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.

Ammonia is a widely produced industrial chemical, primarily for use in the fertilizer industry. Recently, interest has also grown in ammonia as a carbon-free energy carrier because it is easier to store and transport than hydrogen. However, ammonia is primarily produced from natural gas with a considerable carbon footprint if the produced CO2 is not captured and stored. This work therefore presents a new ammonia production method based on membrane-assisted autothermal reforming (MA-ATR) for hydrogen production from natural gas with integrated CO2 capture. The MA-ATR reactor offers great process intensification benefits, leading to considerable efficiency gains as well as a simpler and cheaper plant. In the base case, MA-ATR achieves 10.7% greater efficiency, 14.9% lower NH3 production costs and 16.5%-points greater CO2 avoidance than a conventional ammonia plant where captured CO2 is compressed for transport and storage. This economic advantage of MA-ATR increases with higher natural gas prices, lower electricity prices, lower membrane costs and higher CO2 prices. All elements of the proposed plant are mature technologies aside from the membranes and the oxygen carrier material. Further development and demonstration of these two elements is therefore recommended to realize the promising techno-economic performance reported in this study.

Background and Motivation The Paris Agreement is an important milestone that brought together 196 countries to agree upon climate targets through emission reduction. Although the main focus has been on mitigating CO2in the IPCC's 1.5 °C report [1], mitigating non-CO2greenhouse gases like CH4and N2O will have a significantly higher climate impact. Majority of these non-CO2GHGs are from the agricultural and farming sector, accounting for 39% and 72% of CH4and N2O emissions worldwide in 2017 [2, 3]. One of the main challenges with these emissions is that they are very diverse and dilute. However, the confidence gained through development of Direct Air Capture (DAC) technology for CO2capture from air [4] presents opportunities to mitigate CH4and N2O emissions. The scope of this paper is to provide an insight into an intensified process that can mitigate multiple GHGs (CH4, N 2O and CO2) from air in a single system. The proposed process concept is termed as Multiple Greenhouse Gas Mitigation (MGM) and can accelerate achieving negative emissions. The envisioned process technology can be first applied to mitigate GHGs from air closer to animal ventilation stables, that contains CH4(2-300 ppm). Two types of approaches have been studied to mitigate CH4and/or N2O from air i) gas separation, capture and regeneration, and ii) catalytic conversion/decomposition. In the first approach, CH4and N2O are generally adsorbed over porous zeolites and metal-organic frameworks (MOFs) [5, 6]. However, these processes have challenges with presence of CO2and moisture in air [7]. The second approach is to convert CH4and N2O over a catalyst surface (thermal or photocatalyst). Thermal catalyst can convert CH4and N2O only at temperatures above 300 °C [8-10]. It is worth noting that the studies didn't include results for simultaneous CH4and N2O mitigation. However, photocatalyst have potential to convert both CH4and N2O at room temperatures [11, 12]. Based on this concept, a solar chimney power plant (SCPP) [11] was proposed that can convert CH4and N2O while generating electricity from solar panels. However, there is still a gap in science with respect to mitigating all the three major GHGs (CH4, N2O, CO2) in one single system. This paper presents a first-of-its-kind process intensification concept to mitigate all the three major GHGs (CH4, N 2O, CO2) from air. A simple schematic of the process is shown in Figure 1. Photocatalytic surface is used to convert the CH4into CO2and H2O, and N2O into N2and O2, followed by DAC of CO2. The captured CO2can be then compressed, transported and utilized or stored. The proposed concept can advance the development of DAC technologies and can have greater impact by mitigating CH4and N2O that have higher global warming potential (28 and 265 respectively, following fifth assessment report AR5). In this paper, we propose the intensified process and present analysis with respect to the energy consumed per ton of CO2-equivalent mitigated. Methods A 0D model for the photocatalytic converter is modelled using MATLAB. The 0D model incorporates the thermodynamic and kinetic data, and radiation transport equation to predict the conversion of CH4and N2O in air. 0D model does not consider the shape of the catalytic converter nor the flow profiles. The remainder of the process is modelled using commercial simulation software tools like Aspen Plus. The energy consumed in the process for blowers and regeneration of sorbent is estimated. The energy consumed in the DAC of CO2is considered as the reference. The typical amine?impregnated oxide-based DAC for CO2[4] technology is considered in this study. The key performance indicator in this study is the energy consumed per ton of CO2-equivalent mitigated. The tons of CO2-equivalent includes the tons of CO2and tons of CH4and N2O multiplied by their global warming potential. Results The results from this study mainly compares the estimation of the conversion, material and energy requirements in the process against the DAC for CO2. We will also make a comparison of the results against the process where each gas would been separately mitigated. The amount of greenhouse gases mitigated and the energy consumed per ton of CO2-equivalent mitigated will be calculated. The DAC for CO2capture consumes 12 GJ/ton-CO2for a technology that uses amine impregnated oxide?based DAC. Preliminary results show that the energy consumed per ton of CO2-equivalent mitigated will be 4 GJ in the MGM concept. A detailed process analysis, with material (catalyst and sorbent) and energy consumed, quantum yield (as we consider photocatalysts) and amount of greenhouse gases mitigated will be presented in the final paper. The work is part of the project "Energieffektiv negativa utsläpp från jordbrukssektorn" (project number 50340-1) funded by Energimyndigheten (Swedish Energy Agency). The authors would like to thank the collaborators in the project from KTH Royal Institute of Technology (Stefan Grönkvist), Uppsala University and Swedish University of Agricultural Sciences for their contributions through discussions within the project. This work is also financially supported by the Swedish governmental initiative StandUp for Energy.

Background and Motivation The Paris Agreement is an important milestone that brought together 196 countries to agree upon climate targets through emission reduction. Although the main focus has been on mitigating CO2in the IPCC's 1.5 °C report [1], mitigating non-CO2greenhouse gases like CH4and N2O will have a significantly higher climate impact. Majority of these non-CO2GHGs are from the agricultural and farming sector, accounting for 39% and 72% of CH4and N2O emissions worldwide in 2017 [2, 3]. One of the main challenges with these emissions is that they are very diverse and dilute. However, the confidence gained through development of Direct Air Capture (DAC) technology for CO2capture from air [4] presents opportunities to mitigate CH4and N2O emissions. The scope of this paper is to provide an insight into an intensified process that can mitigate multiple GHGs (CH4, N 2O and CO2) from air in a single system. The proposed process concept is termed as Multiple Greenhouse Gas Mitigation (MGM) and can accelerate achieving negative emissions. The envisioned process technology can be first applied to mitigate GHGs from air closer to animal ventilation stables, that contains CH4(2-300 ppm). Two types of approaches have been studied to mitigate CH4and/or N2O from air i) gas separation, capture and regeneration, and ii) catalytic conversion/decomposition. In the first approach, CH4and N2O are generally adsorbed over porous zeolites and metal-organic frameworks (MOFs) [5, 6]. However, these processes have challenges with presence of CO2and moisture in air [7]. The second approach is to convert CH4and N2O over a catalyst surface (thermal or photocatalyst). Thermal catalyst can convert CH4and N2O only at temperatures above 300 °C [8-10]. It is worth noting that the studies didn't include results for simultaneous CH4and N2O mitigation. However, photocatalyst have potential to convert both CH4and N2O at room temperatures [11, 12]. Based on this concept, a solar chimney power plant (SCPP) [11] was proposed that can convert CH4and N2O while generating electricity from solar panels. However, there is still a gap in science with respect to mitigating all the three major GHGs (CH4, N2O, CO2) in one single system. This paper presents a first-of-its-kind process intensification concept to mitigate all the three major GHGs (CH4, N 2O, CO2) from air. A simple schematic of the process is shown in Figure 1. Photocatalytic surface is used to convert the CH4into CO2and H2O, and N2O into N2and O2, followed by DAC of CO2. The captured CO2can be then compressed, transported and utilized or stored. The proposed concept can advance the development of DAC technologies and can have greater impact by mitigating CH4and N2O that have higher global warming potential (28 and 265 respectively, following fifth assessment report AR5). In this paper, we propose the intensified process and present analysis with respect to the energy consumed per ton of CO2-equivalent mitigated. Methods A 0D model for the photocatalytic converter is modelled using MATLAB. The 0D model incorporates the thermodynamic and kinetic data, and radiation transport equation to predict the conversion of CH4and N2O in air. 0D model does not consider the shape of the catalytic converter nor the flow profiles. The remainder of the process is modelled using commercial simulation software tools like Aspen Plus. The energy consumed in the process for blowers and regeneration of sorbent is estimated. The energy consumed in the DAC of CO2is considered as the reference. The typical amine?impregnated oxide-based DAC for CO2[4] technology is considered in this study. The key performance indicator in this study is the energy consumed per ton of CO2-equivalent mitigated. The tons of CO2-equivalent includes the tons of CO2and tons of CH4and N2O multiplied by their global warming potential. Results The results from this study mainly compares the estimation of the conversion, material and energy requirements in the process against the DAC for CO2. We will also make a comparison of the results against the process where each gas would been separately mitigated. The amount of greenhouse gases mitigated and the energy consumed per ton of CO2-equivalent mitigated will be calculated. The DAC for CO2capture consumes 12 GJ/ton-CO2for a technology that uses amine impregnated oxide?based DAC. Preliminary results show that the energy consumed per ton of CO2-equivalent mitigated will be 4 GJ in the MGM concept. A detailed process analysis, with material (catalyst and sorbent) and energy consumed, quantum yield (as we consider photocatalysts) and amount of greenhouse gases mitigated will be presented in the final paper. The work is part of the project "Energieffektiv negativa utsläpp från jordbrukssektorn" (project number 50340-1) funded by Energimyndigheten (Swedish Energy Agency). The authors would like to thank the collaborators in the project from KTH Royal Institute of Technology (Stefan Grönkvist), Uppsala University and Swedish University of Agricultural Sciences for their contributions through discussions within the project. This work is also financially supported by the Swedish governmental initiative StandUp for Energy.

Gas switching reforming (GSR) is a promising technology for natural gas reforming with inherent CO2 capture. Like conventional steam methane reforming (SMR), GSR can be integrated with water-gas shift and pressure swing adsorption units for pure hydrogen production. The resulting GSR-H2 process concept was techno-economically assessed in this study. Results showed that GSR-H2 can achieve 96% CO2 capture at a CO2 avoidance cost of 15 $/ton (including CO2 transport and storage). Most components of the GSR-H2 process are proven technologies, but long-term oxygen carrier stability presents an important technical uncertainty that can adversely affect competitiveness when the material lifetime drops below one year. Relative to the SMR benchmark, GSR-H2 replaces some fuel consumption with electricity consumption, making it more suitable to regions with higher natural gas prices and lower electricity prices. Some minor alterations to the process configuration can adjust the balance between fuel and electricity consumption to match local market conditions. The most attractive commercialization pathway for the GSR-H2 technology is initial construction without CO2 capture, followed by simple retrofitting for CO2 capture when CO2 taxes rise, and CO2 transport and storage infrastructure becomes available. These features make the GSR-H2 technology robust to almost any future energy market scenario.