Life cycle assessment of three types of hydrogen production methods using solar energy

A comprehensive life cycle assessment (LCA) is carried out for three methods of hydrogen production by solar energy: hydrogen production by PEM water electrolysis coupling photothermal power generation, hydrogen production by PEM water electrolysis coupling photovoltaic power generation, and hydrogen production by thermochemical water splitting method using S–I cycle coupling solar photothermal technology. The assessment also contains an evaluation of four environmental factors which are global warming potential, acidification potential, ozone depletion potential, and nutrient enrichment potential. After conducting a quantitative analysis of all three methods with environmental factors being considered, a conclusion has been drawn: The global warming potential and the acidification potential of the thermochemical water splitting by S–I cycle coupling solar photothermal technology are 1.02 kg CO₂-eq and 6.56E-3 kg SO₂-eq. And this method has significant advantages in the environmental impact of the whole ecosystem.     

Life cycle assessment of hydrogen supply chain with special attention on hydrogen refuelling stations

The controversial and highly emotional discussion about biofuels in recent years has shown that greenhouse gas² (GHG) emissions can only be evaluated in an acceptable way by carrying out a full life cycle assessment (LCA) taking the overall life cycle including all necessary pre-chains into consideration. Against this background, the goal of this paper is it to analyse the overall life cycle of a hydrogen production and provision. A state of the art hydrogen refuelling station in Hamburg/Germany opened in February 2012 is therefore taken into consideration. Here at least 50% hydrogen from renewable sources of energy is produced on-site by water electrolysis based on surplus electricity from wind (mainly offshore wind parks) and water. The remaining other 50% of hydrogen to be sold by this station mainly to hydrogen-fuelled buses is provided by trucks from a large-scale production plant where hydrogen is produced from methane or glycerol as a by-product of the biodiesel production. These two pathways are compared within the following explanations with hydrogen production from biomass and from coal. The results show that – with the goal of reducing GHG emissions on a life cycle perspective – hydrogen production based on a water electrolysis fed by electricity from the German electricity mix should be avoided. Steam methane reforming is more promising in terms of GHG reduction but it is still based on a finite fossil fuel. For a climatic sound provision of hydrogen as a fuel electricity from renewable sources of energy like wind or biomass should be used.     

Life cycle energy and environmental assessment of bio-CNG utilization from cassava starch wastewater treatment plants in Thailand

Global warming, energy security, and the rising costs of oil have added a greater driving force to the development of feasible alternatives to petroleum-based transportation fuels. In parallel, wastes and wastewater generated from various industries should be avoided or converted to energy more in the future in order to reduce environmental problems and provide additional sources of energy. In this aspect, biogas plant is an effective option where gas is produced biologically by the fermentation of animal dungs, sewage, and agricultural residues. To utilize biogas as a transportation fuel, raw biogas has to undergo two major processes: cleaning and upgrading, to achieve natural gas quality. The upgraded biogas (so called bio-methane or bio-CNG) is considered green fuel with respect to environment, climate, and human health. However, the resulting bio-CNG from the processes still needs to be evaluated in terms of greenhouse gas emissions and energy aspects. This paper presents the integrated life cycle energy and environmental assessment of compressed bio-methane gas (CBG or bio-CNG) generated from cassava starch wastewater treatment plant in Thailand. The functional units were set to be 1 MJ of bio-CNG and 1 km of vehicle driven. The system boundary covered six main steps: digestion, purification and upgrading, compression, distribution, refueling, and combustion. The energy analysis result showed that the net energy ratio was higher than one, indicating a net energy gain. For the greenhouse gases aspect, the results showed that the biogas production and biogas upgrading step had the highest impact due to methane loss and high energy consumption. Comparing with other fuels, the global warming potential of bio-CNG was lower than those of fossil-based CNG and gasoline.     

Harmonised life-cycle indicators of nuclear-based hydrogen

When comparing the life-cycle environmental performance of hydrogen energy systems, significant concerns arise due to potential methodological inconsistencies between case studies. In this regard, protocols for harmonised life cycle assessment (LCA) of hydrogen energy systems are currently available to mitigate these concerns. These protocols have already been applied to conventional hydrogen from steam methane reforming as well as to a large number of both fossil and renewable hydrogen options, allowing robust comparisons between them. However, harmonised life-cycle indicators of nuclear-based hydrogen options are not yet available in the literature. This study fills this gap by using the recently developed software GreenH₂armony® to calculate the harmonised carbon, energy and acidification footprints of nuclear-based hydrogen produced through different pathways (viz., low-temperature electrolysis, high-temperature electrolysis, and thermochemical cycles). Overall, the harmonised case studies of nuclear-based hydrogen show a generally good performance in terms of carbon footprint and acidification, but an unfavourable performance in terms of non-renewable energy footprint.     

Life-cycle performance of indirect biomass gasification as a green alternative to steam methane reforming for hydrogen production

The environmental performance of hydrogen production via indirect gasification of poplar biomass was evaluated following a Life Cycle Assessment approach. Foreground data for the study were provided mainly from process simulation. The main subsystems and processes that contribute to the environmental impacts were identified. Thus, poplar production and direct emissions to air from the processing plant were found to be the main sources of environmental impact. Furthermore, a favourable (positive) life-cycle energy balance was estimated for the gasification-based system.     

Life cycle assessment of hydrogen production by methane decomposition using carbonaceous catalysts

Methane decomposition to yield hydrogen and carbon (CH₄ ? 2H₂ + C) is one of the cleanest alternatives, free of CO₂ emissions, for producing hydrogen from fossil fuels. This reaction can be catalyzed by metals, although they suffer a fast deactivation process, or by carbonaceous materials, which present the advantage of producing the catalyst from the carbon obtained in the reaction. In this work, the environmental performance of methane decomposition catalyzed by carbonaceous catalysts has been evaluated through Life Cycle Assessment tools, comparing it to other decomposition processes and steam methane reforming coupled to carbon capture systems. The results obtained showed that the decomposition using the autogenerated carbonaceous as catalyst is the best option when reaction conversions higher than 65% are attained. These were confirmed by 2015 and 2030 forecastings. Moreover, its environmental performance is highly increased when the produced carbon is used in other commercial applications. Thus, for a methane conversion of 70%, the application of 50% of the produced carbon would lead to a virtually zero-emissions process.     

Energy intensity and greenhouse gas emission of a purchase in the retail park service sector: An integrative approach

The aim of this paper is to describe the energetic metabolism of a retail park service system under an integrative approach. Energy flow accounting was applied to a case study retail park in Spain, representative of the sector across Europe, after redefining the functional unit to account for both direct energy use (buildings, gardens and outdoor lighting) and indirect energy use (employee and customer transportation). A life cycle assessment (LCA) was then undertaken to determine energy global warming potential (GWP) and some energy intensity and greenhouse gases (GHG) emission indicators were defined and applied. The results emphasise the importance of service systems in global warming policies, as a potential emission of 9.26 kg CO₂/purchase was obtained for the case study, relating to a consumption of 1.64 KOE of energy, of which 21.9% was spent on buildings and 57.9% on customer transportation. Some strategies to reduce these emissions were considered: increased supply, energy efficiency, changes in distribution of modes of transport, changes in location and changes in the mix of land uses. A combination of all of these elements in a new retail park could reduce GHG emissions by more than 50%, as it is planning strategies, which seem to be the most effective.     

Life cycle assessment of various hydrogen production methods

A comprehensive life cycle assessment (LCA) is reported for five methods of hydrogen production, namely steam reforming of natural gas, coal gasification, water electrolysis via wind and solar electrolysis, and thermochemical water splitting with a Cu–Cl cycle. Carbon dioxide equivalent emissions and energy equivalents of each method are quantified and compared. A case study is presented for a hydrogen fueling station in Toronto, Canada, and nearby hydrogen resources close to the fueling station. In terms of carbon dioxide equivalent emissions, thermochemical water splitting with the Cu–Cl cycle is found to be advantageous over the other methods, followed by wind and solar electrolysis. In terms of hydrogen production capacities, natural gas steam reforming, coal gasification and thermochemical water splitting with the Cu–Cl cycle methods are found to be advantageous over the renewable energy methods.     

Low-carbon energy transition with the sun and forest: Solar-driven hydrogen production from biomass

There is a need to derive hydrogen from renewable sources, and the innovative stewardship of two natural resources, namely the Sun and forest, could provide a new pathway. This paper provides the first comparative analysis of solar-driven hydrogen production from environmental angles. A novel hydrogen production process proposed in this paper, named Solar-Driven Advanced Biomass Indirect-Gasification (SABI-Hydrogen), shows promise toward achieving continuous operation and scalability, the two key challenges to meet future energy needs. The calculated Global Warming Potential for 1 kg of solar-driven hydrogen production is 1.04 kg CO₂-eq/kg H₂, less than half of the current biomass gasification process which emits 2.67 kg CO₂-eq/kg H₂. Further, SABI-Hydrogen demonstrates the least-carbon intensive pathway among all current hydrogen production methods. Thus, solar-driven hydrogen production from biomass could lead to a sustainable supply, essential for a low-carbon energy transition.     

Harmonising methodological choices in life cycle assessment of hydrogen: A focus on acidification and renewable hydrogen

The environmental sustainability of hydrogen energy systems is often evaluated through Life Cycle Assessment (LCA). In particular, environmental suitability is usually determined by comparing the life-cycle indicators calculated for a specific hydrogen energy system with those of a reference system (e.g., conventional hydrogen from steam methane reforming, SMR-H₂). In this respect, harmonisation protocols for comparative LCA of hydrogen energy systems have recently been developed in order to avoid misleading conclusions in terms of carbon footprints and cumulative energy demand. This article expands the scope of these harmonisation initiatives by addressing a new life-cycle indicator: acidification. A robust protocol for harmonising the acidification potential of hydrogen energy systems is developed and applied to both SMR-H₂ and a sample of case studies of renewable hydrogen. According to the results, unlike other energy systems, there is no correlation between acidification and carbon footprint in the case of hydrogen energy systems, which prevents the estimation of harmonised acidification results from available harmonised carbon footprints. Nevertheless, an initial library of harmonised life-cycle indicators of renewable hydrogen is now made available.     

Life cycle sustainability assessment of hydrogen from biomass gasification: A comparison with conventional hydrogen

Hydrogen is a key product for a cleaner energy sector. However, the suitability of the different hydrogen production options should be checked from a life-cycle perspective. The Life Cycle Sustainability Assessment (LCSA) methodology is helpful for this purpose, allowing a thorough interpretation of a product system's performance by integrating economic, environmental and social indicators. This work presents an LCSA of renewable hydrogen from biomass gasification, and its sustainability benchmarking against conventional hydrogen from steam methane reforming. Environmental (global warming and acidification), economic (levelised cost) and social (child labour, gender wage gap, and health expenditure) life-cycle indicators are characterised and jointly interpreted. The results show that hydrogen from biomass gasification cannot yet be thoroughly considered a sustainable alternative to conventional hydrogen mainly due to economic and social concerns. However, improvement actions leading to an increase in process efficiency would significantly enhance the system's performance in each of the three sustainability dimensions.     

Life cycle assessment of hydrogen production from biomass gasification. Evaluation of different Spanish feedstocks

Gasification of biomass can be used for obtaining hydrogen reducing the total greenhouse gases emissions due the fixation of CO₂ during photosynthetic processes. The kind of raw materials is an important variable since has a great influence on the energy balance and environmental impacts. Wastes from forestry are considered as the most appropriate raw materials since they do not compete for land. The aim of this work is to determine the environmental feasibility of four Spanish lignocellulosic wastes (vine and almond pruning and forest waste coming from pine and eucalyptus plantation) for the production of hydrogen through gasification. LCA methodology was applied using global warming potential, acidification, eutrophication and the gross energy necessary for the production of 1 Nm³ of hydrogen as impact categories. As expected, the use of biomass instead of natural gas leads to the reduction of CO₂ emissions. Regarding to the different feedstocks, biomass coming from forestry is more environmental-friendly since does not need cropping procedures. Finally, the distribution of environmental charges between pruning wastes and fruits (grape and almond) and the use of obtained by-products have a great influence, reducing the environmental impacts.     

Exergoenvironmental analysis of a steam methane reforming process for hydrogen production

Steam methane reforming (SMR) is one of the most promising processes for hydrogen production. Several studies have demonstrated its advantages from the economic viewpoint. Nowadays process development is based on technical and economical aspects; however, in the near future, the environmental impact will play a significant role in the design of such processes. In this paper, an SMR process is studied from the viewpoint of overall environmental impact, using an exergoenvironmental analysis. This analysis presents the combination of exergy analysis and life cycle assessment. Components where chemical reactions occur are the most important plant components from the exergoenvironmental point of view, because, in general, there is a high environmental impact associated with these components. This is mainly caused by the exergy destruction within the components, and this in turn is mainly due to the chemical reactions. The obtained results show that the largest potential for reducing the overall environmental impact is associated with the combustion reactor, the steam reformer, the hydrogen separation unit and the major heat exchangers. The environmental impact in these components can mainly be reduced by improving their exergetic efficiency. A sensitivity analysis for some important exergoenvironmental variables is also presented in the paper.     

Environmental and energy life cycle analyses of passenger vehicle systems using fossil fuel-derived hydrogen

Hydrogen energy utilization is expected due to its environmental and energy efficiencies. However, many issues remain to be solved in the social implementation of hydrogen energy through water electrolysis. This analyzes and compares the energy consumption and GHG emissions of fossil fuel-derived hydrogen and gasoline energy systems over their entire life cycle. The results demonstrate that for similar vehicle weights, the hydrogen energy system consumes 1.8 MJ/km less energy and emits 0.15 kg-CO 2 eq./km fewer GHG emissions than those of the gasoline energy system. Hydrogen derived from fossil fuels may contribute to future energy systems due to its stable energy supply and economic efficiency. Lowering the power source carbon content also improved the environmental and energy efficiencies of hydrogen energy derived from fossil fuels.     

Gasification process of palm kernel shell to fuel gas: Pilot-scale experiment and life cycle analysis

This research demonstrates a palm kernel shell gasification system for producing fuel gas, also known as producer gas. Using air as an oxidant, the gasification process converts palm kernel shells into fuel gas which contains combustible gases, such as hydrogen, carbon monoxide, and methane with nitrogen dominating the composition of the gas. This fuel gas can supply heat via direct combustion or generate electricity for fossil fuel substitution of an internal combustion engine. As a biomass-derived gas, the fuel gas is characterized as carbon-neutral inherently. During the conversion process, the system needs electricity to power the screw feeder, air blowers, and cooling-water pumps, and to rotate the gasifier's bottom plate to take the char out. Based on the experiments, mass balance, and energy balance calculations, this study examines the global warming, acidification, and eutrophication potential using the openLCA v1.10.3 software and Environmental Footprint (MID-Point indicator) database for impacts assessment when the system is operated in Indonesia and Malaysia with various electricity sources. It is found that the feedstock contributed most of the global warming potential and eutrophication potential, while the electricity dominated the acidification potential. This study recommends operation at a lower equivalent ratio to reduce environmental impacts.     

A life cycle impact analysis of various hydrogen production methods for public transportation sector

Reducing greenhouse gas emissions is an important task to reduce the adverse effects of climate change. A large portion of greenhouse gas emissions apparently originates from the transportation sector. Therefore, adopting cleaner technologies with lower emission footprints has become vital. For this reason, in this study, a life cycle impact analysis of hydrogen production technologies as an alternative to fossil fuels and the utilization of hydrogen in fuel cell electric buses is carried out. According to the results of this study, the operational contributions of internal combustion engines have a significant impact on life cycle impact analysis indicators. The global warming potentials of clean hydrogen production technologies result in much lower results compared to conventional hydrogen production technologies. Also, almost all indicators for biohydrogen production technologiess yield lower results because of the wastewater removal. The global warming potential results of hydrogen production methods are found to be 6.8, 1.9, 2.1, 0.5, 0.2, and 7.9 kg CO₂ eq./kg H₂ for PV electrolysis, wind electrolysis, high temperature electrolysis, dark fermentation, photo fermentation and conventional hydrogen production, respectively. However, the chemicals used in PV and wind turbine production increased the ecotoxicological indicators. On the other hand, hydrogen utilization in buses is a better option environmentally. The global warming potentials for PV electrolysis, wind electrolysis, high temperature electrolysis, dark fermentation, photo fermentation, conventional hydrogen, compressed natural gas bus, and diesel bus are found to be 0.060, 0.016, 0.018, 0.007, 0.006, 0.053, 0.082, and 0.125 kg CO₂ eq./p.km, respectively. The results are especially important in terms of reducing the effects at the source and optimizing the systems.     

Synergistic roles of off-peak electrolysis and thermochemical production of hydrogen from nuclear energy in Canada

Hydrogen as a clean energy carrier is frequently identified as a major solution to the environmental problem of greenhouse gases, resulting from worldwide dependence on fossil fuels. However, most of the world's hydrogen (about 96%) is currently produced from fossil fuels, which does not address the issue of greenhouse gases. Although there is a large motivation of the “hydrogen economy”, for improvement of urban air quality, energy security, and integration of intermittent renewable energy sources, CO₂ free energy sources are critical to hydrogen becoming a significant energy carrier. Two technologies, applied in tandem, have a promising potential to generate hydrogen without leading to greenhouse gas emissions: 1) electrolysis and 2) thermochemical decomposition of water. This paper will investigate their unique complementary roles to reduce costs of hydrogen production. Together they have a unique potential to serve both de-centralized hydrogen needs in periods of low-demand electricity, and centralized base-load production from a nuclear station. Thermochemical methods have a significantly higher thermal efficiency, but electrolysis can take advantage of low electricity prices during off-peak hours, as well as intermittent and de-centralized supplies like wind, solar or tidal power. By effectively linking these systems, water-based production of hydrogen can become more competitive against the predominant existing technology, SMR (steam-methane reforming).     

Optimized electrolyzer operation: Employing forecasts of wind energy availability,hydrogen demand,and electricity prices

One of the main advantages of fuel cell based mobility over other sustainable mobility concepts is the flexible production of hydrogen via electrolysis. To date, it is unclear how electrolysis at hydrogen refueling stations should be operated in order to achieve the lowest possible costs despite the constraints of hydrogen demand. This study proposes and evaluates an intelligent operating strategy for electrolysis capable of exploiting times of low electricity prices while participating in the spot market and maximizing wind energy utilization when combined with a wind farm. This strategy is based on a simulation model considering imperfect forecasts (e.g. of wind availability or energy prices) and non-linear electrolyzer behavior. Results show that this approach reduces hydrogen production costs by up to 9.2% and increases wind energy utilization by up to 19%, respectively.     

Life cycle assessment of hydrogen fuel cell and gasoline vehicles

A life cycle assessment of hydrogen and gasoline vehicles, including fuel production and utilization in vehicles powered by fuel cells and internal combustion engines, is conducted to evaluate and compare their efficiencies and environmental impacts. Fossil fuel and renewable technologies are investigated, and the assessment is divided into various stages.     

Role of hydrogen storage in renewable energy management for Ontario

Effective energy storage and management is needed to manage intermittent renewable energy systems. Several jurisdictions around the world are planning to reduce or close their coal power plants to allow for renewable energy expansion, such as Ontario, Canada. Hydrogen storage, which is a promising energy storage option, is capable of meeting energy requirements that will arise from the shutdown of coal plants. In this paper, both economic and environmental feasibility of a hydrogen system linked with wind and hydroelectric plants in Ontario will be investigated. The Princefarm wind power plant and Beck1 hydro plant with production capacities of 189 MW and 490 MW, respectively, are analyzed in a case study for comparison purposes. The environmental analysis demonstrates the advantageous role of hydrogen storage and energy conversion. The overall system life-cycle yields 31.02 g CO₂ eq per 1 kW h power output of the system when hydrogen energy storage is adopted. The payback periods of the systems linked with the Princefarm and Beck1 are also analyzed and found to be about 17 years.