Maximum Hydrogen Yield Research Articles

Catalytic steam reforming of waste tire pyrolysis volatiles using a tire char catalyst for high yield hydrogen-rich syngas

The production of hydrogen and syngas (H2/CO) from waste tires by pyrolysis catalytic steam reforming was investigated in a two-stage fixed bed reactor. In this study, tire char served as a sacrificial catalyst, facilitating the combination of catalytic steam reforming and char steam gasification reactions. The tire char acted as both a catalyst and a gasification reactant, enhancing the gas product yield. The process parameters investigated were, a reforming temperature range of 700–1000 °C, steam space velocity between 2 and 12 g h−1 g−1char and reaction times of 0.5–2 h. The influence of the parameters on the yield and composition of the product gases and the characteristics of the used catalyst were analyzed in detail. The results indicated that higher temperature and steam space velocity increased H2 and CO yields in the presence of a tire char catalyst. Elemental analysis of the used tire char, surface morphology and pore structure provided insights into the extent of tire char consumption in the reaction. Prolonged reaction time allowed for more thorough reactions between the pyrolysis volatiles and tire char, promoting the production of H2. At a reaction time of 2 h, the H2 yield reached 223 mmol g−1, representing 74 wt% of the maximum hydrogen yield.

Biohydrogen production from lignocellulosic hydrolysate: Unveiling the synergistic impact of substrate concentration and furfural inhibition.

Lignocellulosic biomass offers substantial potential as an ideal feedstock for dark fermentative hydrogen production due to its sustainability and cost-effectiveness. The current study examined the influence of furfural on fermentative hydrogen production using lignocellulosic hydrolysate in the presence of furfural. Synthetic lignocellulosic hydrolysate, consisting primarily of 76% xylose, 10% glucose, 9% arabinose, and a mixture of other sugars such as galactose and mannose (85% pentose sugars and 15% hexose sugars), was employed as the substrate. Various substrate concentrations ranging from 2 to 32g/L were tested, along with furfural concentrations of 0, 1, and 2g/L. The investigation aimed to assess the effects of initial substrate concentration, initial furfural concentration, furfural-to-biomass ratio (F/B), and furfural-to-substrate ratio (F/S) on biohydrogen production yields. The maximum specific substrate utilization rates at different substrate concentrations were effectively characterized using Haldane's substrate inhibition model. Among the tested concentrations, the 16g/L emerged as the optimal substrate concentration. The initial furfural concentration was identified as the most significant parameter impacting biohydrogen production, with complete inhibition observed at a furfural concentration of 2g/L. Higher F/S ratios at substrate concentrations ranging from 2 to 16g/L resulted in reduced maximum specific hydrogen production rates (MSHPR) and hydrogen yields. Substrate inhibition was observed at 24g/L and 32g/L. Lactate was the predominant metabolite in all batches containing 2-g/L furfural, as well as in batches with 1-g/L furfural and substrate concentrations of 24 and 32g/L. Furfural at a concentration of 1g/L was not inhibitory in any of the batches. Overall, the mixed cultures in this study could efficiently produce hydrogen from lignocellulosic hydrolysates and degrade furfural, providing new insights into fermentative hydrogen-producing bacteria with furfural tolerance.

Synergising hydrothermal pre-treatment and biological processes for enhancing biohydrogen production from palm oil mill effluent

The high quantity of nutrient-rich palm oil mill effluent (POME) waste in the industry will have a severe negative environmental impact and a high cost of treatment. However, POME waste could be converted into bioenergy via environmentally sustainable processes. Several studies have explored using hydrothermal carbonisation for solid biomass products in biofuel production, but the potential of the liquid phase produced during these processes has received less attention. Therefore, this study aims to assess the potential of biohydrogen production from treated POME as a substrate by hydrothermal process. This study is presented in two phases: the first phase involves substrate pre-treatment using a hydrothermal process to improve biomass properties at different temperatures, and the second phase explores the potential for biohydrogen production from treated POME through dark fermentation. Substrate pre-treatment was conducted at 180, 210, and 240 °C using 100% raw POME. Next, the treated POME was incubated for biohydrogen production at 50 °C for 24hours. A microbial analysis was conducted to determine the most dominant species present in the sample. Our findings show that at 180 °C, the total chemical oxygen demand (COD) removal efficiency was 80%, and acetic acid concentration was 28%. Compared to raw POME, treated POME generated a maximum hydrogen yield and rate (HPR) of 52.19mL H2 g-1 CODrem and 0.59mL H2 mL POME-1 day-1 with a 2.32-fold and 1.59-fold increase, respectively. Meanwhile, Clostridium was a dominant bacterial species identified in the treated POME. These findings demonstrated the feasibility of implementing a hydrothermal process to treat POME and improve its biohydrogen production efficiency. The treated POME from the hydrothermal process is more homogenous and readily consumable by microorganisms used in dark fermentation. Hydrothermal pre-treatment could potentially increase the rate and efficiency of microbial digestion, leading to enhanced hydrogen production. The high COD removal efficiency during the process significantly reduces the environmental impact of POME discharge, and converting POME into a valuable resource through the hydrothermal and dark fermentation process aligns with sustainable waste management practices.

VALORIZATION OF LIGNOCELLULOSIC BIOMASS BY DARK FERMENTATION: DEVELOPMENT OF EFFECTIVE CONDITIONS FOR MOLECULAR HYDROGEN BIOSYNTHESIS

Valorization of lignocellulosic biomass (LB) is important to reduce their environmental impact and reduce the risk to human health. Conventional methods for handling secondary raw materials primarily focus on waste disposal, treating lignocellulosic biomass as waste rather than as a source of organic substances for producing value-added products. As an alternative, processes should be developed to add value to waste, producing value-added products with economic and environmental benefits. In this regard, studies have focused on operating parameters, pretreatment, and microbial fermentation to enhance hydrogen yield during dark fermentation. Upper (4%) and lower (20%) concentrations of distillery grain based substrates for biohydrogen synthesis using wild-type E. coli have been established. Conditions for rational formation of reducing sugars by varying feedstock and acid concentrations in distillery grain based substrates have been established. During the study of the effect of acid-hydrothermal treatment of stillage on the total yield of biohydrogen, it was found that the optimal concentration of sulfuric acid is 1,5%, while 10% of the raw material is used. Under these conditions, the maximum yield of molecular hydrogen was achieved, equal to 116 ±1,0 ml/l using wild-type E. coli.

Application of artificial intelligence and red-tailed hawk optimization for boosting biohydrogen production from microalgae

Enhancing biohydrogen production from microalgae is crucial in addressing environmental and energy challenges. It provides a sustainable, clean energy source while reducing greenhouse gas emissions. Moreover, it advances microalgae-based biotechnology, enabling innovative biofuel production and ecological revitalization. The main target of this study is to develop a robust ANFIS model to simulate the biohydrogen production process from microalgae within photobioreactors. The study focuses on enhancing hydrogen yield by optimizing three critical process parameters: sulfur concentration (%), run time (hours), and wet biomass concentration (g/L). Initially, an adaptive neuro-fuzzy inference system (ANFIS) model for biohydrogen production process is constructed based on empirical data. Subsequently, the red-tailed hawk algorithm (RTH) is used to determine the optimal values for the process parameters, corresponding to maximum hydrogen yield. The performance of ANFIS model in predicting hydrogen yield is assessed using root mean square error (RMSE) and coefficient-of-determination (R2) values. The obtained RMSE values for training and testing data are 2.8477 × 10−05 and 1.2807, respectively, while the corresponding R2 values are 1.0 and 0.9911 for training and testing. The introduction of fuzzy logic into the model significantly improves its predictive accuracy, as evidenced by the drop in RMSE from 10.79 with ANOVA to 0.7159 with ANFIS, representing a substantial 93.4 % decrease. The remarkable precision of the ANFIS model, indicated by its low RMSE and high R2 values, underscores the success of the modeling stage. The combination between ANFIS with the RTH technique yields impressive results, leading to a hydrogen yield enhancement of 6.87 % and 26.65 % when compared to both measured data and ANOVA.

Synergistic role of carbon quantum dots on biohydrogen production

Biohybrid system has their distinct ability to improve microbial fermentation. This study demonstrates the role of surface-doped carbon quantum dots (CQDs) on dark fermentative biohydrogen production using lactobacillus organic-hybrid biocatalyst. Herein, nitrogen-doped carbon quantum dots (N-CQDs) with < 5 nm (having a surface charge of +2.6 mV) and un-doped carbon quantum dots (CQDs) (having a surface charge of −4.5 mV) were synthesized via chemical assisted process. Subsequently, the biohybrid systems were constructed via augmentation of N-CQDs and CQDs with Lactobacillus delbreuckii and assessed for biohydrogen production. The results revealed that both the biohybrid systems (N-CQDs- Lactobacillus delbreuckii and CQDs- Lactobacillus delbreuckii) provided improved hydrogen production than that of the native bacterial strain. Interestingly, the obtained N-CQDs- Lactobacillus delbreuckii system provided the maximum hydrogen yield of 2.01 mol/mol hexose, followed by 1.86 mol/mol hexose from CQDs- Lactobacillus delbreuckii, which is about 33 % and 19 % higher than the bare bacterial strain. The electron transfer and metabolic alteration of microbes by carbon quantum dots were assessed using cyclic voltammetry (CV) and VFA production. It was concluded that the improved bio-hydrogen production from N-CQDs- Lactobacillus delbreuckii is attributed to enhanced electron transfer, which regulates the central metabolic pathway of acetate and butyrate synthesis with the least production of lactate and other reduced end product formation.

Bioaugmentation with Clostridium pasteurianum for high-yield continuous bio-hydrogen production in a dynamic membrane bioreactor

This study demonstrated the feasibility of achieving high-yield continuous bio-H2 production through bioaugmentation with Clostridium pasteurianum. C. pasteurianum was introduced during the initial granulation stage in a dynamic membrane bioreactor (DMBR) inoculated with heat-treated digester sludge. Following bioaugmentation, the average hydrogen yield (HY) reached 3.07 ± 0.13 mol H2/mol hexoseconsumed, with a hydraulic retention time (HRT) of 2 h. This high-yield and high-rate hydrogen production performance was achieved alongside a high concentration of suspended and granular biomass as 21.02 ± 1.01 g VSS/L. The DM played a crucial role in prolonging the solid retention time of the suspended biomass to 12.15 h. C. pasteurianum emerged as the predominant species, constituting 92.3 % of the total bacterial population. This dominance significantly contributed to achieving the high HY, reaching 77 % of the theoretical maximum HY (4 mol H2/mol hexoseconsumed) by shifting the metabolic pathway from non-H2 production pathways to hydrogen-producing acetate. However, during further continuous operation, the hydrogen production pathway was gradually shifted towards the butyrate pathway, resulting in a decreased HY of 2.26 mol H2/mol hexoseconsumed along with the decreased population of C. pasteurianum. Additional bioaugmentation of C. pasteurianum during the maturational granulation stage did not impact the metabolic pathways or microbiome significantly, as the added strain was supposed to be washed out. This study provides insights into achieving high-yield continuous bio-H2 production through bioaugmentation with C. pasteurianum during the initial granulation stage. Further studies are necessary to sustain C. pasteurianum-dominated high HY with the acetate pathway during prolonged operation.

Regulating the metabolites through SiC, ZnO, and SnO2 nano-photocatalysts for elevating efficiency of photo fermentative bioH2 from Arundo donax L.

Photo-fermentation offers a promising roadmap for hydrogen production through their ability to harness light energy, however, its lower conversion efficiency is the major bottleneck for its realization. This study investigates the catalytic role of wideband gap nano-photocatalysts (SiC, ZnO, and SnO2) in enhancing hydrogen generation from Arundo donax L. Physio-optical characteristics of SiC, ZnO, and SnO2 nano-photocatalysts were assessed through SEM, XRD, and FT-IR which confirmed that incorporated nano-photocatalysts are spherical with uniform size distribution and there is no secondary phase. Hydrogen production experiments with varying nano-photocatalyst concentrations revealed that the maximum hydrogen yield of 104 and 98.83 mL/g was achieved with SiC and ZnO, respectively, at loading concentration of 200 mg/L, whereas 69.30 mL/g were observed with 100 mg/L of SnO2. The incorporation of SIC, ZnO, and SnO2 nano-photocatalyst permitted to increase the hydrogen content in overall gas production by 41 %, 37.34 %, and 18.26 % as compared to the control group. The increase in hydrogen production is related to the enhanced e-h pair separation lifetime of SiC, confirmed from PL spectroscopy. Addition of SiC caused a longer availability of electrons that helped to increase the metabolic rate by 38 % and 40.29 % in energy conversion efficiency (ECE). ANOVA results revealed significant differences between the control and maximum values of CHP, HC%, byproducts, and ECE. Tukey pairwise comparisons showed that SiC and ZnO had non-significant differences at 200 mg/L but both significantly outperformed SnO2 at 100 mg/L. Thus, the selection of suitable catalysts photocatalysts with enhanced e-h pair separation lifetime may offer promising prospects for sustainable energy technologies by enhancing biohydrogen production.

Factors affecting conversion of methane-hydrogen mixtures into nanostructured carbon and hydrogen

At the catalytic decomposition of methane, along with hydrogen, it is possible to obtain carbon nanofibers. The addition of hydrogen to the initial reaction mixture makes it possible to increase significantly the efficiency of the overall process by minimizing the contribution of the catalyst deactivation process caused by coking. As found, the maximum yields of hydrogen and nanostructured carbon over the NiO–CuO/Al2O3 catalyst is achieved at an inlet hydrogen concentration of 13 vol%. The accumulated carbon is represented by well-structured carbon nanofibers, which are resistant to the gasification reaction. The original stacked structure is preserved after the treatment of these fibers in a hydrogen medium. Using numerical methods, the hydrogen productivity at 610 °C was found to be 49.3 mL/(mgcat·h) at an optimal value of the residence time of 5 × 10−3 s.

NiO-LaCoO3 catalysts for biomass pyrolysis to hydrogen-rich gas

This study presents a new pathway for effective and environmentally friendly hydrogen generation from biomass pyrolysis using perovskite-type catalysts for highly valuable biomass conversion. Firstly, the impact of different Ni doping levels on LaCoO3 catalytic reactivity was investigated. On this basis, the impacts of different carbide slag adding proportions and reaction temperatures on the hydrogen yield and concentration were investigated. Among them, the maximum hydrogen yield at 600 °C under Ni3La2Co2 catalyst is 553.79 mL/gbiomass when the proportion of carbide slag is 5:15, and the volume concentration of hydrogen is 62.67 vol%. The outcomes demonstrated that the prepared NiO-LaCoO3 has excellent cycling performance, and the hydrogen yield of the Ni3La2Co2 catalyst decreased only marginally from 546.98 mL/gbiomass to 503.94 mL/gbiomass after ten cycles, with a comparatively small reduction of only 7.87 %. In particular, a high hydrogen concentration of 63.43 vol% is maintained in the pyrolysis gas.

Anaerobic Two-Phase Co-Digestion for Renewable Energy Production: Estimating the Effect of Substrate Pretreatment, Hydraulic Retention Time and Participating Microbial Consortia

Green and sustainable economies have recently become a key issue in long-term growth and well-being. Co-digestion of various waste materials in an eco-friendly way through biogas production has become the preferred method for their utilization and valorization. The possibility of hydrogen and methane yield maximization depends on the most suitable alkali reagent for pretreatment of waste lignocellulosic material, which was revealed in batch tests to determine the hydrogen production potential. The mixture for digestion consisted of pretreated wheat straw mixed with waste algal biomass in a ratio of 80:20 (w/w). The maximum hydrogen yield was achieved after applying sodium hydroxide thermoalkaline pretreatment, with a two-fold higher yield than the untreated control. Hydrogen production was stable and methane was not present in the resultant gas. The influence of the hydraulic retention time (HRT) on the maintenance of cascade installation was studied. The maximum daily concentration of hydrogen was achieved at an HRT of 2 days—42.5% H2—and the maximum concentration of methane was 56.1% at an HRT of 6 days. Accumulation of volatile fatty acids was registered in the first step and their depletion was noted in the second one. The obtained values of the cellulose content demonstrated that it was utilized by up to 2.75% in the methanogenic bioreactor at the end of the process. Metagenomics analyses revealed the bacteria Thermocaproicibacter melissae (44.9%) and Clostridium cellulosi (41.9%) participated in the consortium, accomplishing substrate hydrolysis and acidogenesis in the first stage. Less in abundance were Thermoanaerobacterium butyriciformans, Calorimonas adulescens, Pseudomonas aeruginosa and Anaerocolumna chitinilytica. Methanogenesis was performed by an archaeon closely related to Bathyarchaeota (99.5%) and Methanobacterium formicicum. The most abundant bacterial strains in the methanogenic fermenter were Abyssalbus ytuae (30%), Proteiniphilum acetatigenes (26%) and Ruficoccus amylovorans (13%).

Enhancing Biohydrogen Production: The Role of Iron-Based Nanoparticles in Continuous Lactate-Driven Dark Fermentation of Powdered Cheese Whey

Here, a comprehensive investigation was conducted under various operational strategies aimed at enhancing biohydrogen production via dark fermentation, with a specific focus on the lactate metabolic pathway, using powdered cheese whey as a substrate. Initially, a batch configuration was tested to determine both the maximum hydrogen yield (100.2 ± 4.2 NmL H2/g CODfed) and the substrate (total carbohydrates) consumption efficiency (94.4 ± 0.8%). Subsequently, a transition to continuous operation was made by testing five different operational phases: control (I), incorporation of an inert support medium for biomass fixation (II), addition of carbon-coated, zero-valent iron nanoparticles (CC-nZVI NPs) at 100 mg/L (III), and supplementation of Fe2O3 nanoparticles at concentrations of 100 mg/L (IV) and 300 mg/L (V). The results emphasized the critical role of the support medium in stabilizing the continuous system. On the other hand, a remarkable increase of 10% in hydrogen productivity was observed with the addition of Fe2O3 NPs (300 mg/L). The analysis of the organic acids’ composition unveiled a positive correlation between high butyrate concentrations and improved volumetric hydrogen production rates (25 L H2/L-d). Moreover, the presence of iron-based NPs effectively regulated the lactate concentration, maintaining it at low levels. Further exploration of the bacterial community dynamics revealed a mutually beneficial interaction between lactic acid bacteria (LAB) and hydrogen-producing bacteria (HPB) throughout the experimental process, with Prevotella, Clostridium, and Lactobacillus emerging as the predominant genera. In conclusion, this study highlighted the promising potential of nanoparticle addition as a tool for boosting biohydrogen productivity via lactate-driven dark fermentation.

Biohydrogen production by a novel strain Petroclostridium sp. X23 isolated from the production water of oil reservoirs

Biohydrogen production from H2-producing has been considered a promising alternative for the replacement of fossil fuels. However, the mechanisms that affect the H2-producing capacities of wild-type strains remain largely elusive. To explore the capabilities of biohydrogen production from microorganisms in the deep subsurface oil-reservoir environment, we isolated an H2-producing bacteria identified as the genus Petroclostridium from a long-term methanogenic crude oil-degrading enrichment culture of the production water from oil reservoir. The impact of various temperature, pH, and glucose concentrations on hydrogen production by Petroclostridium sp. X23 was investigated. Under the conditions of 37 °C, initial pH 8.0, and glucose concentration of 4 g/L, the strain X23 achieved its maximum hydrogen yield at 1.82 ± 0.12 mol H2/mol glucose. When compared to the previously reported strain SK-Y3, X23 exhibited enhanced H2-producing ability, with lesser energy biomass production. Comparative genomic analysis revealed that the genome of X23 contains more genes associated with hydrogen generation than SK-Y3. These findings proposed Petroclostridium sp. X23 is a potential candidate for dark fermentative hydrogen production under alkaline and mesophilic conditions. It also increased our knowledge of genotypes related to high H2-producing capability, which may provide instructions for future selection of high-yielding strains and reasonable metabolic engineering of wild-type H2-producing strains.

Development of a new renewable energy system for clean hydrogen and ethanol production

The present research work aims to present a uniquely designed renewable energy-based integrated system along with an equilibrium model for the processing of feedstock by following a hybrid route of thermochemical and biochemical ways. In this regard, Canadian maple leaves and plastic wastes are selected as potential feedstocks for co-pyrolysis and syngas fermentation. The influence of co-pyrolysis process parameters on the overall system performance is investigated and assessed. Also, several sensitivity analyses are performed to determine the optimal operating parameters that can generate maximum yields of hydrogen and ethanol. The present system is further investigated thermodynamically in terms of energetic and exergetic approaches and efficiencies. The present study shows that a molar flow ratio of 1:1 for maple leaves to plastic wastes, a temperature of 1000°C temperature, and a pressure of 1 bar appear to be the most suitable operating conditions with the net production capacities of 7.43 tons/day for hydrogen and 8.72 tons/day for ethanol. The cold gas efficiency and LHV of the syngas produced are found to be 57.23% and 19.96 MJ/kg, respectively. The overall energetic and exergetic efficiencies of the present system are found to be 30.98% and 26.88%, respectively.

Hydrogen production from wet biomass via a formic acid route under mild conditions

Renewable Hydrogen is a key building block for a sustainable energy economy. An attractive resource for its production is waste biomass. This contribution analyses a promising new Biomass-to-H2 two-step approach, consisting of (1) biomass oxidation to formic acid and methyl formate in the so-called OxFA-Process and (2) hydrogen generation by dehydrogenation or decarbonylation of these intermediates. This contribution explains a novel hydrogen production concept and compares three distinct process routes for their efficient implementation. By using Aspen Plus® V12 the process was designed and optimized to achieve maximum hydrogen yield. An economic analysis allowed to compare the different characteristics of each process concept and to select the most promising option. The chosen concept was subject to a detailed cost and sensitivity analysis showing that this new route has high potential and competitiveness for hydrogen production from waste biomass.

Graphite sheet assisted photovoltaic -thermoelectric generator for hydrogen generation from seawater

ABSTRACT Different intermediate steps exist between solar energy as input and hydrogen as output. Most of the findings in this domain revolved around water electrolysis as an intermediate step to produce hydrogen. Therefore, the discussion in the work is intended to discuss water-splitting-based hydrogen production through electrolysis. The electrolysis process requires continuous electrical input. Installed solar PV is inevitably supposed to be under prolonged solar irradiance. The prolonged solar incidence causes the panel to get heated, leading to lower overall performance. Thermoelectric Generators (TEGs) convert the waste heat into additional electrical energy apart from the panel. In the experimentation of the work, the effect of temperature gradient is explored. During the implementation of PV-TEG, TEG electrical output can be improved with the help of auxiliary heat dissipators. This study includes graphite as a heat dissipator and a Hofmann voltameter for hydrogen production. Under 800 W/m2 of solar irradiation, the maximum hydrogen yield is obtained when PV-TEG (with graphite sheet) is connected to the Hofmann voltameter. The yield ranges from 0.132 bar/sec to 0.137 bar/sec.

Enhancement of biohydrogen production by photo-fermentation of corn stover via visible light catalyzed titanium dioxide/activated carbon fiber

In this study, titanium dioxide/activated carbon fiber (TiO2/ACF) was synthesized by liquid-phase deposition method and the effect of TiO2/ACF on the performance of photo-fermentation biohydrogen production (PFHP) from corn stover under visible light catalysis was discussed. Results show the maximum cumulative hydrogen yield (CHY) obtained under the optimal conditions was 74.0 ± 1.3 mL/g TS with TiO2/ACF addition of 100 mg/L, which was twice that without TiO2/ACF addition (36.9 ± 1.0 mL/g TS). Initial pH value had the most significant effect on CHY. The addition of TiO2/ACF promoted the metabolic pathway of nitrogenase to reduce H+ produced by consuming acetic acid and butyric acid to hydrogen, and also shortened the photo-fermentation period. By scanning electron microscopy and X-ray diffraction analysis, the morphology and phase structure of TiO2/ACF after PFHP did not change significantly. This study laid the foundation for the reuse of TiO2 and its practical application in PFHP.

Two-Stage and One-Stage Anaerobic Co-digestion of Vinasse and Spent Brewer Yeast Cells for Biohydrogen and Methane Production.

This study aimed to evaluate the two-stage and one-stage anaerobic co-digestion of vinasse and spent brewer yeast cells (SBY) for biohydrogen and methane production. Optimization of the vinasse-to-SBY ratio and fly ash concentration of the two-stage and one-stage production processes was investigated. In the two-stage process, the vinasse-to-SBY ratio and fly ash concentration were optimized, and the leftover effluent was used for methane production. The optimum conditions for biohydrogen production were a vinasse-to-SBY ratio of 7:3% v/w and fly ash concentration of 0.4% w/v, in which the maximum hydrogen yield was 43.7ml-H2/g-VSadded. In contrast, a vinasse-to-SBY ratio of 10:0% v/w and fly ash concentration of 0.2% w/v were considered optimal for methane production, and resulted in a maximum methane yield of 214.6ml-CH4/g-VSadded. For the one-stage process, a vinasse-to-SBY ratio of 10:0% v/w and fly ash concentration of 0.1% w/v were considered optimal, and resulted in a maximum methane yield of 243.6ml-CH4/g-VSadded. In the two-stage process, the energy yield from hydrogen (0.05-0.47kJ/g-VSadded) was 0.62%-11.78%, and the major fraction was approximately 88.22%-99.38% gain from methane (3.19-7.73kJ/g-VSadded). For the one-stage process, the total energy yield distribution ranged from 4.20 to 8.77kJ/g-VSadded.

Evaluation of the effect of increasing the organic load in the thermophilic co-fermentation of sugarcane industry by-products on hydrogen, ethanol and lactic acid generation

The effects of increased organic loading rate (OLR) on H2 production and soluble metabolites in a thermophilic anaerobic fluidized bed reactor (AFBR-AT) at 55 °C were evaluated by the fermentation of vinasse and molasses from sugarcane (at a ratio of 1:1). The OLR varied between 30 and 135 kg COD.m−3.d−1, while the hydraulic retention time (HRT) was fixed at 4 h, and the initial co-substrate concentration varied between 5 and 22.5 g COD.L−1. The thermophilic acidogenic reactor showed a maximum hydrogen yield (HY) (2.49 mmol H2.g−1CODapp) at an OLR of 30 kg COD.m−3.d−1 and a higher hydrogen production rate (HPR) (2.8 L H2.L−1.d−1) at an OLR of 45 kg COD.m−3.d−1. Increasing the OLR negatively influenced H2 production. The results showed an increase in ethanol (EtOH) concentrations of up to 47.3 times and lactic acid (HLa) concentrations of up to 15.2 times when comparing OLRs of 30 and 135 kg COD.m−3.d−1, indicating changes in metabolic pathways for acid formation at organic loads ≥90 kg COD.m−3.d−1. Thermoanaerobacterium was the bacteria with higher relative abundance and was directly involved in H2 production, while Lactobacillus was mainly involved in HLa production in higher OLR, decreasing H2 production instead. Besides that, higher OLRs were favorable for sulfidogenesis and the development of sulfate-reducing bacteria, such as Desulfobacterota, due to the higher COD/sulfate ratio in OLR 135 kg COD.m−3.d−1. According to the metabolic inference in this condition, the enzyme activity of sulfite reductase and sulfite dehydrogenase may have occurred, consuming H+, thereby reducing H2 production.

Production of green hydrogen from sewage sludge / algae in agriculture diesel engine: Performance Evaluation

Alternative fuel opportunities can satisfy energy security and reduce carbon emissions. In this regard, the hydrogen fuel is derived from the source of environmental pollutants like sewage and algae wastewater through hydrothermal gasification technique using a KOH catalyst with varied gasification process parameters of duration and temperature of 6–30 min and 500-800 °C. The novelty of the work is to identify the optimum gasification process parameter for obtaining the maximum hydrogen yield using a KOH catalyst as an alternative fuel for agricultural engine applications. Influences of gasification processing time and temperature on H2 selectivity, Carbon gasification efficiency (CE), Lower heating value (LHV), Hydrogen yield potential (HYP), and gasification efficiency (GE) were studied. Its results showed that the gasifier operated at 800 °C for 30 min, offering maximum hydrogen yield (26 mol/kg) and gasification efficiency (58 %). The synthesized H2 was an alternative fuel blended with diesel fuel/TiO2 nanoparticles. It was experimentally studied using an internal combustion engine. Influences of H2 on engine performance, like brake-specific fuel consumption, brake thermal efficiency and emission performances, were measured and compared with diesel fuel. The results showed that DH20T has the least (420g/kWh) brake-specific fuel consumption (BSFC) and superior brake thermal efficiency of about 25.2 %. The emission results revealed that the DH20T blend showed the NOX value increased by almost 10.97 % compared to diesel fuel, whereas the CO, UHC, and smoke values reduced by roughly 31.25, 28.34, and 42.35 %. The optimum fuel blend (DH20T) result is recommended for agricultural engine applications.