Production & Supply Chain

The current work presents the electro-oxidation of olive mill and biodiesel wastewaters in an alkaline medium with the aim of hydrogen production and simultaneous reduction in the organic pollution content. The process is performed at laboratory scale in an own-design single cavity electrolyzer with graphite electrodes and no membrane. The system and the procedures to generate hydrogen under ambient conditions are described. The gas flow generated is analyzed through gas chromatography. The wastewater balance in the liquid electrolyte shows a reduction in the chemical oxygen demand (COD) pointing to a decrease in the organic content. The experimental results confirm the production of hydrogen with different purity levels and the simultaneous reduction in organic contaminants. This wastewater treatment appears as a feasible process to obtain hydrogen at ambient conditions powered with renewable energy sources resulting in a more competitive hydrogen cost.

The depletion of fossil fuels in the current world has been a major concern due to their role as a primary source of energy for many countries. As non-renewable sources continue to deplete there is a need for more research and initiatives to reduce reliance on these sources and explore better alternatives such as renewable energy. Hydrogen is one of the most intriguing energy sources for producing power from fuel cells and heat engines without releasing carbon dioxide or other pollutants. The production of hydrogen via the electrolysis of water using renewable energy sources such as solar energy is one of the possible uses for solid oxide electrolysis cells (SOECs). SOECs can be classified as either oxygen-ion conducting or proton-conducting depending on the electrolyte materials used. This article aims to highlight broad and important aspects of the hybrid SOEC-based solar hydrogen-generating technology which utilizes a mixed-ion conductor capable of transporting both oxygen ions and protons simultaneously. In addition to providing useful information on the technological efficiency of hydrogen production in SOEC this review aims to make hydrogen production more efficient than any other water electrolysis system.

With the rapid growth of photovoltaic installed capacity photovoltaic hydrogen production can effectively solve the problem of electricity mismatch between new energy output and load demand. Photovoltaic electrolysis systems pose unique challenges due to their nonlinear multivariable and complex nature. This paper presents a thorough investigation into the control methodologies for such systems focusing on both Maximum Power Point Tracking (MPPT) and electrolysis cell control strategies. Beginning with a comprehensive review of MPPT techniques including classical intelligent optimization and hybrid approaches the study delves into the intricate dynamics of Proton Exchange Membrane Electrolysis Cells (PEMEL). Considering the nonlinear and time-varying characteristics of PEMEL various control strategies such as Proportional-Integral-Derivative (PID) robust Model Predictive Control (MPC) and Fault Tolerant Control (FTC) are analyzed. Evaluation metrics encompass stability accuracy computational complexity and response speed. This paper provides a comparative analysis encapsulating the strengths and limitations of each MPPT and PEM control technique.

Hydrogen produced from renewable energy holds significant potential in providing sustainable solutions to achieve Net-Positive goals. However one technical challenge hindering its widespread adoption is the absence of open-source precise modeling tools for sizing and simulating integrated system components under realworld conditions. In this work we developed an adaptable user-friendly and open-source Python® model that simulates grid-connected battery-assisted photovoltaic-electrolyzer systems for green hydrogen production and conversion into high-value chemicals and fuels. The code is publicly available on GitHub enabling users to predict solar hydrogen system performance across various sizes and locations. The model was applied to three locations with distinct climatic patterns – Sines (Portugal) Edmonton (Canada) and Crystal Brook (Australia) – using commercial photovoltaic and electrolyzer systems and empirical data from different meteorological databases. Sines emerged as the most productive site with an annual photovoltaic energy yield 39 % higher than Edmonton and 9 % higher than Crystal Brook. When considering an electrolyzer load with 0.5 WEC/Wp PV capacity solely powered by the photovoltaic park the solar-to-hydrogen system in Sines can reach an annual green hydrogen production of 27 g/Wp PV and export 283 Wh/Wp PV of surplus electricity to the grid. Continuous 24/7 electrolyzer operation increased the annual hydrogen output to 33 g/Wp PV with a reduced Levelized Cost of Hydrogen of €6.42/kgH2. Overall this work aims to advance green hydrogen production scale-up fostering a more sustainable global economy.

With the increasing warming of the atmosphere and the growth of energy consumption in the world new methods and highly efficient energy systems take precedence over conventional methods. This study concentrates on the proposition and techno-economical investigation of a hybrid wind-solar energy system encompassing flat plate solar collector for the purpose of clean hydrogen and electricity generation. The proposed system is a combination of flat plate solar collectors wind turbine organic Rankine cycle and proton exchange membrane electrolyser. Wind speed turbine inlet temperature incident solar irradiation and collector-related parameters including its surface area and fluid mass flow rate are selected decision variables the impacts of which on the exergy efficiency and exergy loss of the scheme are examined. The objective functions included total cost rate and total exergy efficiency. The Nelder-Mead optimization method and EES software were utilized to achieve the mentioned goals followed by a comparative case study was conducted for two cities with high potential in Iran. According to the optimization results the exergy efficiency of 13.35% was achieved while the cost rate was equal to $25.48 per hour respectively. According to the sensitivity analysis the increment in the solar collector area incident solar irradiation wind speed and turbine inlet temperature improved the system's technical performance. Furthermore the exergy loss analysis pointed out that the increment in the turbine inlet temperature not only improves the system's performance but also reduces the exergy loss. A comparison of the electricity production in Semnan and Isfahan showed that 1192613.4 and 1188897.6 of electricity were produced in the two cities in one year respectively. The city of Semnan with the production of 2762.86 kg/h of hydrogen presented better system performance compared to the city of Isfahan with 2757.004 kg/h of hydrogen.

By offering promising solutions to two critical issues – the integration of renewable energies into energy systems and the decarbonization of existing hydrogen applications – green hydrogen production through water electrolysis is set to play a crucial role in addressing the major challenges of the energy transition. However the successful integration of renewable energy sources relies on gaining accurate insights into the impacts that intermittent electrical supply conditions induce on electrolyzers. Despite the rising importance of addressing intermittency issues to accelerate the widespread adoption of renewable energy sources the state-of-the-art lacks research providing an in-depth understanding of these concerns. This paper endeavors to offer a comprehensive review of existing research focusing on proton exchange membrane (PEM) and alkaline electrolysis technologies operating under intermittent operation. Despite growing interest over the last ten years the review underscores the scarcity of industrial-scale databases for quantifying these impacts.

The escalating global pursuit of environmentally benign energy alternatives has spurred intensive investigations into sustainable hydrogen generation technologies. Although hydrogen energy can be produced via multiple approaches the integration of nanotechnology materials in its generation results in its production improvements and efficiency of the production methods. Nanotechnology with its astonishing ability to control materials at the atomic and molecular scale has emerged as a vital technology for improving the efficiency and affordability of hydrogen production from renewable energy sources. This technology provides a unique platform for creating materials with specific properties for energy conversion and storage. Nanotechnology is accelerating the transition to a hydrogen economy by boosting hydrogen production efficiency and storage. Its applications span from enhancing water-splitting catalysts to developing advanced membranes and photocatalysts. These nanomaterial-based innovations are crucial for producing clean hydrogen and its effective storage. Nevertheless nanotechnology highlights the significant role of nanomaterials in overcoming the kinetic challenges associated with hydrogen evolution reactions which can be attained through several features like increased surface area enhanced catalytic activity and improved charge transfer. Therefore this study explores the latest advancements in nanomaterials and their catalytic impact on hydrogen generation particularly in photocatalysis electrocatalysis and photoelectrochemical systems. The study has examined the nanomaterials’ production characterization and performance their integration into renewable energy systems and their potential for widespread commercial use.

The U.S. produces 10 million metric tons (MMT) of hydrogen annually emitting about 41 MMT of carbon dioxide equivalents (CO2-eqs). With rising hydrogen demand and new emission regulations integrating conventional and novel hydrogen production systems is crucial. This study presents an integrated optimization framework to model diversified hydrogen economies as mixed integer linear programs (MILPs). Moreover the accounting of emissions extends to the system exterior (scope 3) thus providing a comprehensive sustainability assessment. The primary focus of the presented computational example is to analyze the impact of scope 3 emissions particularly material emissions during the construction phase on process system optimization while complying with stringent environmental constraints such as carbon limits. By evaluating emission reduction scenarios the model highlights the role of power purchase agreements (PPAs) from renewable sources and the trade-offs between conventional and novel hydrogen production technologies. The key findings indicate that while electrolyzer-based systems (PEM and AWE) offer potential for emission reduction their high energy demand and significant scope 3 material emissions pose challenges for a complete transition in the near term. The study identified two optimal design configurations: one utilizing PPAs as the primary energy source coupled with the conventional SMR-CCS process and another that combines both conventional (SMR-CCS) and novel hydrogen production technologies under a hybrid purview. Ultimately the findings contribute toward the ongoing efforts to achieve true net-carbon neutrality.

The urgency for sustainable and efficient hydrogen production has increased interest in heterostructured nanomaterials known for their excellent photocatalytic properties. Traditional synthesis methods often rely on trial-and-error resulting in inefficiencies in material discovery and optimization. This work presents a new AI-driven framework that overcomes these challenges by integrating advanced machine-learning techniques specific to heterostructured nanomaterials. Graph Neural Networks (GNNs) enable accurate representations of atomic structures predicting material properties like bandgap energy and photocatalytic efficiency within ±0.05 eV. Reinforcement Learning optimises synthesis parameters reducing experimental iterations by 40% and boosting hydrogen yield by 15–20%. Physics-Informed Neural Networks (PINNs) successfully predict reaction pathways and intermediate states minimizing synthesis errors by 25%. Variational Autoencoders (VAEs) generate novel material configurations improving photocatalytic efficiency by up to 15%. Additionally Bayesian Optimisation enhances predictive accuracy by 30% through efficient hyperparameter tuning. This holistic framework integrates material design synthesis optimization and experimental validation fostering a synergistic data flow. Ultimately it accelerates the discovery of novel heterostructured nanomaterials enhancing efficiency scalability and yield thus moving closer to sustainable hydrogen production with improvements in photolytic efficiency setting a benchmark for AI-assisted research.

On the path to an emission free energy economy proton exchange membrane water electrolysis (PEMWE) is a promising technology for a sustainable production of green hydrogen at high current densities and thus high production rates. Long lifetime increasing the current density and the reduction of platinum group metal loadings are major challenges for a widespread implementation of PEMWE. In this context this work investigates the aging of a PEMWE stack operating at 4 A cm-2 which is twice the nominal current density of commercial electrolyzers. Specifically an 8-cells PEMWE stack using catalyst coated membranes (CCMs) with different platinum group metal (PGM) loading was operated for 2200 h. To understand degradation phenomena physical ex-situ analyses such as scanning electron microscopy (SEM) atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were carried out. The same aging mechanism were observed in all cells independent on their position in stack or the specific PGM loading of the membrane electrode assembly (CCM): (i) a decrease of ohmic resistance over time related to membrane thinning (ii) a significant loss of ionomer at anodes (iii) loss of noble metal from the electrodes leading to deposition of small Ir and Pt concentrations in the membrane (iv) heterogeneous enrichment of Ti on the cathode side likely originating from the cathode-side of the Ti bipolar plates (BPPs). These results are in good agreement with the electrochemical performance loss. Thus we were able to identify the degradation phenomena that dominate under high-current operation and their impact on performance.

Sorption-enhanced steam reforming (SorESR) is an advanced thermochemical process integrating in-situ CO2 capture via solid sorbents to significantly enhance hydrogen production and purity. By coupling CO2 adsorption with steam reforming SorESR shifts the reaction equilibrium toward increased H₂ yield surpassing the limitations of conventional steam reforming (SR). The efficacy of SorESR critically depends on the physicochemical properties of the solid CO2 sorbents employed. This review critically evaluates widely studied sorbents including Ca-based Mg-based hydrotalcite-like and alkali ceramic sorbents focusing on their CO2 capture capacity reaction kinetics thermal stability and cyclic durability under SR conditions. Furthermore recent progress in multifunctional sorbent-catalysts that synergistically facilitate catalytic steam reforming alongside CO2 sorption is critically discussed. Moreover the review summarises recent performance achievements and proposes strategies to improve sorbent capacity and reaction kinetics thereby making the SorESR process more appealing for commercial applications. Large-scale SorESR implementation is expected to substantially increase hydrogen production efficiency while concurrently reducing CO2 emissions and advancing sustainable energy technologies. This review offers novel insights into the development of advanced sorbent-catalyst systems and provides new strategies for enhancing SorESR efficiency and scalability for commercial H2 Production.

In the context of mounting concerns over carbon emissions and the need to accelerate the energy transition green hydrogen has emerged as a strategic solution for decarbonizing hard-to-abate sectors. This paper introduces a methodological innovation by proposing the Green Hydrogen Efficiency Index (GHEI) a unified and quantitative framework that integrates multiple stages of the hydrogen value chain into a single comparative metric. The index encompasses six core criteria: electricity source water treatment electrolysis efficiency compression end-use conversion and associated greenhouse gas emissions. Each are normalized and weighted to reflect different performance priorities. Two weighting profiles are adopted: a first profile which assigns equal importance to all criteria referred to as the balanced profile and a second profile derived using the analytic hierarchy process (AHP) based on structured expert judgment named the AHP profile. The methodology was developed through a systematic literature review and was applied to four representative case studies sourced from the academic literature covering diverse configurations and geographies. The results demonstrate the GHEI’s capacity to distinguish the energy performance of different green hydrogen routes and support strategic decisions related to technology selection site planning and logistics optimization. The results highlight the potential of the index to contribute to more sustainable hydrogen value chains and advance decarbonization goals by identifying pathways that minimize energy losses and maximize system efficiency

The increasing interest in off-grid green hydrogen production has elevated the importance of reliable techno-economic assessment (TEA) tools to support investment and planning decisions. However limited operational data and inconsistent modeling approaches across existing tools introduce significant uncertainty in cost estimations. This study presents a comprehensive review and comparative analysis of seven TEA tools—ranging from simplified calculators to advanced hourly based simulation platforms—used to estimate the Levelized Cost of Hydrogen (LCOH) in off-grid Hydrogen Production Plants (HPPs). A standardized simulation framework was developed to input consistent technical economic and financial parameters across all tools allowing for a horizontal comparison. Results revealed a substantial spread in LCOH values from EUR 5.86/kg to EUR 8.71/kg representing a 49% variation. This discrepancy is attributed to differences in modeling depth treatment of critical parameters (e.g. electrolyzer efficiency capacity factor storage and inflation) and the tools’ temporal resolution. Tools that included higher input granularity hourly data and broader system components tended to produce more conservative (higher) LCOH values highlighting the cost impact of increased modeling realism. Additionally the total project cost—more than hydrogen output—was identified as the key driver of LCOH variability across tools. This study provides the first multi-tool horizontal testing protocol a methodological benchmark for evaluating TEA tools and underscores the need for harmonized input structures and transparent modeling assumptions. These findings support the development of more consistent and reliable economic evaluations for off-grid green hydrogen projects especially as the sector moves toward commercial scale-up and policy integration.

This study evaluated the economic feasibility of producing hydrogen from natural gas via thermal degradation in a plasma reactor. Plasma pyrolysis where natural gas passes through the space between electrodes and serves as the working medium enables high hydrogen yields without emitting carbon monoxide or carbon dioxide. Instead the primary products are hydrogen and solid carbon. Unlike conventional methods this approach requires no catalysts addressing a major technological limitation. A thermodynamic equilibrium model based on Gibbs free energy minimization was used to analyze the process over a temperature range of 500–2500 K. The results indicate an optimal temperature of approximately 1500 K which achieved a 99.5% methane conversion by mass. Considering the capital and operating costs and profit margins the hydrogen production cost was estimated at 3.49 EUR/kg. The sensitivity analysis revealed that the price of solid carbon had the most significant impact which potentially raised the hydrogen cost to 4.53 EUR/kg or reduced it to 1.70 EUR/kg.

With the intensification of the global energy crisis hydrogen has attracted significant attention as a high-energy-density and zero-emission clean energy source. Traditional hydrogen production methods are dependent on fossil fuels and simultaneously contribute to environmental pollution. The aqueous phase reforming (APR) of renewable biomass and its derivatives has emerged as a research hotspot in recent years due to its ability to produce green hydrogen in an environmentally friendly manner. This review provides an overview of the advancements in APR of lignocellulosic biomass as a sustainable and environmentally friendly method for hydrogen production. It focuses on the reaction pathways of various biomass feedstocks (such as glucose cellulose and lignin) as well as the types and performance of catalysts used in the APR process. Finally the current challenges and future prospects in this field are briefly discussed.

The global emphasis on clean energy has increased interest in producing hydrogen from petroleum reservoirs through in situ combustion-based processes. While field practices have demonstrated the feasibility of co-producing hydrogen and oil the question of which offers greater economic potential oil or hydrogen remains central to ongoing discussions especially as researchers explore ways to produce hydrogen exclusively from petroleum reservoirs. This study presents the first integrated techno-economic model comparing oil and hydrogen production under varying injection strategies using CMG STARS for reservoir simulations and GoldSim for economic modeling. Key technical factors including injection compositions well configurations reservoir heterogeneity and formation damage (issues not addressed in previous studies) were analyzed for their impact on hydrogen yield and profitability. The results indicate that CO2-enriched injection strategies enhance hydrogen production but are economically constrained by the high costs of CO2 procurement and recycling. In contrast air injection although less efficient in hydrogen yield provides a more cost-effective alternative. Despite the technological promise of hydrogen oil revenue remains the dominant economic driver with hydrogen co-production facing significant economic challenges unless supported by policy incentives or advancements in gas lifting separation and storage technologies. This study highlights the economic trade-offs and strategic considerations crucial for integrating hydrogen production into conventional petroleum extraction offering valuable insights for optimizing hydrogen co-production in the context of a sustainable energy transition. Additionally while the present work focuses on oil reservoirs future research should extend the approach to natural gas and gas condensate reservoirs which may offer more favorable conditions for hydrogen generation.

The pyrolysis and oxidative steam reforming (P-OSR) of different types of plastics (HDPE PP PET and PS) has been carried out in a two reactor system provided with a conical spouted bed reactor (CSBR) and a fluidized bed reactor (FBR). The effect plastic composition has on the oxidative steam reforming step has been analyzed using two space time values (3.1 gcatalyst min gplastic − 1 and 12.5 gcatalyst min gplastic − 1 ) at a reforming temperature of 700 ◦C S/P ratio of 3 and ER of 0.2 (optimum conditions for autothermal reforming). The different composition of the plastics leads to differences in the yields and compositions of pyrolysis products and consequently in the performance of the oxidative steam reforming step. High conversions (> 97 %) have been achieved by using a space time of 12.5 gcat min gplastic − 1 with H2 production increasing as follows: PET ≪ PS < HDPE ≤ PP. A maximum H2 production of 25.5 wt% has been obtained by using PP which is lower than that obtained in the process of pyrolysis and in line conventional steam reforming (P-SR) of the same feedstock (34.8 wt%). The lowest H2 production (10.5 wt%) has been achieved when PET was used due to the high oxygen content of this plastic. The results obtained in this study prove that P-OSR performs very well with different feedstock thereby confirming the versatility and efficiency of this process to produce a hydrogen-rich gas.

The integration of renewable energy into industrial processes is crucial for reducing the carbon footprint of conventional hydrogen production. This work presents detailed design optical–thermal simulation and performance analysis of a solar parabolic dish (SPD) system for supplying high-temperature steam to a Steam Methane Reforming (SMR) plant. A 5 m diameter dish with a focal length of 3 m was designed and optimized using COMSOL Multiphysics (version 6.2) and MATLAB (version R2023a). Optical ray tracing confirmed a geometric concentration ratio of 896× effectively focusing solar irradiation onto a helical cavity receiver. Thermal–fluid simulations demonstrated the system’s capability to superheat steam to 551 ◦C at a mass flow rate of 0.0051 kg/s effectively meeting the stringent thermal requirements for SMR. The optimized SPD system with a 5 m dish diameter and 3 m focal length was designed to supply 10% of the total process heat (≈180 GJ/day). This contribution reduces natural gas consumption and leads to annual fuel savings of approximately 141000 SAR (Saudi Riyal) along with a substantial reduction in CO2 emissions. These quantitative results confirm the SPD as both a technically reliable and economically attractive solution for sustainable blue hydrogen production.

Blue hydrogen production typically achieved by combining steam methane reforming with amine-based CO2 capture is widely considered an economical route towards clean hydrogen. However it suffers from high energy demands associated with solvent regeneration. To overcome this limitation we propose a novel hybrid approach integrating steam methane reforming with membrane-based CO2 capture and O2-enriched combustion. Using process simulations we conducted comprehensive techno-economic and environmental analyses to assess critical parameters affecting the levelised cost of hydrogen (LCOH) and CO2 emissions. Optimal results were obtained at an enriched oxygen level of 30% using vacuum pumping and CO2 capture via feed compression at 11 bar. This configuration achieved an LCOH of ~$1.8/kg H2 and total specific CO2 emissions of ~4.9 kg CO2/kg H2. This aligns closely with conventional blue hydrogen benchmarks with direct emissions significantly reduced to around 1 kg CO2/kg H2. Additionally sensitivity analysis showed robust economic performance despite variations in energy prices. Anticipated advancements in membrane technology could reduce the LCOH further to approximately $1.5/kg H2. Thus this hybrid membrane-based process presents a competitive and sustainable strategy supporting the achievement of the 2050 net-zero emissions goals in hydrogen production.

Electrifying heat supply in chemical processes offers a strategic pathway to reduce CO2 emissions associated with fossil fuel combustion. This study investigates the retrofit of an existing terrace-wall Steam Methane Reformer (SMR) in an ammonia plant by replacing fuel-fired burners with electric resistance heaters in the radiant section. The proposed e-REFORMER concept is applied to a real-world case producing hydrogen-rich syngas at 29000 Nm3 /h with simulation and energy analysis performed using Aspen HYSYS®. The results show that electric heating reduces total thermal input by 3.78 % lowers direct flue gas CO2 emissions by 91.56 % and improves furnace thermal efficiency from 85.6 % to 88.9 % (+3.3 %). The existing furnace design and convection heat recovery system are largely preserved maintaining process integration and plant operability. While the case study reflects a medium-scale plant the methodology applies to larger facilities and supports integration with decarbonised power grids and Carbon Capture Utilisation and Storage (CCUS) technologies. This work advances current literature by addressing full-system integration of electrification within hydrogen and ammonia production chains offering a viable pathway to improve energy efficiency and reduce industrial emissions.

According to the international standard ISO 14687:2019 for hydrogen fuel quality the maximum allowable concentration of water in hydrogen for use in refueling stations and storage systems must not exceed 5 µmol/mol. Therefore an adsorption purification process following the electrolyzer is necessary. This study numerically investigates the adsorption of water and the corresponding water loading on zeolite 13X BFK based on the mass flows entering the adsorption column from three 5 MW electrolyzers coupled to a 15 MW offshore wind turbine. As the mass flow is influenced by wind speed a direct comparison between realistic wind speeds and adsorption loading is presented. The presented numerical discretization of the model also accounts for perturbations in wind speed and consequently mass flows. In addition adsorption isobars were measured for water on zeolite 13X BFK within the required pressure and temperature range. The measured data was utilized to fit parameters to the Langmuir–Freundlich isotherm.

Hydrogen offers a promising solution to reduce emissions in the energy sector with the growing need for decarbonisation. Despite its environmental benefits the use of hydrogen presents significant challenges in storage and transport. Many studies have focused on the different types of hydrogen production and analysed the pros and cons of each technique for different applications. This study focuses on techno-economic analysis of onsite hydrogen production through ammonia decomposition by utilising the heat from exhaust gas generated by hydrogen-fuelled gas turbines. Aspen Plus simulation software and its economic evaluation system are used. The Siemens Energy SGT-400 gas turbine’s parameters are used as the baseline for the hydrogen gas turbine in this study together with the economic parameters of the capital expenditure (CAPEX) and operating expenditure (OPEX) are considered. The levelised cost of hydrogen (LCOH) is found to be 5.64 USD/kg of hydrogen which is 10.6% lower than that of the conventional method where a furnace is used to increase the temperature of ammonia. A major contribution of the LCOH comes from the ammonia feed cost up to 99%. The price of ammonia is found to be the most sensitive parameter of the contribution to LCOH. The findings of this study show that the use of ammonia decomposition via heat recovery for onsite hydrogen production with ammonic recycling is economically viable and highlight the critical need to further reduce the prices of green ammonia and blue ammonia in the future.

Hydrogen energy is key for the global green energy transition and biomass thermochemical has become an important option for green hydrogen production due to its carbon neutrality advantage. Pyrolysis is the initial step of thermochemical technologies. A systematic analysis of the mechanism of H2 production from biomass pyrolysis is significant for the subsequent optimal design of efficient biomass thermochemical H2 production technologies. Biomass is mainly composed of cellulose hemicellulose and lignin and differences in their physicochemical properties and structures directly affect the pyrolysis hydrogen production process. In this study thermogravimetry-mass spectrometry-Fourier transform infrared spectroscopy (TG-MS-FTIR) was employed and fixed-bed pyrolysis experiments were conducted to systematically investigate the pyrolysis of biomass component with focusing on hydrogen production. According to the results of TG-MS-FTIR experiments hemicellulose produced hydrogen through the breaking of C-H bonds in short chains and acetyl groups as well as secondary cracking of volatiles and condensation of aromatic rings at high temperatures. Cellulose produced hydrogen through the breaking of C-H bonds in volatiles generated from sugar ring cleavage along with char gasification and condensation of aromatic rings at high temperatures. Lignin produced hydrogen through ether bond cleavage breaking of methoxy groups as well as cleavage of phenylpropane side chains and condensation of aromatic rings at high temperatures. Results from fixed-bed pyrolysis experiments further showed that hemicellulose exhibited the strongest hydrogen production capacity with the maximum H2 production efficiency of 6.09 mmol/g the maximum H2 selectivity of 17.79% and the maximum H2 effectiveness of 59% at 800°C.

Presently there is no single clear route for the near-term production of the huge volumes of CO2-free hydrogen necessary for the global transition to any type of hydrogen economy. All conventional routes to produce hydrogen from hydrocarbon fossil fuels (notably natural gas) involve the production—and hence the emission—of CO2 most notably in the steam methane reforming (SMR) process. Our recent studies have highlighted another route; namely the critical role played by the microwave-initiated catalytic pyrolysis decomposition or deconstruction of fossil hydrocarbon fuels to produce hydrogen with low to near-zero CO2 emissions together with high-value solid nanoscale carbonaceous materials. These innovations have been applied firstly to wax then methane crude oil diesel then biomass and most recently Saudi Arabian light crude oil as well as plastics waste. Microwave catalysis has therefore now emerged as a highly effective route for the rapid and effective production of hydrogen and high-value carbon nanomaterials co-products in many cases accompanied by low to near-zero CO2 emissions. Underpinning all of these advances has been the important concept from solid state physics of the so-called Size-Induced-Metal-Insulator Transition (SIMIT) in mesoscale or mesoscopic particles of catalysts. The mesoscale refers to a range of physical scale in-between the micro- and the macro-scale of matter (Huang W Li J and Edwards PP 2018 Mesoscience: exploring the common principle at mesoscale Natl. Sci. Rev. 5 321-326 (doi:10.1093/nsr/nwx083)). We highlight here that the actual physical size of the mesoscopic catalyst particles located close to the SIMIT is the primary cause of their enhanced microwave absorption and rapid heating of particles to initiate the catalytic—and highly selective—breaking of carbon–hydrogen bonds in fossil hydrocarbons and plastics to produce clean hydrogen and nanoscale carbonaceous materials. Importantly also since the surrounding ‘bath’ of hydrocarbons is cooler than the microwave-heated catalytic particles themselves the produced neutral hydrogen molecule can quickly diffuse from the active sites. This important feature of microwave heating thereby minimizes undesirable side reactions a common feature of conventional thermal heating in heterogeneous catalysis. The low to near-zero CO2 production of hydrogen via microwave-initiated decomposition or cracking of abundant hydrocarbon fossil fuels may be an interim viable alternative to the conventional widely-used SMR that a highly efficient process but unfortunately associated with the emission of vast quantities of CO2. Microwave-initiated catalytic decomposition also opens up the intriguing possibility of using distributed methane in the current natural gas structure to produce hydrogen and high-value solid carbon at either central or distributed sites. That approach will lessen many of the safety and environmental concerns associated with transporting hydrogen using the existing natural gas infrastructure. When completely optimized microwave-initiated catalytic decomposition of methane (and indeed all hydrocarbon sources) will produce no aerial carbon (CO2) and only solid carbon as a co-product. Furthermore reaction conditions can surely be optimized to target the production of high-quality synthetic graphite as the major carbon-product; that material of considerable importance as the anode material for lithium-ion batteries. Even without aiming for such products derived from the solid carbon co-product it is of course far easier to capture solid carbon rather than capturing gaseous CO2 at either the central or distributed sites. Through microwave-initiated catalytic pyrolysis this decarbonization of fossil fuels can now become the potent source of sustainable hydrogen and high-value carbon nanomaterials.

Australia’s path to net-zero emissions by 2050 depends heavily on the development and commercialisation of hydrogen as a substitute for hydrocarbons across transport power generation and industrial heat sectors. With hydrocarbons currently supplying over 90% of national energy needs hydrogen must scale rapidly to fill the gap. Existing low-carbon hydrogen production methods blue hydrogen via steam methane reforming and green hydrogen via electrolysis are constrained by high water requirements posing a challenge in water-scarce regions targeted for hydrogen development. This paper investigates dry reforming of methane (DRM) as a water-independent alternative using CO₂ as a reactant. DRM offers dual benefits: reduced reliance on freshwater resources and the utilisation of CO₂ supporting broader emissions reduction goals. Recent improvements in nickel-copper catalyst performance enhance the viability of DRM for industrial-scale hydrogen production. The Middle Arm Precinct in the Northern Territory is highlighted as an ideal site for implementation given its access to offshore gas fields containing both methane and CO₂ presenting a unique opportunity for resource-integrated low-emission hydrogen production.