of the algal growth and hydrogen production stages. This would typically require separate photobioreactors for each stage as well as a costly and energy intensive medium exchange technique such as centrifugation, making the process difficult to scale up.     

NADPH fluorescence as an indicator of hydrogen production in the green algae Chlamydomonas reinhardtii

This study investigated cellular Nicotinamide Adenine Dinucleotide Phosphate (NADPH) fluorescence as a potential indicator of biohydrogen production in Chlamydomonas reinhardtii and a β-NADPH standard. NADPH fluorescence profiles of cultures grown in TAP-S (Tris-acetate phosphate minus sulphur) media, TAP (Tris-acetate phosphate) media and TAP + 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) were subsequently compared. Hydrogen production induced from sulphur depletion was found to correlate directly (r = 0.941) with NADPH over the ten day period. The addition of leachate was used to increase hydrogen yields, and subsequently increased the NADPH concentration by 50%–70%. A direct correlation was observed (r = 0.929) between NADPH and hydrogen when the leachate supplemented media was used. As NADPH is the terminal electron acceptor in the photosynthetic chain, results show that NADPH has a pivotal role in hydrogen production as a carrier molecule. Under sulphur depletion, cellular NADPH fluorescence can be used as an indicator of hydrogen production.     

Process simulation and optimization for enhanced biophotolytic hydrogen production from green algae using the sulfur deprivation method

This article explores the modeling, simulation and optimization of a biophotolytic cyclic process for enhanced hydrogen production from microalgae, employing the sulfur deprivation method. To achieve sulfur deprivation, each process cycle contained two temporally separated steps of sulfur-controlled algae growth and sulfur-deprived anaerobic hydrogen production.Reaction kinetics were modeled via an empirical logistic model. Reaction times, sulfate concentrations, and medium pH levels of each cycle were controlled to optimize the rate and yield of hydrogen production. Consequently, 65% and 23% improved values were obtained, respectively, with a smaller total process time (?11%), higher ratio of algae growth-to-hydrogen production time (29% vs. 21%), buffered pH (7.8), controlled sulfate injection and intermediary algae concentrations. Two- and 15-times higher hydrogen yields were obtained for 2- and 12-times lower initial algae concentrations. The proposed method is a significant tool for the design and optimization of a process for enhanced hydrogen production from microalgae.     

Performance of a groove-type photobioreactor for hydrogen production by immobilized photosynthetic bacteria

The biofilm technique has been proved to be an effective cell immobilization method for wastewater biodegradation but it has had restricted use in the field of photobiological H₂ production. In the present study, a groove-type photobioreactor was developed and it was shown that a groove structure with large specific surface area was beneficial to cell immobilization and biofilm formation of the photosynthetic bacteria on photobioreactor surface as well as light penetration. A series of experiments was carried out on continuous hydrogen production in the groove-type photobioreactor illuminated by monochromatic LED lights and the performance was investigated. The effects of light wavelength, light intensity, inlet glucose concentration, flow rate and initial substrate pH were studied and the results were compared with those obtained in a flat panel photobioreactor. The experimental results show that the optimum operational conditions for hydrogen production in the groove-type photobioreactor were: inlet glucose concentration 10 g/L, flow rate 60 mL/h, light intensity 6.75 W/m², light wavelength 590 nm and initial substrate pH 7.0. The maximum hydrogen production rate, H₂ yield and light conversion efficiency in the groove-type photobioreactor were 3.816 mmol/m²/h, 0.75 molH₂/molglucose and 3.8%, respectively, which were about 75% higher than those in the flat panel photobioreactor.     

Continuous photosynthetic production of hydrogen peroxide by the blue-green algae Anacystis nidulans R2 as a way to solar energy conversion

Continuous production of hydrogen peroxide by a culture of the blue-green algae Anacystis nidulans R2 is described as a model system for the conversion of solar energy. The redox power from the photolysis of water, promoted by the photosynthetic apparatus of algae, is driven by the redox mediator methyl viologen to oxygen which is reduced, in two successive steps, to superoxide and hydrogen peroxide. Hydrogen peroxide is a chemical compound with a high value since it is extensively used in industry, especially as bleaching agent. Moreover, this product is a powerful source of energy which releases more than 100 kJ per mol upon decomposition into water and oxygen; it is considered a fuel able to drive rockets and engines. Optimum pH and temperature of the photosystem, as well as the effect on H₂O₂ production of the concentration of methyl viologen, amount of cell, and intensity of light have been studied. Under saturation of light and methyl viologen, and and at the temperature of 45°C, a production of hydrogen peroxide higher than 200 μmol/mg Chl · h was reached. In these conditions, 2% of the light energy absorbed by the photosystem is converted in chemical energy as H₂O₂.     

Optimization of photosynthetic hydrogen production from acetate by Rhodobacter sphaeroides RV

In this study, hydrogen production by Rhodobacter sphaeroides RV from acetate was investigated. Ammonium sulphate and sodium glutamate were used to study the effects of nitrogen sources on photosynthetic hydrogen production. The results showed the optimal concentrations for ammonium sulphate and sodium glutamate were in the range of 0.4–0.8 g/L. Orthogonal array design was applied to optimize the hydrogen-producing conditions of the concentrations of yeast, FeSO₄ and NiCl₂. The theoretical optimal condition for hydrogen production was as follow: yeast 0.1 g/L, FeSO₄ 100 mg/L and NiCl₂ 20 mg/L.     

Techno-economic calculation of green hydrogen production and export from Colombia

In the present paper a techno-economic hydrogen production and transportation costs to export from Colombia to Europe and Asia were determined using the open-source Python tools, such as WindPowerLIB, PVLIB, ERA5 weather data, and the Hydrogen-2-Central (H2C) model. Calculations were performed as well for Chile, for comparison as a regional competitor. In addition, a detailed overview of Colombia's energy system and national efforts for a market ramp-up of renewable energy and hydrogen is provided. The application of the model in different scenarios shows Colombia's potential to produce green hydrogen using renewable energies. The prices estimated are 1.5 and 1.02 USD/kgH₂ for 2030 and 2050 with wind power, and 3.24 and 1.65 USD/kgH₂ for 2030 and 2050 using solar energy. Colombia can become one of the most promising hydrogen suppliers to Asian and European countries with one of the lowest prices in the production and transportation of green hydrogen.     

A comparison of hydrogen production among three photosynthetic bacterial strains

The characteristics of hydrogen production from individual and mixed volatile fatty acids (VFAs) were compared among three photosynthetic bacterial strains, Rhodopseudomonas sp., Rhodopseudomonas palustirs W004 and Rubrivivax sp. Rhodopseudomonas sp. and R. palustirs W004 could convert both butyrate and acetate into hydrogen. Rubrivivax sp. could assimilate butyrate and acetate, but could not produce hydrogen from them when individual VFA was used as substrate. The highest hydrogen amount (2191.7 mL/L culture), COD reduction efficiency (85.3%) and H₂ yield (468.3 mL H₂/g COD) were achieved by Rhodopseudomonas sp. with butyrate as carbon source. All the three strains could produce hydrogen from mixed VFAs. Rhodopseudomonas sp. and R. palustirs W004 could digest the substrates completely. Hydrogen production from mixed VFAs by Rubrivivax sp. lasted for 3.7 days and only 38.8% of COD was reduced, for high pH value of the culture harmed hydrogen production.     

Estimating global production and supply costs for green hydrogen and hydrogen-based green energy commodities

Green energy commodities are expected to be central in decarbonising the global energy system. Such green energy commodities could be hydrogen or other hydrogen-based energy commodities produced from renewable energy sources (RES) such as solar or wind energy. We quantify the production cost and potentials of hydrogen and hydrogen-based energy commodities ammonia, methane, methanol, gasoline, diesel and kerosene in 113 countries. Moreover, we evaluate total supply costs to Germany, considering both pipeline-based and maritime transport. We determine production costs by optimising the investment and operation of commodity production from dedicated RES based on country-level RES potentials and country-specific weighted average costs of capital. Analysing the geographic distribution of production and supply costs, we find that production costs dominate the supply cost composition for liquid or easily liquefiable commodities, while transport costs dominate for gaseous commodities. In the case of Germany, importing green ammonia could be more cost-efficient than domestic production from locally produced or imported hydrogen. Green ammonia could be supplied to Germany from many regions worldwide at below the cost of domestic production, with costs ranging from 624 to 874 $/t NH₃ and Norway being the cheapest supplier. Ammonia production using imported hydrogen from Spain could be cost-effective if a pan-European hydrogen pipeline grid based on repurposed natural gas pipelines exists.     

Efficient photochemical hydrogen production under visible-light over artificial photosynthetic systems

Photosynthesis of green plants provides an effective blueprint for transform solar energy into useful hydrogen energy. Thereinto, their hierarchical structures are favorable to the light-harvesting. Meanwhile, the functional components (light-harvesting pigments) can absorb visible wavelengths of sunlight, and offer reaction center for the energy transform. Inspired by these, we contrive an artificial photosynthetic system for the high efficiency of H₂-production rate by introducing a similar functional structure (reticular hierarchical structure) and component (CdS/Pt–TiO₂). The CdS/Pt–TiO₂ with hierarchically reticular structure is prepared by transforming wings into TiO₂ via a sol–gel process, and depositing Pt and CdS nanoparticles onto the TiO₂ substrate by photoreduction and chemical bath deposition method, respectively. Contributing to the couple effect of reticular hierarchical structure and ternary hybrid composition, CdS/Pt–TiO₂ nanocomposites exhibit high visible-light photocatalytic H₂-production rate (12.7% apparent quantum efficiency obtained at 420 nm). This concept provides a new horizon to exploit solar energy for sustainable energy by imitating the photosynthesis process from structure and ingredients.     

Evaluation of DCX converters for off-grid photovoltaic-based green hydrogen production

Photovoltaic (PV) to electrolyzer power systems are an attractive research topic since the PV produced power can be optimized by skipping power conversion into AC and producing a direct DC-DC interface. Existing DC-DC power conversion systems to directly interface the PV generation and Hydrogen (H₂) electrolyzer are mainly based in interleaved structures or multi-resonant converters. Soft-switching characteristics are also suitable for these conversion topologies and DCX converters are then serious candidates to be used. DCX provides an isolated high efficiency solution but the DCX-based two-stage converter topology must be optimized in order to obtain better efficiency and energy yield. In this work a detailed comparison of DCX topologies is given for a PV to H₂ application. The proposed optimized system is validated through simulation in a multi-string electrolysis system, showing the relevance of the solution for this application. The proposed approach reaches a global maximum efficiency of 98.2%.     

Kinetic analysis of photosynthetic growth,hydrogen production and dual substrate utilization by Rhodobacter capsulatus

Rhodobacter capsulatus is purple non-sulfur (PNS) bacterium which can produce hydrogen and CO₂ by utilizing volatile organic acids in presence of light under anaerobic conditions. Photofermentation by PNS bacteria is strongly affected by temperature and light intensity. In the present study we present the kinetic analysis of growth, hydrogen production, and dual consumption of acetic acid and lactic acid at different temperatures (20, 30 and 38 °C) and light intensities (1500, 2000, 3000, 4000 and 5000 lux). The cell growth data fitted well to the logistic model and the cumulative hydrogen production data fitted well to the Modified Gompertz Model. The model parameters were affected by temperature and light intensity. Lactic acid was found to be consumed by first order kinetics. Rate of consumption of acetic acid was zero order until most of the lactic acid was consumed, and then it shifted to first order. The results revealed that the optimum light intensities for maximum hydrogen production were 5000 lux for 20 °C and 3000 lux for 30 °C and 38 °C.     

Effect of culture conditions on the kinetics of hydrogen production by photosynthetic bacteria in batch culture

Biochemical kinetic characteristics of photo-fermentative hydrogen production were experimentally and numerically investigated to optimize the photo-fermentation hydrogen-producing process in this work. It is found that a maximum specific growth rate of 0.26 h⁻¹ was achieved under the optimal conditions of illumination intensity 6000 lux, 30 °C culture temperature and pH 7.0 of culture medium. These experimental results also led to an empirical formula of the maximum specific microbial growth rate (μ_max) as a function of illumination intensity, pH and temperature. With the empirical formula, the modified Monod equation along with the kinetic equations for biomass growth, glucose consumption and hydrogen production is then developed to simulate the photofermentation hydrogen-producing process. The modeling results are in good agreements with the experimental data, indicating that the developed kinetic models are able to objectively describe the characteristics of hydrogen production by PSB under different culture conditions.     

Two-step thermochemical electrolysis: An approach for green hydrogen production

Electrolysis and thermochemical water splitting are approaches to produce green hydrogen that use either an electrical potential (electrolysis) or a chemical potential (thermochemical water splitting) to split water. Electrolysis is technologically mature when applied at low temperatures, but it requires large quantities of electrical energy. In contrast to electrolysis, thermochemical water splitting uses thermal energy, as thermal energy can typically be supplied at a lower unit cost than electrical energy using concentrating solar power. Thermochemical water splitting, however, typically suffers from high thermal losses at the extremely high process temperatures required, substantially increasing the total energy required. We show how, by combining electrical and chemical potentials, a novel and cost-efficient water splitting process can be envisioned that overcomes some of the challenges faced by conventional electrolysis and thermochemical water splitting. It uses a mixed ionic and electronic conducting perovskite with temperature-dependent oxygen non-stoichiometry as an anode in an electrolyzer. If solar energy is used as the primary source of all energy required in the process, the cost of the energy required to produce hydrogen could be lower than in high-temperature electrolysis by up to 7%.     

Co-fermentation of sewage sludge and algae and Fe2+ addition for enhancing hydrogen production

Co-fermentation of sewage sludge and algae was performed for enhancing the hydrogen production, and the effect of Fe²⁺ on co-fermentation process was examined. Results showed that both co-fermentation process and Fe²⁺ addition promoted hydrogen production. Highest hydrogen production of 28 mL/100 mL (14.8 mL H₂/g VS_added) was obtained from the co-fermentation group with 600 mg/L Fe²⁺ addition, which was 2.15 times, 2.00 times and 1.87 times of mono-fermentation of sludge, mono-fermentation of algae, and the co-fermentation group without Fe²⁺ addition. Both volatile solids and protein degradation were stimulated by co-fermentation process. Microbial analysis showed that co-fermentation groups with Fe²⁺ addition enriched Clostridium sensu stricto 13, Clostridium tertium and Terrisporobacter, which were positively correlated with cumulative hydrogen production. This study suggested that the co-fermentation of sludge and algae in the presence of Fe²⁺ could significantly improve the hydrogen production by stimulating the hydrogen-producing metabolism.     

Investigation of hydrogen production methods in accordance with green chemistry principles

Hydrogen, as a clean fuel of future, is always counted environmentalist. However, production of hydrogen is not always green. Therefore, a need appeared to re-design the processes for terminating non-renewable resource dependency, minimizing wastes, increasing efficiency, and becoming greener. A systematic approach, Green Chemistry, which is based on 12 principles can be an instructive. This paper aimed to investigate the hydrogen production methods in accordance with green chemistry principles. Each method was evaluated for 12 principles to decide if they could meet the requirements or not. Hydrogen production methods investigated were classified under 4 groups according to the energy sources: electrical, thermal, hybrid and biological. After an overview of the main hydrogen production processes, we show that water electrolysis among electrical methods, biomass gasification as being CO₂ neutral among thermal methods, photo-electrochemical production among hybrid methods and bio-photolysis and photo-fermentation among biological methods makes hydrogen production “green”.     

微藻生物制氢技术

介绍了微藻光合制氢技术的生物原理及固氮酶和可逆产氢酶的产氢机制.讨论了基于微藻的硫缺乏生理调控而发展起来的一步法与两步法光解制氢的方式,其中微藻可逆产氢酶两步法间接光解制氢是最具发展潜力的制氢方式.分析了实现微藻光合制氢的限制因子及要解决的问题,指出高效光合产氢藻株的筛选及高效光反应器的实现是该技术获得成功的关键,使微藻大规模光合产氢成为可能.