Sustainable hydrogen production via microalgae: Technological advancements, economic indicators, environmental aspects, challenges, and policy implications.

Hydrogen has emerged as an alternative energy source to meet the increasing global energy demand, depleting fossil fuels and environmental issues resulting from fossil fuel consumption. Microalgae-based biomass is gaining attention as a potential source of hydrogen production due to its green energy carrier properties, high energy content, and carbon-free combustion. This review examines the hydrogen production process from microalgae, including the microalgae cultivation technological process for biomass production, and the three main routes of biomass-to-hydrogen production: thermochemical conversion, photo biological conversion, and electrochemical conversion. The current progress of technological options in the three main routes is presented, with the various strains of microalgae and operating conditions of the processes. Furthermore, the economic and environmental perspectives of biomass-to-hydrogen from microalgae are evaluated, and critical operational parameters are used to assess the feasibility of scaling up biohydrogen production for commercial industrial-scale applications. The key finding is the thermochemical conversion process is the most feasible process for biohydrogen production, compared to the pyrolysis process. In the photobiological and electrochemical process, pure hydrogen can be achieved, but further process development is required to enhance the production yield. In addition, the high production cost is the main challenge in biohydrogen production. The cost of biohydrogen production for direct bio photolysis it cost around $7.24 kg-1; for indirect bio photolysis it costs around $7.54 kg-1 and for fermentation, it costs around $7.61 kg-1. Therefore, comprehensive studies and efforts are required to make biohydrogen production from microalgae applications more economical in the future.

Economic and environmental impact assessments of a newly designed energy system for marine applications.

Marine transportation via the world's oceans is a critical way to convey goods and fuels between continents that cannot be performed cost-effectively by any other means. However, big ships heavily rely on fossil fuels, aggravating global carbon emissions. A key resolution to this dilemma is to employ clean fuels to reduce carbon emissions. This research paper introduces a new hybrid compound marine engine comprising a gas turbine, a solid oxide fuel cell, and a steam Rankine cycle. Three types of analyses, such as exergy, exergoeconomic, and exergoenvironmental analyses, are conducted on this proposed engine. It is found that the engine can produce a power of 15.5 MW, which is more than 48% compared to the traditional marine engine power, and the engine performance has up to 61% energy efficiency and 43% exergy efficiency. However, the exergetic efficiency of this engine based on fuel and product principal is 60%, which is more than 17% compared to its exergy efficiency. This engine has a 218 $/h Levelized cost rate and 139 mPt/h environmental rate. Finally, the average overall specific product exergy cost and environment are obtained to be 59 $/GJ and 20 mPt/MJ. By comparing five fuel blends, methane and hydrogen are the most economical and have the least impact on the environment; the second option is ethanol blend.

A review on biological biohydrogen production: Outlook on genetic strain enhancements, reactor model and techno-economics analysis.

Modernisation of industrial and transportation sector would have not imaginable without the help of fossil fuels, but constant usage has led to many environmental concerns. As a step forward, for safer next generation living we are forced to look into green fuels like bio­hydrogen and higher alcohols. This review mainly focuses on bio­hydrogen production via biological pathways, genetic improvements, knowledge gap, economics, and future directions. Dark and photo fermentation process with the factor influence the process (pH regulation, temperature, hydraulic retention time, organic loading rate, Maintenance, Nutrient) is studied. Integration of dark fermentation and microbial electrolysis cell is the most trending progression for sustainable bio­hydrogen production. Genetic improvement of microbe for biohydrogen production via inactivation of hydrogenase (H2ase) and improve oxygen tolerant H2ase. In future, bioaugmentation, multidisciplinary integrated process and microbial electrolysis needs to be experimented in industrial level scale for successful commercialization. About 41.47 mmol H2/g DCW h at 40 g/L of optimum biohydrogen production was obtained through glycerol fermentation. From the studies, the cost of biohydrogen production was found to high with respect to the direct bio photolysis it cost around $7.24 kg-1; for indirect bio photolysis it cost around $7.54 kg-1 and for fermentation it cost around $7.61 kg-1.

Fast Detection of Cadmium in Chocolate by Solid Sampling Electrothermal Vaporization Atomic Absorption Spectrometry and Its Application on Dietary Exposure Risk Assessment.

In this work, a rapid detection method using solid sampling electrothermal vaporization atomic absorption spectrometry (SS-ETV-AAS) was established for cadmium in chocolate. The instrumental system includes a solid sampling ETV unit, a catalytic pyrolysis furnace, an AAS detector, and a gas supply system with only an air pump and a hydrogen generator. Herein, MgO material with 1.0−1.5 mm particle size was first employed to replace the kaolin filler previously used to further shorten the peak width and to thereby improve the sensitivity. With 350 mL/min of air, a chocolate sample was heated for 25 s from 435 to 464 °C to remove water and organic matrices; then, after supplying 240 mL/min hydrogen and turning down air to 120 mL/min, a N2/H2 mixture gas was formed to accelerate Cd vaporization from chocolate residue under 465 to 765 °C. Under the optimized conditions, the detection limit (LOD) was obviously lowered to 70 pg/g (vs. previous 150 pg/g) with R2 > 0.999; the relative standard deviations (RSD) of repeated measurements for real chocolate samples ranged from 1.5% to 6.4%, indicating a favorable precision; and the Cd recoveries were in the range of 93−107%, proving a satisfied accuracy. Thus, the total analysis time is less than 3 min without the sample digestion process. Thereafter, 78 chocolate samples with different brands from 9 producing countries in China market were collected and measured by this proposed method. Based on the measured Cd concentrations, a dietary exposure assessment was performed for Chinese residents, and the target hazard quotient (THQ) values are all less than 1, proving no significant health risk from intaking chocolate cadmium for Chinese residents.

[Life Cycle Assessment and Key Parameter Comparison of Hydrogen Fuel Cell Vehicles Power Systems].

Hydrogen fuel cell vehicles (HFCVs) are regarded as potential solutions to the problems of energy security and environmental pollution. To explore the energy consumption and pollutant emissions of fuel cell vehicle power systems, data inventories of an HFCV power system were established, and quantitative evaluation calculations and prediction analysis were carried out for fuel life cycle energy consumption and greenhouse gas emissions of Chinese fuel cell vehicles in 2030 based on the technology roadmap for new energy vehicles by modeling with GaBi software. The effects of different types of bipolar plates, different energy control strategies, and different hydrogen production methods on the environment were studied, with uncertainty analysis as the key parameter. The results showed that fossil energy consumption (ADPf), global warming potential (GWP, CO2 equivalent), and acidification potential (AP, SO2 equivalent) for the HFCV power system in the fuel life cycle were 1.35×105 MJ, 9108 kg, and 15.79 kg, respectively. The energy consumption and greenhouse gas emissions in the production of the power system were higher than those in the use stage, mainly because of the fuel cell stack and hydrogen storage tank. In the manufacturing process of metal bipolar plates, graphite composite bipolar plates, and graphite bipolar plates, graphite composite bipolar plates had the most comprehensive environmental benefits. Optimizing the energy control strategy will reduce hydrogen energy consumption. When the hydrogen energy consumption was reduced by 22.8%, the life cycle energy consumption and greenhouse gas emissions of the power system were reduced by 10.4% and 8.3%, respectively. For life cycle power systems, the use of hydrogen from electrolysis operated with water power reduced the GWP by approximately 39.6% relative to steam methane reforming. In contrast, the application of hydrogen from electrolysis operated with the Chinese electricity grid mix resulted in an increase in GWP of almost 53.7%. Measures to reduce fossil energy consumption and global warming potential in the life cycle of fuel cell vehicle powertrains include optimizing energy control strategies to reduce hydrogen energy consumption, scaling up the hydrogen production industry using water electrolysis for renewable energy power generation, and focusing on key technologies of fuel cell stacks to improve performance.

Biohydrogen production using algae: Potentiality, economics and challenges.

The biohydrogen production from algal biomass could ensure hydrogen's sustainability as a fuel option at the industrial level. However, some bottlenecks still need to be overcome to achieve the process's economic feasibility. This review article highlights the potential of algal biomasses for producing hydrogen with a detailed explanation of various mechanisms and enzymes involved in the production processes. Further, it discusses the impact of various experimental parameters on biohydrogen production. This article also analyses the significant challenges confronted during the overall biohydrogen production process and comprehends the recent strategies adopted to enhance hydrogen productivity. Furthermore, it gives a perception of the economic sustenance of the process. Moreover, this review elucidates the future scope of this technology and delineates the approaches to ensure the viability of hydrogen production.

Comparative water footprint assessment of fuel cell electric vehicles and compressed natural gas vehicles.

Utilization of renewable energy has become a current energy development trend. In this study, the water footprints of a fuel cell electric vehicle (FCEV) and a compressed natural gas vehicle (CNG) under different fuel scenarios were evaluated. The FCEV exhibits a low water footprint of 27.2 L/100 km under steam methane reforming hydrogen production technology. Hydrogen production using steam methane reforming and water electrolysis via wind can enable the FCEV industry to save more water resources. The percentage difference between different metallic materials in automobiles was analyzed. The water consumption by steel accounted for 73.6% and 80.5%, respectively. The fluctuation law of the water footprint was analyzed based on different power structures and steel water consumption coefficients. It was found that for low steel water consumption coefficient, wind power generation is conducive to slowing down the water consumption during the entire life cycle. In addition, a sensitivity analysis was performed for the FCEV and CNG under different fuel scenarios. Fuel technology and material structure have a significant impact on the total water footprint. The results of this study can provide guidance for the layout of the automobile industry and for water-saving measures in the future.

Social life cycle assessment of the nanoscale zero-valent iron synthesis process for application in contaminated site remediation.

Nanoscale zero-valent iron (nZVI) is the main nanomaterial used in environmental remediation processes. However, as with any remediation technique, the production and the use of nanomaterials can also cause environmental, economic, and social impacts. Thus, the present study investigated the social life cycle analysis (S-LCA) of nZVI production methods applied in environmental remediation. Three production methods of nZVI were selected for analysis: milling, reduction with sodium borohydride, and reduction with hydrogen gas. The social life cycle analysis was developed based on the ISO 14040 standard steps. Limits of the S-LCA system involve the stages of raw material extraction and manufacturing when not considering the use of nZVI postproduction. The analysis of social impact was conducted considering the involved stakeholders, through the application and improvement of an existing methodology and through the following procedures: characterization of social indicators according to a normalized scale, identification of the normalization factor for the indicators, employment of a social questionnaire, calculation of the total points in each impact subcategory (midpoint), calculation of the total points in the impact categories (endpoint), and calculation of the Social Index. The three production methods of nZVI result in significantly equal Social Indices. All methods were classified as socially sustainable according to the implemented methodology. The sensitivity analysis demonstrates the results dependent with the geographic location of the inventory data, while changes in the weighting can affect the Social Index results. Overall, this study significantly contributed to the state-of-the-art application of S-LCA in studies using nanomaterials; however, several limitations were also observed, and thus, steps for future development were suggested to future researches. In addition, this study improved the S-LCA methodology which can be used to assess the social impact of any product.

Effects of operating conditions on biogas production in an anaerobic digestion system of the food and beverage industry.

BACKGROUND: Food residuals (FR) were anaerobically biotransformed to produce biogases (e.g. methane and hydrogen), and different pre-treatment conditions, including particle size, oil content, pH and salt content, were controlled in this study. The bio-solids of a municipal solid waste (MSW) from a wastewater treatment plant were added to assess its effect on anaerobic transformation efficiency and gas yields. RESULTS: The breaking of FR and the application of MSW were effective in enhancing the transformation efficiency and yield of biogases. The energy transfer efficiency value of the combined FRs used in this study was probably 23%. However, it can be very cost effective to apply arbitrary proportions to treat two types of FR in the anaerobic digestion tank of a wastewater treatment plant. It was also found that the alkalinity and pH value were two major parameters that controlled the success of the transformation. About 0.16-0.17 kg of alkalinity was needed during the anaerobic digestion of 1 kg dry FR, but this requirement was decreased by the treatment applying MSW. Olive oil had higher reducing rates when used as a substitute for heat-oxidized oil to study the effect of oil content on methylation. CONCLUSION: The conditions for anaerobic digestion established in this study were practical for the digestion of FR in wastewater treatment plants in Taiwan. However, we nonetheless found that it was cost effective to use arbitrary proportions for both types of FR and integrate the anaerobic digestion process used in wastewater treatment plants. © 2020 Society of Chemical Industry.

Development of cost effective metal oxide semiconductor based gas sensor over flexible chitosan/PVP blended polymeric substrate.

In the present work, biodegradable and flexible chitosan/polyvinylpyrrolidone (CHP) polymeric substrate was fabricated by solvent casting method. This is a novel demonstration of the combination of natural polymer (chitosan) and synthetic polymer (PVP) for next-generation semiconductor device applications. The ZnO thin films were successfully synthesized on these polymeric substrates by facile drop-casting method for gas sensing applications. The hydrogen gas sensing properties of ZnO deposited on the polymeric substrate and SiO2 substrate show similar performance. The structural, morphological, optical, thermal, and tensile strength of the CHP substrate were studied using X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-visible spectroscopy, Derivative thermogravimetric analysis (DTG), and Universal testing machine (UTM), respectively. Our study suggests that the biodegradable CH/PVP flexible polymeric substrate provides a new way for the implementation of an eco-friendly green substrate in numerous electronic device applications.

Experimental Assessment of Lithium Hydride's Space Radiation Shielding Performance and Monte Carlo Benchmarking.

The harmful effects of space radiation pose a serious health risk to astronauts participating in future long-term missions. Such radiation effects must be considered in the design phase of space vessels as well as in mission planning. Crew radioprotection during long periods in deep space (e.g., transit to Mars) represents a major challenge, especially because of the strong restrictions on the passive shielding load allowed on-board the vessel. Novel materials with better shielding performance compared to the "gold standard" high-density polyethylene are therefore greatly needed. Because of the high hydrogen content of hydrides, lithium hydride has been selected as a starting point for further studies of promising candidates to be used as passive shielding materials. In the current experimental campaign, the shielding performance of lithium hydride was assessed by measuring normalized dose, primary beam attenuation and neutron ambient dose equivalent using 430 MeV/u 12C, 600 MeV/u 12C and 228 MeV proton beams. The experimental data were then compared to predictions from the Monte Carlo transport codes PHITS and GRAS. The experimental results show an increased shielding effectiveness of lithium hydride compared to reference materials like polyethylene. For instance, the attenuation length for 600 MeV/u 12C primary particles in lithium hydride is approximately 20% shorter compared to polyethylene. Furthermore, the comparison results between both transport codes indicates that the standard Tripathi-based total reaction cross-section model of PHITS cannot accurately reproduce the presented experimental data, whereas GRAS shows reasonable agreement.

The FAQUIRE Approach: FAst, QUantitative, hIghly Resolved and sEnsitivity Enhanced 1H, 13C Data.

The targeted analysis of metabolites in complex mixtures is a challenging issue. NMR is one of the major tools in this field, but there is a strong need for more sensitive, better-resolved, and faster quantitative methods. In this framework, we introduce the concept of FAst, QUantitative, hIghly Resolved and sEnsitivity enhanced (FAQUIRE) NMR to push forward the limits of metabolite NMR analysis. 2D 1H, 13C 2D quantitative maps are promising alternatives for enhancing the spectral resolution but are highly time-consuming because of (i) the intrinsic nature of 2D, (ii) the longer recycling times required for quantitative conditions, and (iii) the higher number of scans needed to reduce the level of detection/quantification to access low concentrated metabolites. To reach this aim, speeding up the recently developed QUantItative Perfected and pUre shifted HSQC (QUIPU HSQC) is an interesting attempt to develop the FAQUIRE concept. Thanks to the combination of spectral aliasing, nonuniform sampling, and variable repetition time, the acquisition time of 2D quantitative maps is reduced by a factor 6 to 9, while conserving a high spectral resolution thanks to a pure shift approach. The analytical potential of the new Quick QUIPU HSQC (Q QUIPU HSQC) is evaluated on a model metabolite sample, and its potential is shown on breast-cell extracts embedding metabolites at millimolar to submillimolar concentrations.

Assessment of the permeability properties of cryopreservation outer bags used in NHSBT.

This study was carried out to investigate leakage/transport across the bag material of six outer cryopreservation bags in common use within NHS Blood and Transplant. In order to do this two different leak testing procedures; coloured dye and hydrogen tracer gas, were used. The data obtained show that a coloured dye cannot permeate through the materials both at room temperature and following storage at liquid nitrogen temperature (- 196 °C). In addition, when filled with the smallest elemental molecule, hydrogen, in the form of a tracer gas, all of the bags only allowed trace amounts of hydrogen to escape, either through the seal or the bag material. The data indicated that each of the bag materials tested would be capable of preventing bacterial or viral cross-contamination as long as the material remained intact.

Municipal waste liquor treatment via bioelectrochemical and fermentation (H2 + CH4) processes: Assessment of various technological sequences.

In this paper, the anaerobic treatment of a high organic-strength wastewater-type feedstock, referred as the liquid fraction of pressed municipal solid waste (LPW) was studied for energy recovery and organic matter removal. The processes investigated were (i) dark fermentation to produce biohydrogen, (ii) anaerobic digestion for biogas formation and (iii) microbial fuel cells for electrical energy generation. To find a feasible alternative for LPW treatment (meeting the two-fold aims given above), various one- as well as multi-stage processes were tested. The applications were evaluated based on their (i) COD removal efficiencies and (ii) specific energy gain. As a result, considering the former aspect, the single-stage processes could be ranked as: microbial fuel cell (92.4%)> anaerobic digestion (50.2%)> hydrogen fermentation (8.8%). From the latter standpoint, an order of hydrogen fermentation (2277 J g-1 CODremoved d-1)> anaerobic digestion (205 J g-1 CODremoved d-1)> microbial fuel cell (0.43 J g-1 CODremoved d-1) was attained. The assessment showed that combined, multi-step treatment was necessary to simultaneously achieve efficient organic matter removal and energy recovery from LPW. Therefore, a three-stage system (hydrogen fermentation-biomethanation-bioelectrochemical cell in sequence) was suggested. The different approaches were characterized via the estimation of COD balance, as well.

Iron removal, energy consumption and operating cost of electrocoagulation of drinking water using a new flow column reactor.

The goal of this project was to remove iron from drinking water using a new electrocoagulation (EC) cell. In this research, a flow column has been employed in the designing of a new electrocoagulation reactor (FCER) to achieve the planned target. Where, the water being treated flows through the perforated disc electrodes, thereby effectively mixing and aerating the water being treated. As a result, the stirring and aerating devices that until now have been widely used in the electrocoagulation reactors are unnecessary. The obtained results indicated that FCER reduced the iron concentration from 20 to 0.3 mg/L within 20 min of electrolysis at initial pH of 6, inter-electrode distance (ID) of 5 mm, current density (CD) of 1.5 mA/cm2, and minimum operating cost of 0.22 US $/m3. Additionally, it was found that FCER produces H2 gas enough to generate energy of 10.14 kW/m3. Statistically, it was found that the relationship between iron removal and operating parameters could be modelled with R2 of 0.86, and the influence of operating parameters on iron removal followed the order: C0>t>CD>pH. Finally, the SEM (scanning electron microscopy) images showed a large number of irregularities on the surface of anode due to the generation of aluminium hydroxides.

Bioenergy and bioproducts from municipal organic waste as alternative to landfilling: a comparative life cycle assessment with prospective application to Mexico.

A life cycle assessment (LCA) of a four-stage biorefinery concept, coined H-M-Z-S, that converts 1 t of organic fraction of municipal solid waste (OFMSW) into bioenergy and bioproducts was performed in order to determine whether it could be an alternative to common disposal of OFMSW in landfills in the Mexican reality. The OFMSW is first fermented for hydrogen production, then the fermentates are distributed 40 % to the methane production, 40 % to enzyme production, and 20 % to the saccharification stage. From hydrogen and methane, up to 267 MJ and 204 kWh of gross heat and electricity were produced. The biorefinery proved to be self-sustainable in terms of power (95 kWh net power), but it presented a deficit of energy for heating services (-155 MJ), which was partially alleviated by digesting the wastes from the bioproducts stages (-84 MJ). Compared to landfill, biorefinery showed lower environmental impacts in global warming (down to -128 kg CO2-eq), ozone layer depletion (2.96 × 10-6 kg CFC11-eq), and photochemical oxidation potentials (0.011 kg C2H4-eq). The landfarming of the digestates increased significantly the eutrophication impacts, up to 20 % below the eutrophication from landfilling (1.425 kg PO4-eq). These results suggest that H-M-Z-S biorefinery could be an attractive alternative compared to conventional landfilling for the management of municipal solid wastes, although new alternatives and uses of co-products and wastes should be explored and tested. Moreover, the biorefinery system would benefit from the integration into the market chain of the bioproducts, i.e., enzymes and hydrolysates among others.

A Simple, Low-cost, and Robust System to Measure the Volume of Hydrogen Evolved by Chemical Reactions with Aqueous Solutions.

There is a growing research interest in the development of portable systems which can deliver hydrogen on-demand to proton exchange membrane (PEM) hydrogen fuel cells. Researchers seeking to develop such systems require a method of measuring the generated hydrogen. Herein, we describe a simple, low-cost, and robust method to measure the hydrogen generated from the reaction of solids with aqueous solutions. The reactions are conducted in a conventional one-necked round-bottomed flask placed in a temperature controlled water bath. The hydrogen generated from the reaction in the flask is channeled through tubing into a water-filled inverted measuring cylinder. The water displaced from the measuring cylinder by the incoming gas is diverted into a beaker on a balance. The balance is connected to a computer, and the change in the mass reading of the balance over time is recorded using data collection and spreadsheet software programs. The data can then be approximately corrected for water vapor using the method described herein, and parameters such as the total hydrogen yield, the hydrogen generation rate, and the induction period can also be deduced. The size of the measuring cylinder and the resolution of the balance can be changed to adapt the setup to different hydrogen volumes and flow rates.

The Assessment of Total Energy Expenditure During a 14-Day In-Season Period of Professional Rugby League Players Using the Doubly Labelled Water Method.

Rugby League is a high-intensity collision sport competed over 80 min. Training loads are monitored to maximize recovery and assist in the design of nutritional strategies although no data are available on the total energy expenditure (TEE) of players. We therefore assessed resting metabolic rate (RMR) and TEE in six Super League players over 2 consecutive weeks in-season including one game per week. Fasted RMR was assessed followed by a baseline urine sample before oral administration of a bolus dose of hydrogen (deuterium 2H) and oxygen (18O) stable isotopes in the form of water (2H218O). Every 24 hr thereafter, players provided urine for analysis of TEE via DLW method. Individual training load was quantified using session rating of perceived exertion (sRPE) and data were analyzed using magnitude-based inferences. There were unclear differences in RMR between forwards and backs (7.7 ± 0.5 cf. 8.0 ± 0.3 MJ, respectively). Indirect calorimetry produced RMR values most likely lower than predictive equations (7.9 ± 0.4 cf. 9.2 ± 0.4 MJ, respectively). A most likely increase in TEE from Week 1 to 2 was observed (17.9 ± 2.1 cf. 24.2 ± 3.4 MJ) explained by a most likelyincrease in weekly sRPE (432 ± 19 cf. 555 ± 22 AU), respectively. The difference in TEE between forward and backs was unclear (21.6 ± 4.2 cf. 20.5 ± 4.9 MJ, respectively). We report greater TEE than previously reported in rugby that could be explained by the ability of DLW to account for all match and training-related activities that contributes to TEE.