Biohydrogen production from wastewater-based microalgae: Progresses and challenges

Microalgae originating from wastewater has been exhibiting particularly promising results in terms of biohydrogen production and wastewater treatment. This paper aims to review the factors affecting production, pretreatment techniques to improve synthesis, advanced technologies utilized for enhancing biohydrogen production, and techno-economic feasibility evaluation of the processes at a commercial scale. Microalgae possess metabolic components to synthesize biohydrogen using photobiological and fermentative processes but must undergo pretreatment for efficient biohydrogen production. The efficiency of these processes is influenced by factors such as the microalgae species, light intensity, cell density, pH, temperature, substrates, and the type of bioreactors. Moreover, many limitations, such as oxygen sensitivity, altered thylakoid constitution, low photon conversion efficiency, light capture disruption, and the evolution of harmful by-products hinder the sustainability of biohydrogen production processes. High operational and maintenance costs serve as the major bottleneck in the scaling up of the process as an industrial technology. Therefore, future research needs to be directed towards increasing optimization of the processes by reducing energy and resource demand, recycling metabolic wastes and process components, genetically engineered microalgae to adopt more efficient routes, and conducting pilot studies for commercialization.     

A comprehensive review on biohydrogen production pilot scale reactor technologies: Sustainable development and future prospects

The current study focuses on a comprehensive review of the pilot scale production of biohydrogen and various factors affecting the design experiments. Biohydrogen is a clean energy carrier that can be used as a potential alternative to fossil fuels. Biohydrogen as a fuel has several advantageous attributes, including; carbon-neutral or carbon-zero nature, easy renewability, eco-efficient productivity (via biological routes), eco-friendly conversion, and the highest energy content among all existing fuels. Pilot-scale production of biohydrogen is limited because it requires a better understanding of the possible interactions involved in the process. In this review, biohydrogen production on various types of reactors such as stirred tank reactors, packed bed reactors, fluidized bed reactors, trickling filter reactors, etc., have been discussed. However, biohydrogen production has been mostly studied on small scale, the most challenging issue concerning large-scale production of biohydrogen is its relatively high cost over fuels from fossil owing to high feedstock and manufacturing costs. Therefore, cost-effective and eco-friendly biohydrogen production technologies should be necessarily developed and continuously improved to make this biofuel more competitive over its counterpart. In comparison with fossil fuels, biohydrogen has a high energy yield and is highly renewable. It can fulfill the future demand as a transport fuel.     

Biohydrogen production: Current perspectives and the way forward

Global research is moving forward in developing biological production of hydrogen (biohydrogen) as a renewable energy source to alleviate stresses due to carbon dioxide emissions and depleting fossil fuels resource. Biohydrogen has the potential to replace current hydrogen production technologies relying heavily on fossil fuels through electricity generation. While biohydrogen research is still immature, extensive work on laboratory- and pilot-scale systems with promising prospects has been reported. This work presents a review of advances in biohydrogen production focusing on production pathways, microbiology, as well as bioreactor configuration and operation. Challenges and prospects of biohydrogen production are also outlined.     

Biological hydrogen production via dark fermentation: A holistic approach from lab-scale to pilot-scale

Biohydrogen is considered as fuel of future owing to its distinctive attribute for clean energy generation, waste management and high energy content. Suitable feedstock play important role for achieving high rate hydrogen production via dark fermentation process. In this regard, different organic wastes such as cane molasses, distillery effluent and starchy wastewater were examined as potential substrates for biohydrogen production by Enterobacter cloacae IIT-BT 08. Groundnut deoiled cake (GDOC) was considered as additional nutritional supplement to enhance biohydrogen yields. The maximum hydrogen yield of 12.2 mol H₂ kg⁻¹ COD_removed was obtained using cane molasses and GDOC as co-substrates. To further ensure reliability of the process, bench (50 L) and pilot scale (10000 L) bioreactors were customized and operated. The pilot scale study achieved 76.2 m³ hydrogen with a COD removal and energy conversion efficiency of 18.1 kg m⁻³ and 37.9%, respectively. This study provides an extensive strategy in moving from lab to pilot scale biohydrogen production thereby, providing further opportunity for commercial exploitation.     

A review on pretreatment methods,photobioreactor design and metabolic engineering approaches of algal biomass for enhanced biohydrogen production

The development of alternative fuels has been promoted by the extreme fossil fuel consumption brought on by urbanisation and deteriorating pollution. Due to its high energy and combustible qualities, biohydrogen has been perceived as a potential fuel substitute in dealing with issues related to the rising emission of greenhouse gases and global warming. As a source of carbon sequestration and sustainable renewable energy, biohydrogen synthesis by algae species has been prevalent in research scale. This review focuses on the novel and recent metabolic approaches for enhanced algal based biohydrogen production. Pretreatment methods available and scaling techniques used for enhancing the biohydrogen productivity using algal species have been elaborated in the review. Algal characteristics that make them suitable alternative for biohydrogen production are discussed briefly. Various pretreatment methods such as physical, chemical, biological and thermal are elaborated. In addition, the factors involved in influencing the biohydrogen productivity and the metabolic engineering approaches for modifying the pathway in algae are highlighted. Scaling up of process using different types of photobioreactors such as tubular, flat panel, airlift and stirred tank are reported that briefs about merits and demerits of each photobioreactor.     

Biohydrogen production from biomass and industrial wastes by dark fermentation

Hydrogen is a clean energy carrier which has a great potential to be an alternative fuel. Abundant biomass from various industries could be a source for biohydrogen production where combination of waste treatment and energy production would be an advantage. This article summarizes the dark fermentative biohydrogen production from biomass. Types of potential biomass that could be the source for biohydrogen generation such as food and starch-based wastes, cellulosic materials, dairy wastes, palm oil mill effluent and glycerol are discussed in this article. Moreover, the microorganisms, factors affecting biohydrogen production such as undissociated acid, hydrogen partial pressure and metal ions are also discussed.     

Biohydrogen purification by membranes: An overview on the operational conditions affecting the performance of non-porous,polymeric and ionic liquid based gas separation membranes

Many types of membranes are available to enrich hydrogen. Nevertheless, there are some with special potential for biohydrogen purification such as the non-porous, polymeric and ionic liquid based membranes. The attractiveness of these membranes comes from the fact that they can be employed nearly under the conditions where biohydrogen formation taking place. Therefore, they appear as promising candidates to be coupled with hydrogen producing bioreactors and hence giving the chance for in situ biohydrogen concentration. It is known that the feasibility and efficiency of membrane technology – beside material selection and module design – significantly depend on the separation circumstances. Thus, the operation of membranes is a key issue and the most important factors to be considered for gas purification are the composition of gas to be separated, the pressure and temperature applied. The scope of this study is to give a comprehensive overview on the recent applications of non-porous, polymeric and ionic liquid supported membranes for biohydrogen recovery, placing emphasis on the operational conditions affecting membrane's behavior and performance. Furthermore, a novel concept for integrated biohydrogen production and purification using gas separation membranes is demonstrated and discussed.     

A critical literature review on biohydrogen production by pure cultures

Global research is moving forward in developing hydrogen as a renewable energy source in order to alleviate concerns related to carbon dioxide emissions and depleting fossil fuels resources. Biohydrogen has the potential to replace current hydrogen production technologies relying heavily on fossil fuels. Batch and continuous systems employing pure mesophiles and thermophiles isolates and co-cultures of isolates have been investigated. The co-cultures of the isolates achieved better results than mono-cultures of the isolates with respect to different parameters. This paper presents a critical review of the literature reporting on fermentative biohydrogen production by pure cultures of bacteria in different systems. Synergies between different types of bacteria, i.e. strict and facultative, and a comparison between mono- and co-cultures, types of feedstocks, and preferred feedstocks for mono- and cultures are outlined.     

Optimization for simultaneous enhancement of biobutanol and biohydrogen production

Acetone-butanol-ethanol (ABE) fermentation guarantees a sustainable route for biohydrogen and biobutanol production. This research work is committed towards the enhancement of biohydrogen and biobutanol production by single and multi-parameter optimization for the improvement of substrate energy recovery using C. saccharoperbutylacetonicum. Single parameters optimization (SPO) manifested that headspace of 60% (v/v) and butyric acid supplementation of 9 g/L and temperatures of 30 °C and 37 °C were suitable for obtaining maximum biohydrogen and biobutanol production, respectively. The interaction between these parameters was further evaluated by implementing a 5-level 3-factor Central Composite Design (CCD). In the present study, a central composite design was employed to enhance the biohydrogen and biobutanol production. In addition, the experimental results were analyzed by response surface methodology (RSM) and artificial intelligence (AI) techniques such as artificial neural network (ANN). The prediction capability of RSM was further compared with ANN for predicting the optimum parameters that would lead to maximum biohydrogen and biobutanol production. ANN yielded higher values of biohydrogen and biobutanol. ANN was found to be superior as compared to RSM in terms of prediction accuracy for both biohydrogen and biobutanol because of its higher coefficient of determination (R²) and lower root mean square error (RMSE) value. Process temperature (32.65 °C), headspace (58.21% (v/v)) and butyric acid supplementation (9.16 g/L) led to maximum substrate energy recovery of 78% with biohydrogen and biobutanol production of 5.9 L/L and 16.75 g/L, respectively. Process parameter optimization led to a significant increase in substrate energy recovery from Biphasic fermentation.     

Integration of biohydrogen fermentation and gas separation processes to recover and enrich hydrogen

An integrated system for biohydrogen production and separation was designed, constructed and operated where biohydrogen was fermented by Thermococcus litoralis, a heterotrophic archaebacterium, and a two-step gas separation process was coupled to recover and concentrate hydrogen. A special liquid seal system was built to deliver, compress and collect the laboratory scale, low volume gas mixtures consisting of hydrogen, nitrogen and carbon dioxide. As a result, gas mixture with 73% high hydrogen content was produced by a combination of a porous and a non-porous gas separation membrane.     

Biohydrogen as a renewable energy resource—Prospects and potentials

Biohydrogen holds the promise for a substantial contribution to the future renewable energy demands. It seems particularly suitable for relatively small-scale, decentralized systems, integrated with agricultural and industrial activities or waste processing facilities. Biohydrogen is considered as an important key to a sustainable world power supply and is currently being seen as the versatile fuel of the future, with the potential to replace fossil fuels. It has the key prospective to become the ideal means among the range of renewable H₂ production technologies presently existing. This review attempts to delineate the prospects and potentials of biohydrogen as renewable energy resource.     

Multiscale kinetic modeling for biohydrogen production: A study on membrane bioreactors

Hydrogen can be a capable alternative to fossil fuels due to its carbon-free characteristics, in this content, biological hydrogen production is considered a practical approach because technology is green. Due to parameters affecting biohydrogen production, such as operating conditions, it is crucial to predict the process to see the proper yield. There are several conventional and unconventional models used in biohydrogen production prediction. This paper derived a triple first-order prediction model from a previously presented multi-scale kinetic model polynomial built upon the multi-stage growth hypothesis for bio-hydrogen production prediction. The original model was applied to batch and continuous stirred tank reactor studies for their model evaluation, this study evaluated the newly derived model for studies of membrane bioreactors. Due to their increased production yield, membrane bioreactors are an emerging field in biohydrogen production. Although the previous study was mainly applied for batch dark fermentations consisting of various microorganisms, the results presented in this study indicate that it is also applicable for continuous and photo fermentation systems. The original model results reported significant fitness accuracy among different datasheets compared to conventional models like the modified Gompertz model, considering essential factors impacting biohydrogen production suggested in the original model, this paper investigated eleven case studies of dynamic membrane bioreactors with modeling fitness of 99% for most cases. This study reports even higher fitness accuracy compared to the original model, even with different operating conditions.     

Modeling microbial growth of dynamic membrane in a biohydrogen production bioreactor

Biohydrogen is renewable and has a huge potential to replace fossil fuels. Understanding mechanisms of controlling microbial processes of the dynamic membrane is critical for effective dark fermentative biohydrogen production in a dynamic membrane bioreactor (DMBR). This paper aims to develop a sophisticated model of biofilm growth, dynamic membrane formation, and dark fermentative hydrogen production within a platform of coupled lattice Boltzmann and cellular automata. The model was validated against the experimental data available and then was applied for the investigation of biohydrogen production in bioreactors under different membrane structures and inlet velocities. The results showed that porous twisted channels in the dynamic membrane could significantly affect biohydrogen extraction and biofilm patterns. In all cases, the dynamic membrane formation has three phases: the initial bacteria deposit, stable biofilm growth, and stable maximum biofilm biomass. The biohydrogen production could increase by 16.4% by optimizing the porous structure and increase 30%–40% of the hydrogen extraction. Inlet velocity also affects biohydrogen extraction in a range of ?28.3%–71.2%. Both porous structure and inlet velocity would be critical operational parameters for continuous biohydrogen production. The present model demonstrated its capability to investigate dark fermentative hydrogen production and its potential applications to porous bioreactors.     

Biohydrogen production via integrated sequential fermentation using magnetite nanoparticles treated crude enzyme to hydrolyze sugarcane bagasse

This study presents a potential approach to enhance integrated sequential biohydrogen production from waste biomass using magnetite nanoparticle (Fe₃O₄ NPs) which is synthesized through waste seeds of Syzygium cumini. Consequences of 0.5% Fe₃O₄ NPs have been investigated on the thermal and pH stability of fungal crude cellulase. It is noticed that Fe₃O₄ NPs treated enzyme and control exhibits 100% activity in the temperature range of 45–60 °C and 45–55 °C, respectively. Moreover, Fe₃O₄ NPs treated enzyme showed extended thermal stability in the temperature range of 50–60 °C up to 12 h. Beside this, Fe₃O₄ NPs treated enzyme possesses 100% stability in the pH range of 5.0–7.0 whereas control exhibited only at pH 6.0. Enzymatic hydrolysis via Fe₃O₄ NPs treated enzyme has been employed which produces ～68.0 g/L reducing sugars from sugarcane bagasse. Subsequently, sugar hydrolyzate has been utilized as substrate in the sequential integrated fermentation that produces ～3427.0 mL/L cumulative hydrogen after 408 h. This approach may have potential for the pilot scale production of biohydrogen from waste biomass at low-cost in an eco-friendly manner.     

A critical review on limitations and enhancement strategies associated with biohydrogen production

The potential to operate energy efficient and less expensive production methods are important in biohydrogen production. Biological hydrogen production is often constrained by less productivity. However, to obtain industrial level implementation, greater productivity is essential. Researches on various bioreactors configurations and influencing factors were deeply investigated in this regard. The bioreactors operated in batch mode are appropriate for preliminary optimization whereas industrial level execution needs continuous mode. The main objective of this review is to recap the limitations and constraints associated with bioreactor operation and to list out the enhancement approaches that are currently investigated for improved biohydrogen generation. Recent approaches designed towards biohydrogen production enhancement such as substrate pre-treatments, inhibitors removal, bioaugmentation, immobilization, effluent recycling, buffering capacity maintenance, exploitation of by-products etc., are reviewed thoroughly.     

A multi-criteria decision making analysis for feasibility of nanoparticle addition in biohydrogen production enhancement for scaling-up studies

Nanoparticles (NPs) thanks to their unique features such as large surface area, high catalytic activity and intra-cellular electron transfer ability used as an enhancement additive in biohydrogen production. Up to date, inorganic, organic and their mixtures of various NPs were produced from different input sources and synthesis methodology. The NPs properties and cost minimization are the critical factors for the scale up studies of industrial applications. Nevertheless, there have not been any study on the determination of the most efficient and feasible NPs in biohydrogen production for the scaling up the process. In this study, the NPs used for biohydrogen production enhancement over Clostridium sp. by dark fermentation were examined and these studies were evaluated to determine the most effective and feasible NPs using the two-stage TOPSIS method. As a result, iron-containing NPs (hematite, magnetite) were determined as the most effective and economical NPs for increasing the yield.     

Assessment via the modified gompertz-model reveals new insights concerning the effects of ionic liquids on biohydrogen production

Lignocellulosic biofuel, in particular hydrogen gas production is governed by successful feedstock pretreatment, hydrolysis and fermentation. In these days, remarkable attention is paid to the use of ionic liquids to make the fermentable regions of lignocellulose biomass more accessible to the biocatalysts. Although these compounds have great potential for this purpose, their presence during the consecutive fermentation stage may pose a threat on process stability due to certain toxic effects. This, however, has not been specifically elaborated for dark fermentative biohydrogen generation. Hence, in this work, two common imidazolium-type ionic liquids (1-butyl-3-methylimidazolium acetate, ([bmim][Ac]) and 1-butyl-3-methylimidazolium chloride, ([bmim][Cl])) were employed in mixed culture biohydrogen fermentation to investigate the possible impacts related to their presence and concentrations. The batch assays were evaluated comparatively via the modified Gompertz-model based on the important parameters characterizing the process, namely the biohydrogen production potential, maximum biohydrogen production rate and lag-phase time.     

Recent advanced biotechnological strategies to enhance photo-fermentative biohydrogen production by purple non-sulphur bacteria: An overview

Photo-fermentation seems to be an attractive hydrogen production pathway. However, the light conversion efficiency and photo-hydrogen production of purple non-sulphur bacteria (PNSB) are very low, and hence, various biotechnological approaches are investigated to improve biohydrogen production. This article presents an overview of the advanced biotechnological approaches to enhance the photo-fermentative biohydrogen production. The advancements reviewed include optimisation of the medium, abiotic factors, the lighting regime, immobilisation techniques, application of photoluminating nanomaterials, genetic engineering, and other strategies. These approaches show positive results in the enhancement of photo-hydrogen production by PNSB. Some recommendations are suggested for further studies in the enhancement of photo-hydrogen production, such as green nanomaterials application, integrated dark- and photo-fermentation, genetic manipulation, and the application of the non-technological analysis approaches.     

An evaluative report and challenges for fermentative biohydrogen production

Hydrogen, the most abundant and lightest element in the universe, has enormous potential as a future energy. High conversion efficiency, recyclability and nonpolluting nature of hydrogen make it the fuel of future. Various microorganisms are explored for producing hydrogen by exploiting variety of biological organic substrates. The target is the genetic improvement of the organism or the biochemical pathway required for biohydrogen production and devising path even better in comparison to the other production methods.The present review discusses different methods of biohydrogen production specifically by the fermentative route, physical factors affecting its production and other aspects for enhancement in the yield of hydrogen production. Metabolic engineering strategies for enhancement in hydrogen production to overcome different limitation have been also summarized.     

Starch: a potential substrate for biohydrogen production

Hydrogen is a clean energy carrier with great potential to be an alternative fuel. Anaerobic hydrogen fermentation seems to be more favorable, since hydrogen is yielded at high rates and various organic waste and wastewater enriched with carbohydrates as substrate result in low cost for hydrogen production. Abundant biomass from various industries could be a source for biohydrogen production where combination of waste treatment and energy production would be an advantage. Carbohydrate‐rich nitrogen‐deficient solid wastes such as starch residues can be used for hydrogen production by using suitable bioprocess technologies. Alternatively, converting biomass into gaseous fuels, such as biohydrogen, is possibly the most efficient way to use these agroindustrial residues. This review summarizes the potential of starch agroindustrial residues as a substrate for biohydrogen production. Types of potential starch agroindustrial residues, recent developments and bio‐processing conditions for biohydrogen production will be discussed. Copyright © 2014 John Wiley & Sons, Ltd.