A dynamic 2D CFD multilayer particle model was developed and simulated using COMSOL Multiphysics 6.3 to study desulfurization of copper sulfide (Cu2S) with hydrogen (H2). The model solved interstitial velocity and pressure fields in the gas phase coupled to transiently resolved species transport in both gas and solid phases, incorporating reduction kinetics and dynamic pellet porosity change. After model validation with experimental data from literature, a constricted optimization study was carried out to identify optimal conditions necessary to maximize Cu2S conversion and H2 utilization. The optimization solutions (i.e., 100% H2 and 973 K) indicated that both high inlet mole fraction of H2 and temperature improved the objective function steadily, highlighting the trade-off between maximizing conversion and minimizing H2 slip. The current work can serve as a framework for reactor-scale simulations aimed at intensification and decarbonization of primary copper production.

Methane is a greenhouse gas 28 times more potent than CO2, with wetlands and agricultural practices accounting for 32 and 38% of total natural and anthropogenic methane emissions, respectively. The diluted and distributed nature of these emissions makes them hard to mitigate. Therefore, effective mitigation techniques are essential to reduce its impact, with catalytic oxidation emerging as a promising solution. In this study, methane oxidation over transition metal oxides is investigated to remove low-concentration CH4 due to its high efficiency and low secondary pollution. The catalytic performance of different transition metal oxides (Co, Ni, and Mn), including single and binary metal oxides, was investigated under controlled conditions to facilitate direct comparison. The experimental investigation revealed that Co3O4–MnxOy and Co3O4 catalysts achieved a 90% methane conversion rate at 330 and 380 °C. The high surface area and small crystallite size of Co3O4–MnxOy increase the exposure of active sites, while the synergistic effect of Mn and Co promotes oxygen vacancy formation. In contrast, Co3O4 benefits from a high density of surface oxygen vacancies and an optimal acid–base balance, enabling intermediate stabilization and rapid redox cycling. By linking catalytic performance to structural features such as surface morphology, oxygen vacancies, acidity–basicity, and crystallite structures, this study provides insights into the reaction mechanisms governing methane oxidation.

Agri-food systems constitute around one-third of global greenhouse gas (GHG) emissions, with roughly half consisting of non-CO2 GHGs, mainly methane (CH4) and nitrous oxide (N2O). Methods and technologies to mitigate non-CO2 GHGs are currently limited, which is a reason for agriculture being categorised as a hard-to-abate sector. This study examines mitigation of GHG emissions from manure storage headspace through oxidisation of CH4 emissions at low concentrations, using a thermal catalytic process with and without subsequent CO2 capture and storage (CCS). The technology is studied using a combination of process modelling and life cycle assessment at four CH4 concentrations: 300, 1000, 3000 and 10,000 ppmv. The primary energy demand and net climate effect were evaluated, reaching a net climate effect of +0.10, -0.77, -0.91 and -0.97 g CO2-eq emitted/g CO2 mitigated, respectively. The wide range of results is mainly influenced by the process energy demand being strongly correlated to the CH4 concentration. The sensitivity analysis shows that a net negative climate effect can also be achieved at 300 ppmv with access to low emission energy sources. Coupling CCS worsens the net climate effect of the system at all studied CH4 concentrations, mainly due to the additional energy demand for CO2 separation.

Red mud is a hazardous waste of the alumina refining process, with 1–1.5 tons generated per ton of alumina produced. This study presents a first-of-its-kind understanding of a biomass-based pathway for recovering iron from red mud. Simultaneous red mud reduction and biomass gasification (SRG) is proposed as a viable pathway to produce zero-valent iron. This metallic iron can potentially be recovered by weak magnetic separation and integrated into the iron-making industry. The steps of the red mud-biomass phenomena were investigated through thermogravimetric analysis followed by XRD characterization. Complete reduction from Fe³⁺ to Fe⁰ was achieved at temperatures near 900 °C and verified by XRD, XPS, and FTIR. Bench-scale SGR experiments were also performed to survey the compositions of gaseous and tar products. Bench-scale SRG experiments confirmed increased syngas (CO and H₂) production and demonstrated the tar-cracking catalytic activity of red mud.

Due to the growth in the share of renewable energy sources (RES) in the power generation sector worldwide and their intermittency, storage of surplus electricity is needed. The technology known as Power to X (PtX) facilitates the extended storage of excess electricity by converting it into gaseous or liquid fuels such as hydrogen, methane, ammonia, or methanol. This study examines the potential of synthetic natural gas (SNG) technology as a viable energy storage solution. The paper introduces three distinct SNG production systems, all of which are based on the processes of biomass gasification and methanation. Case 1 assumes further CO2 capture from generated SNG, and Cases 2 and 3 additionally assume hydrogen production and almost complete CO2 utilization by syngas hydrogenation via the methanation process. The methanation process converts syngas and hydrogen into SNG with a high methane content (>90 vol% dry), that can be injected into the natural gas grid. The thermodynamic and economic potential of SNG production systems is presented in this work. The simulations were conducted using the AspenONE software. The methanation process was analyzed for various design conditions such as methanation temperature and pressure, and different H2:CO, and H2:CO2 ratios. The estimated cold gas efficiency of proposed SNG production systems varies from 63.27% to 77.10% and can be increased up to about 69.10–75.58% when the recovery of heat from methanation is considered. A sensitivity analysis was conducted to determine the break-even price of SNG, considering different scenarios for the costs of feedstock, specifically biomass and electricity. The results indicate that under the most optimistic conditions, the break-even price of SNG is estimated to be 115 €/MWhSNG, 58 €/MWhSNG and 67 €/MWhSNG for Cases 1, 2, and 3, respectively.

Methane is the second largest contributor to global warming after CO2, and it is hard to abate due to its low concentration in the emission sources and in the atmosphere. However, removing methane from the atmosphere will accelerate achieving net-zero targets, since its global warming potential is 28 over a 100-year period. This work presents first-of-its-kind process concepts for co-removal of methane and CO2 that combines the catalytic conversion of methane step (thermal/photo-catalytic) with CO2 capture. Proposed processes have been analyzed for streams with lean methane concentrations, which are non-fossil emissions originating in the agricultural sector or natural emissions from wetlands. If the proposed processes can overcome challenges in catalyst/material design to convert methane at low concentrations, they have the potential to remove more than 40% of anthropogenic and natural methane emissions from the atmosphere at a lower energy penalty than the state-of-the-art technologies for direct air capture of CO2.

E-fuels are promising alternatives to fossil fuels in the transition towards zero-emission energy system. In this study, a novel chemical-recuperated and humidified gas turbine concept aiming at the application of e-fuel ammonia is proposed to overcome the technical hitches and exploit the waste heat to enhance the cycle performance. The thermodynamic analysis shows that the highest net electrical efficiency (56.7%) under the design conditions exceeds that of the ammonia-fueled Brayton cycle by 20.6%-points. The chemical recuperation of fuel contributes to the efficiency improvement by 7%-points under dry condition, while steam injection provides 8%-points to 12%-points efficiency increase corresponding to the ammonia decomposition ratio of 5%–96%. A non-monotonic relation between the net electrical efficiency and steam-to-air ratio is found to be the result of the competition between the enthalpy change from to the varied steam and air mass flow rates. Analyzing the flame characteristics in the combustor under the design conditions, we found that conditions with high decomposition ratio (>88%) and high steam-to-air ratio (>0.3) exhibit similar flame speed with that of methane fueled combustor and thus existing designs can be reused. The prediction shows the NOx emission can be restricted when the steam-to-air ratio exceeds 0.4.

Gas switching technology (GST) was introduced to facilitate operation and scale-up of pressurized chemical looping-based technologies thus bringing the expected benefits of reducing costs and energy penalty of CO2 capture. GST has so far been applied to generate heat/power, hydrogen, syngas, and oxygen using fossil fuel gas (but also from biomass for negative CO2 emissions) with integrated CO2 capture at minimal energy penalty generating over 50 publication studies demonstrating the technical feasibility of the technology and quantifying the potential energy and cost savings. In contrast to conventional chemical looping, GST inherently avoids solids circulation by alternating oxidizing and reducing conditions into a single fluidized bed reactor with an oxygen carrier, thus removing many of the technical challenges that hinder the scale-up of the technology. GST has successfully been applied and demonstrated for combustion, steam/dry methane reforming, and water splitting, using different oxygen carriers, showing the ease of operation under both atmospheric and pressurized conditions and achieving high products separation efficiency.This paper summarises the different studies completed on the Gas Switching Technology covering experimental demonstration (including the experience from a 50 kW(th) cluster), process modelling and techno-economics, highlighting the advantages and disadvantages of the technology and discussing the way forward.

The agricultural sector is the main contributor for the warming from non-CO2 gases, especially methane and nitrous oxide. Existing measures to mitigate these emissions can only reduce but not eliminate these emissions. Owing to the diffused nature of these emissions, it is hard to design a single point measure to address the emissions from the agricultural sector. In our work, we present the first-of-a-kind direct air capture-based process to mitigate these diverse emissions. The process is designed based on thermal catalytic route for the methane conversion, which is coupled to a direct air capture unit for CO2 capture. The process was modelled based on steady state assumptions to estimate the energy requirement per tonne of CO2 equivalent mitigated. Energy estimations were later compared for the two methane removal systems with and without CO2 capture unit. The energy demand per tonne CO2-equivalent removed from the system without CO2 capture unit (only CH4 removal) was found to be 16.54 GJ. For the methane removal system with CO2 capture unit (co-removal of CO2 and CH4), the energy demand is 15.42 GJ per tonne-CO2 equivalent.

The agriculture sector contributes to ∼40% of methane emissions globally. Methane is also 28 times (Assessment Report 5) more potent greenhouse gas than CO2. In this study, we assess the impact of measures for mitigating methane emissions from the agricultural sector on the achievement of all the 17 United Nations’ Sustainable Development Goals (SDGs). A keyword literature review was employed that focused on finding the synergies and trade-offs with non-fossil methane emissions from the agricultural sector and respective SDGs’ targets. The results were in broad consensus with the literature aimed at finding the relationship between SDGs and measures targeting climate change. There is a total of 88 synergies against eight trade-offs from the 126 SDGs’ targets that were assessed. It clearly shows that measures to mitigate methane emissions from the agricultural sector will significantly help in achieving the SDGs. Since agriculture is the primary occupation and the source of income in developing countries, it can further be inferred that methane mitigation measures in developing countries will play a larger role in achieving SDGs. Measures to mitigate methane emissions reduce poverty; diversify the source of income; promote health, equality, education, sanitation, and sustainable development while providing energy and resource security to the future generations.