Environmental impact categories of hydrogen and ammonia driven transoceanic maritime vehicles: A comparative evaluation

In this study, carbon-free fuels -ammonia and hydrogen-are proposed to replace heavy fuel oils in the engines of maritime transportation vehicles. Also, it is proposed to use hydrogen and ammonia as dual fuels to quantify the reduction potential of greenhouse gas emissions. An environmental impact assessment of transoceanic tanker and transoceanic freight ship is implemented to explore the impacts of fuel substituting on the environment. In the life cycle analyses, the complete transport life cycle is taken into account from manufacture of transoceanic freight ship and tanker to production, transportation and utilization of hydrogen and ammonia in the maritime vehicles. Several hydrogen and ammonia production routes ranging from municipal waste to geothermal options are considered to comparatively evaluate environmentally benign methods. Besides global warming potential, environmental impact categories of marine sediment ecotoxicity and marine aquatic ecotoxicity are also selected in order to examine the diverse effects on marine environment. Being carbon-neutral fuels, ammonia and hydrogen, yield significantly minor global warming impacts during operation. The ecotoxicity impacts on maritime environment vary based on the production route of hydrogen and ammonia. The results imply that even hydrogen and ammonia are utilized as dual fuels in the engines, the global warming potential is quite lower in comparison with heavy fuel oil driven transoceanic tankers. Geothermal energy sourced hydrogen and ammonia fuelled transoceanic tankers release about 0.98 g and 1.65 g CO₂ eq. per tonne-kilometer, respectively whereas current conventional heavy fuel oil tanker releases about 5.33 g/tonne-kilometer CO₂ eq. greenhouse gas emissions.     

Life cycle cost analysis: A case study of hydrogen energy application on the Orkney Islands

Hydrogen can compensate for the intermittent nature of some renewable energy sources and encompass the options of supplying renewables to offset the use of fossil fuels. The integrating of hydrogen application into the energy system will change the current energy market. Therefore, this paper deploys the life cycle cost analysis of hydrogen production by polymer electrolyte membrane (PEM) electrolysis and applications for electricity and mobility purposes. The hydrogen production process includes electricity generated from wind turbines, PEM electrolyser, hydrogen compression, storage, and distribution by H₂ truck and tube trailer. The hydrogen application process includes PEM fuel cell stacks generating electricity, a H₂ refuelling station supplying hydrogen, and range extender fuel cell electric vehicles (RE-FCEVs). The cost analysis is conducted from a demonstration project of green hydrogen on a remote archipelago. The methodology of life cycle cost is employed to conduct the cost of hydrogen production and application. Five scenarios are developed to compare the cost of hydrogen applications with the conventional energy sources considering CO₂ emission cost. The comparisons show the cost of using hydrogen for energy purposes is still higher than the cost of using fossil fuels. The largest contributor of the cost is the electricity consumption. In the sensitivity analysis, policy supports such as feed-in tariff (FITs) could bring completive of hydrogen with fossil fuels in current energy market.     

Modeling of hydrogen production with a stand-alone renewable hybrid power system

Hydrocarbon resources adequately meet today’s energy demands. Due to the environmental impacts, renewable energy sources are high in the agenda. As an energy carrier, hydrogen is considered one of the most promising fuels for its high energy density as compared to hydrocarbon fuels. Therefore, hydrogen has a significant and future use as a sustainable energy system. Conventional methods of hydrogen extraction require heat or electrical energy. The main source of hydrogen is water, but hydrogen extraction from water requires electrical energy. Electricity produced from renewable energy sources has a potential for hydrogen production systems. In this study, an electrolyzer using the electrical energy from the renewable energy system is used to describe a model, which is based on fundamental thermodynamics and empirical electrochemical relationships. In this study, hydrogen production capacity of a stand-alone renewable hybrid power system is evaluated. Results of the proposed model are calculated and compared with experimental data. The MATLAB/Simscape^® model is applied to a stand-alone photovoltaic-wind power system sited in Istanbul, Turkey.     

Water-splitting mechanism analysis of Sr/Ca doped LaFeO3 towards commercial efficiency of solar thermochemical H2 production

Solar thermochemical (STC) technology utilizes the entire spectrum of solar energy to decompose water to produce hydrogen. This technology reduces carbonic fuels, nearly only producing hydrogen rather than hydrogen-oxygen mixture. However, low water-splitting activity of redox materials restricts improvement of water-hydrogen conversion ratio and fuel production efficiency. Recently, a kind of perovskite LaFeO₃ attracts attention, because of the good performance in photocatalysis hydrogen production. Nevertheless, how LaFeO₃ system works in STC water-splitting cycle is rarely studied. In this paper, the first principle method at density functional theory level is adopted to reveal the hydrogen production mechanism of perovskite LaFeO₃ doped with 25% Sr/Ca at A site. Hydrogen migration on material surface determines hydrogen generation rate. The activation energy of 25%-Ca-doped LaFeO₃ is relatively lower 150.09 kJ/mol. In addition, fuel production efficiency has been calculated. When water to hydrogen conversion ratio is 100%, solar-to-fuel efficiency can reach maximum 0.472. The effect of water-splitting kinetics on hydrogen production is also discussed. The results indicate that when T_red = T_oxi = T = 1200K and water to hydrogen conversion ratio is 10%, the dynamic efficiency of La_0.75Ca_0.25FeO₃ can reach 20%. This research can provide index for improving the hydrogen production performance of STC technology.     

Review of hydrogen storage techniques for on board vehicle applications

Hydrogen gas is increasingly studied as a potential replacement for fossil fuels because fossil fuel supplies are depleting rapidly and the devastating environmental impacts of their use can no longer be ignored. H₂ is a promising replacement energy storage molecule because it has the highest energy density of all common fuels by weight. One area in which replacing fossil fuels will have a large impact is in automobiles, which currently operate almost exclusively on gasoline. Due to the size and weight constraints in vehicles, on board hydrogen must be stored in a small, lightweight system. This is particularly challenging for hydrogen because it has the lowest energy density of common fuels by volume. Therefore, a lot of research is invested in finding a compact, safe, reliable, inexpensive and energy efficient method of H₂ storage. Mechanical compression as well as storage in chemical hydrides and absorption to carbon substrates has been investigated. An overview of all systems including the current research and potential benefits and issue are provided in the present paper.     

Hydrogen from solar energy,a clean energy carrier from a sustainable source of energy

Solar energy is going to play a crucial role in the future energy scenario of the world that conducts interests to solar-to-hydrogen as a means of achieving a clean energy carrier. Hydrogen is a sustainable energy carrier, capable of substituting fossil fuels and decreasing carbon dioxide (CO₂) emission to save the world from global warming. Hydrogen production from ubiquitous sustainable solar energy and an abundantly available water is an environmentally friendly solution for globally increasing energy demands and ensures long-term energy security. Among various solar hydrogen production routes, this study concentrates on solar thermolysis, solar thermal hydrogen via electrolysis, thermochemical water splitting, fossil fuels decarbonization, and photovoltaic-based hydrogen production with special focus on the concentrated photovoltaic (CPV) system. Energy management and thermodynamic analysis of CPV-based hydrogen production as the near-term sustainable option are developed. The capability of three electrolysis systems including alkaline water electrolysis (AWE), polymer electrolyte membrane electrolysis, and solid oxide electrolysis for coupling to solar systems for H₂ production is discussed. Since the cost of solar hydrogen has a very large range because of the various employed technologies, the challenges, pros and cons of the different methods, and the commercialization processes are also noticed. Among three electrolysis technologies considered for postulated solar hydrogen economy, AWE is found the most mature to integrate with the CPV system. Although substantial progresses have been made in solar hydrogen production technologies, the review indicates that these systems require further maturation to emulate the produced grid-based hydrogen.     

Electricity,hydrogen—competitors,partners?

Electricity, hydrogen—What they have in common, where they are unique.Electricity and hydrogen have in common that they are secondary energies which can be generated from any primary energy (raw materials). Once generated they are environmentally and climatically clean along the entire length of their respective energy conversion chains. Both electricity and hydrogen are grid delivered (with exceptions); they are interchangeable via electrolysis and fuel cell. Both are operational worldwide, although in absolutely dissimilar capacities. And their peculiarities? Electricity stores and transports information, hydrogen does not. Hydrogen stores and transports energy, electricity transports energy but does not store it (in large quantities). For long (i.e., continental) transport routes, hydrogen has advantages. The electricity sector is part of the established energy economy. Hydrogen, on the other hand, takes two pathways: one where it has been in use materially in the hydrogen economy almost since its discovery in the later 18th century; today, it is traded worldwide as a commodity up to an amount of some 50 million tonnes p.a., e.g., in methanol or ammonia syntheses, for fat hardening in the food industry, as a cleansing agent in glass or electronics manufacturing, and the like. And along the other pathway it serves as an energy carrier in the up coming hydrogen energy economy which started with the advent of the space launching business after WW II. Essentially, the hydrogen energy economy deals with the introduction of the, after electricity, now second major secondary energy carrier, hydrogen, together with its conversion technologies, e.g., fuel cells, into portable electronic equipment such as television cameras, laptops, cellular phones, etc., into the distributed stationary electricity and heat supply in the capacity range of kilowatts to megawatts, and into transport vehicles on earth, at sea, in the air, or space-borne. It is never a question of the energy carrier alone, be it either hydrogen or hydrogen reformat. On the contrary, environmentally and climatically clean hydrogen energy technologies along the entire length of the energy conversion chain, from production via storage, transport and distribution to, finally, end use, are what is of overarching importance. Of course, technologies are not energies, but they are as good as energies. Efficient energy technologies provide more energy services from less primary energy (raw materials). Energy efficiency gains are energies! Especially for energy poor, but technology-rich countries, efficiency gains compare well to indigenous energy sources! The trend is clearly visible: increasingly, the world is moving from national fuels to global fuels, and energy technologies serve as their opening valves. CO₂ capture and sequestration technologies bring hydrogen-dependent clean fossil fuels to life, and hydrogen supported fuel cell technology activates dormant virtual distributed power. Both technologies are key for the hydrogen energy economy which, thus, becomes the linchpin of future world energy.     

Political,economic and environmental impacts of biomass-based hydrogen

The purpose of this study is to assess the political, economic and environmental impacts of producing hydrogen from biomass. Hydrogen is a promising renewable fuel for transportation and domestic applications. Hydrogen is a secondary form of energy that has to be manufactured like electricity. The promise of hydrogen as an energy carrier that can provide pollution-free, carbon-free power and fuels for buildings, industry, and transport makes it a potentially critical player in our energy future. Currently, most hydrogen is derived from non-renewable resources by steam reforming in which fossil fuels, primarily natural gas, but could in principle be generated from renewable resources such as biomass by gasification. Hydrogen production from fossil fuels is not renewable and produces at least the same amount of CO₂ as the direct combustion of the fossil fuel. The production of hydrogen from biomass has several advantages compared to that of fossil fuels. The major problem in utilization of hydrogen gas as a fuel is its unavailability in nature and the need for inexpensive production methods. Hydrogen production using steam reforming methane is the most economical method among the current commercial processes. These processes use non-renewable energy sources to produce hydrogen and are not sustainable. It is believed that in the future biomass can become an important sustainable source of hydrogen. Several studies have shown that the cost of producing hydrogen from biomass is strongly dependent on the cost of the feedstock. Biomass, in particular, could be a low-cost option for some countries. Therefore, a cost-effective energy-production process could be achieved in which agricultural wastes and various other biomasses are recycled to produce hydrogen economically. Policy interest in moving towards a hydrogen-based economy is rising, largely because converting hydrogen into useable energy can be more efficient than fossil fuels and has the virtue of only producing water as the by-product of the process. Achieving large-scale changes to develop a sustained hydrogen economy requires a large amount of planning and cooperation at national and international alike levels.     

An experimental investigation on engine performance and emissions of a single cylinder diesel engine using hydrogen as inducted fuel and diesel as injected fuel with exhaust gas recirculation

Fast depletion of fossil fuels is demanding an urgent need to carry out research work to find out the viable alternative fuels for meeting sustainable energy demand with minimum environmental impact. In the future, our energy systems will need to be renewable and sustainable, efficient and cost-effective, convenient and safe. The technology for producing hydrogen from a variety of resources, including renewable, is evolving and that will make hydrogen energy system as cost-effective. Hydrogen safety concerns are not the cause for fear but they simply are different than those we are accustomed to with gasoline, diesel and other fossil fuels. For the time being full substitution of diesel with hydrogen is not convenient but use of hydrogen in a diesel engine in dual fuel mode is possible. So Hydrogen has been proposed as the perfect fuel for this future energy system. The experiment is conducted using diesel–hydrogen blend. A timed manifold induction system which is electronically controlled has been developed to deliver hydrogen on to the intake manifold. The solenoid valve is activated by the new technique of taking signal from the rocker arm of the engine instead of cam actuation mechanism. In the present investigation hydrogen-enriched air has been used in a diesel engine with hydrogen flow rate at 0.15 kg/h. As diesel is substituted and hydrogen is inducted, the NO_x emission is increased. In order to reduce NO_x emission an EGR system has been developed. In the EGR system a lightweight EGR cooler has been used instead of bulky heat exchanger. In this experiment performance parameters such as brake thermal efficiency, volumetric efficiency, BSEC are determined and emissions such as oxides of nitrogen, carbon dioxide, carbon monoxide, hydrocarbon, smoke and exhaust gas temperature are measured. Dual fuel operation with hydrogen induction coupled with exhaust gas recirculation results in lowered emission level and improved performance level compared to the case of neat diesel operation.     

A pioneering study of biomethane and hydrogen production from the wine industry in Brazil: Pollutant emissions,electricity generation and urban bus fleet supply

The thematic area studied in this paper considers environmental issues such as atmospheric pollution from the combustion of fossil fuels, and the environmental impacts from the generation of urban agricultural solid wastes. This study has estimated the potential for hydrogen and biogas production from solid urban waste (SUW) and wine waste from Bento Gonçalves, which is a region in Brazil with the largest wine throughput and subsequent waste generation, thus providing a potential high-energy feedstock. The resulting hydrogen and biogas are assumed to displace the existing fuels in the local bus fleet. The analytical work consisted of three scenarios - scenario 1: production of biogas using SUW, sourced exclusively from the municipality of Bento Gonçalves; Scenario 2: the possibility to supply SUW from Bento Gonçalves and surrounding cities, to produce biogas; Scenario 3: the possibility to use wine waste and SUW for biogas production. Scenario 3 showed the greatest energy yield with 37.9 Gg of biomethane produced per year, which can supply the entire public bus fleet of Bento Gonçalves. The resulting hydrogen production potential using steam reforming of biomethane is 1.09 E+08 Nm³H₂.d^?1 which can generate 2.62 TW h.year^?1 of electrical energy, avoiding approximate emissions of 355 ktonCO₂.year^?1. These findings indicate value in the production of biogas from urban and agricultural wastes, especially for the generation of methane, hydrogen and useful energy outputs. Its production from renewable and clean sources contributes to the gradual transformation of an economy currently dependent on non-renewable resources into a circular and renewable economy.     

Micro-algae cultivation for biofuels: Cost,energy balance,environmental impacts and future prospects

Micro-algae have received considerable interest as a potential feedstock for producing sustainable transport fuels (biofuels). The perceived benefits provide the underpinning rationale for much of the public support directed towards micro-algae research. Here we examine three aspects of micro-algae production that will ultimately determine the future economic viability and environmental sustainability: the energy and carbon balance, environmental impacts and production cost. This analysis combines systematic review and meta-analysis with insights gained from expert workshops.We find that achieving a positive energy balance will require technological advances and highly optimised production systems. Aspects that will need to be addressed in a viable commercial system include: energy required for pumping, the embodied energy required for construction, the embodied energy in fertilizer, and the energy required for drying and de-watering. The conceptual and often incomplete nature of algae production systems investigated within the existing literature, together with limited sources of primary data for process and scale-up assumptions, highlights future uncertainties around micro-algae biofuel production. Environmental impacts from water management, carbon dioxide handling, and nutrient supply could constrain system design and implementation options. Cost estimates need to be improved and this will require empirical data on the performance of systems designed specifically to produce biofuels. Significant (>50%) cost reductions may be achieved if CO₂, nutrients and water can be obtained at low cost. This is a very demanding requirement, however, and it could dramatically restrict the number of production locations available.     

Autothermal reforming of n-dodecane and desulfurized Jet-A fuel for producing hydrogen-rich syngas

Catalytic reforming is a technology to produce hydrogen and syngas from heavy hydrocarbon fuels in order to supply hydrogen to fuel cells. A lab-scale 2.5 kW_t autothermal reforming (ATR) system with a specially designed reformer and combined analysis of balance-of-plant was studied and tested in the present study. NiO–Rh based bimetallic catalysts with promoters of Ce, K, and La were used in the reformer. The performance of the reformer was studied by checking the hydrogen selectivity, CO_x selectivity, and energy conversion efficiency at various operating temperatures, steam to carbon ratios, oxygen to carbon ratios, and reactants' inlet temperatures. The experimental work firstly tested n-dodecane as the surrogate of Jet-A fuel to optimize operating conditions. After that, desulfurized commercial Jet-A fuel was tested at the optimized operating conditions. The design of the reformer and the catalyst are recommended for high performance Jet-A fuel reforming and hydrogen-rich syngas production.     

Effects of ammonia borane on the combustion of an ethanol droplet at atmospheric pressure

Adding compounds rich in hydrogen to liquid fuels has the potential to change combustion behavior and enhance performance. One potential additive is ammonia borane (AB), which contains 19.6 wt.% hydrogen and can be dissolved in anhydrous ethanol (up to 6.5 wt.%). The particular system studied here would have limited use due to energy density and stability but is studied as a model system. Single droplet combustion experiments were performed with AB concentrations in ethanol varying from 0 to 6 wt.%. Measurements performed using high speed (5 kHz) planar laser-induced fluorescence (PLIF) indicate that hydrogen gas addition from the decomposition of AB continues throughout the droplet burning process. The hydrogen addition leads to an increase in the D² law rate constant, k₀, of up to 16%. While AB (and residual material) participates throughout the combustion process, it dramatically impacts the combustion behavior at the end of the droplet lifetime as the concentration of AB residual grows within the droplet. This results in droplet shattering, causing fine atomization and rapid combustion of the remaining fuel. Boron is also oxidized in this short period of time, increasing the energy released. In combustors, droplet shattering could enhance mixing and increase combustion efficiency. Thus, the approach of adding compounds rich in hydrogen is a promising method to introduce H₂ gas to practical combustion systems, while enhancing performance.     

Nanometallic fuels for transportation: a well‐to‐wheels analysis

Nanometallic iron and aluminium, along with hydrogen and electricity, are among the proposed alternatives to the petroleum‐based fuels for future transportation. The advantages of the metallic fuels appear to be high volumetric energy densities and zero greenhouse gas emissions during the operation of the vehicle. However, nanometallic fuels do not exist in nature, and a well‐to‐wheel analysis of the fuel manufacture‐utilization system is required to quantify the energy consumption and assess the true environmental impact of the proposed alternative. The three‐component nanometallic fuel system consisting of a metal production process, a nanoparticle formulation process and the metal combustion process is analysed in this paper. The energy balance and the environmental impact are estimated for nanometallic iron and aluminium based systems. The sustainability of once‐through systems that do not involve recycle of combustion products is questionable because of resource limitations. A viable system for satisfying the transportation fuel demands will involve the reduction and recycle of the combustion products. A comparison of these nanometallic fuels with gasoline and hydrogen indicates that nanometallic fuels are the least efficient, with primary energy consumption greater than 11 MJ km^?1 compared to 0.625 MJ km^?1 for gasoline and 8.6 MJ km^?1 for hydrogen. The nanometallic fuels will also have the most severe impact of the three, with CO₂‐equivalent emissions of 13.44 billion tons year^?1 for iron and 21.1 billion tons year^?1 for aluminium as compared to approximately 0.8 billion tons year^?1 for gasoline. These emissions from nanometallic fuels are at least an order‐of‐magnitude higher than those for gasoline and hydrogen. The results of the analysis emphasize the need for well‐to‐wheel assessment for determining the true impact of technologies proposed as replacements for the current technologies. Copyright © 2006 John Wiley & Sons, Ltd.     

Alginate encapsulated nanobio-hybrid system enables improvement of photocatalytic biohydrogen production in the presence of oxygen

Bacterial encapsulation for the generation of fuels and other valuable chemicals through fermentation emerges as a novel biotechnological strategy that provides significant advantages over the use of free cells. In the present study, we established an optimal alginate encapsulated TiO₂/Escherichia coli hybrid system by varying the initial concentrations of alginate (2–5%) and initial inoculum concentration (OD₆₀₀ 0.5–2.5) to form the hydrogel beads for efficient production of hydrogen in the presence of oxygen with the given visible-light intensity of 2000 W m^?2. The maximum hydrogen production of 2.8 mmol H₂/mmol glucose was obtained with hydrogel beads consisting of 4% sodium alginate and initial inoculum with a cell density of 1.5 OD₆₀₀. Natural sunlight could also be used to produce hydrogen under the same optimized condition. The optimization of the encapsulated nano bio-hybrid system with respect to alginate and inoculum concentration allows for the enhancement of hydrogen production even in the presence of oxygen.     

Hydrogen production using fusion energy and thermochemical cycles

Thermochemical cycles for the production of synthetic fuels would be especially suited for operation in conjunction with controlled thermonuclear fusion reactors because of very high temperature energy which such reactors could supply. Furthermore, fusion energy when developed is considered to be an inexhaustible supply of energy. Several high-temperature, two step thermochemical cycles for the production of hydrogen are examined. A thermodynamic analysis of the Fe₃O₄-FeO, CrCl₃-CrCl₂, and UCl₄-UCl₃ pairs reveals the feasibility of the processes. A more detailed process analysis is given for the Fe₃O₄-FeO system using steam as the heat transfer medium for decomposing the higher valent metal oxide for oxygen production, and hydrolyzing the lower oxide for hydrogen production. The steam could be heated to high temperatures by refractory materials absorbing the 14 MeV neutrons in the blanket region of a fusion reactor. Process heat transfer and recovery could be accomplished by regenerative reactors. Proposed operating conditions, the energy balance, and the energy efficiency of water decomposition process are presented. With a fusion blanket temperature of 2500 K, thermal efficiencies for hydrogen production (HHV) of 74.4% may be obtained.     

A review on process modeling and design of biohydrogen

The current energy supply depends on fossil fuels which have increased carbon dioxide emissions leading to global warming and depleted non-renewable fossil fuels resources. Hydrogen (H₂) fuel could be an eco-friendly alternative since H₂ consumption only produces water. However, the overall impacts of the H₂ economy depend on feedstock types, production technologies, and process routes. The existing process technologies for H₂ production used fossil fuels encounter the escalation of fossil fuel prices and long-term sustainability challenges. Therefore, biohydrogen production from renewable resources like biomass wastes and wastewaters has become the focal development of a sustainable global energy supply. Different from other biohydrogen production studies, this paper emphasizes biohydrogen fermentation processes using different renewable sources and microorganisms. Moreover, it gives an overview of the latest advancing research in different biohydrogen process designs, modeling, and optimization. It also presents the biohydrogen production routes and kinetic modeling for biohydrogenation.     

Reduction in greenhouse gas and other emissions from ship engines: Current trends and future options

The impact of ship emission reductions can be maximised by considering climate, health and environmental effects simultaneously and using solutions fitting into existing marine engines and infrastructure. Several options available enable selecting optimum solutions for different ships, routes and regions. Carbon-neutral fuels, including low-carbon and carbon-negative fuels, from biogenic or non-biogenic origin (biomass, waste, renewable hydrogen) could resemble current marine fuels (diesel-type, methane and methanol). The carbon-neutrality of fuels depends on their Well-to-Wake (WtW) emissions of greenhouse gases (GHG) including carbon dioxide (CO₂), methane (CH₄), and nitrous oxide emissions (N₂O). Additionally, non-gaseous black carbon (BC) emissions have high global warming potential (GWP). Exhaust emissions which are harmful to health or the environment need to be equally removed using emission control achieved by fuel, engine or exhaust aftertreatment technologies. Harmful emission species include nitrogen oxides (NO_x), sulphur oxides (SO_x), ammonia (NH₃), formaldehyde, particle mass (PM) and number emissions (PN). Particles may carry polyaromatic hydrocarbons (PAHs) and heavy metals, which cause serious adverse health issues. Carbon-neutral fuels are typically sulphur-free enabling negligible SO_x emissions and efficient exhaust aftertreatment technologies, such as particle filtration. The combinations of carbon-neutral drop-in fuels and efficient emission control technologies would enable (near-)zero-emission shipping and these could be adaptable in the short- to mid-term. Substantial savings in external costs on society caused by ship emissions give arguments for regulations, policies and investments needed to support this development.     

Vacuum-assisted production of hydrogen and volatile fatty acids from lignocellulosic biomass derived from energy-crops pruning

Energy crops are promising sources of liquid biofuels, but large amounts of lignocellulosic biomass must be harvested from these cultivations, which have remained unexplored to produce additional chemicals and energy. In the present study, pruning derived from energy crops (Jatropha curcas and Ricinus communis) was evaluated, for the first time, as feedstock for the production of hydrogen (H₂) and volatile fatty acids (VFA) by anaerobic sludge. The highest H₂ production rate and yield were obtained with hydrolysate derived from J. curcas, producing up to 44.6 mL H₂/L-h and 66.6 mL H₂/g residue. Application of intermittent vacuum increased the production of H₂ (up to 5-fold) and VFA (up to 3-fold) as compared to fermentations performed without vacuum. This study proposes an integrative exploitation of these energy crops, by harnessing their pruning to produce extra fuels and chemicals within a bio-refinery framework.     

Modification of NaAlH4 properties using catalysts for solid-state hydrogen storage: A review

Energy is an essential requirement in our daily lives. Currently, most of our energy demands are fulfilled by fossil fuels. After 20 years, non-renewable fossil fuels are estimated to plummet rapidly. The world will face energy shortage and will seek for a new environmental method of energy generation for transportation, economy and application. Hydrogen is a fascinating energy carrier that is considered as ‘hydrogen economy’ for the future. The key challenge in developing the hydrogen economy is the context of hydrogen storage. Storing hydrogen via the solid-state method has received special attention and consideration because of its safety and larger storage capacity. A light complex hydride, NaAlH₄, is considered as an attractive material for solid-state hydrogen storage owing to its high hydrogen capacity, bulk in availability and low cost. Sluggish sorption kinetics and poor reversibility have driven research into various catalysts to enhance its hydrogen storage properties. This review article examines the development of different catalysts and their effects on the hydrogen storage properties of NaAlH₄. The addition of catalyst offers synergistic catalytic effect on the dehydrogenation performance of NaAlH₄. Doping NaAlH₄ with catalyst promote promising results such as lower decomposition temperature, improved kinetics and reduced activation energy. Superior performance on the dehydrogenation performance of NaAlH₄ doping with the catalyst may be due to the nanosized catalyst particle and in situ formed active species that may serve as nucleation sites at the surface of the NaAlH₄ matrix and benefiting the kinetics properties of NaAlH₄.