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.     

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.     

Current challenges and future technology in photofermentation-driven biohydrogen production by utilizing algae and bacteria

Biohydrogen is perceived as the versatile fuel of the future, having the ability to replace fossil fuels in many industrial and commercial sectors and offering the promise of fulfilling future renewable energy demands. Among various options available for the generation of biohydrogen, photofermentation with the help of microbes and algae is one of the most eye-catching approaches due to its relative efficiency, cost economics, and reduced environmental impacts. Generation of biohydrogen by dark fermentation, microbial electrolysis cell as well as photofermentation, along with their bioprocesses, already have been discussed in earlier literature. Photofermentation offers advantages of both biophotolysis (utilization of light energy) and dark fermentation (utilization of organic waste materials as substrate). Many researchers have been reported successful biohydrogen production from photofermentation-based techniques, however not much information is available regarding the considerable gap in industrial and economic challenges in the production of biohydrogen at the commercial level through photofermentation. Efforts have been made in this review to provide updated information on various new technologies being used in this sector, such as the integration of photofermentation with dark fermentation, the use of recombinant DNA technology, and the use of bionanotechnology to improve biohydrogen production through the utilization of various waste. Various challenges in this sector, as well as future perspectives, have been meticulously addressed in order to explore the future of green biohydrogen production for a sustainable future.     

Biohydrogen production by dark fermentation: Experiences of continuous operation in large lab scale

Hydrogen is a clean energy carrier which can be used as fuel in fuel cells. Today, hydrogen is produced mainly by steam reforming of fossil fuels like natural gas or oil. But only hydrogen produced by renewable sources can be called clean energy production. One possibility for hydrogen production is the biological fermentation of biogenous wastes by hydrogen producing bacteria. For the experimental setup four 30-L-working-volume reactors were constructed for continuous biohydrogen production. As inoculum, heat-treated sludge of a wastewater treatment plant was used. Different hydraulic retention times (HRT) were tested and an organic loading rate (OLR) of 2–14 kg VS/m³*d. As starting substrate, waste sugar medium was used. The pH and other parameters were observed to find boundary conditions for a stable continuous process with a minimum of online-control measurements. The high concentration of organic acids in the reactor led to a very low pH, which was controlled manually and online > 4 up to 5.5, otherwise the biohydrogen production decreased rapidly. The gas amount varied with the different OLRs, but could be stabilised on a high level as well as the hydrogen concentration in the gas with 44–52%. No methane was detected in the gas. It turned out, that continuous biohydrogen production with stable gas amounts and qualities could be achieved at different operation conditions. The results showed, that the operation of a continuous biohydrogen reactor has to be observed very carefully to ensure a constant gas production, and that pH-control is necessary to ensure stable operation conditions.     

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.     

Recent advances in reuse of waste material as substrate to produce biohydrogen by purple non-sulfur (PNS) bacteria

Hydrogen is the fuel of the future mainly due to its high conversion efficiency, recyclability and non-polluting nature. Biological hydrogen production processes, mostly mediated photosynthetic bacteria, are more favorable candidates for biological hydrogen production due to their high conversion efficiency and versatility in the substrates (including wastewater) they can utilize. The potential utilization of waste material is being investigated extensively with suitable bioprocess technologies for providing cheaper raw materials with simultaneous waste treatment and bioremediation. Thus, this review article summarizes the biohydrogen production metabolism of purple non-sulfur (PNS) bacteria and research works involving biohydrogen production using various wastes such as tofu wastewater, palm oil mill effluent, olive mill wastewater, brewery wastewater, etc. by photosynthetic PNS bacteria. Waste materials used, yields and rates are reviewed, together with a discussion of the economics and perspectives of biohydrogen production from waste materials.     

Microbial hydrogen production by bioconversion of crude glycerol: A review

Hydrogen is a clean source of energy with no harmful byproducts produced during its combustion. Bioconversion of different organic waste materials to hydrogen is a sustainable technology for hydrogen production and it has been investigated by several researchers. Crude glycerol generated during biodiesel manufacturing process can also be used as a feedstock for hydrogen production using microbial processes. The possibility of using crude glycerol as a feedstock for biohydrogen production has been reviewed in this article. A review of recent global biodiesel and crude glycerol production and their future market potential has also been carried out. Similarly, different technical constraints of crude glycerol bioconversion have been elaborately discussed and some strategies for improved hydrogen yield have also been proposed. It has been underlined that use of crude glycerol from biodiesel processing plants for hydrogen production has many advantages over the use of other organic wastes as substrate. Most importantly, it will give direct economic benefit to biodiesel manufacturing industries, which in turn will help in increasing biofuel production and it will partially replace harmful fossil fuels with biofuels. However, different impurities present in crude glycerol are known to inhibit microbial growth. Hence, suitable pretreatment of crude glycerol is recommended for maximum hydrogen yield. Similarly, by using suitable bioreactor system and adopting continuous mode of operation, further investigation of hydrogen production using crude glycerol as a substrate should be undertaken. Furthermore, isolation of more productive strains as well as development of engineered microorganism with enhanced hydrogen production potential is recommended. Strategies for application of co-culture of suitable microorganisms as inoculum for crude glycerol bioconversion and improved hydrogen production have also been proposed.     

A review on process modeling and design of biohydrogen

The current energy supply depends on fossil fuels which have increased carbon dioxide emissions leading to global warming and depleted non-renewable fossil fuels resources. Hydrogen (H₂) fuel could be an eco-friendly alternative since H₂ consumption only produces water. However, the overall impacts of the H₂ economy depend on feedstock types, production technologies, and process routes. The existing process technologies for H₂ production used fossil fuels encounter the escalation of fossil fuel prices and long-term sustainability challenges. Therefore, biohydrogen production from renewable resources like biomass wastes and wastewaters has become the focal development of a sustainable global energy supply. Different from other biohydrogen production studies, this paper emphasizes biohydrogen fermentation processes using different renewable sources and microorganisms. Moreover, it gives an overview of the latest advancing research in different biohydrogen process designs, modeling, and optimization. It also presents the biohydrogen production routes and kinetic modeling for biohydrogenation.     

Thermophilic biohydrogen production for commercial application: the whole picture

Hydrogen is a promising alternative to fossil fuel for a source of clean energy. Thermophilic biohydrogen production is beneficial for obtaining high H₂ production yield. This review recapitulates the basic metabolic pathways in bacteria for hydrogen production and the enzymes involved in various thermophilic hydrogen producing pathways in microorganisms. It also focuses on the current status of thermophilic biohydrogen production through fermentation of commercially viable substrates, such as agricultural residues. The use of metabolic engineering to attain certain physiological desirable characteristics in H₂‐producing microorganisms, culture conditions, and types of bioreactors to be used are reviewed. Major obstacles in industrial production of biohydrogen like low volumetric hydrogen production and its environmental impact are identified. The review has further identified current limitations in the commercial thermophilic hydrogen production and suggested methods like the use of heat exchangers and effluent recirculation to reduce the production cost. Copyright © 2015 John Wiley & Sons, Ltd.     

Hydrogen production from agricultural waste by dark fermentation: A review

The degradation of the natural environment and the energy crisis are two vital issues for sustainable development worldwide. Hydrogen is considered as one of the most promising candidates as a substitute for fossil fuels. In this context, biological processes are considered as the most environmentally friendly alternatives for satisfying future hydrogen demands. In particular, biohydrogen production from agricultural waste is very advantageous since agri-wastes are abundant, cheap, renewable and highly biodegradable. Considering that such wastes are complex substrates and can be degraded biologically by complex microbial ecosystems, the present paper focuses on dark fermentation as a key technology for producing hydrogen from crop residues, livestock waste and food waste. In this review, recent findings on biohydrogen production from agricultural wastes by dark fermentation are reported. Key operational parameters such as pH, partial pressure, temperature and microbial actors are discussed to facilitate further research in this domain.     

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.     

Bioreactors and biophoton-driven biohydrogen production strategies

Given the current issues with global warming and rising greenhouse gas emissions, biohydrogen is a viable alternative fuel option. Technologies to produce biohydrogen include photo fermentation, dark fermentation, direct and indirect bio-photolysis, and two-stage fermentation. Biological hydrogen generation is a green and promising technique with mild reaction conditions and low energy consumption compared to thermochemical and electrochemical hydrogen generation. To optimize hydrogen gas output using this method, the activity of hydrogen-consuming bacteria should be restricted during the production stages of hydrogen and acetate to prevent or limit hydrogen consumption. Raw material costs, poor hydrogen evolution rates, and large-scale output are the main limitations in biological hydrogen generation systems. Organic wastes would be the most preferred target feedstock for hydrogen fermentation, aside from biodegradable wastes, due to their high amount and simultaneous waste treatment advantage. This study examined the three primary methods for converting waste into bio-hydrogen: microbial electrolysis cell, thermochemical gasification, and biological fermentation, from both a technological and environmental standpoint. The effectiveness and applicability of these bioprocesses in terms of aspects influencing processes and their constraints are discussed. Alternative options for improving process efficiency, like microbial electrolysis, bio-augmentation, and multiple process integration, are also considered for industrial-level applications. Biohydrogen generation might be further enhanced by optimization of operating conditions and adding vital nutrients and nanoparticles. Cost reduction and durability enhancement are the most significant hindrances to fuel-cell commercialization. This review summarizes the biohydrogen production pathways, the impact of used organic waste sources, and bacteria. The work also addresses the essential factors, benefits, and challenges.     

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.     

A review of hydrogen production via biomass gasification and its prospect in Bangladesh

Hydrogen has been using as one of the green fuel along with conventional fossil fuels which has enormous prospect. A new dimension of hydrogen energy technology can reduce the dependency on non-renewable energy sources due to the rapid depletion of fossil fuels. Hydrogen production via Biomass (Municipal solid waste, Agricultural waste and forest residue) gasification is one of the promising and economic technologies. The study highlights the hydrogen production potential from biomass through gasification technology and review the parameters effect of hydrogen production such as temperature, pressure, biomass and agent ratio, equivalence ratios, bed material, gasifying agents and catalysts effect. The study also covers the all associated steps of hydrogen separation and purification, WGS reaction, cleaning and drying, membrane separation and pressure swing adsorption (PSA). To meet the huge and rising energy demand, many countries made a multidimensional power development plan by adding different renewable, nuclear and fossil fuel sources. A large amount of biomass (total biomass production in Bangladesh is 47.71 million ton coal equivalent where 37.16, 3.49 and 7.04 MTCE are agricultural, MSW and forest residue based biomass respectively by 2016) is produced from daily uses by a big number of populations in a country. It also includes total feature of biomass gasification plant in Bangladesh.     

Application of modern approaches to the synthesis of biohydrogen from organic waste

Hydrogen production with the use of biological processes and renewable feedstock may be considered an economical and sustainable alternative fuel. The high calorific value and zero emission in the production of biohydrogen make it the best possible source for energy security and environmental sustainability. Solar energy, microorganisms, and feedstock such as organic waste and lignocellulosic biomasses of different feedstock are the only requirements of biohydrogen production along with specific environmental conditions for the growth of microorganisms. Hydrogen is also named as ‘fuel of the future’. This study presents different pathways of biohydrogen production. Because of breakthroughs in R&D, biohydrogen has been elevated to the status of a viable biofuel for the future. However, significant problems such as the cost of preprocessing, oxygen-hypersensitive enzymes, a lack of uniform light illumination for photobiological processes, and other expenses requiring intensification process limits are faced throughout the biohydrogen production process. Despite concerns regarding nanoparticle (NP) toxicity at higher concentrations, proper NP concentrations may improve hydrogen production dramatically by dissolving the substrates for bacterial hydrogen transformation. The data-driven Machine Learning (ML) model allows for quick response approximation for fermentative biohydrogen production while accounting for non-linear interactions between input variables. Scaling up biohydrogen production for future commercial-scale applications requires combining cost-benefit evaluations and life cycle effects with machine learning.     

Critical assessment of anaerobic processes for continuous biohydrogen production from organic wastewater

Production of biohydrogen using dark fermentation has received much attention owing to the fact that hydrogen can be generated from renewable organics including waste materials. The key to successful application of anaerobic fermentation is to uncouple the liquid retention time and the biomass retention time in the reactor system. Various reactor designs based on biomass retention within the reactor system have been developed. This paper presents our research work on bioreactor designs and operation for biohydrogen production. Comparisons between immobilized-cell systems and suspended-cell systems based on biomass growth in the forms of granule, biofilm and flocs were made. Reactor configurations including column- and tank-based reactors were also assessed. Experimental results indicated that formation of granules or biofilms substantially enhanced biomass retention which was found to be proportional to the hydrogen production rate. Rapid hydrogen-producing culture growth and high organic loading rate might limit the application of biofilm biohydrogen production, since excessive growth of fermentative biomass would result in washout of support carrier. It follows that column-based granular sludge process is a preferred choice of process for continuous biohydrogen production from organic wastewater, indicating maximum hydrogen yield of 1.7 mol-H₂/mol-glucose and hydrogen production rate of 6.8 L-H₂/L-reactor h.     

Toward a clean energy economy: With discussion on role of hydrogen sectors

This study analyzes how advances in clean energy production technology have facilitated related economic development and intensified competition between clean energy sources and fossil fuels. A forecasting model, the Taiwan general equilibrium model–Clean Energy (TAIGEM-CE), is adopted to elucidate the role of wind, solar, tidal current, geothermal, algal biodiesel, biohydrogen, hydrogen fuel cell, biodiesel and bioethanol. Baseline results indicate that biohydrogen, hydrogen fuel cell, biofuels and wind perform satisfactorily when external support is unavailable. Additionally, strong governmental investment in clean energies significantly contributes to development of biodiesel, wind, biohydrogen and hydrogen fuel cell sectors. Results of this study provide feasible means of allocating resources to achieve a smooth transition to a clean energy economy, in which biohydrogen and fuel cell will play a prominent role.     

Biohydrogen production from autoclaved fruit and vegetable wastes by dry fermentation under thermophilic condition

Dark fermentative hydrogen production from organic waste is an attractive technique that simultaneously treats waste along with generation of renewable fuel. In this study, a relative new technology named dark dry fermentation was tested in a 55-L reactor to treat fruit and vegetable waste (FVW) along with simultaneous generation of biohydrogen. To understand the effect of autoclaving as a pretreatment method on FVW for subsequent biohydrogen production, two independent experiments were performed; one with autoclaved waste (experiment I) and another by using non autoclaved waste (experiment II). From the analyses, it was found that maximum hydrogen % obtained for experiment I was 41% (v/v%) whereas, for experiment II was 21%. In terms of total hydrogen produced, around 30% higher production was observed with experiment I compared to experiment II. The hydrogen yields for experiment I and experiment II were respectively, 27.19 and 20.81 NmL H₂/gVS (VS = volatile solid added), and the metabolites (VFAs) preferentially produced were acetic acid and iso-butyric acid.     

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.     

Techno-economic evaluation of biohydrogen production from wastewater and agricultural waste

The world is facing serious climate change caused in part by human consumption of fossil fuel. Therefore, developing a clean and environmentally friendly energy resource is necessary given the depletion of fossil fuels, the preservation of the earth's ecosystem and self-preservation of human life. Biological hydrogen production, using dark fermentation is being developed as a promising alternative and renewable energy source, using biomass feedstock. In this study, beverage wastewater and agricultural waste were examined as substrates for dark fermentation to produce clean biohydrogen energy.