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

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

Preparation of active hydrogen-producing cultures from palm oil mill sludge for biohydrogen production system

Methods are investigated to prepare active hydrogen (H₂)-producing cultures originating from palm oil mill sludge using dark fermentation. The first successful method that produces potent H₂-producing cultures and avoids growing H₂-consuming methanogens involves heat pretreatment of the sludge at 100 °C for 2 h and then the sludge sample is shocked in an ice bath for 15 min. Subsequently, a glucose solution rich in nutrients (glucose-based substrate) of 14.80 g chemical oxygen demand (COD)/L is fed in to enrich the H₂-producing cultures. The H₂ production reaches 78.63% on day 31. The second method involves acid pretreatment of sludge with 10 M hydrochloric acid at pH 3 for 48 h. Glucose-based substrate of 25.47 g COD/L is fed into the system. The H₂ production is 69.41% on day 27. For both methods, the H₂ production is stable after the H₂ content reached its maximum. The operation is performed semi-continuously using a hydraulic retention time of 1 day and at 30 °C. The optimum bacterial cells-to-COD level of substrate is approximately 0.60 in the start-up medium. The fermentation medium has an optimum initial pH of 5 and a final pH of 5.2–5.3. These two methods are recommended to produce active H₂-producing cultures for plant start-up in bio-H₂ production.     

Effect of fermentation conditions on biohydrogen production from lipid-rich food material

Among the basic components of organic materials, such as carbohydrate, protein, and lipid, the hydrogen yield of carbohydrate fermentation has been reported to be significantly higher than that of lipid. This study used lard as a model organic matter for lipid and investigated its H₂ production potential in batch anaerobic fermentation experiments under various combinations of stirring and CO₂-scavenging conditions. A significant increase in the hydrogen yield was observed in both CO₂-scavenging and stirring conditions; the CO₂-scavenging condition yield was 2.9 times higher than the stirring condition (116.7 and 40.3 mL H₂/g volatile solid [VS], respectively), which was much greater than reported previously. A maximal hydrogen yield of 185.8 mL H₂/g VS was obtained in the presence of both CO₂-scavenging and stirring, and the H₂ content of the total biogas was as high as 99% (v/v). In addition, there was less H₂ and more CH₄ production in the absence of CO₂-scavenging and/or stirring, which suggests that the consumption of H₂ and CO₂ for methanogenesis was the major mechanism of the poor hydrogen yield from lipid. The volatile fatty acids in all the tests consisted primarily of valeric (47.2–54.9%) and propionic acids (26.6–30.3%), and higher concentrations of these acids remained in the fermentation liquid without CO₂ removal. These results suggest that lipid-rich food waste is a potential source for H₂ production if the fermentation process is optimized to minimize the partial pressure of CO₂ and H₂ and restrain the activities of H₂-consuming bacteria.     

Modeling of biohydrogen production using generalized multi-scale kinetic model: Impacts of fermentation conditions

This paper presents a new multi-scale kinetic model built upon the multi-stage growth Hypothesis for predicting biohydrogen production. The proposed model represents the significant factors affecting biohydrogen production using a sum of first-order kinetic terms with varying dynamics from slow to fast one. The current work investigates 52 case studies of biohydrogen production that show the double first-order kinetic model provides the best modeling fitness (R² > 0.99). This result suggests two prevalent pathways or microbial groups with distinct dynamics (i.e., fast and slow modes) in biohydrogen production. An increase in temperature (30 °C–43 °C) or substrate concentration (10 g/L to 40 g/L) and the use of simple substrates or mixed cultures can increase the fast-mode dominance up to 100% contribution. Model analysis suggests that the fast mode corresponds to the butyrate production pathway, the growth-associated hydrogen-producing activity, the easily-biodegradable substrates, or the quick hydrogen-producing groups.     

A critical literature review on biohydrogen production by pure cultures

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

Fermentative biohydrogen production from starch-containing textile wastewater

The present study deals with the biohydrogen production from starch-containing wastewater collected from the textile industry in Taiwan. The effects of inoculums collected from different sources (sewage sludge, soil and cow dung), substrate concentrations (5–25 g COD/L) and pH (4.0–8.0) on hydrogen production from wastewater were investigated.     

Mathematical modelling for biohydrogen production by Clostridium beijerinckii

Hydrogen is an energy source that can be produced by Clostridium sporogenes microorganism. In the present work, modeling of dark fermentation using Clostridium beijerinckii and dextrose as substrate was performed to evaluate how the gases and liquid by-products affect the biological process. A mathematical model was developed according to ADM1. The developed model takes into account biochemical reactions, physicochemical equilibrium as well as mass transfer processes during dark fermentation. Findings revealed that Clostridium beijerinckii reached a yield as high as 3.58 mol of H₂/mol of dextrose and generates by-products in the aqueous phase that may either be used as raw materials in a chemical process. Clostridium beijerinckii is very sensitive to acid media (pH < 5.0) and shows a low rate of biohydrogen production (even the absence of metabolic activity) at pH lower than 4.5. The developed model is able to predict (R² > 0.95) dextrose consumption profile, cumulative biohydrogen production and the maximum concentrations of liquid by-products.     

Dark fermentation of starch factory wastewater with acid- and base-treated mixed microorganisms for biohydrogen production

Biohydrogen (Bio-H₂) can be produced from starch factory wastewater and mixed microorganisms using dark fermentation. Acidic and basic chemicals were used to treat the microorganisms to select the hydrogen (H₂)-producing culture. The experiment used a 120 mL bioreactor at 35 °C and the operation commenced with the initial pH level of wastewater in the pH range 4–7 in batch mode. The bacteria:chemical oxygen demand (COD) ratio was 0.2. The initial pH level of the wastewater in the fermentation process affected the H₂ yield and the specific hydrogen production rate (SHPR). For acid-treated bacteria, the maximum H₂ yield and SHPR were produced at an initial pH of 6.5. The maximum H₂ yield and SHPR were 138 mL/g COD degraded and 7.42 mL/g cells?h, respectively. For the base-treated bacteria, the maximum H₂ yield and SHPR were produced at initial pH of 6.5 and pH 7, respectively. The maximum H₂ yield and SHPR were 182 mL/g COD degraded and 25.60 mL/g cells?h, respectively. The COD degradation efficiency levels were 16 and 20% for acid- and base-treated bacteria, respectively. The digested wastewater remained acidic at pH 4.79–4.83. Throughout the study, no methane gas was observed in the gas mixture produced.     

Feedback control strategy for optimizing biohydrogen production from organic solid waste in a discontinuous process

The use of control strategies for the biological process of hydrogen (H₂) production can increase productivity, stability, and robustness, increasing the viability of the implementation of these systems at the industrial level. A feedback control strategy for optimizing biohydrogen production from organic solid waste in a discontinuous process was proposed and pragmatically tested. The control strategy, which is based on recursively fitting a modified Gompertz model to gathered online data of the cumulative H₂ volume, could eventually stabilize the system at an optimal reaction time. The control strategy was evaluated during 140 degradation cycles maintaining a stable H₂ production with a reproducible form in the cumulative H₂ production curve. Independent of the changes in the microbial population dynamics in the reactor, the control strategy maintained a stable H₂ production avoiding the presence of methanogenic archaea. With the proposed controller, a compromise between the needed HRT and the H₂ production was obtained.     

An integrated system development including PEM fuel cell/biogas purification during acidogenic biohydrogen production from dairy wastewater

Biohydrogen production from dairy wastewater with subsequent biogas purification by hollow fiber membrane module was investigated in this study. The purified and not purified (raw) biohydrogen were used as fuel in polymer electrolyte membrane (PEM) fuel cell. Furthermore, the effect of CO₂ on the performance of PEM fuel cell was evaluated considering cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and polarization curves. The maximum H₂ production rate was 0.015 mmol H₂/mol glucose and the biohydrogen concentration in biogas was ranged 33%–60% (v/v). CO₂/H₂ selectivity decreased with increasing pressure and maximum selectivity was obtained as 4.4 at feed pressure of 1.5 bar. The electrochemical active surface (EASA) areas were decreased with increasing CO₂ ratio. The maximum power densities were 0.2, 0.08 and 0.045 W cm⁻² for 100%, 80% and 60% (v/v) H₂, respectively. The results indicated that integrated PEM fuel cell/biogas purification system can be used as a potential clean energy sources during acidogenic biohydrogen production from dairy wastewater.     

Effect of Ni2+ concentration on fermentative hydrogen production using waste activated sludge as substrate

The influence of Ni²⁺ concentration on biohydrogen production was investigated using waste activated sludge as substrate. The degradation of substrate, accumulation of volatile fatty acids (VFAs) and distribution of microbial community were analyzed to provide information for influencing mechanisms of Ni²⁺ addition. The experimental results demonstrated that the efficiency of hydrogen fermentation from waste activated sludge could be significantly improved. The optimal Ni²⁺ concentration was 5 mg/L, and under this concentration, the cumulative hydrogen production was 1.29 times of the control group. The degradation of soluble chemical oxygen demand (SCOD) increased from 25.21% to 27.69% when the added Ni²⁺ concentration was 5 mg/L. The analysis of microbial community distribution revealed that Ni²⁺ decreased the microbial diversity, and provided more suitable condition for the microbial growth and activity of hydrogen-producers. Citrobacter was the dominant hydrogen-producers in the control group, they changed into Enterococcus when 5 mg/L Ni²⁺ was added. Besides, the proportion of Clostridium_sensu_stricto_1, which is regarded as the primary hydrogen-producing bacteria under numerous operating conditions, was also significantly increased in the presence of Ni²⁺.     

A rapid and simple protocol for evaluating biohydrogen production potential (BHP) of wastewater with simultaneous process optimization

Biohydrogen production utilizing negative valued waste through dark-fermentation process is one of the emerging areas. Reported conditions for H₂ production are significantly variable and comparative analysis of data is major problem for unified understanding. A simple, rapid and generalized two phase methodology/protocol was developed to evaluate the biohydrogen production potential (BHP) of negative valued wastewater as substrate/feed-stock for renewable biohydrogen production using mixed consortia. Critical factors that can influence the overall process viz., redox condition, organic load and biocatalyst were considered in the designing the methodology. Feasibility of protocol was initially evaluated with synthetic wastewater and further validated with real field composite food and slaughter house wastewaters. The selected operational factors showed marked influence on both H₂ production and wastewater treatment. The reported methodology/protocol not only provides the ability of selected wastewater to generate H₂ but also facilitates process understanding based on selected factors and finally acquiesce optimum conditions.     

Optimization of conditions for hydrogen production from complex dairy wastewater by anaerobic sludge using desirability function approach

Present study deals with the multiple-response optimization for biohydrogen production using anaerobic sludge and outstanding approach to overcome the drawbacks of conventional response surface methodology (RSM). Dairy wastewater was used as source in batch fermentation was followed for this study. Response surface methodology (RSM), based on a three level, four variable Box–Behnken design, was employed to obtain the best possible combination of substrate concentration, pH, COD/N ratio and COD/P ratio for maximum H₂ yield (HY) and specific hydrogen production rate (SHPR). Experimental data were evaluated by applying RSM integrating a desirability function approach. The optimum H₂ yield and SHPR conditions were: substrate concentration 15.3 g COD/L, pH 5.5, COD/N ratio 100.5 and COD/P ratio 120 with maximum overall desirability D of 0.94. The confirmation experiment under these optimal condition showed a HY and SHPR of 13.54 mmol H₂/g COD and 29.91 mmol H₂/g-VSS.d, respectively. This was only 0.22% and 0.20%, respectively, different from the predicted values, suggesting that the desirability function approach with RSM was a useful technique to get the maximum H₂ yield and SHPR simultaneously.     

Biohydrogen production from wastewater by Clostridium beijerinckii: Effect of pH and substrate concentration

An investigation of biological hydrogen production from glucose by Clostridium beijerinckii was conducted in a synthetic wastewater solution. A study examining the effect of initial pH (range 5.7–6.5) and substrate loading (range 1–3 g COD/L) on the specific conversion and hydrogen production rate has shown interaction behaviour between the two independent variables. Highest conversion of 10.3 mL H₂/(g COD/L) was achieved at pH of 6.1 and glucose concentration of 3 g COD/L, whereas the highest production rate of 71 mL H₂/(h L) was measured at pH 6.3 and substrate loading of 2.5 g COD/L. In general, there appears to be a strong trend of increasing hydrogen production rate with an increase in both substrate concentration and pH. Butyrate (14–63%), formate (10–45%) and ethanol (16–40%) were the main soluble products with other volatile fatty acids and alcohols present in smaller quantities.     

Enhancement of fermentative biohydrogen production from textile desizing wastewater via coagulation-pretreatment

A real textile desizing wastewater (TDW) was coagulation-pretreated to enhance its potential of biohydrogen production. Batch fermentation showed that the hydrogen production was efficiently enhanced (550 and 120% increments for hydrogen production rate and hydrogen yield, respectively) and the production performance was substrate-concentration dependent. A peak hydrogen production rate of 3.9 L/L-d and hydrogen yield of 1.52 mol/mol hexose were obtained while using coagulant GGEFloc-653 at a dosage of 1 g/L to pretreat TDW with the concentration of 15 g total sugar/L. The coagulation-pretreatment could have butyrate-type fermentation with high biohydrogen production and the removed some toxic materials that might drive the metabolic pathways to those not favoring biohydrogen production. Based on the data obtained, strategies to operate the coagulation and biohydogen fermentation are suggested. Moreover, fermentation effluent utilization such as for two-stage biogas production and further biohythane (a mixture of H₂ and CH₄) generation are also elucidated.     

Dark fermentative biohydrogen production from confectionery wastewater in continuous-flow reactors

The production of biohydrogen from industrial wastewater through the dark fermentation (DF) process has attracted increased interest in recent years. To implement a DF process on a large scale, a thorough knowledge of laboratory scale process control is required. The operating parameters and design features of the reactors have a great influence on the efficiency of the process. In this work, the possibility of continuous production of biohydrogen from confectionery wastewater was evaluated. The DF process was carried out at 37 ± 1 °C in two different reactors: an upflow anaerobic filter (AF) and a fluidized bed reactor (AFB). Polyurethane foam (PU) was used to immobilize the biomass. The DF process was studied at four hydraulic retention times (HRT) (1.5, 2.5, 7.5 and 15 days) and the corresponding organic loading rates (OLR) (9.21, 6.12, 2.04 and 1.02 g COD_init/(L day)). The highest hydrogen yield (HY) (44.73 ml/g COD_init) and hydrogen production rate (HPR) (92.5 ml/(L day)) was observed in AFB at HRT of 7.5 days and 2.5 days, respectively. The highest concentration of hydrogen in biogas was 34% in AF and 36% in AFB at HRT of 7.5 days. In contrast to AF, the COD removal efficiency in AFB increased with increasing HRT. The pH of the effluent was low (3.95–4.38). However, due to the use of PU for biomass immobilization, it is possible that there were local zones in the reactor that were optimal for the functioning of not only acidogens, but also methanogens. This was evidenced by a rather high content of methane in biogas (2.5% in AF and 9.6% in AFB at HRT of 15 days). These results provide valuable data for optimizing the continuous DF of wastewater from confectionery and other food industries to produce biohydrogen or biohythane.     

Catalytic biohydrogen production from organic waste materials: A literature review and bibliometric analysis

Global population growth and accelerated urbanisation have resulted in massive amounts of fossil fuel use and waste production. Because of its high energy content, pure nature, and fuel quality, hydrogen fuel is a viable option to fossil fuels. Biohydrogen from agricultural waste, in particular, piques concern because it generates hydrogen while still disposing of waste. This review conducted a bibliometric analysis of biohydrogen production from organic waste to trace the research trends and hotspots based on the literature in the Web of Science (WOS) database from 1970 to 2020. The present review article also focuses on highlighting various processes for converting organic waste into hydrogen, raw materials for biohydrogen production, and catalysts that could distil the latest perceptions that could shed light on a route advancing for successful catalyst design. It also seems that some intentions have been paid on studying waste materials such as pure polysaccharides, disaccharides, and monosaccharides. Among all the catalysts used, non-noble and low-cost active metals over reduced graphene oxide (rGO) support can significantly affect the activity of fermentative hydrogen production from organic waste materials. However, researches focusing on developing anaerobic membrane bioreactors for these technologies are still needed.     

Strategies for improvement of biohydrogen production from organic-rich wastewater: A review

Biohydrogen can be produced from organic wastewater but the process is limited by low production yields. The aim of this review is to summarize the production strategies which are recently researched for enhancing biohydrogen yield and productivity from organic wastewater. The survey of published work indicates that the dark hydrogen fermentation is the most promising production mode. Current strategies geared towards improving biohydrogen production include: microbial culture immobilization, bioreactor modifications, the optimization of process conditions (temperature, pH, OLR and HRT), culture selection and enrichments, substrate choice, and the metabolic engineering of biohydrogen specialists. Comparative analysis of energy recovery from anaerobic digestion using vinasse-related substrates indicates that the production of methane has a higher energy yield than production of hydrogen. A sequential combination of biohydrogen and biomethanation production phases has the potential for even higher bioenergy recovery from organic wastewater.     

Integration of acidogenic and methanogenic processes for simultaneous production of biohydrogen and methane from wastewater treatment

Feasibility of integrating acidogenic and methanogenic processes for simultaneous production of biohydrogen (H₂) and methane (CH₄) was studied in two separate biofilm reactors from wastewater treatment. Acidogenic bioreactor (acidogenic sequencing batch biofilm reactor, AcSBBR) was operated with designed synthetic wastewater [organic loading rate (OLR) 4.75 kg COD/m³-day] under acidophilic conditions (pH 6.0) using selectively enriched acidogenic mixed consortia. The resultant outlet from AcSBBR composed of fermentative soluble intermediates (with residual carbon source), was used as feed for subsequent methanogenic bioreactor (methanogenic/anaerobic sequencing batch biofilm reactor, AnSBBR, pH 7.0) to generate additional biogas (CH₄) utilizing residual organic composition employing anaerobic mixed consortia. During the stabilized phase of operation (after 60 days) AcSBBR showed H₂ production of 16.91 mmol/day in association with COD removal efficiency of 36.56% (SDR_A—1.736 kg COD/m³-day). AnSBBR showed additional COD removal efficiency of 54.44% (SDR_M—1.071 kg COD/m³-day) along with CH₄ generation. Integration of the acidogenic and methanogenic processes enhanced substrate degradation efficiency (SDR_T—4.01 kg COD/m³-day) along with generation of both H₂ and CH₄ indicating sustainability of the process.     

Optimization of culture conditions for biohydrogen production from sago wastewater by Enterobacter aerogenes using Response Surface Methodology

Sago wastewater (SWW) causes pollution to the environment due to its high organic content. Annually, about 2.5 million tons of SWW is produced in Malaysia. In this study, the potential of SWW as a substrate for biohydrogen production by Enterobacter aerogenes (E. aerogenes) was evaluated. Response Surface Methodology (RSM) was employed to find the optimum conditions. From preliminary optimization, it was found that the most significant factors were yeast extract, temperature, and inoculum size. According to Face Centered Central Composite Design (FCCCD), the maximum hydrogen concentration and yield were 630.67 μmol/L and 7.42 mmol H₂/mol glucose, respectively, which is obtained from the sample supplemented with 4.8 g/L yeast extract concentration, 5% inoculum, and incubated at the temperature of 31 °C. Cumulative hydrogen production curve fitted by the modified Gompertz equation suggested that H_max, R_max, and λ from this study were 15.10 mL, 2.18 mL/h, and 9.84 h, respectively.