Life-cycle analysis of greenhouse gas emission and energy efficiency of hydrogen fuel cell scooters

The well-to-wheels (WTW) analysis of energy conservation and greenhouse gas emission of advanced scooters associated with new transportation fuels is studied in the present work. Focus is placed on fuel cell scooter technologies, while the gasoline-powered scooter equipped with an internal combustion engine (ICE) serves as a reference technology. The effect of various pathways of hydrogen production on the well-to-tank (WTT) efficiency for energy is examined. Both near-term and long-term hydrogen production options are explored, such as purification of coke oven gas (COG), steam reforming of natural gas, water electrolysis by generation mix and renewable electricity, and gasification of herbaceous biomass. Then, the WTW efficiency of fuel cell scooters for various hydrogen production options is compared with that of the conventional ICE scooters and electric scooters. Results showed that the fuel cell scooters fueled with COG-based hydrogen could achieve the highest reduction benefits in energy consumption and GHG emission. Finally, the potential for hydrogen production from COG resulting from the coking process in steelworks is evaluated, which is anticipated as a near-term hydrogen production for helping transition to a hydrogen energy economy in Taiwan.     

Biomass gasification for sustainable energy production: A review

Gasification process is considered as one of the best routes of energy recovery from biomass by producing syngas mostly including H₂, CO, and CH₄. Biomass as the main renewable energy resources has great advantages regarding its diversity, availability, and sustainability for supplying energy needs in heat, electricity production, biofuel production for transportation, etc. Various gasifiers based on the gasifying process and agents have been examined. This paper reviewed the theory of biomass gasification by comparing and analyzing different gasification models-designs and configurations, also different operational conditions. It aimed to bring a holistic approach for hydrogen rich syngas production based on the present technologies, techno-economic analysis, and industrial/commercialization pathways. The biomass gasification technologies need to be improved for hydrogen production regarding the global environmental and economic issues. The review provided better insights into the enhancement of syngas production from biomass.     

Lifecycle performance assessment of fuel cell/battery electric vehicles

This paper has performed an assessment of lifecycle (as known as well-to-wheels, WTW) greenhouse gas (GHG) emissions and energy consumption of a fuel cell vehicle (FCV). The simulation tool MATLAB/Simulink is employed to examine the real-time behaviors of an FCV, which are used to determine the energy efficiency and the fuel economy of the FCV. Then, the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model is used to analyze the fuel-cycle energy consumption and GHG emissions for hydrogen fuels. Three potential pathways of hydrogen production for FCV application are examined, namely, steam reforming of natural gas, water electrolysis using grid electricity, and water electrolysis using photovoltaic (PV) electricity, respectively. Results show that the FCV has the maximum system efficiency of 60%, which occurs at about 25% of the maximum net system power. In addition, the FCVs fueled with PV electrolysis hydrogen could reduce about 99.2% energy consumption and 46.6% GHG emissions as compared to the conventional gasoline vehicles (GVs). However, the lifecycle energy consumption and GHG emissions of the FCVs fueled with grid-electrolysis hydrogen are 35% and 52.8% respectively higher than those of the conventional GVs. As compared to the grid-based battery electric vehicles (BEVs), the FCVs fueled with reforming hydrogen from natural gas are about 79.0% and 66.4% in the lifecycle energy consumption and GHG emissions, respectively.     

Techno-economic assessment of hydrogen production processes for the hydrogen economy for the short and medium term

Hydrogen is expected to play a significant role in the future energy system. A key enabler to a hydrogen-including economy will be the development and deployment of processes that can produce hydrogen whilst satisfying the criteria for sustainability, i.e. economic competitiveness, environmental protection and security of energy supply. This paper evaluates selected hydrogen production processes based on natural gas steam reforming, coal and biomass gasification and water electrolysis. These options are expected to play a significant role in the short to medium term. Industrial large-scale processes, using natural gas and coal, will constitute the most important routes. However, increasing prices for natural gas are likely to make coal gasification more competitive. Biomass gasification could become important if present technological barriers are overcome. Electrolytic hydrogen, however, will likely be practical for niche applications in the short term due to the high electricity costs, especially when electricity is generated by renewable energy sources.     

Design of an integrated process for simultaneous chemical looping hydrogen production and electricity generation with CO2 capture

This study was aimed at proposing a novel integrated process for co-production of hydrogen and electricity through integrating biomass gasification, chemical looping combustion, and electrical power generation cycle with CO₂ capture. Syngas obtained from biomass gasification was used as fuel for chemical looping combustion process. Calcium oxide metal oxide was used as oxygen carrier in the chemical looping system. The effluent stream of the chemical looping system was then transferred through a bottoming power generation cycle with carbon capture capability. The products achieved through the proposed process were highly-pure hydrogen and electricity generated by chemical looping and power generation cycle, respectively. Moreover, LNG cold energy was used as heat sink to improve the electrical power generation efficiency of the process. Sensitivity analysis was also carried out to scrutinize the effects of influential parameters, i.e., carbonator temperature, steam/biomass ratio, gasification temperature, gas turbine inlet stream temperature, and liquefied natural gas (LNG) flow rate on the plant performance. Overall, the optimum heat integration was achieved among the sub-systems of the plant while a high energy efficiency and zero CO₂ emission were also accomplished. The findings of the present study could assist future investigations in analyzing the performance of integrated processes and in investigating optimal operating conditions of such systems.     

Multi-objective,multi-period optimization of biomass conversion technologies using evolutionary algorithms and mixed integer linear programming (MILP)

The design and operation of energy systems are key issues for matching energy supply and demand. A systematic procedure, including process design and energy integration techniques for sizing and operation optimization of poly-generation technologies is presented in this paper. The integration of biomass resources as well as a simultaneous multi-objective and multi-period optimization, are the novelty of this work. Considering all these concepts in an optimization model makes it difficult to solve. The decomposition approach is used to deal with this complexity.Several options for integrating biomass in the energy system, namely back pressure steam turbines, biomass rankine cycles (BRC), biomass integrated gasification gas engines (BIGGE), biomass integrated gasification gas turbines, production of synthetic natural gas (SNG) and biomass integrated gasification combined cycles (BIGCC), are considered in this paper. The goal is to simultaneously minimize costs and CO₂ emission using multi-objective evolutionary algorithms (EMOO) and Mixed Integer Linear Programming (MILP).Finally the proposed model is demonstrated by means of a case study. The results show that the simultaneous production of electricity and heat with biomass and natural gas are reliable upon the established assumptions. Furthermore, higher primary energy savings and CO₂ emission reduction, 40%, are obtained through the gradual increase of renewable energy sources as opposed to natural gas usage. However, higher economic profitability, 52%, is achieved with natural gas-based technologies.     

The impact of carbon sequestration on the production cost of electricity and hydrogen from coal and natural-gas technologies in Europe in the medium term

Carbon sequestration is a distinct technological option with a potential for controlling carbon emissions; it complements other measures, such as improvements in energy efficiency and utilization of renewable energy sources. The deployment of carbon sequestration technologies in electricity generation and hydrogen production will increase the production costs of these energy carriers. Our economic assessment has shown that the introduction of carbon sequestration technologies in Europe in 2020, will result in an increase in the production cost of electricity by coal and natural gas technologies of 30–55% depending on the electricity-generation technology used; gas turbines will remain the most competitive option for generating electricity; and integrated gasification combined cycle technology will become competitive. When carbon sequestration is coupled with natural-gas steam reforming or coal gasification for hydrogen production, the production cost of hydrogen will increase by 14–16%. Furthermore, natural-gas steam reforming with carbon sequestration is far more economically competitive than coal gasification.     

CO2 emission balances for different black liquor gasification biorefinery concepts for production of electricity or second-generation liquid biofuels

Black liquor gasification (BLG) is currently being developed as an alternative technology for energy and chemical recovery at chemical pulp mills. This study examines how different assumptions regarding systems surrounding the pulp mill affect the CO₂ emission balances for different BLG concepts. The syngas from the gasification process can be used for different applications; this study considers production of renewable motor fuels and electricity generation. Both a market pulp mill and an integrated pulp and paper mill are considered as host mill for the BLG plant. Furthermore, the consequences of limited availability of biomass are shown, i.e., increasing the use of biomass in a mill is not necessarily CO₂-neutral. The results show that the potential to reduce CO₂ emissions by introducing BLG is generally much higher for a market pulp mill than for an integrated pulp and paper mill. Electricity generation from the syngas is favoured when assuming high grid electricity CO₂ emissions where as motor fuel production is favoured when assuming low grid electricity CO₂ emissions. When considering the consequences of limited availability of biomass, the CO₂ emission balances are strongly affected, in some cases changing the results from a decrease to an increase of the CO₂ emissions.     

Comparative life cycle assessment of hydrogen pathways from fossil sources in China

Emissions of multiple hydrogen production pathways from fossil sources were evaluated and compared with that of fossil fuel production pathways in China by using the life cycle assessment method. The considered hydrogen pathways are gasoline reforming, diesel reforming, natural gas reforming, soybean‐derived biodiesel (s‐biodiesel) reforming, and waste cooking oil‐derived biodiesel reforming. Moreover, emissions and energy consumption of fuel cell vehicles utilizing hydrogen from different fossil sources were presented and compared with those of the electric vehicle, the internal combustion engine vehicle, and the compression ignition engine vehicle. The results indicate both fuel cell vehicles and the electric vehicle have less greenhouse gas emissions and energy consumption compared with the traditional vehicle technologies in China. Based on an overall performance comparison of five different fuel cell vehicles and the electric vehicle in China, fuel cell vehicles operating on hydrogen produced from natural gas and waste cooking oil‐derived biodiesel show the best performance, whereas the electric vehicle has the worse performance than all the fuel cell vehicles because of very high share of coal in the electricity mix of China. The emissions of electric vehicle in China will be in the same level with that of natural gas fuel cell vehicle if the share of coal decreases to around 40% and the share of renewable energy increases to around 20% in the electricity mix of China. Copyright © 2016 John Wiley & Sons, Ltd.     

Technoeconomic analysis of a methanol plant based on gasification of biomass and electrolysis of water

Methanol production process configurations based on renewable energy sources have been designed. The processes were analyzed in the thermodynamic process simulation tool DNA. The syngas used for the catalytic methanol production was produced by gasification of biomass, electrolysis of water, CO₂ from post-combustion capture and autothermal reforming of natural gas or biogas. Underground gas storage of hydrogen and oxygen was used in connection with the electrolysis to enable the electrolyser to follow the variations in the power produced by renewables. Six plant configurations, each with a different syngas production method, were compared. The plants achieve methanol exergy efficiencies of 59–72%, the best from a configuration incorporating autothermal reforming of biogas and electrolysis of water for syngas production. The different processes in the plants are highly heat integrated, and the low-temperature waste heat is used for district heat production. This results in high total energy efficiencies (∼90%) for the plants. The specific methanol costs for the six plants are in the range 11.8–25.3 €/GJ_exergy. The lowest cost is obtained by a plant using electrolysis of water, gasification of biomass and autothermal reforming of natural gas for syngas production.     

Reducing life cycle greenhouse gas emissions of corn ethanol by integrating biomass to produce heat and power at ethanol plants

A life-cycle assessment (LCA) of corn ethanol was conducted to determine the reduction in the life-cycle greenhouse gas (GHG) emissions for corn ethanol compared to gasoline by integrating biomass fuels to replace fossil fuels (natural gas and grid electricity) in a U.S. Midwest dry-grind corn ethanol plant producing 0.19 hm³ y⁻¹ of denatured ethanol. The biomass fuels studied are corn stover and ethanol co-products [dried distillers grains with solubles (DDGS), and syrup (solubles portion of DDGS)]. The biomass conversion technologies/systems considered are process heat (PH) only systems, combined heat and power (CHP) systems, and biomass integrated gasification combined cycle (BIGCC) systems. The life-cycle GHG emission reduction for corn ethanol compared to gasoline is 38.9% for PH with natural gas, 57.7% for PH with corn stover, 79.1% for CHP with corn stover, 78.2% for IGCC with natural gas, 119.0% for BIGCC with corn stover, and 111.4% for BIGCC with syrup and stover. These GHG emission estimates do not include indirect land use change effects. GHG emission reductions for CHP, IGCC, and BIGCC include power sent to the grid which replaces electricity from coal. BIGCC results in greater reductions in GHG emissions than IGCC with natural gas because biomass is substituted for fossil fuels. In addition, underground sequestration of CO₂ gas from the ethanol plant’s fermentation tank could further reduce the life-cycle GHG emission for corn ethanol by 32% compared to gasoline.     

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.     

Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier

Biomass gasification is an important method to obtain renewable hydrogen. However, this technology still stagnates in a laboratory scale because of its high-energy consumption. In order to get maximum hydrogen yield and decrease energy consumption, this study applies a self-heated downdraft gasifier as the reactor and uses char as the catalyst to study the characteristics of hydrogen production from biomass gasification. Air and oxygen/steam are utilized as the gasifying agents. The experimental results indicate that compared to biomass air gasification, biomass oxygen/steam gasification improves hydrogen yield depending on the volume of downdraft gasifier, and also nearly doubles the heating value of fuel gas. The maximum lower heating value of fuel gas reaches 11.11 MJ/N m³ for biomass oxygen/steam gasification. Over the ranges of operating conditions examined, the maximum hydrogen yield reaches 45.16 g H₂/kg biomass. For biomass oxygen/steam gasification, the content of H₂ and CO reaches 63.27–72.56%, while the content of H₂ and CO gets to 52.19–63.31% for biomass air gasification. The ratio of H₂/CO for biomass oxygen/steam gasification reaches 0.70–0.90, which is lower than that of biomass air gasification, 1.06–1.27. The experimental and comparison results prove that biomass oxygen/steam gasification in a downdraft gasifier is an effective, relatively low energy consumption technology for hydrogen-rich gas production.     

Using non-parametric statistics to identify the best pathway for supplying hydrogen as a road transport fuel

The wealth of estimates quantifying the well-to-tank (WTT) impacts of hydrogen vary significantly. This variation is due to both methodology and the chosen production pathway (gasification, electrolysis, or steam reforming). The statistical distribution of the WTT estimates is non-Gaussian and this work demonstrates the adaptive kernel density estimator as a robust, non-parametric statistical method for determining the underlying probability density function. The approach is flexible, expandable and can be used to investigate the development of hydrogen supply pathways through time. The adaptive kernel density estimator outperforms the first generation (oversmoothed and least squares cross-validation), second generation Sheather and Jones Plug-In and the median. In particular, it represents the multimodal features of the data set better than both the first and second generation methods with less variability than the least squares cross-validation approach. The peak of the distribution represents the most likely pathway (best estimate) for supplying hydrogen. This work suggests that the overall best estimate for supplying hydrogen is by natural gas from Europe via central reforming, subject to a trade-off between the energy impacts and the resultant emissions. Through time, the overall hydrogen production process has become more energy efficient at the expense of greater emissions per MJ delivered to the tank. The best-in-class pathway is that with the lowest greenhouse gas emissions per MJ hydrogen delivered and represents the state-of-the-art. Overall, the best-in-class pathway combination for providing hydrogen is by electricity from renewables via electrolysis.     

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.     

Well-to-Wheels analysis of hydrogen production from bio-oil reforming for use in internal combustion engines

The environmental profile of hydrogen depends greatly on the nature of the feedstock and the production process. In this Well-to-Wheels (WTW) study, the environmental impacts of hydrogen production from lignocellulosic biomass via pyrolysis and subsequent steam reforming of bio-oil were evaluated and compared to the conventional production of hydrogen from natural gas steam reforming. Hydrogen was assumed to be used as transportation fuel in an internal combustion engine vehicle. Two scenarios for the provision of lignocellulosic biomass were considered: wood waste and dedicated willow cultivation. The WTW analysis showed that the production of bio-hydrogen consumes less fossil energy in the total lifecycle, mainly due to the renewable nature of the fuel that results in zero energy consumption in the combustion step. The total (fossil and renewable) energy demand is however higher compared to fossil hydrogen, due to the higher process energy demands and methanol used to stabilize bio-oil. Improvements could occur if these are sourced from renewable energy sources. The overall benefit of using a CO₂ neutral renewable feedstock for the production of hydrogen is unquestionable. In terms of global warming, production of hydrogen from biomass through pyrolysis and reforming results in major GHG emissions, ranging from 40% to 50%, depending on the biomass source. The use of cultivated biomass aggravates the GHG emissions balance, mainly due to the N₂O emissions at the cultivation step.     

Production of hydrogen for export from wind and solar energy,natural gas,and coal in Australia

Hydrogen production for export to Japan and Korea is increasingly popular in Australia. The theoretically possible paths include the use of the excess wind and solar energy supply to the grid to produce hydrogen from natural gas or coal. As a contribution to this debate, here I discuss the present contribution of wind and solar to the electricity grid, how this contribution might be expanded to make a grid wind and solar only, what is the energy storage needed to permit this supply, and what is the ratio of domestic total primary energy supply to electricity use. These factors are required to determine the likeliness of producing hydrogen for export. The wind and solar energy capacity, presently at 6.7 and 11.4 GW, have to increase almost 8 times up to values of 53 and 90 GW respectively to support a wind and solar energy only electricity grid for the southeast states only. Additionally, it is necessary to build-up energy storage of actual power >50 GW and stored energy >3000 GW h to stabilize the grid. If the other states and territories are considered, and also the total primary energy supply (TPES) rather than just electricity, the wind and solar capacity must be increased of a further 6–8 times. It is concluded that it is extremely unlikely that hydrogen for export could be produced from the splitting of the water molecule by using excess wind and solar energy, and it is very unlikely that wind and solar may fully cover the local TPES needs. The most likely scenario is production hydrogen via syngas from either natural gas or coal. Production from natural gas and coal needs further development of techniques, to include CO₂ capture, a way to reuse or store CO₂, and finally, the better energy efficiency of the conversion processes. There are several challenges for using natural gas or coal to produce hydrogen with near-zero greenhouse gas emissions. Carbon capture, utilization, and storage technologies that ensure no CO₂ is released in the production process, and new technologies to separate the oxygen from the air, and in case of natural gas, the water, and the CO₂ from the combustion products, are urgently needed to make sense of the fossil fuel hydrogen production. There is no benefit from producing hydrogen from fossil fuels without addressing the CO₂ issue, as well as the fuel energy penalty issue during conversion, that is simply translating in a net loss of fuel energy with the same CO₂ emission.     

Thermo-economic optimisation of the integration of electrolysis in synthetic natural gas production from wood

Converting wood to grid quality methane allows to distribute a CO₂ free, renewable energy resource in a conventional energy distribution system and use it in transportation applications. Applying a multi-objective optimisation algorithm to a previously developed thermo-economic process model for the thermochemical production of synthetic natural gas from wood, the present paper assesses the prospect of integrating an electrolyser in conversion systems based on directly and indirectly heated gasification. Due to an inherent lack of hydrogen for complete conversion of wood into methane and the possibility for rational use of oxygen, it is shown that electrolysis is an efficient and economically interesting option for increasing the gas output of the process while storing electricity and producing fuel that mitigates CO₂ emissions.     

Life cycle environmental impact comparison of solid oxide fuel cells fueled by natural gas,hydrogen, ammonia and methanol for combined heat and power generation

This study aims to provide a comprehensive environmental life cycle assessment of heat and power production through solid oxide fuel cells (SOFCs) fueled by various chemical feeds namely; natural gas, hydrogen, ammonia and methanol. The life cycle assessment (LCA) includes the complete phases from raw material extraction or chemical fuel synthesis to consumption in the electrochemical reaction as a cradle-to-grave approach. The LCA study is performed using GaBi software, where the selected impact assessment methodology is ReCiPe 1.08. The selected environmental impact categories are climate change, fossil depletion, human toxicity, water depletion, particulate matter formation, and photochemical oxidant formation. The production pathways of the feed gases are selected based on the mature technologies as well as emerging water electrolysis via wind electricity. Natural gas is extracted from the wells and processed in the processing plant to be fed to SOFC. Hydrogen is generated by steam methane reforming method using the natural gas in the plant. Methanol is also produced by steam methane reforming and methanol synthesis reaction. Ammonia is synthesized using the hydrogen obtained from steam methane reforming and combined with nitrogen from air in a Haber-Bosch plant. Both hydrogen and ammonia are also produced via wind energy-driven decentralized electrolysis in order to emphasize the cleaner fuel production. The results of this study show that feeding SOFC systems with carbon-free fuels eliminates the greenhouse gas emissions during operation, however additional steps required for natural gas to hydrogen, ammonia and methanol conversion, make the complete process more environmentally problematic. However, if hydrogen and ammonia are produced from renewable sources such as wind-based electricity, the environmental impacts reduce significantly, yielding about 0.05 and 0.16 kg CO₂ eq., respectively, per kWh electricity generation from SOFC.     

Non-catalytic plasma-arc reforming of natural gas with carbon dioxide as the oxidizing agent for the production of synthesis gas or hydrogen

The world's energy consumption is increasing constantly due to the growing population of the world. The increasing energy consumption has a negative effect on the fossil fuel reserves of the world. Hydrogen has the potential to provide energy for all our needs by making use of fossil fuel such as natural gas and nuclear-based electricity. Hydrogen can be produced by reforming methane with carbon dioxide as the oxidizing agent. Hydrogen can be produced in a Plasma-arc reforming unit making use of the heat energy generated by a 500 MWt Pebble Bed Modular Reactor (PBMR). The reaction in the unit takes place stoichiometrically in the absence of a catalyst. Steam can be added to the feed stream together with the Carbon Dioxide, which make it possible to control the H₂/CO ratio in the synthesis gas between 1/1 and 3/1. This ratio of H₂/CO in the synthesis gas is suitable to be used as feed gas to almost any chemical and petrochemical process. To increase the hydrogen production further, the Water–Gas Shift Reaction can be applied. A techno-economic analysis was performed on the non-catalytic plasma-arc reforming process. The capital cost of the plant is estimated at $463 million for the production of 1132 million N m³/year of hydrogen. The production cost of hydrogen is in the order of $12.81 per GJ depending on the natural gas cost and the price of electricity. The purpose of this study is to demonstrate that plasma-arc reforming is competitive with SMR for synthesis gas production and to reduce CO₂ discharge at the same time.