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Carbon/Nitrogen-ratio Effect on Fermentative Hydrogen Production by Mixed Microflora
Abstract
Anaerobic sewage sludge acclimated with sucrose was used as the seed in a batch experiment to investigate the carbon/nitrogen (C/N)-ratio effects on biological hydrogen production from sucrose. Experimental results indicated that the hydrogen production ability of the anaerobic microflora (dominated by Clostridium pasteurianum) in the sewage sludge was dependent on the influent C/N-ratio. At a C/N-ratio of 47, the hydrogen productivity and hydrogen production rate reached and , respectively. This increased by 500% and 80%, respectively, compared with the blank. Proper C/N-ratio on hydrogen production enhancement was accomplished by shifting the metabolic pathway. Strategies for optimal hydrogen production are also proposed.
... The fermentation experiments performed with PS100/WAS0, which had the highest C/N ratio consistently yielded higher VFA production than the fermentation with PS0/WAS100, these results are consistent with observations from other researchers that found that higher C/N ratios improve the production of VFA (Lin and Lay, 2004;Liu et al., 2008). The presence of easily biodegradable COD in primary sludge combined with lower total nitrogen content provided a lower C/N ratio. ...
... Other researchers have also found that a low C/N ratio indicates high ammonia concentrations (Lin and Lay, 2004;Shi et al., 2017). High-free ammonia has also been linked to the inhibition and reduced activity of anaerobic microorganisms in anaerobic conditions where pH and temperature play an important role in forming free ammonia (Bitton, 2005). ...
... PS0/WAS100 had the highest rate of soluble NH 4 + -N release, on day five, the release reached 36.55 ± 3.28 mg NH 4 + -N/g VSS, additionally, it had the lowest C/N ratio. Other researchers have also found that a low C/N ratio is an indication of high ammonium concentrations (Lin and Lay, 2004;Shi et al., 2017). High ammonium has also been linked to the inhibition and reduced activity of anaerobic microorganisms in anaerobic conditions (Bitton, 2005). ...
Enhanced hydrolysis of sludges during fermentation is an important factor to achieve solubilization of complex carbon sources and increase the amount of soluble COD that microorganisms could use as food during biological nutrient removal processes. This research shows that a combination of mixing, bioaugmentation, and co-fermentation can be used to increase the hydrolysis of sludges and enhanced the production of volatile fatty acids (VFA). Mixing of primary sludge (PS) at 350 revolutions per minute (RPM) during fermentation increased the hydrolysis of the sludge and increased the soluble chemical oxygen demand (sCOD) by 72% compared to no mixing. Mixing also increased the production of VFA by 60% compared to no mixing conditions. PS hydrolysis was also evaluated using bioaugmentation with the bacteria Bacillus amyloliquefacients, a known producer of the biosurfactant surfactin. Results showed that bioaugmentation enhanced the hydrolysis of the PS by increasing the amount of soluble carbohydrates and soluble proteins present in the form of sCOD. Methanogenesis experiments performed with co-fermentation of decanted primary sludge (PS) and raw waste-activated sludge (WAS) at 75:25 and 50:50 ratios displayed a decreased in production of total biogas by 25.58% and 20.95% and a reduction on methane production by 20.00% and 28.76% respectively, compared to co-fermentation of raw sludges. Compared to fermentation of the sludges separately, co-fermentation of PS and WAS increased the production of VFA and it was determined that 50:50 was the optimum co-fermentation ratio for production of VFA while reducing the reintroduction of nutrients produced during the fermentation process to BNR processes.
... Table 4 summarises the research results focused on the statistical optimisation of production and some other variables (i.e., HLac accumulation, ΣVOA). These works explored a great variety of substrates, from glucose and sucrose (Lin and Lay, 2004;Chen et al., 2011;Akhbaria et al., 2019;Yin and Wang, 2019;Alvarez-Guzmán et al., 2020) to solid or semisolid organic wastes (Robledo-Narváez et al., 2013;Muñoz-Páez et al., 2014;Astie et al., 2018;Ghimire et al., 2018;López-Hidalgo et al., 2018), passing by fermentation effluents (Astie et al., 2018). Factors typically tested were temperature (in 8 works), either initial total solids (in 3 works) or initial substrate concentration (in 5 works), pH (in 6 works), ratio C/N (in 2 works), and concentration of yeast extract (as a supplement, only in 1 work). ...
... Few works have addressed the effect of C/N ratio on biological H2 generation. One work assayed the effect of the ratio C/N of the feed (in the range 40-139; Lin and Lay, 2004); it was found that the maximum value occurred at a C/N ratio of 47; glucose was the substrate. Abdullah et al. (2020) analysed a C/N range from 47 to 190; they found that the highest H 2 production occurred at C/N 140. ...
... Kalil et al. (2008) studied the range from 36 to 230 and reported an optimal value of 70. In our work, we found that maximum biohydrogen production occurred at C/N 43, a comparatively lower value than those of Abdullah et al. (2020) and Kalil et al. (2008), but close to results reported by Lin and Lay (2004) ( Table 4). The practical consequence of our optimum C/N ratio of 43 is that diapers and lignocellulosic substrates should be supplemented with nitrogen sources, preferably wastes rich in N, before fermentation. ...
Waste diapers (WD) handling and disposal in Mexico are typically based on their burial in dumping sites and landfills. Practically reclaiming and recycling of WD are non-existent. The clean diapers are composed of cellulose fibres (37–43% db), hemicellulose (5–9%), lignin (4–7%), protein (<1), plastics (polypropylene and polyethylene) (12–16%), absorbent sodium polyacrylate (14–18%), and elastic and adhesives tapes (9–12%). The latter can be valuable resources. WD composition is similar to clean diaper, although humidity is very high, and the ranges of faeces and urine are 1.5–2.5 and 6–9% dry weight, respectively. International literature searches indicate that there is some research on composting, fungal biodegradation, and methanogenic co-digestion of waste activated sludge with the organic fraction of waste diapers (OFWD.) However, research on dark fermentation of OFWD is limited. In this work, the generation of biohydrogen from dark fermentation of OFWD was optimised. We used the response surface methodology (RSM). Independent variables were the temperature of operation (37–55°C), ratio C/N of the feed (30, 40 gC/gN), and initial total solids of the feed (TSi) (15, 25%). The dependent (response) variables examined were Y’H2 (H2 produced per initial g of dry matter), contents of low molecular weight organic solvents and acids, lactic acid, the ratio A/B (acetic-to-butyric acid), and the quotient organic acids C2 to C4-to-solvents. The predicted maximum Y’H2 occurred at the combination of factors of 43 gC/gN, 12% and 31°C; its value was 2.79 mmolH2/gTS; its experimental validation gave 2.48 mmolH2/gTS, which shows a good agreement between values (11% lower than the predicted value). The maximum of Y’H2 with OFWD compared very favourably with bioH2 values obtained from a wide variety of wastes (organic municipal residues, agricultural wastes, etc.) using the same batch type fermentation with intermittent venting. Interestingly, the predicted temperature optimum fell in the lower side of the mesophilic range. Process heating savings would be in the order of 60.0 and 27.2% for thermophilic and mesophilic operation, respectively. In this way, it would be a contribution to the sustainability of the dark fermentation of OFWD. This result was somewhat counterintuitive and strongly indicates the usefulness of the response surface methodolog for analyzing the experimental results and uncovering favourable, although unexpected conditions.
... However, the composition and type of the employed substrate can affect the optimum C/N ratio . One study found that the ability of H 2 production of the anaerobic microflora in the SS is dependent on the influent C/N ratio (Lin, 2004). With a C/N ratio of 47:1, the H 2 productivity (mol H 2 /mol-sucrose) and H 2 production rate (mmol H 2 /Lday) were both improved by 500 % and 80 %, respectively compared to blank (Lin, 2004). ...
... One study found that the ability of H 2 production of the anaerobic microflora in the SS is dependent on the influent C/N ratio (Lin, 2004). With a C/N ratio of 47:1, the H 2 productivity (mol H 2 /mol-sucrose) and H 2 production rate (mmol H 2 /Lday) were both improved by 500 % and 80 %, respectively compared to blank (Lin, 2004). ...
... The correlation between a reduction in the carbon/nitrogen (C/N) ratio and a metabolic shift from VFA production to solvent production (e.g. ethanol) was observed by Lin and Lay (2004). Few studies have been reported in the literature on lipid-rich substrates. ...
... The bacteria most commonly involved in DF are the obligate anaerobes of Clostridium sp., effective in converting a wide range of carbohydrates with high H 2 and organic acid yields, or the facultative anaerobes of Escherichia coli and Enterobacteriaceae sp., although characterized by a lower H 2 yield (O-Thong et al., 2018). To enhance VFA production, fermentative bacteria should be selected from the inoculum and the activity of methanogens suppressed by appropriately adjusting operating parameters such as pH and HRT (as better described in Section 'Operating parameters'), applying thermal or pH shock pretreatment (Cappai et al., 2014;Lin and Lay, 2004) or using chemical inhibitors of methanogenesis . However, inoculum pretreatments could affect the economic viability of the process and require careful consideration. ...
Volatile fatty acids (VFAs) are high-value chemicals that are increasingly demanded worldwide. Biological production via food waste (FW) dark fermentation (DF) is a promising option to achieve the sustainability and environmental benefits typical of biobased chemicals and concurrently manage large amounts of residues. DF has a great potential to play a central role in waste biorefineries due to its ability to hydrolyze and convert complex organic substrates into VFAs that can be used as building blocks for bioproducts, chemicals and fuels. Several challenges must be faced for full-scale implementation, including process optimization to achieve high and stable yields, the development of efficient techniques for selective recovery and the cost-effectiveness of the whole process. This review aims to critically discuss and statistically analyze the existing relationships between process performance and the main variables of concern. Moreover, opportunities, current challenges and perspectives of a FW-based and fermentation-centred biorefinery layout are discussed.
... respectively. It has been shown that the C/N ratio significantly affects the production of biohydrogen as a result of changes in metabolic pathways during dark fermentation [57]. The yield of hydrogen and the hydrogen production rate during the dark fermentation of wheat flour with the addition of nitrogen were maximum at C/N of 200/1 [58]. ...
... The optimal C/ N ratio of 137/1 to obtain 3.5 mol H 2 /mol sucrose was calculated using a mathematical approximation [16]. Lin and Lei achieved an increase in the yield and rate of hydrogen production by 500 and 80%, respectively, at a C/N ratio of 47/1 [57]. The C/N ratio of 21/1 was optimal in terms of the specific yield and rate of biohydrogen production in the combined DF of cheese whey and vegetable and fruit waste [59]. ...
The hydrogen-producing bacterium SP-H2 was isolated from a thermophilic acidogenic reactor inoculated with municipal sewage sludge and processing a carbohydrate-rich simulated food waste. Based on the 16S rRNA gene sequence, the bacterium was identified as Thermoanaerobacterium thermosaccharolyticum. The maximum growth rate was observed at 55–60 °C and pH 7.5. The H2-producing activity of the bacterium was studied using mono-, di- and tri-saccharides related to both hexoses (maltose, glucose, mannose, fructose, lactose, galactose, sucrose, raffinose, cellobiose) and pentoses (xylose and arabinose), as well as using real wastewaters (cheese whey, confectionery wastewater, sugar-beet processing wastewater). The highest H2 yield was observed during dark fermentation (DF) of maltose (1.91 mol H2/mol hexose or 77.8 mmol H2/L). The maximum H2 production rate was observed during DF of xylose (13.3 ml H2/g COD/h) and cellobiose (2.47 mmol H2/L/h). The main soluble metabolite products were acetate, ethanol and butyrate. The acetate concentration had a statistically significant positive correlation with the H2 content in biogas and the specific H2 yield. Based on the results of the correlation analysis, it was tentatively assumed that in the formic acid (mixed-acid) type fermentation, the rate of H2 production was higher than in the butyric acid type fermentation. With regard to real wastewater, cheese whey and confectionery wastewater were distinguished by a higher H2 yield (152 ml H2/g COD) and H2 production rate (0.57 mmol H2/L/h), respectively. The highest concentrations of confectionery wastewater and cheese whey, at which the DF process took place, were 5915 and 7311 mg COD/L, respectively. At the same time, SP-H2 dominated in the microbial community, despite the presence of indigenous microorganisms in wastewater. Thus, T. thermosaccharolyticum SP-H2 is a promising strain for DF of carbohydrate-rich unsterile wastewater under thermophilic conditions.
... Concerning the C/N ratio, cheese whey showed a value of 31.8/1 and Gummi WW -109.9/1. Studies by other authors have shown that the correct C/N ratio significantly affects the production of biohydrogen by altering the metabolic pathways during dark fermentation [14]. A C/N ratio of 200 yielded the highest hydrogen yield and specific hydrogen production rate in the dark fermentation of wheat powder solution upon the addition of nitrogen [15]. ...
... An optimal C/N ratio of 137 to produce 3.5 mole H2/mole sucrose was estimated by a mathematical approximation [16]. Lin and Lei [14] achieved an increase in hydrogen yield of 500% and 80% and a hydrogen production rate, respectively, at a C/N ratio of 47. C/N ratio of 21 was optimal in terms of the specific biohydrogen production rate and yield during co-digestion of cheese whey and vegetable fruit waste [17]. Although the optimal C/N values are in a fairly large range, however, Gummi WW had a more optimal value. ...
The aim of this work was a comparative study of biohydrogen production from cheese whey and confectionary wastewater by a newly isolated thermophilic microbial strain Thermoanaerobacterium thermosaccharolyticum SP-H2. Experimental results showed that the fermentative hydrogen was successfully produced with the highest hydrogen yield of 3.9 mL H 2 /mL cheese whey or 80 mL H 2 /g chemical oxygen demand. The profile of soluble metabolite products showed that hydrogen generation by a new isolate was mainly acetate-type fermentation in the case of confectionary wastewater and mixed ethanol-acetate-lactate type fermentation in the case of cheese whey. The more optimal metabolic pathway of confectionary wastewater fermentation was confirmed by the better kinetic characteristics according to the Gompertz model.
... An optimal carbon-nitrogen ratio (C/N) for AD has been reported as 15-30 [3,9,28,46]. A fluctuating C/N ratio may cause shifts in the digester communities as explained by the various metabolic pathways utilized [47][48][49]. Microbes in the digester environment also require other micronutrients (e.g. iron, phosphorus, sodium, magnesium, potassium, and calcium) for growth and maintenance of cellular structures and activities [9,29]. ...
... Co-digestion of FW requires specific operating conditions dependent on its characterization. Temperature, pH, nutrient availability, hydraulic/sludge residence time (HRT/SRT), and organic loading rate (OLR) all significantly impact treatment success [9,35,47,[58][59][60][61]. ...
Utilization of food waste (FW) and food processing waste streams in waste-to-energy technologies has increased over the years in United States (US). This review paper compiled information from published literature and open data sources to obtain a holistic view of the current state of FW availability and its management using anaerobic digestion (AD). The review examined the usage of FW as a feedstock for AD by considering the feedstock composition and availability of FW in the US as well as challenges and opportunities with implementing FW in mono- and co-digestion. Also presented are global trends in FW digestion and the current status of FW co-digestion in the US. FW in the US was characterized with regard to volume and composition to show a need for waste management and an opportunity for valuable resource recovery. Challenges and opportunities of processing via AcoD were presented to review best practices for successful operations. Environmental standards, economic incentives, and governmental policies in the US and around the world regarding waste management and utilization were discussed to identify barriers and sources of opportunity for large-scale implementation of AcoD. A range of facilities throughout the US was examined for information regarding digestion type, feedstock(s), biogas production and utilization, and energy self-sufficiency to better understand the current status of FW digestion. Several US facilities were outlined as case studies that co-digest FW and produce and utilize biogas for various applications. Future strategies, perspectives, and roadmaps were discussed to elucidate the shaping of future FW management practices.
... Actually, it is a very important component for nucleic acids, proteins and enzymes (Abdallah et al., 2016). Excess in nitrogen concentrations may inhibit hydrogen production by shifting the metabolic pathway, but low concentrations might compromise the cell growth (Lin and Lay, 2004). Thus, the addition of nitrogen at an adequate level is favorable to bacterial growth and to hydrogen production (Bisaillon et al., 2006). ...
... Most of the published papers regarding the carbon/nitrogen (C/N) ratio attempted to evaluate the adequate nitrogen concentrations, but defining an optimum C/N ratio does not seem possible because of the differences between the microbial consortia, the reactor designs, the operating conditions and the biomass feedstocks in the literature which can affect this optimum. As a result, Lin et Lay (2004) investigated the effect of the C/N ratio on fermentative hydrogen production by mixed microflora; the highest hydrogen yield of 2.4 mol H2/mol hexose consumed was obtained with a C/N ratio of 47. In contrast, argued that the highest hydrogen yield of 281 mL H2/g of starch consumed was enriched with a C/N ratio of 200. ...
Cette thèse de doctorat porte sur la valorisation du déchet solide issu de la préparation de la mélasse de caroube libanaise pour la production de bioénergie et de molécules à valeur ajoutée. L’analyse de la composition de ce déchet a montré qu’il contient 45 % (g/g) de sucres, substrats exploitables pour la fermentation alcoolique ou lactique, la production de biohydrogène, ou comme source de carbone pour la croissance d’une algue dans un procédé de phycoremédiation (traitement des eaux par les algues) pour l’élimination de micropolluants pharmaceutiques. Les résultats obtenus ont montré que la fermentation alcoolique en phase liquide à partir d’extraits de déchet de caroube peut conduire à des rendements élevés en bioéthanol sous réserve d’enrichir le milieu de culture par les éléments nécessaires pour la croissance de la levure Saccharomyces cerevisiae (en particulier l’azote), tandis qu’il est possible de produire directement le bioéthanol sur le déchet par fermentation en milieu solide sous réserve de contrôler précisément l’humidité. Nous avons également démontré que la fermentation lactique par immobilisation de Lactobacillus rhamnosus sur des billes d’alginate constitue une alternative possible au bioéthanol pour les sucres extraits du déchet. Cependant, un enrichissement du milieu de culture, ainsi que l’utilisation d’une invertase en prétraitement sont nécessaires afin de maximiser le rendement et la productivité de l’acide lactique. L’immobilisation des microorganismes a permis de réutiliser les mêmes billes d’alginate au cours de cinq cycles successifs de production. Une autre alternative potentielle aux voies précédentes est la fermentation sombre pour la production de biohydrogène directement à partir du déchet. Si des rendements intéressants ont été atteints, il faut noter que comme précédemment dans le cas de la fermentation solide du déchet, une forte dépendance aux conditions initiales de broyage a été mise en évidence ; de plus, à la carence en azote qui obligeait à supplémenter les milieux en fermentation en phase liquide s’ajoutent des besoins en fer. Enfin, l’utilisation du déchet comme substrat carboné dans un procédé de phycoremédiation avec l’algue Ankistrodesmus braunii a montré que l’élimination de 90% du diclofénac initial pouvait être atteinte en conditions de mixotrophie, même si seulement un tiers du diclofénac éliminé est effectivement métabolisé par l’algue.
... Many literature also has studied the effect of over dosing ammonia and different C/ N ratio on hydrogen production. The suitable ratio of C/N was in the range of 20e130 [9,74]. C/N ratio lower than this range may bring ammonia inhibition. ...
... Ammonia inhibition is related to C/N, according to the literature, the optimal C/N ratio falls in to the range of 47e200 [8,9,74,104]. To reduce the inhibitory effect of ammonia by changing C/N needs to cooperate with the increase of the biomass of hydrogen-producing bacteria, because it has been reported that a high F/M (food/microorganism) ratio can be negative for hydrogen production [108]. ...
Dark fermentative hydrogen production is an effective and feasible technology for biological hydrogen production. However, this technology has not been commercially applied yet. One of the major reasons is that several inhibitory factors limit hydrogen production and the commercial potential. In this review paper, the various inhibitory factors which influence the dark fermentation hydrogen production were systematically analyzed and summarized, including inorganic inhibitors (heavy metal ions, light metal ions, ammonia, sulfate and hydrogen gas), organic inhibitors (volatile fatty acids, furan derivative and phenolic components), and bio-inhibitors (bacteriocins and thiosulfinate). The inhibitory concentration and mechanism were discussed in-depth and comprehensively. The strategies for mitigating these inhibitory factors were also introduced and discussed. Suggestion for future study in this aspect was proposed to promote the scale-up and commercial application of dark fermentative hydrogen production.
... When relating the characteristics of the feedstock to the UMY (Table 3), the results indicated that AgrMun-2, 4, and 5 (which had a C/N ratio of near 25) had the highest UMYs compared to AgrMun-1 and 3 that had C/N ratios of over 30. It can be suggested that optimal methane production is achieved when C/N values are in the range of 20e30, which is consistent with values indicated in literature (Hassan et al., 2016;Ndegwa and Thompson, 2000;Lin and Lay, 2004). If the C/N ratio is very high, bacteria will consume the nitrogen rapidly, and the carbon will no longer react. ...
Agricultural waste and animal manure (dung) pose an environmental threat in developing countries. This investigation focused on the possible use of such waste as an energy source in the form of biogas produced via anaerobic digestion (AD). The impact of single and mixed substrates on methane production under controlled batch and continuous experimental setups was considered. The study was extended to investigate the effect of substrate size and the impact of an intermediate ozonation process on enhancing the production of biogas from single and mixed substrates. Cumulative methane production (CMP), ultimate methane yield (UMY), methane production potential (MPP), methane production rate (MPR), and maximum methane production rate (MPR max) were used as performance indicators of the effectiveness of the anaerobic digestion process. CMP and MPP from mixed substrates were found to be higher than values obtained from a single substrate feeds, which may be attributed to a more balanced nutrient and organic matter found in mixed substrates. The large surface area of fine substrate influenced MPR and MPR max values in the first 30 days of digestion. In later AD stages, the effect of substrate size was negligible. The MPR max for fine substrates was 12.3 ± 0.3 LkgVS À1 compared to 8.8 ± 0.2 LkgVS À1 obtained for coarse substrate. Continuous AD with organic loading rate (OLR) of 4 kgVSm À1 d À1 showed a % AD efficiency of 62%, an average specific methane production in the range of 98e230 LkgVS À1 and a volumetric methane production rate in the range of 1.94e2.35 m 3 m À3 d À1. Increasing the OLR increased the accumulation of volatile fatty acids in the system and resulted in decreased methane production. Two-stage AD with an intermediate ozonation process showed a significant increase in CMP and % AD efficiency compared with single-stage AD. The %AD efficiency for two-stage AD ranged from 63% to 83%, and for single-stage AD, it was in the range of 42.2%e64.3%. Anaerobic digestion of mixed agricultural waste improved the filtration, dewaterability, and settling ability of the final substrate, making it suitable for use as a soil fertilizer.
... In this regard, Kim et al. (2004b) increased the hydrogen production from the initial amount of 75.2 ml/g COD to 121.6 ml/g COD as VS and COD were increased to 3%. To confirm the effect of substrate concentration, the ratio of COD to TKN for different substrates was in the range of 2.3 to 11.8, indicating that nitrogen was also sufficient for hydrogen production (Lin and Lay, 2004;Mizuno et al., 2000). The TKN content of PPL was the highest amount at 18.75 g/Kg, presenting PPL as a good nitrogen source to be supplied along with AP and Ts. ...
Volatile fatty acids (VFAs) supplementation in ruminants' diet as a source of energy and chemical precursors and their effect on animal's physiology and well-being has long been of scientific interest. Production of VFAs through anaerobic digestion of agro-industrial residues not only creates value but also presents an alternative sustainable approach for ruminant feed supplementation. Therefore, this study aimed to investigate the bioconversion of agro-industrial residues produced in large quantities such as apple pomace (AP), thin stillage (Ts), and potato protein liquor (PPL) to VFAs, fully complying to regulations set for ruminant feed supplement production. In this regard, batch acidogenic fermentation assays (pH 6-10) and semi-continuous immersed membrane bioreactor (iMBR) were applied. In batch assays, at pH 10 the co-digestion of Ts and PPL produced the highest VFAs concentration (14.2 g/L), indicating a yield of 0.85 g COD VFAs /g volatile solids (VS) added. The optimum batch condition was then applied in the iMBR for in situ fermentation and recovery of VFAs at different organic loading rates (OLR). With increasing the OLR to 3.7 gVS/L.day, the highest VFAs concentration of 28.6 g/L (1,2 g COD VFAs /gVS added) was achieved. Successful long-term (114 days) membrane filtration was conducted in a media with a maximum of 40 g/L of total solids (TS), facing irreversible membrane fouling in the final stages. Acidogenic fermentation using an iMBR has the potential to play an important role in the future of feed additive provision through the biorefining of agro-industrial wastes via the carboxylate platform, given the role of VFAs production from organic residues.
... Maximum hydrogen yield is reported to happen between pH 5.0 and 6.0, or down to 4.5 in thermophilic conditions [46]. At the same time, a C/N ratio of 47 was reported as the most effective for biohydrogen production [54]. As both these parameters are quite far from the optimum for biogas production and classical anaerobic digestion, the production of biohydrogen can be called a distinct process, or at least a distinct phase in the life of an anaerobic reactor. ...
Manure production is currently growing with the demand of meat products. Manure is a nutrient-rich biomass containing carbon, nitrogen, sulfur and phosphorous compounds which can at the same time be useful as fertilizing agents and harmful as pollutants in large quantities. Nitrogen and phosphorous can pollute surface and groundwater, leading to algal blooms and damage to aquatic ecosystems, while carbon, nitrogen and sulfur can lead to atmospheric emissions which can be strongly odorous, dangerous for human health and act as greenhouse gases. Composting and anaerobic digestion are two ways to treat manure to reduce these impacts, but only anaerobic digestion can also recover the energy still contained in manure. This chapter shows the basis of anaerobic digestion with a focus on manure as biomass. The effect on the anaerobic digestion of manure composition, which can vary widely depending on livestock species and feedstock, is explored. The most common types of anaerobic digestion reactors are summarized, detailing their advantages and disadvantages. The operative parameters to check for and control in managing an anaerobic digestion reactor are analyzed thoroughly, examining their effect on the process and how they interact in a complex system. Finally, as biogas is a green energy source and methane is an important energy carrier, its production and characteristics are evaluated, with a special focus on manure anaerobic digestion.
... For instance, after testing several C:N ratios (40-130) using sucrose as substrate and Clostridium pasteurianum as inoculum. Lin and Lay (2004) reported an optimum H 2 production (4.8 mol H 2 / mol sucrose) applying C:N ratio of 47. Those authors concluded that higher C:N ratios (> 47) lead to a low H 2 production due to nitrogen-limited growth while lower ratios (C:N < 47) lead to potential free ammonia inhibition. ...
The implementation of a sustainable bio-based economy is considered a top priority today. There is no doubt about the necessity to produce renewable bioenergy and bio-sourced chemicals to replace fossil-derived compounds. Under this scenario, strong efforts have been devoted to efficiently use organic waste as feedstock for biohydrogen production via dark fermentation. However, the technoeconomic viability of this process needs to be enhanced by the valorization of the residual streams generated. The use of dark fermentation effluents as low-cost carbon source for microalgae cultivation arises as an innovative approach for bioproducts generation (e.g., biodiesel, bioactive compounds, pigments) that maximizes the carbon recovery. In a biorefinery context, after value-added product extraction, the spent microalgae biomass can be further valorised as feedstock for biohydrogen production. This integrated process would play a key role in the transition towards a circular economy. This review covers recent advances in microalgal cultivation on dark fermentation effluents (DFE). BioH2 via dark fermentation processes and the involved metabolic pathways are detailed with a special focus on the main aspects affecting the effluent composition. Interesting traits of microalgae and current approaches to solve the challenges associated to the integration of dark fermentation and microalgae cultivation are also discussed.
... However, VFA productivity for C-N 10 fermentation was higher than C-N 5 before day 13. Higher TVFA production was also observed with higher C-N ratios during anaerobic co-digestion of algal sludge and waste paper as well as in the production of fermentative hydrogen by mixed cultures [76][77][78]. The above findings disclose that the C-N ratio is essential in the acidification of substrates. ...
This study evaluates the production of volatile fatty acids (VFAs) from the acidogenic anaerobic digestion of sucrose in continuous-stirred tank reactors. A semi-continuously feed operational process was employed to observe the influence of different carbon-nitrogen ratios (C-N), from 5 to 100, on the volume and composition of VFA production. With a steady increase in VFA production, the C-N 5 assay attained the highest concentration with a VFA value of 26.08 g L −1 after 15 days of incubation, while on the 13th day of incubation, the maximum VFA concentration of 23.82 g L −1 , 20.44 g L −1 , 16.76 g L −1 , 11.88 g L −1 , and 11.60 g L −1 was attained in C-N 10, C-N 20, C-N 30, C-N 50, and C-N 70 assays respectively. Acetic acid and butyric acid were the principal VFAs observed in all the different C-N assays tested in this study. The mean values of acetic acid ranged from 64.58 to 79.12% for C-N increase between 5 and 100. On the other hand, C-N variations between 5 and 100 resulted in a significant decrease in butyric acid production from 30.33 to 13.93%. Volatile solid degradation and carbohydrate utilization rates decreased from 41.86 to 32.45% and 78.56 to 61.25% respectively as C-N ratios increased from 5 to 100. This aligns with the hypothesis that increasing the nitrogen content of substrate increases VFA production. Our findings provide new information regarding the C-N ratios for improved VFA production from acidogenic fermentation of sucrose.
... Acetic , Butaeric and Propaionic Acid are the cardinal products in hydrogen production that make judicial use of the anaerobic dark fermentation of carbohydrates. [31,32,33,34].But methane is not produced as a byproduct since it is eliminated by heat digestion sludge [35,36,37]. A comparative study made in India between exotic and local group of earthworms meant for the calculating the efficiency during vermicomposting of solid waste. ...
... Besides nitrogen and sulfur, phosphorus is another nutrient required to enhance hydrogen production [136]. It was observed that a high rate of H2 can be obtained in the presence of 600 mg L −1 K2HPO4 [137]. A 40% increase in the production of H2 was observed at a 30% increase or decline in the respective chemical compound. ...
Energy plays a crucial role in the sustainable development of modern nations. Today, hydrogen is considered the most promising alternative fuel as it can be generated from clean and green sources. Moreover, it is an efficient energy carrier because hydrogen burning only generates water as a byproduct. Currently, it is generated from natural gas. However, it can be produced using other methods, i.e., physicochemical, thermal, and biological. The biological method is considered more environmentally friendly and pollution free. This paper aims to provide an updated review of biohydrogen production via photofermentation, dark fermentation, and microbial electrolysis cells using different waste materials as feedstocks. Besides, the role of nanotechnology in enhancing biohydrogen production is examined. Under anaerobic conditions, hydrogen is produced during the conversion of organic substrate into organic acids using fermentative bacteria and during the conversion of organic acids into hydrogen and carbon dioxide using photofermentative bacteria. Different factors that enhance the biohydrogen production of these organisms, either combined or sequentially, using dark and photofermentation processes, are examined, and the effect of each factor on biohydrogen production efficiency is reported. A comparison of hydrogen production efficiency between dark fermentation, photofermentation, and two-stage processes is also presented.
... Nitrogen is a necessary element for microbial metabolism, replication, and growth; the production of several essential enzymes (e.g., hydrogenase); and substrate uptake [16,17]. Hence, high or low N/C ratios influence anaerobic microorganism activity due to an excess or lack of nitrogen supply [18]. Increasing the xylose concentration to certain values enhances the hydrogen yield, as it improves the bacterial growth, but an excessive increase lowers the hydrogen yield due to substrate inhibition [19]. ...
Green hydrogen is considered to be one of the best candidates for fossil fuels in the near future. Bio-hydrogen production from the dark fermentation of organic materials, including organic wastes, is one of the most cost-effective and promising methods for hydrogen production. One of the main challenges posed by this method is the low production rate. Therefore, optimizing the operating parameters, such as the initial pH value, operating temperature, N/C ratio, and organic concentration (xylose), plays a significant role in determining the hydrogen production rate. The experimental optimization of such parameters is complex, expensive, and lengthy. The present research used an experimental data asset, adaptive network fuzzy inference system (ANFIS) modeling, and particle swarm optimization to model and optimize hydrogen production. The coupling between ANFIS and PSO demonstrated a robust effect, which was evident through the improvement in the hydrogen production based on the four input parameters. The results were compared with the experimental and RSM optimization models. The proposed method demonstrated an increase in the biohydrogen production of 100 mL/L compared to the experimental results and a 200 mL/L increase compared to the results obtained using ANOVA.
... Argun et al. also reported a maximum VFA yield at the same C/N ratio, producing 11 g/L of total VFAs. A C/N ratio of 47 was reported as optimum for biohydrogen production in a sewage sludge reactor, whilst the same study determined a C/N ratio of 130 resulted in the maximum VFA yield [168]. ...
Utilising ‘wastes’ as ‘resources’ is key to a circular economy. While there are multiple
routes to waste valorisation, anaerobic digestion (AD)—a biochemical means to breakdown organic
wastes in the absence of oxygen—is favoured due to its capacity to handle a variety of feedstocks.
Traditional AD focuses on the production of biogas and fertiliser as products; however, such low�value products combined with longer residence times and slow kinetics have paved the way to
explore alternative product platforms. The intermediate steps in conventional AD—acidogenesis
and acetogenesis—have the capability to produce biohydrogen and volatile fatty acids (VFA) which
are gaining increased attention due to the higher energy density (than biogas) and higher market
value, respectively. This review hence focusses specifically on the production of biohydrogen and
VFAs from organic wastes. With the revived interest in these products, a critical analysis of recent
literature is needed to establish the current status. Therefore, intensification strategies in this area
involving three main streams: substrate pre-treatment, digestion parameters and product recovery
are discussed in detail based on literature reported in the last decade. The techno-economic aspects
and future pointers are clearly highlighted to drive research forward in relevant areas.
... The ideal concentration of nitrogen is necessary for hydrogen production. According to Lin and Lay [31], C/N ratio of 47 provided the optimal bio-hydrogen production. In addition, Mohammedawi et al. [32] evaluated the co-fermentation of brewery WW with banana peel waste, and the C/N ratio ranged from 7.4 to 22.47. ...
The present study evaluated the anaerobic co-fermentation of brewery by-products for hydrogen production. The biochemical hydrogen potential was conducted at thermophilic (55 °C) and acidogenic conditions (pH around 5) mixing brewery wastewater, brewer’s spent grains (BSG), and sludge from the brewery wastewater treatment plant. The results revealed that the removal efficiency of total volatile solids (TVS) reached a maximum of 30.86%. The dominant volatile fatty acids produced were acetic (3648.86 mg L⁻¹) and butyric (2300.22 mg L⁻¹), while propionic (765.56 mg L⁻¹) and isovaleric (827.80 mg L⁻¹) were detected in much lower amounts. The reactor operated only with wastewater decreased the nitrogen concentration at the end of co-fermentation (190 mg N–NH3 L⁻¹), while the addition of BSG promoted an increase of nitrogen (> 300 mg N–NH3 L⁻¹). The highest hydrogen yield was obtained for the reactor operated only with wastewater (25.11 mL H2 g⁻¹ TVS), and the yield decreased according to the addition of BSG, reaching 9.55 mL H2 g⁻¹ TVS for the reactor containing 17.5% of BSG. The suppression of hydrogen production with BSG addition can be associated with the ammonia inhibition. The Gompertz, Cone, and first-order kinetic models predicted the hydrogen production with a difference lower than 1.5% of the experimental volume obtained. Finally, this study advanced our knowledge regarding the use of BSG and the inhibition of hydrogen production due to excessive ammonia generation during the dark fermentation of brewery by-products.
Graphical abstract
... Glucose has also been reported as an important carbon source in the evaluation of bioflocculant yield 19,20 . Earlier research established that ratios of C/N were critical in microbe metabolic processes, such as modifying the composition of fatty acids produced by the heterotrophic Chlorella sorokiniana and strengthening biological hydrogen production by Clostridium pasteurianum 29 . Additionally, magnesium has been identified as a critical inorganic ion that influences various physiological processes, including enzyme activity, cell development, and cell division 19,30 . ...
This study was designed to evaluate the potential of bioflocculant producing strains isolated from wastewater sludge. According to the Plackett–Burman design, the response surface revealed glucose, magnesium sulfate, and ammonium sulfate as critical media components of the nutritional source, whereas the central composite design affirmed an optimum concentration of the critical nutritional source as 16.0 g/l (glucose), 3.5 g/l magnesium sulfate heptahydrate (MgSO4.7H2O), and 1.6 g/l ammonium sulfate ( (NH4)2SO4), yielding an optimal flocculation activity of 96.8%. Fourier Transformer Infrared Spectroscopy (FTIR) analysis confirmed the presence of hydroxyl, carboxyl and methoxyl in the structure of the bioflocculant. Additionally, chemical analysis affirmed the presence of mainly a polysaccharide in the main backbone of the purified bioflocculant with no detection of protein. Energy Dispersive X-ray analysis affirmed the presence of chlorine, phosphorous, oxygen and chlorine as representatives of elemental composition. Thermogravimetric (TGA) analysis revealed over 60% weight was retained at a temperature range of 700 °C. The purified bioflocculant remarkably removed chemical oxygen demand, biological oxygen demand and turbidity in brewery wastewater. This study suggested that the bioflocculant might be an alternate candidate for wastewater treatment.
... Pérez-Rangel et al. (2020) discussed a high nitrogen requirement, such as C/N ratios in the range of 4-50:1 for complex substrates such as paper waste hydrolyzates and microcrystalline cellulose. This is supported by Lin and Lay (2004), who obtained maximal productivity of 4.8 mol-H 2 /mol sucrose using a mixed culture at a C/N ratio of 47:1, and Pérez-Rangel et al. (2020), who reported an optimal C/N ratio of 17.5:1 using wheat straw as a substrate, producing 504 ml/L. ...
This study modeled and optimized a novel simultaneous saccharification and fermentation (SSF) dark fermentative hydrogen production system using pharmaceutical wastewater (PW) as a nitrogen source to obtain a suitable C/N for paper mill sludge (PMS). Optimized hydrogen yields of 54.8, 53.6 and 39.3 mL/g PMS were obtained using PW, yeast extract and ammonium nitrate as the nitrogen source, respectively, using the developed models. The process kinetics were evaluated against yeast extract and ammonium nitrate, using the modified Gompertz model. SSF production generated a slightly lower hydrogen yield than yeast extract, of 54.8 mL/g PMS, and a peak hydrogen gas fraction of 45.6% when using PW. Optimized processes showed that PW gave comparable kinetic data, shown in a 3.3 h variation in process lag time between PW and yeast extract and an 8.7% increase in maximum potential hydrogen production rate when PW was used in place of ammonium nitrate. Implications from this study suggest that using waste to enhance the beneficiation and treatment of waste PMS could significantly reduce the time and costs associated with its valorization.
... Many anaerobic organisms can produce hydrogen from carbohydrate containing organic wastes. The obligate anaerobic and spore forming bacteria belonging to genus Clostridium such as C. thermolacticum (Collet et al. 2004), C. buytricum (Yokoi et al. 2001), C. paraputri cum M-21 (Evvyernie et al. 2001), C. pasteurianum (Lin and Lay 2004;Liu and Shen 2004) and C. bifermentans (Wang et al. 2003) have been reported to produce hydrogen during log phase. These fermentation reactions do not need light energy resulting in continuous production of hydrogen from organic compounds. ...
Over the past few decades, increasing concentrations of different
greenhouse gases including methane, carbon dioxide and nitrous
oxide is the main cause of global climate changes such as weakening
of thermohaline circulation, rising sea levels and coral reef
eradication (O’Neill and Oppenheimer 2002; Stocker 2014). In
the past 400,000 years, CO2 concentration changed from about
180 parts per million (ppm) during the deep glaciations of the
Holocene and Pleistocene to 280 ppm during the interglacial
periods. The continuously growing population and their demands
for energy have revolutionized the industrial sector, due to which
concentration of CO2 in the atmosphere has reached over 400
ppm and continue to increase, causing the phenomenon of global
warming (Stocker 2014). If increases in CO2 concentration continue
at the present rate, the CO2 release rate will be doubled
by 2050 and CO2 concentration in the atmosphere may rise up
to 500 ppm, with a 2°C rise in temperature as compared to the
level of temperature in 1900 (Pacala and Socolow 2004) which
possess a huge risk of adverse effects on society, the economy
and the environment. Therefore, there is a need to minimize the
release of greenhouse gases.
... Nutrients are also an indispensable parameter for biohydrogenproducing microorganism growth. It has been reported that the C/N ratio affects both bacterial growth and biohydrogen generation for mixed fermentative consortia or pure cultures [253]. The biohydrogen yield of ~4.8 mol H 2 /mole of sucrose and the production rate of ~270 mmol H 2 /L per day were achieved at a C/N ratio of ~47 [245]. ...
The continuous surge in global energy demand, fossil fuel depletion, and related climate change issues have oriented the worldwide researchers' endeavors to the investigation and development of sustainable and co-effective technology to satisfy the global energy needs. Referring to the non-toxic properties of hydrogen, it is considered as a suitable renewable energy source that could replace fossil fuel-based energy. It is the cleanest energy carrier, combustible with high calorific value, high energy yield. Producing biohydrogen energy from renewable resources such as lignocellulosic agricultural residues could be a sustainable carbon-neutral most cost-effective approach. Dark fermentation has been widely applied as a promising eco-friendly technique to produce biohydrogen from agricultural residues. However, it has shown drawbacks owing to the recalcitrance of ligno-cellulose structure, and the accumulation of acid-rich intermediate by-products. Microbial electrolysis cells use bio-electrochemical reactions to upgrade H 2 production in a dark fermentation reactor by promoting further decomposition of the generated volatile fatty acids. Therefore, integrating microbial electrohydrogenesis with dark fermentation can be a promising strategy to optimize the straw biomass conversion to biohydrogen. This review aims in delineating the structural composition and recalcitrance of the agricultural residues and their major effects on biohydrogen production. It summarizes all possible pre-treatment methods of the lignocellulosic agricultural residues; elucidates the stable operational conditions of microbial electrolysis cell and dark fermentation integrated system and discusses its performance for biohydrogen production. This study also reviewed the current technical challenges of this integrated system application and suggested sustainable solutions towards its industrial implementation.
... Kukec et al. (2002) found that propionic acid fermentation occurred more easily at ORP range of -200 to 100 mV, and butyric acid dominated when the ORP was between -350 and -200 mV. In addition, the initial C/N ratio of the substrate plays an important role in anaerobic acidification of organic matters ( Lin et al., 2004 ). According to Ren et al. (1997) , the ratio of NADH/NAD + in microbial cells was an important factor affecting the type of fermentation, and acetic acid was always produced along with various amounts of propionic acid, butyric acid and ethanol to maintain a proper NADH/NAD + ratio in cell. ...
Optimization of acetic acid and formic acid production efficient methanogenesis is always the research hot spot in anaerobic digestion. It is a promising approach to adjust the operation parameters to influence the functional microorganisms for better acetic acid and formic acid production in acidogenesis. Herein, the effects of pH, oxidation-reduction potential (ORP) and carbon–nitrogen (C/N) ratio were determined in batch experiments to probe acetic and formic acids production, and were further verified in continuous stirred tank reactor (CSTR). The results revealed that the content of volatile fatty acids (VFAs) reached to maximum at pH 6.0 or ORP -350 mV, while the production of acetic and formic acids was the highest at pH 7.0 or ORP -450 mV in 9 h fermentation. Also, fermentation products dominated by acetic and formic acids were adjusted in the CSTR under the operating conditions of pH 7.0 and ORP -450 mV. Microbiological analysis from batch test showed that fermentation at pH value of 7.0 enriched the diversity of microorganism, and provided a niche for microbes (Petrimonas, norank_f__Synergistaceae, vadinBC27_wastewater-sludge_group, and Trichococcus) to produce acetic and formic acids. Correspondingly, 78.70% of the carbon was converted to acetic and formic acids in pH 7.0. This study provides a promising strategy for the targeted regulation of acetic and formic acids production in acidogenesis of anaerobic digestion.
... Macronutrients and micronutrients are essential in dark fermentation which includes: carbon and nitrogen sources (Lin & Lay, 2004a), ammonium, phosphate (Lin & Lay, 2004b), sulphur, sulphate , iron (Yang & Shen, 2006), and elemental traces (Lin & Lay, 2005). The concentration of these nutrients also influences the growth of microbes and hydrogen production. ...
Malaysia is one of the largest producers and exporters of palm oil, thus, a large amount of palm oil mill effluent (POME) is generated through this process. POME contributes to environmental pollution if it is not properly treated. This complex effluent consists of colloidal matters and mainly organic components with more than 90% water. Thus, it is useful to be used as a substrate for fermentative processes, including biohydrogen production. Biohydrogen from POME is a renewable source that can potentially serve as an alternative to substitute fossil fuels. The abundance of POME and the rising price of fossil fuels in the global market create a demand for this source of energy. However, the complexity of the substituents in POME makes the optimisation of this effluent as a substrate in dark fermentation a challenge. This review article explores the important parameters that need to be considered for optimal biohydrogen production, such as the bioreactor operational parameters and the microbial consortium. Besides, the potential of metabolic engineering as a tool to overcome the limitations of the microbial strains to metabolise POME for increased biohydrogen production was also reviewed. However, further research and development are needed to increase the biohydrogen yield on par with commercial demand.
... Similarly, the ultimate analysis showed that Lemna has higher carbon content and low nitrogen content which suggests the possibility of higher biogas conversion efficiency. The ideal C/N ratio is 20:1 to 30:1 for efficient biogas production [36,37]. Higher C/N ratio favours microbes for carbon utilization, while lower C/N ratio suggests high nitrogen content resulting in high ammonium content that is toxic to the microbes. ...
... Similar results (1398.0 mlH 2 /l-culture) were obtained by Li et al. [43], for co-fermentation of cow dung compost, with glucose and apple pomace at C/N ratio of 10.6. A lower HY of 4.8 mol-H 2 /mol-sucrose was achieved at C/N ratio of 47 [46]. C/P ratio is significantly affected on the yield of biogas rich CH 4 and H 2 as shown in Fig. 3b. ...
Mono-and di-fermentation of black liquor (BL) and livestock wastewater (LW) was extensively investigated in batch assay experiments. Methane production was the dominant in mono-fermentation of BL and partially co-digested with LW (90% BL+10% LW). Increasing the fraction of LW in the feedstock shifted the microbial activities from biomethanisation into bio-hydrogen generation process. The hydrogen potential (A) was significantly increased from 468 ± 12 to 969 ± 10 ml at increasing the LW ratio in the di-fermentation process from 30% LW + 70% BL to 50% LW + 50% BL. The enzymes activities of α-amylase, xylanase, CM-cellulase, polygalacturonase and protease were maximized at a levels of 420 ± 2.5, 509 ± 5.4, 560 ± 3.9, 686 ± 7.9 and 127.2 ± 6.3 U/100 ml respectively for di-fermentation of 50% LW + 50% BL. Similarly, the valerate (HVa), butyrate (HBu) and acetate (HAc) was highly increased in the digestate of 50% LW + 50% BL up to 654 ± 122.9, 2464.6 ± 67.9 and 657 ± 11.8 mg/l respectively. The Methanobacterium and Methanosaeta were dominated for 10% LW + 90% BL and hydrogen producers i.e., Clostridium, was the major for di-fermentation of the batches containing 50% LW + 50% BL.
Biohydrogen refers to the production of hydrogen gas (H2) from organic wastes through microorganisms for renewable and sustainable energy sources and recycling operations. The present research work aims for anaerobic digestion of organic waste, i.e. orange peel, core, and skeletons, as a remarkable feedstock for the production of biohydrogen and methane gas in a food-to-microorganism (F/M) ratio of 1–10 and initial substrate concentrations of 20–100 g total sugar/l. The kinetics of batch anaerobic digestion with a mixed culture of domestic wastewater inoculums and acid treatment was investigated under mesophilic (30 °C) and thermophilic (45–60 °C) circumstances. A favourable biohydrogen production has been observed by 27 g VS/l organic substrate mixture with 0.3 N H2SO4 acid pretreatment. The acid pretreatment of 0.2 N substrate improvises fermentation with a cumulative yield of 0.89 ml/g in 10–45% hydrogen volume. Peel fermentation resulted in total gas production at a rate of 3.5 ml STP/gram VS, whereas core fermentation yielded an H2 volume ratio ranging from 5 to 32%. A maximized yield production of hydrogen was observed at 57 ml/mg of VS at F/M ratio of 7 after 44h of anaerobic ebullition under thermophilic circumstances. On the other hand, in mesophilic states, the hydrogen production rate was at a narrow F/M interval of 6 with a yield of 39 ml/mg of VS and 46% VS reduction. The uttermost specific progression rate of mixed culture was obtained at 40 g total sugar/l with a pH of 5.5 under thermophilic circumstances of 55 °C. Thus, the well-established experimental work illuminates a unique approach for H2 generation under controlled anaerobic fermentation environments.
Unlabelled:
The staggering increase in pollution associated with a sharp tightening in global energy demand is a major concern for organic substances. Renewable biofuel production through simultaneous waste reduction is a sustainable approach to meet this energy demand. This study co-fermentation of dairy whey and SCB was performed using mixed and pure bacterial cultures of Salmonella bongori, Escherichia coli, and Shewanella oneidensis by dark fermentation process for hydrogen production. The maximum H2 production was 202.7 ± 5.5 H2/mL/L, 237.3 ± 6.0 H2/mL/L, and 198 ± 9.9 H2/mL/L obtained in fermentation reactions containing dairy whey, solid and liquid hydrolysis of pretreated sugarcane bagasse as mono-substrates. The H2 production was greater in co-substrate by 347.3 ± 18.5 H2/mL/L under optimized conditions (pH 7.0, temperature 37 °C, substrate concentration 30:50 g/L) than expected in mono-substrate conditions, which confirms that co-fermentation of different substrates enhances the H2 potential. Fermentation medium during bio-H2 production under GC analysis has stated that using mixed cultures in dark fermentation favored acetic acid and butyric acid. Co-substrate degradation produces ethyl alcohol, benzoic acid, propionic acid, and butanol as metabolic by-products. The difference in the treated and untreated substrate and carbon enrichment in the substrates was evaluated by FT-IR analysis. The present study justifies that rather than the usage of mono-substrate for bio-H2 production, the co-substrate provided highly stable H2 production by mixed bacterial cultures. Fabricate the homemade single-chamber microbial fuel cell to generate electricity.
Supplementary information:
The online version contains supplementary material available at 10.1007/s13205-023-03687-9.
Recent technological developments have led to a significant increase in energy consumption in daily life. The search for alternative means of energy production has become an important task for applied sciences and modern technology. Hydrogen technology has great potential as a source of clean energy. The production of green hydrogen is a desirable and beneficial way to contribute to the decarbonization of the energy sector. In response to the demand for environmentally friendly and economically feasible approaches, biohydrogen production from waste materials has recently attracted interest. Waste materials from industrial or municipal production can be used as low-cost substrates for biohydrogen production through microbial degradation. Green energy needs could be met through a form of sustainable development that moves hand in hand with the harnessing of the microbial potential of waste biomass. Reuse of waste materials leads to pollution reductions and energy recycling. The aim of this review is to provide informative insights for researchers and engineers to help them better understand microbial biohydrogen production from low-cost waste substrates, such as industrial wastewater and waste activated sludge.
Biohydrogen is a carbon-free alternative energy source, that can be obtained from fermentation of organic waste, biomass-derived sugars, and wastewater. This article reviews the current processes for fermentative biohydrogen production from biomass including its appropriate storage and transport challenges. The review showed that a comparison of fermentation pretreatment methods across the literature is complicated and that fermentability tests are necessary to determine the best combination of pretreatment/feedstock. Operational parameters, such as temperature, pH, macro/micronutrients addition are widely dependent on the type of fermentation and microorganisms used and hence their content need to be tailored to the process. For immobilized cells, the range of hydrogen production rate values reported for granulation processes using mixed microbial cultures, were higher (13-297 mmol H 2 /L h) than those reported for entrapment (1-115 mmol H 2 /L h) and adsorption (3-83 mmol H 2 /L h), suggesting an achievable and sustainable route for full-scale applications. A purification phase is mandatory before the final use of biohydrogens. Sorption techniques and the use of membranes are the most widely used approaches. Pressure swing adsorption has the highest recovery rate (it reaches 96%). In addition, storage of biohydrogen can have several forms with varying storage capacities (depending on the form and/or storage materials used). The transport of biohydrogen often faces technical and economic challenges requiring optimization to contribute to the development of a biohydrogen economy.
Biohydrogen is a carbon-free alternative energy source, that can be obtained from fermentation of organic waste, biomass-derived sugars, and wastewater. This article reviews the current processes for fermentative biohydrogen production from biomass including its appropriate storage and transport challenges. The review showed that a comparison of fermentation pretreatment methods across the literature is complicated and that fermentability tests are necessary to determine the best combination of pretreatment/feedstock. Operational parameters, such as temperature, pH, macro/micronutrients addition are widely dependent on the type of fermentation and microorganisms used and hence their content need to be tailored to the process. For immobilized cells, the range of hydrogen production rate values reported for granulation processes using mixed microbial cultures, were higher (13-297 mmol H 2 /L h) than those reported for entrapment (1-115 mmol H 2 /L h) and adsorption (3-83 mmol H 2 /L h), suggesting an achievable and sustainable route for full-scale J o u r n a l P r e-p r o o f 2 applications. A purification phase is mandatory before the final use of biohydrogens. Sorption techniques and the use of membranes are the most widely used approaches. Pressure swing adsorption has the highest recovery rate (it reaches 96%). In addition, storage of biohydrogen can have several forms with varying storage capacities (depending on the form and/or storage materials used). The transport of biohydrogen often faces technical and economic challenges requiring optimization to contribute to the development of a biohydrogen economy.
Biohydrogen generation from various waste materials is quite promising in renewable energy exploration. Biohydrogen is a cost-effective biofuel that produces both water vapor and energy when burned. However, biohydrogen production is more appreciable in utilizing various waste materials, thereby compromising both socioeconomic and technical strategies of energy exploration. The substrate, inoculum employed and their concentrations, culture kinds, and pretreatment procedure have all been found to be important in biohydrogen production. Physiological variables such as pH, temperature, redox potential, and partial pressure also significantly impact biohydrogen generation. The utilization of several growth factors, mainly the substrate, nitrogen, and phosphorus, also confronts extensive applications during biohydrogen production. This present study explores the enhancing activity engaged by the parameters and focuses on the inhibitory effects of the operating conditions.
In the present study, the effect of Iron Nanoparticles (Fe NPs), Nickel Nanoparticles (Ni NPs) and co-additions of Iron and Nickel nanoparticles (CNPs) for the production of biohydrogen from the effluent collected brewery processing was investigated. Free and co-culture (immobilized) of EtBr mutated Rhodobacter M 19 and Enterobacter aerogenes wereused for biohydrogen production. The biohydrogen productions is found to be enhanced by using nanoparticles as active catalyst. The results showed the maximum biohydrogen production of 96.21% by using combined nanoparticles (CNPs) with immobilized EtBr mutated co-culture. The proportion used is 30:30 mixed nanoparticles (CNPs) atpH 6.9. Additionally, Gompertz equation was adopted to fit the enhanced biohydrogen productions and Richard’s and Logistics equation were best suited for the biomass growth with minimal error. The batch kinetics of biohydrogen productions using nano catalysts were examined under batch fermentations. Thus, the addition of mixed nanoparticles showed significant yields in biohydrogen production for mixed nanoparticles and also be the promising method of fermentative yield of biohydrogen.
Herein, recent reports on hydrogen production from wastewater were comprehensively evaluated. There are numerous methods of biohydrogen production from various types of wastewater. Fermentation is one of the most promising methods of biohydrogen production from industrial wastewater owing to its ease of operation and rapid hydrogen production. The sequential dark/photo fermentation approach generated a maximum hydrogen yield (HY) of 7.1 mol H2/mol glucose with an estimated hydrogen production cost of 2.57 US $/kg and 2.83 US $/kg for dark and photo-fermentation, respectively. Pre-existing studies demonstrated that the successful implementation of pilot-scale fermentation bioreactors with a maximum hydrogen production rate (HPR) of 17 m³/m³·d, but HPR is negatively correlated with reactor volume; more pilot-scale studies using high-strength wastewater for optimum performance are needed. The current implementation and commercialization challenges during hydrogen production were also highlighted in this review. Furthermore, a literature survey revealed research gaps associated with optimum conditions for maximized biohydrogen yield. Numerous review studies in literature focus on biohydrogen potential from solid biowaste; nevertheless, a comprehensive review on biohydrogen from wastewater is still needed. The recommendations of this review are designed to facilitate researchers and policymakers in achieving sustainable development goals (SDGs), including clean water and sanitation (SDG 6), renewable energy (SDG 7), sustainable communities (SDG 11), and climate action (SDG 13).
One of the strategies to mitigate the environmental problems associated with the increased accumulation of various forms of wastes is to convert the wastes into useful products. In this study different pretreatment and hydrolysis of garden wastes to produce hydrogen using Escherichia coli was investigated. The maximum hydrogen production of 97 mL of H2/g dry garden wastes was obtained after the fermentation by E. coli of hydrolyzate derived from the combined hydrolysis of garden wastes, i.e., acid followed by enzyme treatment. The yield was a 2.7-fold increase when compared to the untreated garden wastes. The hydrolysis solely by enzymes and acid produced 89 and 74 mL of H2/g dry garden wastes, respectively. In addition, 2% sulfuric acid and 2% Viscozyme L were found to be the optimal conditions to obtain maximum hydrogen production from garden wastes. The overall results demonstrated the utilization of garden wastes for the efficient production of hydrogen after appropriate treatment.
The effect of butyrate on hydrogen production and the potential mechanism were investigated by adding butyric acid into dark fermentative hydrogen production system at different concentrations at pH range of 5.5–7.0. The results showed that under all the tested pH from 5.5 to 7.0, the addition of butyric acid can inhibit the hydrogen production, and the inhibitory degree (from 10.5% to 100%) increased with the increase of butyric acid concentration and with the decrease of pH values, which suggested that the inhibition effect is highly associated with the concentration of undissociated acids. Substrate utilization rate and VFAs accumulation also decreased with the addition of butyric acid. The microbial community analysis revealed that butyrate addition can decrease the dominant position of hydrogen-producing microorganisms, such as Clostridium, and increase the proportion of other non-hydrogen-producing bacteria, including Pseudomonas, Klebsiella, Acinetobacter, and Bacillus.
The development of a clean energy alternative is a crucial aspect of current scientific research concerning the ever-growing surge in demand for energy. The use of traditional sources (fossil sources) for energy generation has raised critical climate issues that are threatening human life on the planet earth. In order to sustain energy demand, hydrogen has emerged as an assuring energy alternative. Recently, biohydrogen gas production from renewable sources has received significant attention. Lignocellulose biomass is one such potential renewable source that can be employed to generate energy, fuel, and value-added chemicals. Biohydrogen generated from lignocellulosic biomass is a clean, efficient, environment-friendly fuel and has no harmful emissions. However, the utilization of lignocellulose is still challenging due to their complex structures. Researchers around the globe are exploring various aspects affecting the process of biohydrogen production using lignocellulosic biomass while making the process sustainable. The current chapter presents an overview of bioconversion of lignocellulosic residue to hydrogen along with potential pretreatments. A systematic approach for efficient H2 production and factors affecting the hydrogen generation are comprehensively discussed. Further, the current challenges and opportunities concerning hydrogen production via lignocellulosic biomass bioconversion are also discussed.
Clostridium butyricum TM-9A strain was employed as pure strain for scale up of fermentative hydrogen production in batch mode. In laboratory scale batch fermentations, 46 mmol/L hydrogen produced from molasses at optimum pH, molasses concentration and C/N ratio of; 7.5, 2.5 %, and 10, respectively. Scale up of molasses fermentation in 13.5 L scale bioreactor under decreased partial pressure at regulated pH, hydrogen production performance of TM-9A strain enhanced from 46 mmol of H2/L (in laboratory scale) to 73 mmol of H2/L (1.58 fold increase). Hydrogen productivity was 1650 ml/L. Scale up of fermentation from glucose by TM-9A in 13.5 L scale bioreactor at optimum condition produced; 71.9 mmol H2/L (hydrogen productivity was, 1634 mL/L). The biogas was composed of 65-60% H2 and 35-40% CO2. Hydrogen yield of TM-9A from glucose and molasses in the proto scale fermentation process was, 3.335 mol H2/mol glucose and 73 mmol H2/9 g of COD reduced, respectively. These studies imply that Clostridum butyricum TM-9A strain has significant potential for hydrogen production from spent organic matter in pilot scale.
This chapter describes new developments and achievements in industrial scale‐up fermentation processes in the key sectors of food, chemistry, and pharmaceuticals. It includes various achievements in the fields of enzymes, alcoholic beverages, biofuels, syngas, organic acids, as well as drugs and recombinant proteins. Besides, the current progresses in industrial fermentation to achieve higher production yields, better fermentation conditions, and lower processing cost were discussed. The achievements include the application of genetic engineering of microorganisms, ultrasonic treatment and electrofermentation, optimization of the mechanistic and computational fluid dynamic process modeling, and the recognition of inhibitor factors in fermentation processes. The chapter provides suitable links between academic research and industry, too. This in turn might give a better understanding to develop new energy‐saver green industrial fermentation processes.
Dwindling fossil fuels, and the rise in energy demand have urged us to explore alternative renewable energy forms. An integrated process of dark fermentation and microalgal cultivation to deliver biofuels are gaining momentum in recent times. In this study, in the first stage, the starchy wastewater (SWW) with poultry manure (PM) was treated to produce a maximum hydrogen yield of 4.11 mol H2/Kg COD reduced to 5.03 mol H2/Kg COD reduced. The reutilization of soluble spent wash for the cultivation of Chlamydomonas reinhardtii yielded a biomass concentration of 1.45–1.02 g/L. The potentiality of algae to produce biodiesel was checked effectively, and it was reported that a biodiesel of 90.34 g/Kg Algal Biomass to 119.61 g/Kg Algal was yielded. The integration of the process enhanced the overall energy with an efficient removal of organic content. In conclusion, the valorisation of PM with SWW through dark fermentation and microalgal cultivation will open avenues to generate sustainable bioenergy forms.Graphic abstract
A bacterium was newly isolated from cow dung, and identified as Enterococcus faecium YA002 by 16S rRNA gene sequence analyzing. It showed high H2 production performance in dark fermentation with xylose as substrate, the fermentative conditions including xylose concentration, ratio of nitrogen source to carbon source in mass (N/C ratio), temperature, and initial pH were optimized by response surface methodology (RSM) with a Box-Behnken design (BBD). After regression analyzing, it could be found that H2 production was well fitted by a quadratic polynomial equation, and significantly affected by the four studied factors. The optimal conditions were xylose concentration of 22.69 g/L, N/C ratio of 0.127, temperature of 37.2 °C, and initial pH of 8.0, and the experimental H2 production under the conditions was 2918.91 ± 125.49 mL/L, which was 97.91% of the predicted H2 production. The results indicated that Enterococcus faecium YA002 was an ideal inoculum for dark fermentative H2 production from xylose, and the conditions for the H2 production were successfully optimized by response surface methodology.
Hydraulic retention time (HRT) is the main process parameter for biohydrogen production by anaerobic fermentation. This paper investigated the effect of the different HRT on the hydrogen production of the ethanol-type fermentation process in two kinds of CSTR reactors (horizontal continuous stirred-tank reactor and vertical continuous stirred-tank reactor) with molasses as a substrate. Two kinds of CSTR reactors operated with the organic loading rates (OLR) of 12kgCOD/m3•d under the initial HRT of the 8 h condition, and then OLR was adjusted as 6kgCOD/m3•d when the pH drops rapidly. The VCSTR and HCSTR have reached the stable ethanol-type fermentation process within 21 days and 24 days respectively. Among the five HRTs settled in the range of 2–8 h, the maximum hydrogen production rate of 3.7LH2/Ld and 5.1LH2/Ld were investigated respectively in the VCSTR and HCSTR. At that time the COD concentration and HRT were 8000 mg/L and 5 h for VCSTR, while 10000 mg/L and 4 h for HCSTR respectively.
Through the analysis on the composition of the liquid fermentation product and biomass under the different HRT condition in the two kinds of CSTR, it can found that the ethanol-type fermentation process in the HCSTR is more stable than VCSTR due to enhancing biomass retention of HCSTR at the short HTR.
This study investigates the effect of C/N ratio on the production of biomass and total carotenoids on a Scenedesmus sp. Initially, three different carbon sources (sodium carbonate, sodium bicarbonate and sodium acetate) were tested under different concentrations of a nitrogen source (sodium nitrate) in 250 mL tubular air-lift reactors. The reactors were operated at 25° C for 40 days. in light:dark cycle of 12:12, under a continuous flow of air. Results showed that by the adjustment of the concentration of the carbon and nitrogen source, it is possible to increase the concentration of biomass up to 0.8 g/L. However, by the regulation on the concentration of sodium carbonate and sodium nitrate, the final content of total carotenoids was increased two times (from 0.3 to 0.66 % w/w). Results from this study shows that an specific ratio between the carbon source employed and the concentration of the nitrogen source shows that an outstanding increase on the final biomass and the concentration of total carotenoids that can be produced. Finally, the effect of well-known strategies such as light, salinity and pH, coupled with C/N ratio must be studied to achieve a proper method to stress the cell culture and enhance the synthesis of carotenoids in Scenedesmus sp.
Production of hydrogen by anaerobes, facultative anaerobes, aerobes, methylotrophs, and photosynthetic bacteria is possible. Anaerobic Clostridia are potential producers and immobilized C. butyricum produces 2 mol H2/mol glucose at 50% efficiency. Spontaneous production of H2 from formate and glucose by immobilized Escherichia coli showed 100% and 60% efficiencies, respectively. Enterobactericiae produces H2 at similar efficiency from different monosaccharides during growth. Among methylotrophs, methanogenes, rumen bacteria, and thermophilic archae, Ruminococcus albus, is promising (2.37 mol/mol glucose). Immobilized aerobic Bacillus licheniformis optimally produces 0.7 mol H2/mol glucose. Photosynthetic Rhodospirillum rubrum produces 4, 7, and 6 mol of H2 from acetate, succinate, and malate, respectively. Excellent productivity (6.2 mol H2/mol glucose) by co-cultures of Cellulomonas with a hydrogenase uptake (Hup) mutant of R. capsulata on cellulose was found. Cyanobacteria, viz., Anabaena, Synechococcus, and Oscillatoria sp., have been studied for photoproduction of H2. Immobilized A. cylindrica produces H2 (20 ml/g dry wt/h) continually for 1 year. Increased H2 productivity was found for Hup mutant of A. variabilis. Synechococcus sp. has a high potential for H2 production in fermentors and outdoor cultures. Simultaneous productions of oxychemicals and H2 by Klebseilla sp. and by enzymatic methods were also attempted. The fate of H2 biotechnology is presumed to be dictated by the stock of fossil fuel and state of pollution in future.
Effective hydrogen production from starch-manufacturing wastes by microorganisms was investigated. Continuous hydrogen production in high yield of 2.7molH2mol−1 glucose was attained by a mixed culture of Clostridium butyricum and Enterobacter aerogenes HO-39 in the starch waste medium consisting of sweet potato starch residue as a carbon source and corn steep liquor as a nitrogen source in a repeated batch culture. Rhodobacter sp. M-19 could produce hydrogen from the supernatant of the culture broth obtained in the repeated batch culture of C. butyricum and E. aerogenes HO-39. Hydrogen yield of 4.5molH2mol−1 glucose was obtained by culturing Rhodobacter sp. M-19 in the supernatant supplemented with 20μgl−1 Na2MoO4·2H2O and 10mgl−1 EDTA in a repeated batch culture with pH control at 7.5. Therefore, continuous hydrogen production with total hydrogen yield of 7.2molH2mol−1 glucose from the starch remaining in the starch residue was attained by the repeated batch culture with C. butyricum and E. aerogenes HO-39 and by the successive repeated batch culture with Rhodobacter sp. M-19.
Hydrogen is the fuel of the future mainly due to its high conversion efficiency, recyclability and nonpolluting nature. Biological hydrogen production processes are found to be more environment friendly and less energy intensive as compared to thermochemical and electrochemical processes. They are mostly controlled by either photosynthetic or fermentative organisms. Till today, more emphasis has been given on the former processes. Nitrogenase and hydrogenase play very important role. Genetic manipulation of cyanobacteria (hydrogenase negative gene) improves the hydrogen generation. The paper presents a survey of biological hydrogen production processes. The microorganisms and biochemical pathways involved in hydrogen generation processes are presented in some detail. Several developmental works are discussed. Immobilized system is found suitable for the continuous hydrogen production. About 28% of energy can be recovered in the form of hydrogen using sucrose as substrate. Fermentative hydrogen production processes have some edge over the other biological processes.
Experiments on hydrogen production using chemostat-type anaerobic digesters were conducted. The results indicate that the anaerobic acidogenic conversion of glucose can produce hydrogen. The hydrogenic activity of acclimated anaerobic sewage sludge is high at a short solids retention time (SRT) and low pH. At pH 5.7, SRT 0.25 days and an organic loading rate of 416 mmol-glucose dm−3 day−1, each mole of glucose in the mesophilic acidogenic reactor can produce 1.7 mol of hydrogen; each gram of biomass produces 0.456 mole of hydrogen per day. Moreover, the hydrogen productivity of the sludge is comparable to that of an enrichment culture.© 1999 Society of Chemical Industry
The influence of operational, parameters, such as hydraulic retention time, organic loading rate, influent substrate concentration, pH, and temperature, on the performance of the first phase of anaerobic digestion has been investigated. A complex substrate based on beef extract was used, and six series of experimental runs were conducted, each one showing the effect of one operational variable. The predominant fermentation products were always acetic and propionic acid, independent of the values of the operational parameters. For initial COD concentrations and hydraulic retention times above the critical values identified as 3 g/L and 6 h, respectively, the degree of acidification achieved was between 30 and 60%. The degree of acidification was found to increase with the hydraulic retention time and decrease with the influent substrate concentration and organic loading rate, while the opposite held true for the rate of product formation. Furthermore, it has been demonstrated that acidification is primarily determined by the hydraulic retention time and the rate of product formation by the influent substrate concentration. The concentration of the acetic acid produced was found to depend on the operational parameters. However, the concentration of propionic acid produced depended only on the substrate availability with a consistent proportion of 8% initial COD converted to it. The optimum pH and temperature were 7 and 40°C, respectively. The percentage of acetic acid as a proportion of the total volatile fatty acids produced was found to increase with increasing pH and temperature, while the percentage of propionic acid seemed to decrease accordingly. Finally the effect of the temperature on the rate of acidification followed an Arrhenius type equation with an activation energy equal to 4739 cal/mol.
Continuous production of hydrogen from sugary wastewater by anaerobic microflora in chemostat culture was examined as a function of hydraulic retention time (HRT) in the reactor. The measured volumes of the evolved gas at each HRT were almost constant (Avg. 3590 ml/l-feed) and the composition of the gas was approximately 64% hydrogen, 36% carbon dioxide, and less than 0.13% methane. Steady states on evolution of gas were observed for 190 d at HRTs from 0.5 to 3 d giving hydrogen production rates from 198 to 34 mmol/l/d. Significant amounts of acetate and butyrate were formed as by-products. A maximum production yield of hydrogen of 14 mmol/g carbohydrate removed was obtained at an HRT of 0.5 d. The maximum removal efficiency of carbohydrates was approximately 97% at an HRT of 3 d. The patterns of fermentation by anaerobic microflora changed with HRT, i.e., acid formation decreased with decreasing HRT.
Continuous production of hydrogen from the anaerobic acidogenesis of a high-strength rice winery wastewater by a mixed bacterial flora was demonstrated. The experiment was conducted in a 3.0-l upflow reactor to investigate individual effects of hydraulic retention time (HRT) (2–), chemical oxygen demand (COD) concentration in wastewater (14– COD/l), pH (4.5–6.0) and temperature (20–55°C) on bio-hydrogen production from the wastewater. The biogas produced under all test conditions was composed of mostly hydrogen (53–61%) and carbon dioxide (37–45%), but contained no detectable methane. Specific hydrogen production rate increased with wastewater concentration and temperature, but with a decrease in HRT. An optimum hydrogen production rate of was achieved at an HRT of , COD of , pH 5.5 and 55°C. The hydrogen yield was in the range of 1.37–. In addition to acetate, propionate and butyrate, ethanol was also present in the effluent as an aqueous product. The distribution of these compounds in the effluent was more sensitive to wastewater concentration, pH and temperature, but was less sensitive to HRT. This upflow reactor was shown to be a promising biosystem for hydrogen production from high-strength wastewaters by mixed anaerobic cultures.
This paper investigated hydrogen production from a model lignocellulosic waste in inhibited solid substrate anaerobic digesters. Acetylene at 1% in the headspace was as effective as bromoethanesulfonate in inhibiting methanogenic activity in batch anaerobic composters containing 25% () total organic solids inoculated with an undefined cellulotytic consortium derived from anaerobic digesters. Acetylene also had no effect on the rate and amount of hydrogen produced from a pure culture of Clostridium thermocellum grown under the same conditions.
An investigation on anaerobic hydrogen production was conducted in fixed-bed bioreactors containing hydrogen-producing bacteria originated from domestic sewage sludge. Three porous materials, loofah sponge (LS), expanded clay (EC) and activated carbon (AC), were used as the support matrix to allow retention of the hydrogen-producing bacteria within the fixed-bed bioreactors. The carriers were assessed for their effectiveness in biofilm formation and hydrogen production in batch and continuous modes. It was found that LS was inefficient for biomass immobilization, while EC and AC exhibited better biomass yields. The fixed-bed reactors packed with EC or AC (denote as EC or AC reactors) were thus used for continuous hydrogen fermentation at a hydraulic retention time (HRT) of 0.5–. Sucrose was utilized as the major carbon source. With a sucrose concentration of ca. COD/l in the feed, the EC reactor () was able to produce H2 at an optimal rate of at . In contrast, the AC reactor ( in volume) exhibited a better hydrogen production rate of , which occurred at . When the AC reactor was scaled up to , the hydrogen production rate was nearly 0.53– for HRT=1–, but after a short thermal treatment (75°C, ) the rate rose to ca. at . The biogas produced with EC and AC reactors typically contained 25–35% of H2 and the rest was mainly CO2, while production of methane was negligible (less than 0.1%). During the efficient hydrogen production stage, the major soluble metabolite was butyric acid, followed by propionic acid, acetic acid, and ethanol.
Batch and continuous experiments were conducted to study the influence of dairy wastewater strength (2-30g-COD/L) on acidification at pH 5.5 and 37 degrees C. Results of batch experiments showed that carbohydrate was preferentially acidified as compared to protein and lipid. Production of VFAs (mainly acetate, propionate and butyrate) and hydrogen corresponded to carbohydrate acidification, whereas production of alcohols (mainly ethanol, propanol and butanol), plus i-butyrate and higher molecular-weight VFAs, corresponded to protein acidification. In treating high-strength wastewaters (8-30 g-COD/ L), acetate, butyrate and P(H2) decreased after reaching their peak levels before leveling off. Results of continuous experiments with 12h of hydraulic retention showed that acidification decreased with the increase of wastewater COD, from 57.1% at 2 g-COD/L to 28.8% at 30 g-COD/L; among the constituents in dairy wastewater, 92-99% of carbohydrates, 59-85% of protein and 12-42% of lipid were acidified. High-strength wastewater favored production of hydrogen and alcohols, especially propanol and butanol. The biomass yield was 0.258g-VSS/g-COD.
In this study, local sewage sludge was acclimated to establish H2-producing enrichment cultures, which were used to convert sucrose to H2 with continuously stirred anaerobic bioreactors. The steady-state behaviors of cell growth, substrate utilization, and product formation were closely monitored. Kinetic models were developed to describe and predict the experimental results from the H2-producing cultures. Operation at dilution rates (D) of 0.075–0.167 h–1 was preferable for H2 production, resulting in a H2 concentration of nearly 0.02 mol/l. The optimal hydrogen production rate was 0.105 mol/h occurring at D=0.125 h–1. The major volatile fatty acid produced was butyric acid (HBu), while acetic acid and propionic acid were also produced in lesser quantities. The major solvent product was ethanol, whose concentration was only 15% of that of HBu, indicating that the metabolic flow favors H2 production. The proposed model was able to interpret the trends of the experimental data. The maximum specific growth rate (µ
max), Monod constant (K
s
), and yield coefficient for cell growth (Y
x/s
) were estimated as 0.172 h–1, 68 mg COD/l, and 0.1 g/g, respectively. The model study also suggests that product formation in the continuous hydrogen-producing cultures was essentially a linear function of biomass concentration.
The conversion of organics in wastewaters into hydrogen gas could serve the dual role of renewable energy production and waste reduction. The chemical energy in a sucrose rich synthetic wastewater was recovered as hydrogen gas in this study. Using fractional factorial design batch experiments, the effect of varying pH (4.5-7.5) and substrate concentration (1.5-44.8 g COD/L) and their interaction on hydrogen gas production were tested. Mixed bacterial cultures obtained from a compost pile, a potato field, and a soybean field were heated to inhibit hydrogen-consuming methanogens and to enrich sporeforming, hydrogen-producing acidogens. It was determined that the highest rate (74.7 mL H2/(L*h)) of hydrogen production occurred at a pH of 5.5 and a substrate concentration of 7.5 g COD/Lwith a conversion efficiency of 38.9 mL H2/(g COD/L). The highest conversion efficiency was 46.6 mL H2/(g COD/L).
The effect of pH, growth rate, phosphate and iron limitation, carbon monoxide, and carbon source on product formation by Clostridium pasteurianum was determined. Under phosphate limitation, glucose was fermented almost exclusively to acetate and butyrate independently of the pH and growth rate. Iron limitation caused lactate production (38 mol/100 mol) from glucose in batch and continuous culture. At 15% (vol/vol) carbon monoxide in the atmosphere, glucose was fermented to ethanol (24 mol/100 mol), lactate (32 mol/100 mol), and butanol (36 mol/100 mol) in addition to the usual products, acetate (38 mol/100 mol) and butyrate (17 mol/100 mol). During glycerol fermentation, a completely different product pattern was found. In continuous culture under phosphate limitation, acetate and butyrate were produced only in trace amounts, whereas ethanol (30 mol/100 mol), butanol (18 mol/100 mol), and 1,3-propanediol (18 mol/100 mol) were the major products. Under iron limitation, the ratio of these products could be changed in favor of 1,3-propanediol (34 mol/100 mol). In addition, lactate was produced in significant amounts (25 mol/100 mol). The tolerance of C. pasteurianum to glycerol was remarkably high; growth was not inhibited by glycerol concentrations up to 17% (wt/vol). Increasing glycerol concentrations favored the production of 1,3-propanediol.
Biohydrogen production with bioÿlm processes
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Biohydrogen production with bioÿlm processes
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Chang JS, Lee KS, Lin PJ. Biohydrogen production with
bioÿlm processes. Int J Hydrogen Energy 2002;27:1167-74.