bio-H2 Production Research Articles

Effect of Inoculum Pretreatment and Operational Mode of Reactor on BioH2 Production from Nixtamalization (Nejayote) and Abattoir Wastewater

Effect of Inoculum Pretreatment and Operational Mode of Reactor on BioH2 Production from Nixtamalization (Nejayote) and Abattoir Wastewater

Reaching the operating limit of the continuous multiple tube reactor: Still a promising technology for maximizing fermentative biohydrogen production?

This study simulated the application of the continuous multiple tube reactor (CMTR), a promising technology capable to replace fixed-film reactors in biohydrogen (bioH2) production via dark fermentation, in the processing of sucrose-rich wastewater (COD of up to 16 g L−1). The long-term impacts on both the bioH2 evolution and the dynamics of biomass growth and retention were assessed, aiming to identify the operating limits of the reactor. The bioH2 production was maximized (1445 NmL H2 L−1 d−1) when using moderately concentrated wastewaters (COD = 8 g L−1) at an OLR of 48.0 g COD L−1 d−1, with much lower hydrogenogenic activity (< 200 NmL H2 L−1 d−1) observed at OLR levels of 72.0 and 96.0 g COD L−1 d−1. Inhibition of the fermentative activity by excess substrate and limitations in the retention capacity of suspended biomass in the reactor still limit the application of higher OLR at the current stage of the technology. Strategies stimulating the cell growth (nitrogen dosing) and biofilm formation (calcium dosing) have potential to expand the operating limit of the CMTR without requiring constructive modifications.

Biodigestion of easily-acidifying cheese whey in a sequential fermentative-methanogenic process: Strategies for boosting energy production and minimizing alkalinization costs

The biodigestion of cheese whey towards enhanced bioenergy production still challenges researchers, considering incipient biohydrogen (bioH2) production during fermentation and the great dependence on an efficient (usually high-cost) alkalinization strategy to achieve high and stable methane production. Using a sequential fermentative-methanogenic process in fixed-film reactors, this study assessed strategies to boost bioH2 production (pH control at ca. 5.5 + prevention of biomass accumulation) and achieve a low-cost stable methanogenic process (replacing NaHCO3 dosing by effluent recirculation and further eliminating any alkalinization approaches). Maintaining fermentation pH values between 5.0 and 5.5 favored bioH2 and butyrate production, but the enhanced establishment of homoacetogenesis (accounting for 70–100 % of the acetate produced) associated with the selective removal of hydrogen-producing bacteria in biomass discharges resulted in a marked unstable hydrogenogenic activity. Processing fermented cheese whey without applying any alkalinization strategy in methanogenesis was further demonstrated to be technically feasible at an OLR of 5.0 kg COD m−3 d−1. COD removal (70–75 %) and the methane yield (150–170 NmL CH4 g−1COD) were equivalent regardless of the alkalinization (NaHCO3 dosing or effluent recirculation) or non-alkalinization approach. However, the alkalinization-derived production cost of methane was reduced from 1.55 USD Nm−3CH4 to zero when fully removing NaHCO3.

Natural fermentation as an inoculation strategy for dark fermentation of Ulva spp. hydrolysate

Dark fermentation from Ulva spp. hydrolysate, a third-generation feedstock, can be exploited as sustainable alternative for biofuel production as it possesses a high carbohydrate content, contributes to decarbonisation and allows the simultaneous production of bioH2 and chemicals. However, it requires microorganisms with enzymatic capability to metabolise the sugars released by the macroalgae. In the present study, the natural fermentation process exploring the microbial community growing attached onto the Ulva spp. was for the first time assessed as an alternative inoculation method for bioH2 production from Ulva spp. hydrolysate. Inoculum enrichment from Ulva spp was tested at 4, 30 and 55 °C in a batch experiment. Then, the liquid phase was assessed as inoculum of a continuous up-flow anaerobic structured bed reactor (AnSTBR) fed with diluted acid-thermal Ulva spp. hydrolysate at 30 and 55 °C. At initial pH 6.5 the sulfidogenic pathway was predominant, however decreasing the pH to 5.5 stimulated the bioH2 production, with higher production at 55 °C, resulting in a median volumetric hydrogen production rate (VHPR) of 297.5 NmL L−1 d−1. The main soluble metabolites (SM) at 55 °C were butyric acid (HBu) and acetic acid (HAc), reaching medians of 912.9 and 483.4 mg L−1. At 30 °C, the primary pathway was solventogenic, resulting in ethanol (EtOH) and HAc production at a ratio 2.5:1. Therefore, the natural fermentation strategy was found to be a suitable strategy to inoculate the dark fermentation reactor.

Magnetic nitrogen-doped activated carbon improved biohydrogen production.

Low biological hydrogen (bioH2) production due to non-optimal metabolic pathways occurs frequently. In this work, magnetic nitrogen-doped activated carbon (MNAC) was prepared and added into the inoculated sludge with glucose as substrate to enhance hydrogen (H2) yield by mesophilic dark fermentation (DF). The highest H2 yield appeared in 400 mg/L AC (252.8 mL/g glucose) and 600 mg/L MNAC group (304.8 mL/g glucose), which were 26.02% and 51.94% higher than that of 0 mg/L MNAC group (200.6 mL/g glucose). The addition of MNAC allowed for efficient enrichment of Firmicutes and Clostridium-sensu-stricto-1, accelerating the metabolic pathway shifted towards butyrate type. The Fe ions released by MNAC facilitated electron transfer and favored the reduction of ferredoxin (Fd), thereby obtaining more bioH2. Finally, the generation of [Fe-Fe] hydrogenase and cellular components of H2-producing microbes (HPM) during homeostasis was discussed to understand on the use of MNAC in DF system.

Effects of adding micro- and nano-sized biomass fly ash on two-stage biohythane production from the urban organic solid waste

In this work, the effect of ash particle size on the sequential production of bioH2 and bioCH4 for biohythane recovery from the organic fraction of municipal solid waste (OFMSW) was investigated for the first time using micro- and nano-sized biomass fly ash (FA). In the first hydrogenogenic stage, the highest bioH2 yield of 215 mL/g VSadded was noticed in the reactor added with micro-sized FA. On the contrary, in the second methanogenic stage, the maximum bioCH4 yield of 676 mL/g VSadded was witnessed in the reactor fed with acidogenic effluent containing nano-sized FA. In the integrated two-stage process, the addition of FA with nano-sized particles showed superiority over micro-sized FA supplementation and led to an increase of about 582 and 595% in organic matter conversion and energy yield, respectively, compared to the control test, as well as achieving biohythane with an optimal hydrogen content of 15% v/v.

Effect of static magnetic field exposure on biohydrogen production via dark fermentation of glucose

The effect of a static magnetic field (SMF) on the microbial activity of anaerobic granular sludge was investigated using a SMF field provided by a magnetic platform with intensities between 30 and 90 mT. BioH2 production was assessed in fed batch fermentation tests from glucose using anaerobic granular sludge with (HT) and without (WHT) heat shock pretreatment (100 ºC, 1 h). Under the conditions tested, 70 mT SMF was the best condition for bioH2 production, with a threefold decrease of lag time, a 12–50% increase in bioH2 production rate, and an improved consumption of iron and phosphate, compared to the controls (no SMF). Exposure to the SMF induced modifications in volatile fatty acid (VFA) production, pH and conductivity, biomass concentration, exopolysaccharide (EPS) composition as well as size and settleability of the granular anaerobic sludge. Microbial analysis showed that in the presence of the SMF, the relative abundance (RA) of Clostridium and Lactobacillus increased in both HT and WHT sludges, while it decreased the RA of Methanosaeta and Methanobacterium. The RA of Terrisporobacter increased with the heat shock, and also the stimulation along the fed batch cycles improved the RA of Terrisporobacter with and without SMF. The application of the SMF as a pre-treatment of inoculum and during bioH2 production seems to be an interesting and easy scaling up strategy to shorten the start-up of the dark fermentation process and help reducing the microbial diversity of the sludge, favouring more specialized species for bioH2 production.

Biohydrogen production through dark fermentation: Recent trends and advances in transition to a circular bioeconomy

Fossil fuel reserves have drastically decreased over the past two decades, contributing to a worldwide decline in energy sources. The volatility of energy prices and their serious ecological consequences have drawn the attention of researchers to alternative carbon-neutral renewable energy sources. Furthermore, ineffective waste management contributes to environmental contamination, harms human health, and negatively affects the global economy. Biohydrogen (Bio-H2) derived from waste biomass via dark fermentation is a valuable green fuel to solve the issues of clean energy production and waste management. Bio-H2 has several advantages over other biofuels, including carbon-neutral production, ease of generation, low carbon dioxide (CO2) emissions, and high energy efficiency. Besides, by using biowaste to produce bio-H2, global warming and CO2 emissions associated with biowaste incineration can be reduced. Although dark fermentation produces the most efficient and clean bio-H2, the yield and rate of production of the process are very low. This review article summarizes the recent developments in dark fermentation processes to enhance bio-H2 yield and productivity, including pre-treatment, additives inclusion, and integrated solutions. Additionally, this article highlights the metabolic pathways of Bio-H2 production and inhibitory substances that negatively affect dark fermentation. Challenges related to bio-H2 technology transfer from lab to industry are discussed, and prospects for future research to realize the technology transfer are briefed. Further, an integrated carbon-neutral approach by dark fermentation-assisted bio-H2 production is also discussed as a contribution to circular bioeconomy.

Pretreatment optimisation of Ulva spp. for production of bioH2 and lactic acid as added-value product

This study compares hydrothermal and diluted acid-thermal pretreatments at 100 °C for hydrolysate production from Ulva spp. Aiming at bioH2 production at 55 °C. Three extractants were evaluated in hydrothermal pretreatment: distilled water (H-DW), natural (H-NS) and synthetic seawater (H-SS). The HCl concentration (N), the Ulva spp. Percentage (% w/v), and hydrolysis time (h) in diluted acid-thermal pretreatment were optimised using a central composite design and a desirability function to maximise the total carbohydrate concentration and yield while minimising the HMF and furfural concentration. The hydrolysate from hydrothermal pretreatments, depending on the pretreatment time and %Ulva, achieved bioH2 production from 20 to 47% lower than the optimised diluted acid-thermal pretreatment (0.3 N HCl, 35%Ulva, and 2.5 h), which was 66.83 (±3.89) NmL gglucose−1. The hydrolysate also indicates potential for lactic acid (HLa) production, resulting in 1.47 molHLa molglucose−1, before being consumed after 1.6 days and contributing to the bioH2 production.

Biohydrogen production from lignocellulosic feedstock: Abiotic and biotic methods

Bioenergy is known as green energy produced from organic biomass, such as food leftovers, non-edible agri-residues, and municipal wastes through biotic and abiotic methods. Globally, generation of the most common renewable fuels including biohydrogen (bioH2), biogas, bioethanol, biofertilizers and bio plastics as fossil fuel substitutes by means of circular bioeconomy is gaining tremendous focus in support of environmental concerns. Carbon free bioH2 is considered as deemed fuel due to its multifaceted applications and potent ecological features. As the present commercial energy manufacturing methods tap on non-renewable fuels and associated high cost, there is an immediate need for full scale sustainable bioH2 production systems in accordance with regional demand through domestic innovations. Though, research on hydrogen production is not less common via conventional thermo chemical methods, it is essential to understand much regarding biological methods to achieve feasible transition from depleting fossil fuels to eco-friendly renewable energy. Thus, this review primarily focuses on different sustainable approaches for lignocellulosic biomass valorization towards bioH2 production along with potential thermo chemical approaches. In particular, bioH2 production from lignocellulosic biomass in the presence and absence of light by photo fermentation and dark fermentation, respectively, reactor configuration, importance of biocatalyst pretreatment and potential methods, and natural and mutant microalgal bioH2 evolution have been discussed in detail to address their industrial level applicability.

Recent trends in engineering algae for biohydrogen production: State of art strategies

Hydrogen (H2) is one of the renewable and sustainable energy since it reduces greenhouse gas emissions producing water in its purest form. However, the production of H2 from conventional thermochemical technologies needs a switchover to biological processes to avoid replenishment of nonrenewable energy reservoirs. This may include algae which switch over from oxygen to bioH2 production and simultaneously produce various renewable energy products like biomass, carbon storage products, biofuel, lipids and alcohol. On the offset, the selection of algae entrenched on its metabolic and genomic pathways to screen enzymes and genes enhancing the production of bioH2 inside algal cell is crucial. However, they can be an immense reservoir of bioH2 only if its pretreatment process is economized. The current review identifies the metabolic pathway, enzymes and genes involved for bioH2 production. The review also discusses the state of art techniques, advancements, challenges, and techno-economic aspects for sustainable bioH2 production.

Catalytic hydrothermal deoxygenation of sugarcane bagasse for energy dense bio-oil and aqueous fraction acidogenesis for biohydrogen production

The study focuses on the effective conversion of sugarcane bagasse (SCB) by catalytic deoxygenation using various alkali and metal-based catalysts under N2 pressure employing water as solvent. The specific influence of catalyst over bio-crude yields (bio-oil and aqueous fraction) including energy recovery ratio was explored. The optimum catalytic condition (Ru/C) resulted in ∼ 70% of bio-crude and 28% of bio-oil with an improved HHV (31.6 MJ/kg) having 11.6% of aliphatic/aromatic hydrocarbons (C10–C20) which can be further upgraded to drop-in fuels. The biocrude composed of 44% of aqueous soluble organic fraction (HTL-AF). Further, the carbon-rich HTL-AF was valorized through acidogenic fermentation to yield biohydrogen (Bio-H2). The maximum bio-H2 production of 201 mL/g of TOC conversion (K2CO3 catalyst) was observed with 7.7 g/L of VFA. The SCB was valorized in a biorefinery design with the production of fuels and chemical intermediates in a circular chemistry approach.

Recent advances in process improvement of dark fermentative hydrogen production through metabolic engineering strategies

Biological means of hydrogen (H2) production has attracted tremendous research and development attention. Dark fermentation provides a possible way of producing H2 from a range of renewable energy sources, including wastewater. During fermentation, various metabolites are formed to create a complex metabolic flux network. Insufficient focus has been placed on the metabolic engineering that is intrinsic to fermentation. This current review summarizes the biochemical pathways occurring in the metabolic network of dark fermentation and how the key operational factors influence metabolism during dark fermentation. Recent developments and strategies for metabolic engineering that have been described to enhance H2 production are recommended. Finally, the economic analysis related to bio-H2 production and prospects is examined. It is envisaged that this study can give beneficial aspects in terms of fundamental knowledge, understanding, and the latest technology for scientists and research engineers in the field of bio-based H2 generation.

A Review of Biohydrogen Production from Saccharina japonica

Saccharina japonica (known as Laminaria japonica or Phaeophyta japonica), one of the largest macroalgae, has been recognized as food and medicine for a long time in some Asian countries, such as China, South Korea, Japan, etc. In recent years, S. japonica has also been considered the most promising third-generation biofuel feedstock to replace fossil fuels, contributing to solving the challenges people face regarding energy and the environment. In particular, S. japonica-derived biohydrogen (H2) is expected to be a major fuel source in the future because of its clean, high-yield, and sustainable properties. Therefore, this review focuses on recent advances in bio-H2 production from S. japonica. The cutting-edge biological technologies with suitable operating parameters to enhance S. japonica’s bio-H2 production efficiency are reviewed based on the Scopus database. In addition, guidelines for future developments in this field are discussed.

Enhanced anaerobic hydrogen production from cotton straws assisted by copper molybdate.

Hydrogen production from dark fermentation has potential application due to its environmental friendliness, low production cost, and sustainability. However, there is still an obstacle to improving the efficiency of bioH2 production to meet the requirements in practical applications. In this research, copper molybdates are synthesized under different pH conditions as additives to study their different influence processes during anaerobic hydrogen production from cotton straws with the pure cultural system. A series of results indicate that CuMoO4 with appropriate experimental conditions has the highest H2 yield at 191.3mL/g straws at 37°C, which is 236% higher than the control group. It can be shown that O. ethanolica 8KG-4 has an obvious accompanying with high stability and low cytotoxicity for this clean energy production system as well as the improvement of metabolic pathway. These results extend new thinking of obtaining higher H2 yield as a biofuel in future production.

BioH2 Production Using Microalgae: Highlights on Recent Advancements from a Bibliometric Analysis

Demand for clean energy has increased due to the proliferation of climate change impact from excessive emission of greenhouse gases (GHG) from the combustion of fossil fuels. H2 is a clean energy source since water vapor is the only byproduct after its combustion. Growing microalgae offers a promising low-energy and low-cost approach for bioH2 production. In this study, a bibliometric analysis was performed for the production of H2 using microalgae to evaluate the conceptual, intellectual, and social structure of the dataset. In addition, a scoping review of articles was conducted to highlight recent advancements and identify future research recommendations. A total of 184 relevant publications over 23 years (2000–2022) were retrieved from the Scopus database for analysis. The results demonstrated an exponential increase in citations from 283 to 996 in the last decade, indicating the interest in bioH2 production from microalgae. Results also revealed that the International Journal of Hydrogen Energy accounted for more than 25% of the published articles, of which China contributed almost 28%. Oxygen sensitivity of the H2ase enzyme and sulfur deprivation were highlighted as the main limiting factors of bioH2 production using microalgae. It was also evident that the most widely studied microalgae species were green algae, especially Chlamydomonas and Chlorella. Effective process modifications, particularly hybridizing microalgae with bacteria consortium and implementing oxygen regulating strategies, were shown to give up to a 10-fold increase in H2 yield. This study also discusses recent developments in technologies, strategies, microalgal species, and optimizing controlling factors affecting bioH2 production.

High biohydrogen yield from fresh cassava waste pulps via gas dissolution in a dark fermentative environment

The improper disposal of wastes like cassava waste pulps (CWP) in the environment could likely result in putrefaction stench, leachate contamination of water bodies, illnesses/diseases in local populations, and many other adverse effects. This study exploited the use of CWP for the possible production of valuable biofuel such as biohydrogen (bio-H2). Acid hydrolysis was used to prepare the CWP, whereas heat shock was used to prepare the cow dung inoculum. Pretreated organic wastes were used as substrates for dark fermentation, which considered the effects of pH and hydraulic retention duration on bio-H2 generation. The gas chromatography analysis showed 99.89% bio-H2 component of the total biogas produced through dark fermentation. The dissolution of the produced carbon monoxide and carbon dioxide in water enhanced bio-H2 production. At 6.09 pH and 83.24 h HRT, a kilogram of fresh CWP can produce 12.39 ± 0.8 L bio-H2. Overall, the current research has shown that underutilized CWP from starch-producing companies can be used to make sustainable biofuel, which can help to reduce fossil-fuel-related emissions.

Effect of nitrogen and iron supplementation on the process performance and microbial community structure of a hydrogen-producing reactor continuously fed with tequila vinasse

Dark fermentation is gaining importance as a bioprocess able to valorize different organic wastes/wastewaters through the co-production of organic acids and biogenic hydrogen (bioH2). In this study, the process performance and microbial community structure of a mesophilic lab-scale fermenter inoculated with an enriched hydrogenogenic consortium and fed with undiluted tequila vinasse (TV) were evaluated for 28 days equivalent to 112 hydraulic retention times (HRT). The influence of external nutrients supply on process performance was carefully evaluated. The fermenter was operated at 6 h HRT and fed with i) TV without additional nutrients, ii) TV with additional nitrogen (0.3 g/L), and iii) TV supplemented with nitrogen (0.3 g/L) and iron (0.01 g/L) chemical sources. Despite the inherent presence of macro- and micronutrients in TV, the use of raw TV with no additional nutrients resulted in a very low hydrogen production rate of 24 NmL-H2 L−1h−1. Contrarily, a nitrogen dosing of 1.2 g-NH4Cl L−1 led to a sudden increase in the bioH2 production, reaching productivity and yield values of 283 NmL-H2 L−1h−1 and 82 NmL-H2 g−1-volatile solids added, respectively. The further addition of FeSO4·7H2O (0.05 g/L) did not improve the TV-to-bioH2 conversion. Bridging hydrogen production and organic acids with molecular analysis, 16S rRNA gene sequencing, indicated that maintaining a suitable C/N ratio in the fermenter could ensure balance and syntrophy between lactic acid bacteria (e.g., Sporolactobacillus, Lactobacillus) and bioH2 producers (Clostridium). Further biochemical methane potential tests with the fermentation broth demonstrated that biohythane process (bioH2 + CH4) resulted in 5 % higher bioenergy recovery than that derived from the single-stage anaerobic digestion.

Simultaneous Production of Biohydrogen (bioH2) and Poly-Hydroxy-Alkanoates (PHAs) by a Photoheterotrophic Consortium Bioaugmented with Syntrophomonas wolfei

Mixed cultures represent better alternatives to ferment organic waste and dark fermentation products in anerobic conditions because the microbial associations contribute to electron transfer mechanisms and combine metabolic possibilities. The understanding of the microbial interactions in natural and synthetic consortia and the strategies to improve the performance of the processes by bioaugmentation provide insight into the physiology and ecology of the mixed cultures used for biotechnological purposes. Here, synthetic microbial communities were built from three hydrogen (bioH2) and poly-hydroxy-alkanoates (PHA) producers, Clostridium pasteurianum, Rhodopseudomonas palustris and Syntrophomonas wolfei, and a photoheterotrophic mixed consortium C4, and their performance was evaluated during photofermentation. Higher hydrogen volumetric production rates (H2VPR) were determined with the consortia (28–40 mL/Lh) as compared with individual strains (20–27 mL/Lh). The designed consortia reached the highest bioH2 and PHA productions of 44.3 mmol and 50.46% and produced both metabolites simultaneously using dark fermentation effluents composed of a mixture of lactic, butyric, acetic, and propionic acids. When the mixed culture C4 was bioaugmented with S. wolfei, the bioH2 and PHA production reached 32 mmol and 50%, respectively. Overall, the consumption of organic acids was above 50%, which accounted up to 55% of total chemical oxygen demand (COD) removed. Increased bioH2 was observed in the condition when S. wolfei was added as the bioaugmentation agent, reaching up to 562 mL of H2 produced per gram of COD. The enhanced production of bioH2 and PHA can be explained by the metabolic interaction between the three selected strains, which likely include thermodynamic equilibrium, the assimilation of organic acids via beta-oxidation, and the production of bioH2 using a proton driving force derived from reduced menaquinone or via electron bifurcation.

An efficient process for improvement of biohydrogen and biomethane production from tomato waste: Inhibitory effects of ultrasonic pretreatment

The present study was undertaken to determine the effect of ultrasonic pretreatment of tomato wastes on improving the production of bio-H2 and bio-CH4. Furthermore, inhibitory effects of phenolic and tannin compounds that may be produced during the breaking of complex structures using the ultrasonic irradiations were investigated. For this purpose, anaerobic digestion of different mixtures of tomato waste and cow manure, ultrasonically pretreated with different acoustic powers and sonication times, was studied based on a combined d-optimal experimental design. A two-stage optimization process was developed by integrating multivariate modeling and desirability analysis. The first stage of the optimization process showed that the ultrasonic pretreatment of 197.21 W (0.33 W/mL) at 21.47 min for the mixtures with high amounts of tomato wastes (>90 %) produced small amounts of the total phenolic compounds (2.03 mg equivalent gallic acid/g: mg/g) and tannin content (4.37 mg catechin equivalent/g: mg/g). These conditions produced high amounts of total solid (6.53 %), total volatile solid (77.84 %) and total carbohydrate (6.95 mg glucose equivalent/g: mg/g). These values led to producing Bio-H2 > 18 %vol and Bio-CH4 > 2 %vol. The second stage of the optimization process indicated that total phenolic compounds < 12.5 mg/g and tannin content < 25.5 mg/g were needed to maximize both bio-H2 and bio-CH4 production and optimize the desirability of biogas production.