Comparative assessment of various gasification fuels with waste tires for hydrogen production

In this paper, waste tires are comparatively studied and assessed as a feedstock relative to coal and coconut char. An Integrated Gasification Combined Cycle (IGCC) is developed by using the Aspen Plus to assess the suggested gasification feedstocks based on their carbon dioxide emissions and hydrogen production to feed rate ratios. Note that many tires are disposed of every year in North America and are stockpiled in the masses in landfills, which cause various environmental implications. In the present study, it is found that waste tires as a feedstock for gasification are a viable solution to this ever-rising problem. The hydrogen production to feed rate ratio is found to be 0.158 which is very competitive with high-quality coals and coconut char. The net power production from the combined cycle when tires are used as the feedstock for the gasifier is found to be 11.1kW. The optimal hydrogen production to feed rate ratio is also achieved at the maximum net power production rate. The energy and exergy efficiencies of the overall system are found to be 55.01% and 52.31% when the waste tires are used as a feedstock.     

Potassium catalytic hydrogen production in sorption enhanced gasification of biomass with steam

Sorption enhanced gasification (SEG) of biomass with steam was investigated in a fixed-bed reactor to elucidate the effects of temperature, catalyst type and loading on hydrogen production. K₂CO₃, CH₃COOK and KCl were chosen as potassium catalyst precursors to improve carbon conversion efficiency in gasification process. It was indicated that from 600 °C to 700 °C, the addition of K₂CO₃ or CH₃COOK catalyzed the gasification for hydrogen production, and hydrogen yield and carbon conversion increased with increasing catalyst loadings of K₂CO₃ or CH₃COOK. However, the hydrogen yield and carbon conversion decreased as the amount of KCl was increased due to inhibition of KCl on gasification. The maximum carbon conversion efficiency (88.0%) was obtained at 700 °C corresponding to hydrogen yield of 73.0 vol.% when K₂CO₃ of 20 wt.% K loading was used. In particular, discrepant catalytic performance was observed between K₂CO₃ and CH₃COOK at different temperatures and the corresponding mechanism was also discussed.     

Techno-economic analysis and life cycle assessment of hydrogen production from different biomass gasification processes

The paper presents techno-economic analyses and life cycle assessments (LCA) of the two major gasification processes for producing hydrogen from biomass: fluidized bed (FB) gasification, and entrained flow (EF) gasification. Results indicate that the thermal efficiency of the EF-based option (56%, LHV) is 11% higher than that of the FB-based option (45%), and the minimum hydrogen selling price of the FB-based option is $0.3 per kg H₂ lower than that of the EF-based option. When a carbon capture and liquefaction system is incorporated, the efficiencies of the EF- and FB-based processes decrease to 50% and 41%, respectively. The techno-economic analysis shows that at a biomass price of $100 per tonne, either a minimum price of $115/tonne CO_2e or a minimum natural gas price of $5/GJ is required to make the minimum hydrogen selling price of biomass-based plants equivalent to that of commercial natural gas-based steam methane reforming plants. Furthermore, the LCA shows that, biomass as a carbon-neutral feedstock, negative life cycle GHG emissions are achievable in all biomass-based options.     

Effect of bioaugmentation on hydrogen production from organic fraction of municipal solid waste

In the present study, the effect of bioaugmentation with three bacterial species (i.e. E. coli, Bacillus subtilis and Enterobacter aerogenes) on the hydrogen production from organic fraction of municipal solid waste was evaluated at different bacteria/sludge ratios (0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35 and 0.40). Cumulative hydrogen production, lag phases, and maximum hydrogen production rates were analyzed using modified Gompertz model. The highest cumulative and volumetric hydrogen production of 564.4 ± 10.9 mL and 1.61L_H2/L_substrate respectively was achieved for bioaugmentation with Bacillus subtilis at bacteria/sludge ratio of 0.25. The corresponding highest hydrogen yield was 43.68 mLH₂/gCarbo. For bioaugmentation with E. coli and Enterobacter aerogenes, the maximum cumulative hydrogen production of 423.4 ± 10.6 mL and 486.3 ± 10.6 mL respectively was obtained from bacteria/sludge ratio of 0.20. Corresponding highest hydrogen yields were 32.9 mLH₂/gCarbo and 37.1 mLH₂/gCarbo respectively. Bioaugmentation shortened the lag phases and improved COD removal. Volatile fatty acid generation was also improved with the bioaugmentation.     

Electro-stimulated biological production of hydrogen from municipal solid waste

Hydrogen production from municipal solid wastes was investigated by applying a weak current (0.06 A) to a slurry of municipal solid waste in an anaerobic reactor at 55 °C using 4 electrodes (carbon graphite for the cathode and platinum electroplated titanium for the anode). Current application to the organic waste stimulated the hydrogen producing bacteria especially bacteria related to the Thermotogales and Bacillus families. Measured hydrogen production rates were comprised between 16 and 41 mL/h. Comparison of bacterial and archaeal communities in methane-producing (control) and electro-stimulated reactors showed similar species but with different dynamics correlated to hydrogen or methane production. Energy efficiency of the overall bioelectrolysis process using municipal solid waste and an applied voltage of 3V was approximately 12.4%, which is relatively low compared to values reported in the literature for organic wastes and can be explained by the low organic carbon content and availability in the municipal solid waste. Results of this study highlight some important operational constraints with respect to electro-stimulated hydrogen production from organic wastes; related in particular to electrode lifetime expectancies. Results nevertheless illustrate the potential for hydrogen production from municipal solid waste as a possible route for energy recovery.     

Process simulation and techno-economic assessment of SER steam gasification for hydrogen production

In the SER (sorption enhanced reforming) gasification process a nitrogen-free, high calorific product gas can be produced. In addition, due to low gasification temperatures of 600–750 °C and the use of limestone as bed material, in-situ CO₂ capture is possible, leading to a hydrogen-rich and carbon-lean product gas. In this paper, results from a bubbling fluidised bed gasification model are compared to results of process demonstration tests in a 200 kW_th pilot plant.Based upon that, a concept for the hydrogen production via biomass SER gasification is studied in terms of efficiency and feasibility. Capital and operational expenditures as well as hydrogen production costs are calculated in a techno-economic assessment study. Furthermore, market framework conditions are discussed under which an economic hydrogen production via SER gasification is possible.     

Modelling of methane sorption enhanced reforming for blue hydrogen production in an adiabatic fixed bed reactor: unravelling the role of the reactor's thermal behavior

Methane sorption enhanced reforming (SER) is investigated in this work as a promising route for blue H₂ production. A 1-D dynamic heterogeneous model is developed to evaluate the thermal behavior of a fixed bed reactor under adiabatic conditions. The heterogeneous model allows to decouple the feed gas temperature from the initial solid one in order to investigate the behavior of the reforming step in a temperature swing reforming/regeneration process. The effects of the feed gas temperature, the initial bed temperature, and the bed thermal capacity are studied by evaluating the global impact of each parameter through a set of key performance indices (CH₄ conversion, H₂ yield and purity, carbon capture ratio) calculated as integrals over the duration of the reforming step. The results highlight the minor effect of the initial bed temperature on the process performances showing the potential of minimizing the extent of a cooling step between regeneration and reforming stages. Besides, due to the endothermic nature of the methane sorption enhanced reforming process at high temperatures, thermal energy must be provided to the SER process to achieve high CH₄ conversion and high carbon capture ratio. This can be made either in the form of high feed temperature or by utilizing the energy stored in the bed benefiting from the bed thermal capacity.     

Liquid metal activated hydrogen production from waste aluminum for power supply and its life cycle assessment

Hydrogen energy draws increasing concerns as a kind of renewable and clean energy. Liquid metal (LM) activated Al–H₂O reaction is recently emerging as an alternative for real-time hydrogen production. In this study, the energy consumption and environmental impact of this newly emerging method are evaluated via the life cycle assessment (LCA), which indicates that the utilization of waste Al could significantly relieve the energy and environmental issues. In addition, conceptual experiments were conducted to verify the feasibility of hydrogen generation from waste Al, and to disclose the hydrogen generation performances of Al samples in different forms. To balance the cost of LM and reaction efficiency, the optimum mass ratio of LM to Al were explored, and the reusability of LM was demonstrated. Further, a SWOT analysis is adopted to interpret the Strengths and Weakness of such hydrogen production method, and to evaluate the Opportunities and Threats it confronts. Overall, waste Al could provide an energy-saving and environmentally friendly approach to produce hydrogen, which is expected to exploit a new way towards the green hydrogen era.     

Integrated adsorption steam gasification for enhanced hydrogen production from palm waste at bench scale plant

The generation of hydrogen-enriched synthesis gas from catalytic steam gasification of biomass with in-situ CO₂ capture utilizing CaO has a high perspective as clean energy fuels. The present study focused on the process modeling of catalytic steam gasification of biomass using palm empty fruit bunch (EFB) as biomass for hydrogen generation through experimental work. Experiment work has been carried out using a fluidized bed gasifier on a bench-scale plant. The established model integrates the kinetics of EFB catalytic steam gasification reactions, in-situ capturing of CO₂, mass and energy balance calculations. Chemical reaction constants have been calculated via the parameters fitting optimization approach. The influence of operating parameters, mainly temperature, steam to biomass, and sorbent to biomass ratio, was investigated for the hydrogen purity and yield through the experimental study and developed model. The results predicted approximately 75 vol% of the hydrogen purity in the product gas composition. The maximum H₂ yield produced from the gasifier was 127 gH₂/kg of EFB via experimental setup. The increase in both steam to biomass ratio and temperature enhanced the production of hydrogen gas. Comparing the results with already published literature showed that the current system enables to produce a high amount of hydrogen from EFB.     

Parametric optimization of the dark fermentation process for enhanced biohydrogen production from the organic fraction of municipal solid waste using Taguchi method

In this work, the Taguchi method was used to optimize the dark fermentative H₂ production from the organic fraction of municipal solid waste (OFMSW). The experiments were planned using the L16 orthogonal array design with each trial conducted at different levels of substrate concentration, inoculum-to-substrate ratio (ISR), and temperature. Based on the results, the optimal setting of the process parameters was the substrate concentration of 6 g-VS/L, ISR 0.5, and temperature of 55 °C. Furthermore, substrate concentration was the most important parameter affecting bio-H₂ production among the three process parameters considered. Finally, a confirmation experiment under optimal conditions yielded 62.5 mL H₂/g-VS_added, which was higher than all the bio-H₂ yield values obtained in the other conditions tested in this study. The measured and predicted bio-H₂ yields in the verification test were also very close to each other, confirming the reliability of the Taguchi method in optimizing the bio-H₂ production process.     

Techno-economic comparison of three biodiesel production scenarios enhanced by glycerol supercritical water reforming process

In this study, techno-economic comparison of three different biodiesel production scenarios integrated with glycerol supercritical water reforming (SCWR) process to produce electricity is conducted. In the first scenario, biodiesel is synthesized from acid-pretreated waste cooking oil (WCO) in the presence of alkali catalyst. In the second scenario, biodiesel is obtained from WCO by acid catalyst. In the third scenario, biodiesel is derived from WCO using acid catalyst, followed by hexane extraction of the produced methyl esters. The glycerol evolved from all the above-mentioned pathways is then subjected to the SCWR process in order to produce hydrogen. The produced hydrogen is then combusted to provide thermal energy required by biodiesel production and purification processes as well as to generate electricity. All the developed scenarios are modeled and simulated in Aspen HYSYS software environment. In order to simplify the simulation process, canola-based WCO is considered as triolein with 6 wt% oleic acid (free fatty acid) and, accordingly, the prepared biodiesel is taken into account as methyl oleate. In order to compare the economic profitability of the developed approaches, several economic indicators including net present value (NPV), internal rate of return (IRR), payback period (PBP), discounted payback period (DPBP), and return on investment (ROI) are used. A sensitivity analysis is also carried out to show how variations in feedstock, biodiesel, and electricity prices can affect the NPV of the developed scenarios. According to the results obtained, the highest IRR and ROI values as decision-making parameters are obtained for the first scenario, manifesting its suitability from the techno-economic viewpoint. The economic indicators of the second scenario are also acceptable and very close to the first approach. Overall, upgrading glycerol into hydrogen using SCWR process appears to be an attractive strategy for enhancing the economic viability of biodiesel production plants.     

Techno-economic and environmental assessment of LNG export for hydrogen production

A critical requirement of a widely contemplated hydrogen economy is the development of a low carbon hydrogen supply chain that is cost competitive. This comprehensive techno-economic assessment demonstrates, for the first time, the viability of a complete hydrogen supply chain based on the transport of liquefied natural gas (LNG). This is demonstrated via the established LNG trade route from Australia to Japan against three key performance indicators (KPIs): delivered hydrogen cost, CO₂ emissions intensity (EI) across the entire supply chain, and technology readiness level (TRL). The hydrogen supply chain entails LNG export to Japan where it is used for blue hydrogen production; the by-product CO₂ is then liquefied and repatriated to Australia for sequestration or utilisation. Within this supply chain, various hydrogen production technologies are assessed, including steam methane reforming (SMR), autothermal reforming (ATR) and natural gas pyrolysis (NGP). SMR with carbon capture and storage (CCS) resulted in the lowest total hydrogen supply cost of 19 USD/GJ (2.3 USD/kgH2) which comfortably meets the 2030 Japanese hydrogen cost target of 25 USD/GJ (3 USD/kgH2) and is very close to the 17 USD/GJ 2050 Japanese hydrogen cost target. This technology also obtained the lowest CO₂ emission intensity (EI) of 38 kgCO2/GJ (4.5 kgCO2/kgH2); this was surprisingly lower than ATR with CCS primarily due to the emissions associated with ATR electricity provision for air separation. Future technologies and strategies are detailed so as to further reduce cost and supply chain emissions; these were shown to be able to reduce total CO2 EI to 14 kgCO2/GJ (1.6 kgCO2/kgH2). Hence this analysis indicates that this supply chain can act to significantly reduce CO2 emissions whilst uniquely meeting targeted hydrogen supply costs up to 2050. As such it is proposed here as an eminently viable hydrogen export option deploying both existing technology and capacity, at least until other hydrogen supply chain vectors (such as liquid hydrogen and ammonia) derived from green hydrogen production become competitive across all the KPIs.     

Air-steam gasification of municipal solid wastes (MSWs) for hydrogen production

Gasification process can be considered as a partial thermal oxidation, which results in the production of a mixture of useful gases (CO, H₂, CH₄, and other gaseous hydrocarbons), little quantities of carbon black (char), ash, and several organic impurities (tar). In this study, we introduced an artificial neural network (ANN) model to simulate the influence of operating conditions on the concentration of products during the gasification process of municipal solid wastes (MSW). Results showed when increasing the residence time, more char is gasified, leading to an increase in the greenhouse gas emissions. It is also found that a further increase in the residence time results in a constant rate of products due to the heat and mass transfer limitations.     

Techno-economic evaluation and parametric study of generating green hydrogen from waste heat recovery of efficient solid oxide fuel cell

According to the United Nations Population Division, the world population is expanding, and this rise has been more pronounced in the last century. As an instance, the population in 2020 is almost two times more than the population in 1970. As a result, the population will have increased by around 4.1 billion people in 50 years (according to Worldometers.info). Energy may be considered to be one of the most fundamental prerequisites for human survival. This research presents a newly projected energy system based on FC and RR-ORC and PEME for green generation on hydrogen and power. The system actually has two power blocks and one hydrogen generation unit. The system has three subsystems that are modeled incomplete form based on the thermodynamic and economic model. The effect of strategic proposal variables are foreseen on the LCOE, overall cost, and exergetic efficiency. Also, the variation of hydrogen production and net power output is predicted. The results show that current density, as well as fuel and air utilization factor, has a crucial effect on the system performance while the parameters of the bottoming cycle as ORC and pinch point variables have little effect on cycle performance; on the other hand, they affect the downstream cycles much, like hydrogen production system. Increasing current density has the highest effect on the system performance by an 8% reduction in exergy efficiency.     

Modeling of fractal heat conduction of semi-coke bed in waste heat recovery steam generator for hydrogen production

With the steam obtained from the waste heat of high temperature semi-coke, the hydrogen production through gasification method is considered more commercial. In order to improve the efficiency of waste heat recovery, the fractional model for heat conduction of semi-coke bed in waste heat recovery process was established. The non-destructive CT was employed to obtain the inner morphology of semi-coke bed and the image binarization processing was used to segment the CT image. With the MATLAB program, the box-counting method was used to calculate the fractal dimension of semi-coke bed. The fractional model for heat conduction of semi-coke bed was established by the fractal theory. The results showed that, the CT image and bit binary image of semi-coke bed can really reflect the inner morphology of semi-coke bed, and the inner morphology of semi-coke bed can be regarded as a fractal medium. The fractal dimension of semi-coke bed is 1.7537, which is very close to golden mean, 1.618, this could be the optimal structure for the heat conduction of semi-coke bed under the condition of natural accumulation. The one-dimensional heat conduction fractional equation of semi-coke bed was established and it can be accurately solved by fractal complex transformation and traveling wave transformation.     

Techno-economic feasibility of distributed waste-to-hydrogen systems to support green transport in Glasgow

Distributed waste-to-hydrogen (WtH) systems are a potential solution to tackle the dual challenges of sustainable waste management and zero emission transport. Here we propose a concept of distributed WtH systems based on gasification and fermentation to support hydrogen fuel cell buses in Glasgow. A variety of WtH scenarios were configured based on biomass waste feedstock, hydrogen production reactors, and upstream and downstream system components. A cost-benefit analysis (CBA) was conducted to compare the economic feasibility of the different WtH systems with that of the conventional steam methane reforming-based method. This required the curation of a database that included, inter alia, direct cost data on construction, maintenance, operations, infrastructure, and storage, along with indirect cost data comprising environmental impacts and externalities, cost of pollution, carbon taxes and subsidies. The levelized cost of hydrogen (LCoH) was calculated to be 2.22 GB P/kg for municipal solid waste gasification and 2.02 GB P/kg for waste wood gasification. The LCoHs for dark fermentation and combined dark and photo fermentation systems were calculated to be 2.15 GB P/kg and 2.29 GB P/kg. Sensitivity analysis was conducted to identify the most significant influential factors of distributed WtH systems. It was indicated that hydrogen production rates and CAPEX had the largest impact for the biochemical and thermochemical technologies, respectively. Limitations including high capital expenditure will require cost reduction through technical advancements and carbon tax on conventional hydrogen production methods to improve the outlook for WtH development.     

Techno-economic study of hydrogen production using CSP technology

There are different processes for hydrogen production and different sources of energy could be used to drive these processes. However, a hydrogen production technique won't insure market penetration unless it succeeds in securing the economic competitiveness.In the present work, techno-economic study of the solar-electrolysis based hydrogen production techniques is carried out. The present study is limited to the case of hydrogen production using a hybrid solar parabolic trough-gas power plant-electrolysis system. The effect on hydrogen production cost of different factors, such the direct normal irradiance and the solar fraction are investigated.This technique of hydrogen production is considered for the case of Algeria. In order to determine the effect of the climatic conditions on the cost of hydrogen production, two different sites have been chosen: one in Northern Algeria and the other one in Southern Algeria.The results indicate that the cost of hydrogen production is dominated by the cost of hydrogen related to the cost of energy production. This cost is highly dependent on solar fraction and solar insolation. The results show also that solar CSP based hydrogen production technique is more competitive than the conventional PV based hydrogen production technique but as competitive or less competitive than CPV based hydrogen production technique.     

Continuous high-purity hydrogen production by sorption enhanced steam reforming of ethanol over modified lithium silicate

Sorption-enhanced steam reforming of ethanol (SE-SRE) with in-situ CO₂ removal is an environmentally friendly and sustainable approach for hydrogen production. Researches on continuous production of high-purity H₂ by SE-SRE over the modified Li₄SiO₄ sorbent were conducted using two parallel reactor in this work. The low cost Li₄SiO₄ derived from rice husk ash (RHA) is a promising high-temperature CO₂ sorbent. However, the poor adsorption kinetics of RHA-Li₄SiO₄ sorbent at low CO₂ concentration is the major challenge. The metallic elements (K, Ca, Al, Mg) were employed to modify the RHA-Li₄SiO₄ for efficient CO₂ capture. The developed sorbents were characterized and tested to study the role of dopants on the crystal, textural, microstructure and CO₂ adsorption kinetics and cyclic stability. Results indicated that K doping effectively inhibited the growth of crystal aggregation and resulted in a fluffy morphology with abundant pores and higher specific surface area, while the addition of Ca, Al and Mg formed a nubby structure with larger particle size. K-doped RHA-Li₄SiO₄ exhibited the best CO₂ uptake properties and the optimal K doping molar content was 0.02 with the maximum capture capacity of 34.16 wt%, which is higher than 27.1 wt% of pure RHA-Li₄SiO₄. Then, the effect of operating conditions on the enhancement behaviors was considered in the SE-SRE system. High-purity H₂ (above 96%) was achieved by coupling K(0.02)/RHA-Li₄SiO₄ sorbent with Ni-based catalyst under the optimum condition (T: 525 °C, liquid hourly space velocity: 0.9 mL/(g·h), sorbent/catalyst: 4 and steam/carbon: 8.0). The adsorption activity of K(0.02)/RHA-Li₄SiO₄ maintained at a high level in ten SE-SRE/regeneration cycles. Finally, a scheme including two parallel fixed-bed reactors was designed and operated periodically for continuous production of high-purity H₂. The reaction switching time was shown to depend strongly on the pre-breakthrough time and operating conditions. As the reaction switching time was 40 min, the products were always only H₂ and CH₄ (no CO and CO₂ appear) and the H₂ purity remained above 90% during 400 min, confirming high purity hydrogen stream can be obtained continuously.     

Membrane reactors for green hydrogen production from biogas and biomethane: A techno-economic assessment

This work investigates the performance of a fluidized-bed membrane reactor for pure hydrogen production. A techno-economic assessment of a plant with the production capacity of 100 kg_H2/day was carried out, evaluating the optimum design of the system in terms of reactor size (diameter and number of membranes) and operating pressures. Starting from a biomass source, hydrogen production through autothermal reforming of two different feedstock, biogas and biomethane, is compared.Results in terms of efficiency indicates that biomethane outperforms biogas as feedstock for the system, both from the reactor (97.4% vs 97.0%) and the overall system efficiency (63.7% vs 62.7%) point of views. Nevertheless, looking at the final LCOH, the additional cost of biomethane leads to a higher cost of the hydrogen produced (4.62 €/kg_H2@20 bar vs 4.39 €/kg_H2@20 bar), indicating that at the current price biogas is the more convenient choice.