Production Of Energy Carriers Research Articles

Multiperiod Modeling and Optimization of Hydrogen-Based Dense Energy Carrier Supply Chains

The production of hydrogen-based dense energy carriers (DECs) has been proposed as a combined solution for the storage and dispatch of power generated through intermittent renewables. Frameworks that model and optimize the production, storage, and dispatch of generated energy are important for data-driven decision making in the energy systems space. The proposed multiperiod framework considers the evolution of technology costs under different levels of promotion through research and targeted policies, using the year 2021 as a baseline. Furthermore, carbon credits are included as proposed by the 45Q tax amendment for the capture, sequestration, and utilization of carbon. The implementation of the mixed-integer linear programming (MILP) framework is illustrated through computational case studies to meet set hydrogen demands. The trade-offs between different technology pathways and contributions to system expenditure are elucidated, and promising configurations and technology niches are identified. It is found that while carbon credits can subsidize carbon capture, utilization, and sequestration (CCUS) pathways, substantial reductions in the cost of novel processes are needed to compete with extant technology pathways. Further, a research and policy push can reduce the levelized cost of hydrogen (LCOH) by upwards of 2 USD/kg.

Improvement of Current Efficiency of PEM Electrolyzer for Organic Chemical Hydride Energy Carrier Production with Water Electrolysis by Humidified Air Supply to Anode

Introduciton To improve hydrogen energy carrier synthesis, we have studied toluene electrohydrogenation and water decomposition using proton exchange membrane (PEM) electrolysis. The cathode reaction is electrohydrogenation of toluene to synthesis methylcyclohexane instead of hydrogen evolution reaction of water electrolysis. Only side reaction of the cathode is hydrogen evolution reaction, which was affected by electroosmotic water from the anode to cathode. Sulfuric acid solution feeds as anolyte that is not only reactant reduces water transportation and increases current efficiency [1, 2]. As practical system, water transportation from anode to cathode should be suppressed without sulfuric acid utilizationIn this study, to improve current efficiency by water management, we have investigated humidified air feed to reduce water transfer to cathode compare with liquid water feed. Experimental A single cell electrolyzer made of titanium with 16 cm2 of projected electrode area was used. Figure 1 shows the schematic drawing of toluene direct hydrogenation electrolyzers with humidified air feed. Membrane-electrodes assembly was consisted of Nafion® 117 (DuPont), 0.6 mg cm-2 of PtRu/C (TEC61E54, TKK, I/C = 0.8) cathode catalyst layer and 2.0 mg cm-2 of IrOx (TEC77100, TKK, I/IrOx = 0.28). Cathode backing was a carbon paper (10BC, SGL) of 0.02 mg cm-2 of Pt loading, which works flow filed of toluene-methylcyclohexane, too. Anode baking as a Pt plated sintered Ti web (Bekaert), and anode flow filed was serpentine type. 10 mL min-1 of toluene or 10% toluene – methylcyclohexane was fed to cathode. 5.0 L min-1 (313 mL min-1 cm-2) of fully humidified air or liquid water was fed to cathode. Operation temperature was 80oC. Internal resistance was determined by high frequency intercept of real axis of the electrochemical impedance spectroscopy in the current density region between 0.1 to 0.6 A cm-2. The water transportation through the membrane was determined by separated water in outlet liquid from cathode during constant current electrolysis, and the Faraday efficiency was determined by generated gas volume from the cathode, simultaneously. Results and discussion Figure 2 shows the cell voltage and current efficiency as a function of the current density for 10% toluene-methylcyclohexane or 100% toluene to cathode and 5.0 L min-1 of fully humidified air or liquid water to anode feed. Cell voltages were almost same for all experiments in less than 0.3 Acm-2 of current density region, while cell voltages of humidified air feed were higher than that of liquid water feed in higher current density region. Here, internal resistance of humidified air and liquid water feed were 0.29 and 0.21 Ω cm2. Therefore, membrane condition of the humidified air feed was drier than that of the liquid water feed. Water transportation through the membrane around 0.2 mg min-1 cm-2, which was less than 1/10 of the liquid water or 1 M H2SO4 feed electrolysis. The current efficiency for 100% toluene feed was more than 95% at 1 A cm-2, and slightly decreased with current density. In this case, the current efficiency of the liquid water feed was a little higher than that of the humidified air feed. The current efficiency of the humidified air feed was more than 95% up to 0.5 Acm-2, while the current efficiency of the liquid water feed decreased 95% around 0.2 Acm-2. In addition, the current efficiency of 10% toluene-methylcyclohexane significantly decrease with current density.The current efficiency would be affected by the cathode potential and toluene transportation in the catalyst layer. For the 100% toluene feed, toluene transportation would less affect and cathode potential would much affect to the current efficiency. Larger internal resistance of the humidified air feed would correspond to dry condition of cathode ionomer, and it would decrease the cathode potential. Therefore, the current efficiency of humidified air was slightly lower than liquid water feed. On the other hand, the current efficiency of 10% toluene feed would be controlled by toluene transportation in the cathode catalyst layer and is significantly affected by the water transportation through the membrane. Therefore, the current efficiency of the humidified air feed significantly higher than that of the liquid water feed. Acknowledgement This study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project (P14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Nagasawa, K. Tanimoto, J. Koike, K. Ikegami, S. Mitsushima, J Power Sources, 439, 227070 (2019).Oi, K. Nagasawa, T. Takamura, Y. Misu, K. Matsuoka, S. Mitsushima, ECS Meeting s, MA2021-02, 1737 (2021). Figure 1

A Concise Review of Nanoparticles Utilized Energy Storage and Conservation

Nanoparticles have revolutionized the landscape of energy storage and conservation technologies, exhibiting remarkable potential in enhancing the performance and efficiency of various energy systems. This review explores the versatile applications of nanoparticles in three key domains: battery technologies, supercapacitors, and solar energy conversion. In the realm of battery technologies, nanostructured particles have emerged as crucial catalysts and electrode materials, significantly elevating the energy density, cycling stability, and charge/discharge rates of batteries. By manipulating the surface chemistry and structure of nanoparticles, researchers have achieved breakthroughs in overcoming traditional limitations, paving the way for next-generation high-capacity and long-lasting batteries. The integration of tiny particles in supercapacitors has led to remarkable advancements in energy storage and rapid energy delivery. Nanoparticle-based electrodes have exhibited exceptional surface area, porosity, and conductivity, contributing to enhanced energy and power densities. The synergy of nanomaterials with novel electrolytes has also extended the operational lifespan of supercapacitors, addressing concerns regarding energy loss over cycles. Furthermore, nanoparticles have played a pivotal role in the field of solar energy conversion. In photovoltaics, nanoparticles with tailored optoelectronic properties have enabled improved light absorption, charge separation, and electron transport, ultimately boosting the efficiency of solar cells. Moreover, nanoparticles have been employed as catalysts in photocatalytic systems for solar fuel generation, driving the sustainable production of clean energy carriers. In this concise review, we highlight the recent advancements, challenges, and future prospects of nanoparticles in these critical energy domains. While the transformative impact of nanoparticles is evident, several challenges such as large-scale synthesis, cost-effectiveness, and long-term stability must be systematically addressed to ensure their seamless integration into practical energy applications. As researchers continue to explore novel synthesis techniques and innovative nanoarchitectures, nanoparticles are poised to reshape the energy landscape, accelerating the transition toward a more sustainable and efficient energy future.

Efficient photocatalytic production of hydrogen peroxide using dispersible and photoactive porous polymers

Developing efficient artificial photocatalysts for the biomimetic photocatalytic production of molecular materials, including medicines and clean energy carriers, remains a fundamentally and technologically essential challenge. Hydrogen peroxide is widely used in chemical synthesis, medical disinfection, and clean energy. However, the current industrial production, predominantly by anthraquinone oxidation, suffers from hefty energy penalties and toxic byproducts. Herein, we report the efficient photocatalytic production of hydrogen peroxide by protonation-induced dispersible porous polymers with good charge-carrier transport properties. Significant photocatalytic hydrogen peroxide generation occurs under ambient conditions at an unprecedented rate of 23.7 mmol g–1 h–1 and an apparent quantum efficiency of 11.3% at 450 nm. Combined simulations and spectroscopies indicate that sub-picosecond ultrafast electron “localization” from both free carriers and exciton states at the catalytic reaction centers underlie the remarkable photocatalytic performance of the dispersible porous polymers.

Valorizing the Input and Output Waste Streams from Three PtX Case Studies in Denmark—Adopting a Symbiotic Approach

This study aimed to investigate the waste streams from the production of hydrogen energy carriers from PtX technology and identify how they can be valorized by applying a symbiotic approach to enable greater utilization of the inputs and outputs from such plants. Various electrolysis development projects are under development or in the pipeline in Europe and Denmark, but in many cases, it is not clear how waste streams are emphasized and valued in these projects. Thus, three exploratory case studies (a city, a rural, and an energy hub case) were investigated herein exemplifying state-of-the-art electrolysis projects currently being deployed, with a focus on identifying how and to what extent waste streams are being valorized in these projects and energy system integration is being pursued. Inspired by the industrial symbiosis literature, we analyzed how internal, regional, and long-distance symbiotic collaboration is realized within these cases and found them to be very different in terms of the energy carrier produced, the current development stage, and the access to appropriate energy infrastructure. This paper concludes that the co-location of PtX technology near biogas plants would provide a great opportunity for the integration of the produced energy carriers and waste streams into the existing energy system and, hence, could assist in stabilizing fluctuating renewable energy sources to enable their more efficient use in the energy system.

A REVIEW OF WASTE MANAGEMENT IN THE EU COUNTRIES AND THE EXPERIENCE OF ITS ENERGY USE

The article is devoted to the review of waste management in the EU countries and the study of the practices of their energy use. The amount and sources of waste generation in the EU countries and the current trends in its management are analyzed. Special attention is paid to the analysis of production and collection of organic (food) waste by the population; evaluated the top 5 best European models of their collection (open container; door-to-door collection; open container on the street, accessible only to owners; collection of household waste divided into two streams «wet/dry»; composting directly on the territory of their generation). The door-to-door model has shown the highest efficiency when implemented by the households in most European countries in most cases. Two main directions of organic waste management were analyzed: composting and anaerobic fermentation with biogas production. These directions of waste use correspond to the principles of the circular economy and help to use the available potential of waste. Anaerobic digestion of waste is preferred to the composting because it produces both energy resources (biogas, which can be purified to biomethane and also converted into electrical and thermal energy) and biofertilizers (digestate). The experience of individual European countries in the energy use of the organic fraction of municipal solid waste (hereinafter referred to as MSW) is presented. It is substantiated that the use of waste of various origins (households, enterprises, municipal wastewater, etc.) for the production of biogas is actively developing in European countries; both the number of manufacturing enterprises and their production capacities are growing. A trend towards an increase in the production of biomethane – purified biogas, which has a wider application then biogas – has been noted. The production of biomethane and biogas in relation to the total gas consumption in the sixteen largest European countries is analyzed, the largest percentage of substitution as of 2021 is noted in Denmark – 5% of natural gas was replaced by biogas, 19% – by biomethane. It has been confirmed that European countries are intensifying the production of energy carriers from waste in order to reduce dependence on buying natural gas from russia. An increase in energy independence on russian energy resources is expected to accelerate as a reaction to hostilities in Ukraine.

Comprehensive assessment of solar cracking of natural gas for the production and transportation of turquoise energy carriers

Bridge technologies incorporating integrated energy production systems are used to adapt to the growing global energy demand while reducing greenhouse gas emissions. This study aims to propose a system to produce energy in the form of turquoise hydrogen, ammonia, and urea from natural gas. In this study, natural gas is fed to a fluidized bed reactor where high temperatures crack the light-end hydrocarbons into hydrogen and solid carbon. The hydrogen is split between the stored final product and the remainder is further processed as an intermediate product to produce ammonia and urea. This integrated process uses a zero-emission thermochemical cracking unit utilizing solar power as the primary heat source. This work analyzes the feasibility of transporting the produced energy carrier fuels; turquoise hydrogen, ammonia, and urea, overseas for fuel cell power production. The processes are modelled using Aspen Plus© and Engineering Equation Solver software. The main system feed is 4969 kg/h of natural gas, 3733 kg/h nitrogen, and 1991 kg/h of oxygen producing 397 kg/h of hydrogen, 2136 kg/h of ammonia and 4752 kg/h of urea. An integrated Rankine cycle generates 957 kW of power in a steam turbine from waste heat. The supply chain's boil-off gas rates are 1% and 0.02% for hydrogen and ammonia, respectively. The total electrical energy output of the energy carriers used in the fuel cells is 185,900 MWh from hydrogen, 362,100 MWh from ammonia and 458,700 MWh from the urea fuel.

Formation of legal support of climate-protective farming in Ukraine: problems under martial period

Formation of legal support of climate-protective farming in Ukraine: problems under martial period

An evaluation of direct dimethyl ether (DME) synthesis from hydrogen and carbon dioxide based on CFD reactor simulations

To mitigate the effects of anthropogenic climate change, various options for decarbonizing the transport sector are under investigation. One promising approach is the chemical production of energy carriers and fuels from renewable sources. Among various options, dimethyl ether (DME) is discussed as one of the top candidates. However, the production of DME from a renewable raw material supply is associated with certain challenges. This study analyzes the direct synthesis of DME from CO2 and H2 based on computational fluid dynamics (CFD) simulations of the relevant reactors. For the CFD simulations, the software ANSYS Fluent was applied. Kinetic models were integrated by user-defined functions to describe the multiple heterogeneous catalyzed reactions in the synthesis reactor. Several kinetic models were tested with respect to their accuracy and applicability with regard to describing DME formation. A quasi-isothermal reactor model was implemented as base case. It is shown that the progressive formation of water slows down the reaction of direct DME formation. Moreover, a model for a membrane reactor was developed and analyzed in detail. In comparison to the base case, a significant increase in reactor performance was obtained. In conclusion, it can be stated that, for the direct conversion of CO2 to DME, techniques for reducing the accumulation of water need to be adopted such as in-situ water removal or implementing an upstream reverse water-gas shift reactor.

Costs of Gasification Technologies for Energy and Fuel Production: Overview, Analysis, and Numerical Estimation

During recent years, gasification technology has gained a high potential and attractiveness to convert biomass and other solid wastes into a valuable syngas for energy production or synthesis of new biofuels. The implementation of real gasification facilities implies a good insight of all expenses that are involved, namely investments required in equipment during the project and construction phases (capital expenditures, CapEx) and costs linked to the operation of the plant, or periodic maintenance interventions (operational expenditures, OpEx) or costs related to operations required for an efficient and sustainable performance of a gasification plant (e.g., feedstock pre-treatment and management of by-products). Knowledge of these economic parameters and their corresponding trends over time may help decision-makers to make adequate choices regarding the eligible technologies and to perform comparisons with other conventional scenarios. The present work aims to provide an overview on CapEx associated with gasification technologies devoted to convert biomass or solid waste sources, with a view of reducing the carbon footprint during energy generation or production of new energy carriers. In addition, an analysis of technology cost trends over time using regression methods is also presented, as well as an evaluation of specific capital investments according to the amount of output products generated for different gasification facilities. The novelty of this work is focused on an analysis of CapEx of existing gasification technologies to obtain distinct products (energy and fuels), and to determine mathematical correlations relating technology costs with time and product output. For these purposes, a survey of data and categorization of gasification plants based on the final products was made, and mathematical regression methods were used to obtain the correlations, with a statistical analysis (coefficient of determination) for validation. Specific investments on liquid biofuel production plants exhibited the highest decreasing trend over time, while electricity production became the least attractive solution. Linear correlations of specific investment versus time fitted better for electricity production plants (R2 = 0.67), while those relating the product output were better for liquid biofuel plants through exponential regressions (R2 = 0.65).

Electrified CO2 valorization driven by direct Joule heating of catalytic cellular substrates

The growing environmental concerns have driven catalytic CO2 valorization as a forward-looking solution to mitigate the carbon footprint of valuable chemical products. CO2 conversion processes into synthesis gas, such as CO2 reforming of methane (CRM) or reverse water–gas shift (RWGS), may have a strategic role for the future sustainable production of chemicals and energy carriers. However, fuel combustion to supply the heat of the associated endothermic reactions would result in unwanted CO2 emissions, frustrating the overall objective. Electrification of the endothermic processes may represent the technological solution to such an issue. Here we report a promising approach for the direct electrification of the CO2 reforming of methane (eCRM) and reverse water–gas shift (eRWGS) processes in washcoated structured reactors. We employ catalytically activated open-cell foams that provide optimal heat and mass transfer properties and serve as Joule heating substrates for the catalytic conversion of CO2 via reaction with methane or hydrogen. The proposed reactor system with Joule-heated Rh/Al2O3-coated foam exhibited excellent catalytic and electrical stability for more than 75 h, operating up to 800 °C and approaching equilibrium conversion at high space velocity, i.e., GHSV of 600 and 100 kNl/kgcat/h for eRWGS and eCRM, respectively. Such a reactor concept has potential to ensure remarkably low specific energy demand for CO2 valorization. Assuming an optimized process configuration approx. 0.7 kWh/Nm3CO2 is calculated for eRWGS. By replacing fuel combustion with Joule heating driven by renewable electricity, the electrified CO2 valorization processes provide an important approach for dealing with the intermittent nature of renewable sources by storing the energy in chemicals with a low carbon footprint.

Biotechnological Approaches to Generate Biogenic Solvents and Energy Carriers from Renewable Resources

Abstract Background: Current threats connected to the ongoing depletion of fossil resources and elevated levels of greenhouse gases accelerating climate change and global warming provoke a renaissance of biotechnological production of various organic bulk chemicals, which, particularly during the second half of the 20th century, were almost exclusively produced from fossil resources via chemosynthetic processes. Scope: Besides the manufacture of bioethanol, a product obtained by microbial fermentation, biogenic production of solvents and energy carriers like acetone, isopropanol, 2,3-butanediol, or 1-butanol, hence, processes known since the beginning of the last century, experiences now a substantial revival. Summary of new synthesis and conclusions reached in the review: The review illustrates how to produce these products by resorting to fossil raw materials instead of petrochemical production processes, and how this can be accomplished by the cultivation of anaerobic organisms, namely facultatively anaerobic yeasts and bacteria (production of ethanol or 2,3-butanediol), and strictly anaerobic Clostridia (1-butanol, acetone, or isopropanol) on renewable resources. Moreover, novel methods for producing biodiesel-like methyl-esters of aerobically produced bacterial polyhydroxyalkanoate biopolyester building blocks combine the synthesis of microbial biopolyesters from wastewater with the progress of innovative renewable energy carriers. The biochemical background, the current state of research and development, and the status of industrialization of these processes are reviewed. Conclusion: Challenges to make these bioprocesses, based on inexpensive renewable resources, competitive with or even superior to petrochemical production routes in terms of sustainability, scalability, and economic feasibility still exist: however, they can be overcome by the concerted action of various scientific disciplines.

Minimum-Variance Model Predictive Control for Dual Fluidized Bed Circulation Control

Dual fluidized bed steam gasification enables the production of gaseous energy carriers from woody biomass or biogenic residues. The circulation of bed material in dual fluidized bed gasifiers strongly affects the process behavior. Therefore, precise control of the bed material circulation is desired. This paper presents a control algorithm addressing two aspects of the given problem setting: On the one hand, redundant control actuators are available. Typically, there are several air streams to the reactors influencing the bed material circulation. On the other hand, only black box models with uncertainties in their model parameters are available for model-based control design. The presented control algorithm uses a model predictive controller considering known uncertainties in the model parameters and drives the process in a region with the lowest model uncertainties. This results in an improvement of the closed-loop performance when the actual plant deviates from the internal model used for the model predictive control predictions. Simulations show 66 % less offset from the design trajectory with the presented algorithm when compared to a standard model predictive controller.

Інвестування нафтогазовидобутку в ТНК: тенденції, еколого-економічні проблеми та пріоритети

It is substantiated that the intensification of the global environment protection movement in recent decades, the key component of which is the development of tools for transferring national economies to a model of low-carbon development, has had a decisive impact on the dynamics of investment in projects for the development of natural resource potential, primarily hydrocarbons. It has been found that the reduction of dependence of individual countries of the world on oil and natural gas directly depends on the diversification of energy sources to meet the needs of socioeconomic development through the development of the industry for the production of energy from renewable sources. It is proved that the decrease in the volume of production of hydrocarbons and energy carriers produced on its basis is an important factor in the transition of national economies to the model of low-carbon development, in particular, reducing the negative impact on climate processes. It is found that in the sector of «hydrocarbon» TNCs (BP, Shell and Chevron) during 2011–2022 there was a generally downward trend in the dynamics of investments in oil and natural gas production, which has led to significant conjunctural fluctuations in the global markets of hydrocarbons and to structural shifts in the energy balance of many countries of the world. It has been found that BP, Shell and Chevron, along with investing in oil and gas production, finance projects related to the production of energy from alternative sources, which has led to a reduction in capital injections into fossil fuel production and diversified the investment portfolio of these companies, minimizing the risks of reducing their capitalization in the context of diversification of the range of energy carriers in the global and national energy markets. It is proved that the decrease in the volume of investment in oil and gas production in the sector of «hydrocarbon» TNCs (BP, Shell and Chevron) has led to a reformatting of the global energy landscape and created additional prerequisites for increasing the amount of funding for alternative energy projects and solving a set of ecological and economic problems associated with the transition to a low-carbon development model.

Mathematical modeling of the mass transfer of the drying process of a multilayer thermal insulation coating

Polymer thermal insulation materials are widely used in modern industry and technological production of energy carriers. Thermal insulation with polymer coatings is one of the main ways to protect thermal equipment from temperature effects, corrosion, cavitation, erosion, and other influences, reducing the consumption of expensive materials. However, although polymeric materials can significantly reduce the cost of heat losses, their use is kept at a relatively low level. This is due to the low level of culture in the construction industry and the desire to save on projects, even at the expense of quality. The important issue of forming a reliable system “polymer sheet – adhesive film – environment” is given minimal attention, which, as a result, greatly affects the performance and efficiency of the operation of power facilities. In this paper, we studied the problem of mathematical modeling of the mass transfer of the process of drying a multilayer thermal insulation coating on a polymer basis. The proposed method for calculating the concentration and temperature fields allows for optimizing the drying process and improving the quality and reliability of the technological process.

A fossil free future - scenarios for Austria - implications for Europe

If the energy transition completely away from fossil fuels to renewable energies due to climate change and to reduce the dependency from not or semi democratic countries is taken serious, many implications and needed measures have to be faced. In the keynote a general approach with the options reduction of energy demand, generation of renewables within the countries and, if not enough renewable energy is available locally, where could the additional renewable energy be imported from, will be shown. Additionally, the question of energy storage is tackled to overcome the timely variation of the production of renewable energy carriers and the demand. The whole process is shown in detail for the province of Tyrol/Austria, where the possible potential of renewables is compared to the energy need after possible reduction of the energy demand in the whole energy system. The sectors housing, mobility/transportation and industry are included. It will be shown, that the energy efficiency of the whole system needs to be as high as possible and that not only technologic measures are needed but also many other aspects like laws, democracy, micro- and macroeconomics etc. have to be looked at and several dilemmas have to be solved. Concerning the cost it has to be stated that no transition if the energy system will become far more expensive due to the costs of climate change compared to the costs for the energy change, which ranges in about 1 %/GNP.

Entrained flow gasification-based biomass-to-X processes: An energetic and technical evaluation

A large number of process routes is available for the production of sustainable energy carriers from biogenic residues. Benchmarking these routes usually suffers from a lack of comparable performance data. The present work addresses this through a comprehensive model-based comparison of various biomass-to-X routes. Herein, seven routes (methanol, synthetic natural gas, dimethyl ether, Fischer-Tropsch syncrude, ammonia, and hydrogen with and without carbon capture) are modelled in detailed Aspen Plus® simulations. The evaluation itself is based on various key performance indicators, which capture both energetic (i.e. energy yield and usable heat per feedstock) and material-based (i.e. carbon and hydrogen conversion efficiency, and CO2 emissions) properties of the routes. The results show, that no simple correlations can be drawn between energetic and material-based indicators. In summary across all considered properties, the methanol route exhibits the best combined results, in particular with the highest carbon efficiency of 40 %. Fischer-Tropsch is more suitable for integration into existing industrial parks due to the lowest energy yield of 40 % with a lot of by-product formation and the highest amount of useable heat per feedstock of 211.3kWMW-1. Whereas dimethyl ether and synthetic natural gas have potential for integration into heat grids, mainly due to their good conversion and simultaneous large heat dissipation. Ammonia and hydrogen should only be considered in combination with carbon capture. Therefore, the key performance indicators determined herein must be considered together with project- and location-specific requirements and the market outlook for the product.

Innovative Technological Approach for the Cyclic Nutrients Adsorption by Post-Digestion Sewage Sludge-Based Ash Co-Formed with Some Nanostructural Additives under a Circular Economy Framework.

This paper presents a new, innovative technological approach, in line with Circular Economy principles, to the effective management of sludge generated during municipal wastewater treatment processes and subsequently used for biogas production. This approach allows for optimal, functional, and controlled cascade-type biotechnological thermal conversion of carbon compounds present in sewage sludge, later in solid digestate residues (after biogas production), and finally in the ash structure (after incineration, purposefully dosed nanostructural additives make the production of a useful solid product possible, especially for cyclic adsorption and slow release of nutrients (N, P, K) in the soil). The idea is generally targeted at achieving an innovative conversion cycle under a Circular Economy framework. In particular, it is based on an energy carrier (methane biogas) and direct energy production. The functionalized combustion by-products can be advantageous in agriculture. The use of ashes with nanostructural additives (halloysite, kaolinite) from combustion of sewage sludge after the anaerobic fermentation as an adsorbent of selected nutrients important in agriculture (Na+, K+, NO3−, SO42−, PO43−, Cl−) was verified at laboratory scale. The tests were carried out both for pure ash and for the ash derived from combustion with the purposeful addition of kaolinite or halloysite. The equilibrium conditions for nitrate, potassium, sodium, phosphate(V), sulphate(VI), and chloride ions from aqueous solutions with the use of the three adsorbent structures were determined. The obtained innovative results were interpreted theoretically with adsorption isotherm models (Langmuir, Freundlich, Temkin, Jovanović). The most spectacular and clearly favorable results related to the influence of nanostructural additives in the process of sludge combustion, and formation of sorption surfaces under high temperature conditions were identified in the case of sorption-based separation of phosphate(V) ions (an increase from 1.13% to 61.24% with the addition of kaolinite, and even up to 76.19% with addition of halloysite).

Recent Advances on CO2 Mitigation Technologies: On the Role of Hydrogenation Route via Green H2

The increasing trend in global energy demand has led to an extensive use of fossil fuels and subsequently in a marked increase in atmospheric CO2 content, which is the main culprit for the greenhouse effect. In order to successfully reverse this trend, many schemes for CO2 mitigation have been proposed, taking into consideration that large-scale decarbonization is still infeasible. At the same time, the projected increase in the share of variable renewables in the future energy mix will necessitate large-scale curtailment of excess energy. Collectively, the above crucial problems can be addressed by the general scheme of CO2 hydrogenation. This refers to the conversion of both captured CO2 and green H2 produced by RES-powered water electrolysis for the production of added-value chemicals and fuels, which are a great alternative to CO2 sequestration and the use of green H2 as a standalone fuel. Indeed, direct utilization of both CO2 and H2 via CO2 hydrogenation offers, on the one hand, the advantage of CO2 valorization instead of its permanent storage, and the direct transformation of otherwise curtailed excess electricity to stable and reliable carriers such as methane and methanol on the other, thereby bypassing the inherent complexities associated with the transformation towards a H2-based economy. In light of the above, herein an overview of the two main CO2 abatement schemes, Carbon Capture and Storage (CCS) and Carbon Capture and Utilization (CCU), is firstly presented, focusing on the route of CO2 hydrogenation by green electrolytic hydrogen. Next, the integration of large-scale RES-based H2 production with CO2 capture units on-site industrial point sources for the production of added-value chemicals and energy carriers is contextualized and highlighted. In this regard, a specific reference is made to the so-called Power-to-X schemes, exemplified by the production of synthetic natural gas via the Power-to-Gas route. Lastly, several outlooks towards the future of CO2 hydrogenation are presented.

Investigation of an Intensified Thermo-Chemical Experimental Set-Up for Hydrogen Production from Biomass: Gasification Process Integrated to a Portable Purification System—Part II

Biomass gasification is a versatile thermochemical process that can be used for direct energy applications and the production of advanced liquid and gaseous energy carriers. In the present work, the results are presented concerning the H2 production at a high purity grade from biomass feedstocks via steam/oxygen gasification. The data demonstrating such a process chain were collected at an innovative gasification prototype plant coupled to a portable purification system (PPS). The overall integration was designed for gas conditioning and purification to hydrogen. By using almond shells as the biomass feedstock, from a product gas with an average and stable composition of 40%-v H2, 21%-v CO, 35%-v CO2, 2.5%-v CH4, the PPS unit provided a hydrogen stream, with a final concentration of 99.99%-v and a gas yield of 66.4%.