Fermentative hydrogen production - An alternative clean energy source

Hydrogen generation from wastewater is one of the promising approaches through biological route. So, exploitation of wastewater as substrate for hydrogen production with concurrent wastewater treatment is an attractive and effective way of tapping clean energy from renewable resources in a sustainable approach. In this direction, considerable interest is observed on various biological routes of hydrogen production using bio-photolysis, photo fermentation and heterotrophic dark fermentation process or by a combination of these processes. Therefore, in this communication, utilizing industrial wastewater as primary substrate for dark fermentation process is reviewed and different parametric aspects associated with this sustainable approach for better energy production is discussed. The industrial wastewaters that could be the source for bio hydrogen generation, such as rice slurry wastewater, food and domestic wastewaters, citric acid wastewater and paper mill wastewater, are also discussed in this article.     

A review on biomass based hydrogen production technologies

Hydrogen is a renewable energy carrier that is one of the most competent fuel options for the future. The majority of hydrogen is currently produced from fossil fuels and their derivatives. These technologies have a negative impact on the environment. Furthermore, these resources are rapidly diminishing. Recent research has focused on environmentally friendly and pollution-free alternatives to fossil fuels. The advancement of bio-hydrogen technology as a development of new sustainable and environmentally friendly energy technologies was examined in this paper. Key chemical derivatives of biomass such as alcohols, glycerol, methane-based reforming for hydrogen generation was briefly addressed. Biological techniques for producing hydrogen are an appealing and viable alternative. For bio-hydrogen production, these key biological processes, including fermentative, enzymatic, and biocatalyst, were also explored. This paper also looks at current developments in the generation of hydrogen from biomass. Pretreatment, reactor configuration, and elements of genetic engineering were also briefly covered. Bio-H₂ production has two major challenges: a poor yield of hydrogen and a high manufacturing cost. The cost, benefits, and drawbacks of different hydrogen generation techniques were depicted. Finally, this article discussed the promise of biohydrogen as a clean alternative, as well as the areas in which additional study is needed to make the hydrogen economy a reality.     

Effect of Green synthesized silver oxide nanoparticle on biological hydrogen production

Investigation of the effect of different nanoparticles on dark fermentation is very popular nowadays. Among the nanoparticle production methods, the use of nanoparticles produced by the green synthesis method, which is more environmentally friendly, is important for a sustainable environment. This study investigated the effect of green synthesized silver oxide nanoparticles on bio-hydrogen yield. Nanoparticle synthesis was carried out by using Chlorella sp. microalgae as a reducing agent. SEM, EDX and UV–Visible spectrum analyzes were performed for the characterization of the synthesized nanoparticles. The synthesized silver nanoparticles have a uniform structure and an average particle size of 85 nm. Hydrogen production performance by Clostridium sp. was evaluated using different ratios of produced nanoparticles (100–600 μg/L). The addition of 400 μg/L nanoparticles increased the production of dark fermentative bio-hydrogen by 17% compared to the control group. The highest hydrogen yield was 2.44 mol H₂/mol glucose.     

Integrated biological hydrogen production

Biological systems offer a variety of ways by which to generate renewable energy. Among them, unicellular green algae have the ability to capture the visible portion of sunlight and store the energy as hydrogen (H₂). They hold promise in generating a renewable fuel from nature's most plentiful resources, sunlight and water. Anoxygenic photosynthetic bacteria have the ability of capturing the near infrared emission of sunlight to produce hydrogen while consuming small organic acids. Dark anaerobic fermentative bacteria consume carbohydrates, thus generating H₂ and small organic acids. Whereas efforts are under way to develop each of these individual systems, little effort has been undertaken to combine and integrate these various processes for increased efficiency and greater yields. This work addresses the development of an integrated biological hydrogen production process based on unicellular green algae, which are driven by the visible portion of the solar spectrum, coupled with purple photosynthetic bacteria, which are driven by the near infrared portion of the spectrum. Specific methods have been tested for the cocultivation and production of H₂ by the two different biological systems. Thus, a two-dimensional integration of photobiological H₂ production has been achieved, resulting in better solar irradiance utilization (visible and infrared) and integration of nutrient utilization for the cost-effective production of substantial amounts of hydrogen gas. Approaches are discussed for the cocultivation and coproduction of hydrogen in green algae and purple photosynthetic bacteria entailing broad utilization of the solar spectrum. The possibility to improve efficiency even further is discussed, with dark anaerobic fermentations of the photosynthetic biomass, enhancing the H₂ production process and providing a recursive link in the system to regenerate some of the original nutrients.     

Life cycle assessment of various hydrogen production methods

A comprehensive life cycle assessment (LCA) is reported for five methods of hydrogen production, namely steam reforming of natural gas, coal gasification, water electrolysis via wind and solar electrolysis, and thermochemical water splitting with a Cu–Cl cycle. Carbon dioxide equivalent emissions and energy equivalents of each method are quantified and compared. A case study is presented for a hydrogen fueling station in Toronto, Canada, and nearby hydrogen resources close to the fueling station. In terms of carbon dioxide equivalent emissions, thermochemical water splitting with the Cu–Cl cycle is found to be advantageous over the other methods, followed by wind and solar electrolysis. In terms of hydrogen production capacities, natural gas steam reforming, coal gasification and thermochemical water splitting with the Cu–Cl cycle methods are found to be advantageous over the renewable energy methods.     

Analysis of the three-phase state in biological hydrogen production from coal

The production of biohydrogen from coal is a new research direction in the bioengineering of coalbed methane. In order to study the transformation process and mechanism of the gas-liquid-solid tripe phase in biohydrogen production from coal, a biohydrogen production experiment from low-rank coal is carried out under laboratory conditions. The results show that: The daily gas production of hydrogen reaches a peak value of 1.23 mL/g on the fifth day. The cumulative hydrogen production is 6.24 mL/g. The pH of the liquid products gradually decreases to 5, and the Eh gradually increased from −180 to −50 mV during the experiment. The peak value of lignin degradation rate is 0.42% on the 7th day. The chemical oxygen demand (COD) first increases and then decreases. The highest COD is 4068 mg/L, and the final COD degradation rate is 46.3%. The peak values of cellulase are 0.021 mg/(mL h) and 0.223 mmol H₂/(min mg) at 3 d later than that of hydrogenase. The absorbance of bacterial turbidity first increases and then decreases, with the community structure proving that the hydrolytic bacteria are dominated by Acinetobacter, Comamonas, Intestinimonas, and some fermentation bacteria, including Macellibacteroides. The changes of carbon, oxygen, nitrogen, sulfur and functional groups of carbon and oxygen in coal are obvious, with aliphatic carbon (methoxy, carbonyl, and so on) representing the main part of the biochemical reaction in the macromolecular structure of coal. The analysis of the three-phase state in the process of coal hydrogen production is helpful to study the mechanism of hydrogen production by coal fermentation from different perspectives, and also provides a reference for the promotion of coal hydrogen production by fermentation in the next step.     

Fermentative hydrogen production using a real-time fuzzy controller

This work builds a real-time monitoring and control system for bio-hydrogen production fermentation plants using LabVIEW software. The best fermentation environment factors pH and temperature are successfully estimated with stable control ability to create the best hydrogen production environment. The concentrate molasses fermentation waste is as nutrients to hold biomass hydrogen production by dark fermentation in a continuous stirred anaerobic bioreactor, CSABR. In order to verify the applicability of this system, this study compares the proposed anaerobic bioreactor system which's maximum hydrogen production was 3.12 (L/Day) and the system with the fuzzy controller which's hydrogen production rose to 13.44 (L/Day). The result shows that the proposed fuzzy control can not only control feeding pump and heater operations, but also successfully reduce the energy required for hydrogen production, making sure the growth of micro-organisms is in the best environmental conditions for the best growth rate and raise of the maximum hydrogen production.     

Experimental design methods for fermentative hydrogen production: A review

This review summarized the experimental design methods used to investigate the effects of various factors on fermentative hydrogen production processes, including one-factor-at-a-time design, full factorial design, Taguchi design, Plackett–Burman design, central composite design and Box–Behnken design. Each design method was briefly introduced, followed by the introduction of its analysis. In addition, the advantages and disadvantages of each design method were briefly discussed. Moreover, the application of each design method to the study of fermentative hydrogen production was analyzed and discussed. Based on the discussion in this review, an experimental design strategy for optimizing fermentative hydrogen production processes was proposed. In the end, the software packages that can carry out the above mentioned factorial design and analysis were briefly introduced.     

Thermophilic fermentative hydrogen production from starch-wastewater with bio-granules

In this study, the effects of the hydraulic retention time (HRT), pH and substrate concentration on the thermophilic hydrogen production of starch with an upflow anaerobic sludge bed (UASB) reactor were investigated. Starch was used as a sole substrate. Continuous hydrogen production was stably attained with a maximum H₂ yield of 1.7 mol H₂/mol glucose. A H₂-producing thermophilic granule was successfully formed with diameter in the range of 0.5–4.0 mm with thermally pretreated methanogenic granules as the nuclei. The metabolic pathway of the granules was drastically changed at each operational parameter. The production of formic or lactic acids is an indication of the deterioration of hydrogen production for H₂-producing thermophilic granular sludge.     

Comprehensive modeling of photo-fermentation process for prediction of hydrogen production

Hydrogen production via modern technologies and without using fossil fuels has been found considerably important recently. Photo-fermentation is introduced as one of the most effective methods without high risk for bio-hydrogen production. In this study, comprehensive modeling and simulation of bio-hydrogen production is carried out through photo-fermentation process. In this way, different applicable models are considered to predict the kinetics of microbial growth. Also, new modified mathematical models are particularly proposed for photo-fermentation to forecast the specific growth rate of microorganisms, substrate consumption and hydrogen production rates. Various combinations of the models are applied and predictions of the models are validated by experimental data related to the growth of Rhodobacter Sphaeroides on malate as the substrate. The combination, entitled as MVA1, is introduced as the best one to predict kinetic factors in photo-fermentation. The presented models can be used as an excellent starting point to accomplish experimental and industrial works.     

Performance of batch solid state fermentation for hydrogen production using ground wheat residue

Ground wheat (21 g) was subjected to batch solid state dark fermentation for bio-hydrogen production. Clostridium acetobutylicum (B-527) was used as the culture of dark fermentation bacteria at mesophilic conditions. Effects of moisture content on the rate and yield of bio-hydrogen formation were investigated. The highest CHF (1222 ml), hydrogen yield (63 ml H₂ g^?1 starch), formation rate (10.64 ml H₂ g^?1 starch h^?1) and specific hydrogen formation rate (0.28 ml H₂ g^?1 biomass h^?1) were obtained with a moisture content of 80%. Nearly complete starch hydrolysis and glucose fermentation were achieved with more than 80% moisture content and the highest substrate conversion rate (21.9 mg L^?1 h^?1) was obtained with 90% moisture content at batch solid state fermentation producing volatile fatty acids (VFA) and H₂.     

Hydrogen production characteristics from dark fermentation of maltose by an isolated strain F.P 01

A hydrogen producing strain F.P 01 was newly isolated from cow dung sludge in an anaerobic bioreactor. The strain F.P 01 was a mesophilic and facultative anaerobic bacterium, which exhibited gram-negative staining in both the exponential and stationary growth phases, and a regular long rod-shaped bacteria with the size of 0.6–0.9 μm × 1.2–2.5 μm, and also could biodegrade a variety of carbohydrates such as glucose, xylose, maltose, etc. The effects of important process parameters on hydrogen producing of F.P 01 were further investigated from hydrogen fermentation of maltose by strain F.P 01, including substrate concentration, medium pH, etc. And the results showed that hydrogen production potential and hydrogen production rate from maltose of this strain F.P 01 was180 mLH₂/g-maltose and 4.0 mLH₂/h, respectively. The corresponding hydrogen concentration of 58–73% was also be observed. Both butyric acid and acetic acid as main by-product was left in the reactor.     

Synthesis of novel biocatalyst from organic waste protonated with acid treatment for hydrogen production

In this research study, orange peel-based biocatalysts developed from different acid protonation were used as a metal-free catalyst for hydrogen production from sodium borohydride (NaBH₄). In order to prepare the orange peel-based biocatalyst with higher catalytic activity, experiments were conducted with pure orange peel, different acid molar concentrations, and calcination temperatures. The physical morphology, surface texture, and chemical interaction were thoroughly analyzed by XRD, FTIR Raman, FESEM, BET, and TGA. As a result of the experiment, it was determined that the highly acid-treated biocatalyst (40% H₃PO₄, 40% H₂SO₄, 40% HCl) and calcinated at 450 °C for 1 h had higher catalytic activity. As a result, bio-hydrogen production at 35 °C and 70 °C methanolysis with 3% NaBH₄ catalyzed by a mixture of acid-treated catalysts were found as 46,213 and 63,842 ml min⁻¹g.cat⁻¹, respectively. However, with the increase of molar concentration of biocatalyst with 40% individual acid prolonged samples, the HGR rates will not have a satisfactory value in comparison with the 40% mixture of the acid-treated catalyst due to less number of active sites.     

Emerging technologies for hydrogen production from wastewater

Wastewater treatment is essential to shield the environment. The production of H₂ is substantial for prospering its applications in diversified sectors; hence the study of wastewater treatment for H₂ production is accomplished. Various technologies have been developed and studied considering the potential of wastewater to generate hydrogen-rich gas. These technologies have different mechanisms, diversified setups, and processes. Perhaps these technologies are proven to be exceptional exposures for hydrogen production. Fortunately, a valuable contribution to the environment and the H₂ economy is that some technological processes have been promoted to synthesize H₂ from lab scale to pilot scale. Contemplating such comprehensive exposure to H₂ synthesis from wastewater, the critical information of eight emerging technologies, including their mechanism and reaction parameters influencing the process, pros, cons, and future developmental scopes, are described in this review by classifying them into three different classes, namely light-dependent technologies, light-independent technologies, and other technologies.     

Value analysis for commercialization of fermentative hydrogen production from biomass

In addition to producing hydrogen gas, biohydrogen production is also used to process wastewater. Therefore, this study specifically conducted value analyses of two different scenarios of fermentative hydrogen production from a biomass system: to increase the value of a wastewater treatment system and to specifically carry out hydrogen production. The analytical results showed that fermentative hydrogen production from a biomass system would increase the value of a wastewater treatment system and make its commercialization more feasible. In contrast, fermentative hydrogen production from a biomass system designed specifically for producing hydrogen gas would have a lower system value, which indicated that it is not yet ready for commercialization. The main obstacle to be overcome in promoting biohydrogen production technology and system application is the lack of sales channels for the system's products such as hydrogen gas and electricity. Thus, in order to realize its commercialization, this paper suggests that governments provide investment subsidies for the use of biohydrogen production technology and establish a buy-back tariff system for fuel cells.     

Green methods for hydrogen production

This paper discusses environmentally benign and sustainable, as green, methods for hydrogen production and categorizes them based on the driving sources and applications. Some potential sources are electrical, thermal, biochemical, photonic, electro-thermal, photo-thermal, photo-electric, photo-biochemical, and thermal-biochemical. Such forms of energy can be derived from renewable sources, nuclear energy and from energy recovery processes for hydrogen production purposes. These processes are analyzed and assessed for comparison purposes. Various case studies are presented to highlight the importance of green hydrogen production methods and systems for practical applications.     

Effects of different pretreatment methods on fermentation types and dominant bacteria for hydrogen production

In order to enrich hydrogen producing bacteria and to establish high-efficient communities of the mixed microbial cultures, inoculum needs to be pretreated before the cultivation. Four pretreatment methods including heat-shock pretreatment, acid pretreatment, alkaline pretreatment and repeated-aeration pretreatment were performed on the seed sludge which was collected from a secondary settling tank of a municipal wastewater treatment plant. In contrast to the control test without any pretreatment, the heat-shock pretreatment, acid pretreatment and repeated-aeration pretreatment completely suppressed the methanogenic activity of the seed sludge, but the alkaline pretreatment did not. Employing different pretreatment methods resulted in the change in fermentation types as butyric-acid type fermentation was achieved by the heat-shock and alkaline pretreatments, mixed-acid type fermentation was achieved by acid pretreatment and the control, and ethanol-type fermentation was observed by repeated-aeration pretreatment. Denaturing gradient gel electrophoresis (DGGE) profiles revealed that pretreatment method substantially affected the species composition of microbial communities. The highest hydrogen yield of 1.96 mol/mol-glucose was observed with the repeated-aeration pretreatment method, while the lowest was obtained as the seed sludge was acidified. It is concluded that the pretreatment methods led to the difference in the initial microbial communities which might be directly responsible for different fermentation types and hydrogen yields.