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.     

Energy analysis of the system of two-stage anaerobic processing of liquid organic waste with production of hydrogen- and methane-containing biogases

In recent years, public attention has been increasingly attracted to solving two inextricably linked problems - preventing the depletion of natural resources and protecting the environment from anthropogenic pollution. The annual consumption of livestock waste for biogas production is about 240 thousand m³ per year, which is 0.17% of the total manure produced at Russian agricultural enterprises. At present, the actual use of organic waste potentially suitable for biogas production is 2–3 orders of magnitude lower than the existing potential for organic waste. Currently, hydrogen energy is gaining immense popularity in the world due to the problem of depletion of non-renewable energy sources - hydrocarbons, and environmental pollution caused by their increasing consumption. Of particular interest is the dark process of producing hydrogen-containing biogas in the processing of organic waste under anaerobic conditions, which allows you to take advantage of both energy production and solving the problem of organic waste disposal. An energy analysis of a two-stage anaerobic liquid organic waste processing system with the production of hydrogen- and methane-containing biogases based on experimental data obtained in a laboratory plant with increased volume reactors was performed. The energy efficiency of the system is in the range of 1.91–2.74. Maximum energy efficiency was observed with a hydraulic retention time of 2.5 days in a dark fermentation reactor. The cost of electricity to produce 1 m³ of hydrogen was 1.093 kW·h with a hydraulic retention time of 2.5 days in the dark fermentation reactor. When the hydraulic retention time in the dark fermentation reactor was 1 day, the specific (in ratio to the processing rate of organic waste) energy costs to produce of 1 m³ of hydrogen were minimal in the considered hrt range, and amounted to 26 (W/m³ of hydrogen)/(m³ of waste/day). Thus, the system of two-stage anaerobic processing of liquid organic waste to produce hydrogen and methane-containing biogases is an energy-efficient way to both produce hydrogen and process organic waste.     

Enhancing photo fermentative hydrogen production using ethanol rich dark fermentation effluents

The present study demonstrates the feasibility of a two-phase biorefinery process applied to waste substrates producing ethanol rich effluents. The process includes a dark fermentation step followed by photo fermentation and it is able to optimize hydrogen production from waste biomass. The study was conducted using winery wastewater as feedstock. The results indicate that no additional treatments are required when an appropriate dilution of the initial waste is applied. Microbial consortia contained in the winery wastewater promoted a fermentative ethanol pathway. The ethanol rich effluent was converted into hydrogen by phototrophic microorganisms. Despite the presence of inhibiting compounds, the adoption of a mixed phototrophic culture allowed to obtain good results in terms of hydrogen production. Specifically, up to 310 mLH₂ gCOD_consumed^?1 were obtained in the photo fermentative stage. The effectiveness of ethanol rich dark fermentation effluents for hydrogen production enhancement was demonstrated. Noteworthy, polyhydroxybutyrate was also produced during the experiments. The work faces two of the major challenges in the sequential dark fermentation and photo fermentation technology applied to real waste substrates: the minimization of pre-treatments and the enhancement of the hydrogen production yields using ethanol rich DFEs.     

Dark fermentation for H2 production from food waste and novel strategies for its enhancement

Hydrogen is an attractive energy vector that can be obtained through biological methods such as dark fermentation, allowing organic wastes to be used as substrates. This means an advantage compared to other methods since dark fermentation enables the revalorization of waste, such as food waste, with generation and disposal contributing to the current environmental issue. However, the complex composition of food waste and the microbial dynamics involved in dark fermentation have made it difficult to obtain maximum yields. Although several strategies have been evaluated to improve hydrogenogenic systems, the common limitations have been the economic costs and the re-emergence of unwanted microorganisms. Therefore, developing and evaluating novel strategies such as lactate-driven dark fermentation, bioaugmentation with native strains, metabolic engineering, and construction of synthetic microbiomes are innovative proposals to enhance H₂ production from food waste.     

Efficient hydrogen gas production from cassava and food waste by a two-step process of dark fermentation and photo-fermentation

A two-step process of sequential anaerobic (dark) and photo-heterotrophic fermentation was employed to produce hydrogen from cassava and food waste. In dark fermentation, the average yield of hydrogen was approximately 199 ml H₂ g⁻¹ cassava and 220 ml H₂ g⁻¹ food waste. In subsequent photo-fermentation, the average yield of hydrogen from the effluent of dark fermentation was approximately 611 ml H₂ g⁻¹ cassava and 451 ml H₂ g⁻¹ food waste. The total hydrogen yield in the two-step process was estimated as 810 ml H₂ g⁻¹ cassava and 671 ml H₂ g⁻¹ food waste. Meanwhile, the COD decreased greatly with a removal efficiency of 84.3% in cassava batch and 80.2% in food waste batch. These results demonstrate that cassava and food waste could be ideal substrates for bio-hydrogen production. And a two-step process combining dark fermentation and photo-fermentation was highly improving both bio-hydrogen production and removal of substrates and fatty acids.     

Hydrogen production via dark fermentation by bacteria colonies on porous PDMS-scaffolds

The development of biofuels and the question of finding renewable energy sources are important issues nowadays, due to the increasing shortage of other supplies. Hydrogen has gained very much attention as biofuel, as it is highly energetic and a clean energy source. A very interesting method to produce hydrogen is dark fermentation. It generates a clean energy from organic wastes with low value and at low energy requirements. The production of hydrogen and bio-hydrogen from waste and wastewaters can have a positive environmental impact in terms of creation of highly effective energy fuel and reduction of waste. Due to their nutrients, organic waste and wastewaters are suitable substrates to obtain bio-hydrogen. In this paper we investigate the behaviour and the stability of porous scaffolds containing iron oxide particles in a dark fermentation environment and explore the possibility of hosting mixed cultures of clostridia on them, aiming to an increase in hydrogen production. We address the effect of embedding hematite particles (in different concentrations) in the scaffolds, to see whether there is an increase in bio-hydrogen-production. This latter can be enhanced, if particles of various metal oxides are present, as they can increase bacterial growth and encourage the bioactivity of species that produce hydrogen. The scaffolds analysed consist of polydimethylsiloxane (PDMS) containing Fe₂O₃ particles and were produced via the sugar template method. X-ray diffraction patterns, SEM images as well as dark fermentation tests in batch procedure are presented and discussed. Bacteria colonies could be detected after long treatment in municipal wastewater and production of biohydrogen was ascertained for all samples investigated.     

Direct hydrogen production from cellulosic waste materials with a single-step dark fermentation process

Biohydrogen production from cellulosic waste materials using dark fermentation is a promising technology for producing renewable energy. The purpose of this study was to evaluate residual cellulosic materials generated from local sources for their H₂ production potential without any pretreatment. Clostridium thermocellum ATCC 27405, a cellulolytic, thermophilic bacterium that has been shown to be capable of H₂ production on both cellobiose and α-cellulose substrates, was used in simultaneous batch fermentation experiments with dried distillers grain (DDGs), barley hulls (BH) and fusarium head blight contaminated barley hulls (CBH) as the carbon source. Overall, the dried distillers grain produced the highest concentration of hydrogen gas at 1.27 mmol H₂/glucose equivalent utilized. CBH and BH produced 1.18 and 1.24 mmol H₂/glucose equivalent utilized, respectively. Overall, this study indicates that hydrogen derived from a variety of cellulosic waste biomass sources is a possible candidate for the development of sustainable energy.     

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.     

Approbation of an innovative method of pretreatment of dark fermentation feedstocks

According to the International Energy Agency, only a small part of the full potential of biomass energy is currently used in the world. The annual amount of agricultural waste in the Russian Federation is estimated at about 152 million tons, and the energy potential of animal waste is 201 PJ/year. Anaerobic digestion is an efficient method of converting organic waste into renewable energy sources. Previously, the positive effect of pretreatment of various organic feedstocks in vortex layer apparatus (VLA) on the characteristics of anaerobic digestion and energy efficiency was shown. Currently, there is a significant interest in the world in obtaining biohydrogen from organic waste using the dark fermentation (DF) process. During pretreatment in the VLA, the iron working bodies are abraded and iron particles are introduced into the feedstock of the DF reactor. This may have a positive effect on the production rate and yield of hydrogen, which has not been previously studied. This work is aimed at evaluating the possibility of using the VLA as a method for pretreatment of a dark fermentation feedstock for the intensification of biohydrogen production. To achieve this goal, an experimental setup was constructed. It consisted of a 45 L DF reactor, a VLA and a process control system to collect data on the DF process parameters every 5 min. At a hydraulic retention time in the DF reactor of 24 h and in the VLA of 30 s, the hydrogen content in the biogas increased from 51.1% to 52.2%. At the same time, the pH increased from 3.85 to 4.8–4.9, and the hydrogen production rate increased by 16% to 1.941 L/(L day). The hydrogen yield was 80.9 ml/g VS. Thus, pretreatment of the feedstock in VLA can be an effective way to intensify the DF process; however, further study of the VLA operating modes is required in order to optimize the concentrations of iron particles introduced into the feedstock for the most efficient continuous production of dark fermentative biohydrogen.     

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.     

Maximizing biohydrogen production from water hyacinth by coupling dark fermentation and electrohydrogenesis

Biohydrogen production via dark fermentation has shown immense potential for simultaneous energy generation and waste remediation. However, the low substrate conversion rates limit its practical feasibility. Therefore, the present work attempts to develop a single chamber microbial electrolysis cell (MEC) as an additional means for biohydrogen production. Different organic substrates including simple sugars and volatile fatty acids were demonstrated as potential substrates for H₂ production in MEC. The use of water hyacinth as sole substrate for H₂ production was examined. Furthermore, the feasibility of using MEC for second stage energy recovery after dark fermentation was explored. The two-stage process exhibited improved performance as compared to single stage MEC process with overall hydrogen yield of 67.69 L H₂/kg COD_consumed, COD removal of 70.33% and energy recovery of 46%. These results suggest that coupled dark fermentation-MEC process can be a promising means for obtaining high yield biohydrogen from water hyacinth.     

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.     

A review on biomass‐based hydrogen production for renewable energy supply

This article gives an overview of the state‐of‐the‐art biomass‐based hydrogen production technologies. Various biological and thermochemical processes of biomass are taken into consideration to find the most economical method of hydrogen production. Biohydrogen generated by biophotolysis method, photo‐fermentation and dark fermentation is studied with respect to various feedstocks in Malaysia. The fermentation approaches of biohydrogen production have shown great potential to be a future substitute of fossil fuels. Dark fermentation method is a simple biological hydrogen production method that uses a variety of substrate and does not require any light as a source of energy. A promising future for biohydrogen production is anticipated by this process both industrially and commercially. Feasibility of hydrogen production from pyrolysis and water gasification of various biomass feedstock confirm that supercritical water gasification (SCWG) of biomass is the most cost‐effective thermochemical process. Highly moisturized biomass could be employed directly in SCWG without any high‐cost drying process. Indeed, a small amount of energy is required to pressurize hydrogen in the storage tank because of highly pressurized SCWG process. The cost of hydrogen produced by SCWG of biomass is about US$3/GJ (US$0.35/kg), which is extremely lower than biomass pyrolysis method (in the range of US$8.86/GJ to US$15.52/GJ) and wind‐electrolysis systems and PV‐electrolysis systems (US$20.2/GJ and US$41.8/GJ, respectively). The best feedstock for biomass‐based hydrogen production is identified based on the availability, location of the sources, processes required for the preparation of the feedstock and the total cost of acquiring the feedstock. The cheapest and most abundantly available biomass source in Malaysia is the waste of palm industry. Hydrogen production from palm oil mill effluent and palm solid residue could play a crucial role in the energy mix of Malaysia. Malaysia has this great capability to supply about 40% of its annual energy demand by hydrogen production from SCWG of palm solid waste. Copyright © 2015 John Wiley & Sons, Ltd.     

Fungal solid-state fermentation of food waste for biohydrogen production by dark fermentation

The dark fermentation process was evaluated for biohydrogen production from food waste through fungal solid-state fermentation (SSF). Three fungal cultures (one strain of Aspergillus tubingensis and two strains of Meyerozyma caribbica) were compared, being A. tubingensis the best hydrolyser culture for releasing soluble carbohydrates. The biochemical hydrogen potential of food waste hydrolysate (FWH) at different substrate-inoculum ratios obtained a lower hydrogen yield than untreated food waste (RFW). The highest hydrogen yield value corresponded to treatments RFW-20 and RFW-30 with 77.0 ± 2.6 and 76.9 ± 1.4 mL H₂ normalized by per gram volatile solid added (NmL H₂/gVS_added), respectively. The microbial community of food waste was analysed, being detected lactic-acid bacteria genera as Latilactobacillus and Leuconostoc. The presence of actively growing bacteria during the SSF could explain the lowest hydrogen yield (20.1–36.0 NmL H₂/gVS_added) in the FWH treatment due to the substrate competition between lactic-acid bacteria and hydrogen-producing bacteria, where the lactic-acid bacteria were favoured by their faster growth rate.     

Commercial application scenario using patent analysis: Fermentative hydrogen production from biomass

The main purpose of this study is to use patent analysis to investigate scenarios for future commercial applications of dark fermentation or anaerobic fermentation using biomass or organic matter as feedstock materials. The first step in this study includes a patent search procedure and patent content interpretation, in which 29 technology patents were identified from the US patent database and divided into five groups in accordance with the scope of their technical applications. The following five scenarios of commercial applications of biomass fermentation for hydrogen production were established through a combination of group applications: screening and cultivation of hydrogen-producing bacteria, biomass waste sources, biomass energization application, value enhancement of waste or wastewater treatment systems, and the application of a multi-functional hydrogen production system integrated with other technologies.     

Oleaginous yeast Cryptococcus curvatus culture with dark fermentation hydrogen production effluent as feedstock for microbial lipid production

Volatile fatty acids (VFA) from dark fermentation hydrogen production were tested as carbon sources for the culture of oleaginous yeast Cryptococcus curvatus, which is a promising feedstock for biofuel production. The optimal acetate concentration and pH were investigated when potassium acetate was used as the sole carbon source. Comparisons were then made when hydrogen production effluent (HPE) from synthetic wastewater was tested as feedstock. A pH-stat culture fed with acetic acid ultimately produced 168 g/L biomass, with a lipid content of 75.0%. No inhibitor to yeast growth was produced in the hydrogen production process. However, inhibition occurred in culture with HPE from food waste (FW), indicating that inhibitors may be present in the original raw food waste. This inhibition could be avoided by a process that uses glucose as the initial carbon source and then is continuously fed with FW-HPE. The biomass productivity in this continuous culture process reached 0.34 g/L/h, but the lipid content was only 13.5%. These results suggest that FW-HPE alone is not an optimal feedstock, but HPE derived from nitrogen-deficient waste streams could be good feedstocks. This study provides preliminary evidence for the feasibility of using organic waste for the co-production of hydrogen and lipid.     

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.     

Hydrogen production by Escherichia coli without nitrogen sparging and subsequent use of the waste culture for fast mass scale one-pot green synthesis of silver nanoparticles

In view of the transition to hydrogen as a major energy carrier in the future, new routes for bringing down the cost of biological hydrogen production need to be explored. The current study was devoted to optimizing the dark fermentation by Escherichia coli HD701 for hydrogen production from an acid-hydrolyzed potato starch residue stream without nitrogen sparging to reduce the cost. To further increase the economic feasibility of hydrogen production by E. coli, this study explores the use of the waste culture after hydrogen production in mass scale one-pot green synthesis of silver nanoparticles.     

Waste to biogas through anaerobic digestion: Hydrogen production potential in the developing world - A case of Bangladesh

Waste management is one of the greatest global challenges, for which one reason is the composition of waste, which varies not only from one region to another but also over time. Recent studies considered waste treatment options for the developed world, where management schemes include waste to hydrogen generation. Although there is great potential for producing hydrogen from waste (e.g. biogas) in the developing world, this has received less attention. This study explores hydrogen production potential from waste in the developing world, particularly focusing on Bangladesh. Results show that anaerobic digestion is the most suitable waste management technology for the developing world predominantly due to waste's composition. The waste composition is dominated by organic food wastes (varying between 50% and 87%), of which the moisture content is more than 50%, thus being unsuitable for self-combustion. National energy policy making should consider this potential source of energy/hydrogen towards a sustainable future.     

Feasibility of biohydrogen production by anaerobic co-digestion of food waste and sewage sludge

Anaerobic co-digestion of food waste and sewage sludge for hydrogen production was performed in serum bottles under various volatile solids (VS) concentrations (0.5–5.0%) and mixing ratios of two substrates (0:100–100:0, VS basis). Through response surface methodology, empirical equations for hydrogen evolution were obtained. The specific hydrogen production potential of food waste was higher than that of sewage sludge. However, hydrogen production potential increased as sewage sludge composition increased up to 13–19% at all the VS concentrations. The maximum specific hydrogen production potential of 122.9 ml/g carbohydrate-COD was found at the waste composition of 87:13 (food waste:sewage sludge) and the VS concentration of 3.0%. The relationship between carbohydrate concentration, protein concentration, and hydrogen production potential indicated that enriched protein by adding sewage sludge might enhance hydrogen production potential. The maximum specific hydrogen production rate was 111.2 ml H₂/g VSS/h. Food waste and sewage sludge were, therefore, considered as a suitable main substrate and a useful auxiliary substrate, respectively, for hydrogen production. The metabolic results indicated that the fermentation of organic matters was successfully achieved and the characteristics of the heat-treated seed sludge were similar to those of anaerobic spore-forming bacteria, Clostridium sp.