Net-zero CO2 Emissions Research Articles

FROT: A Framework to comprehensively describe radiative contributions to temperature responses

Abstract Different human activities and associated emissions of CO2 and non-CO2 radiative forcing agents and feedbacks determine the final state of Earth’s climate. To understand and explain contributions to global temperature changes, many emission-based metrics have been employed, such as CO2-equivalent or -forcing equivalent. None of these metrics, however, include dynamic responses from Earth system feedbacks in terms of carbon and heat redistribution, known to play an increasingly important role in ambitious mitigation scenarios. Here we introduce a framework that allows for an assessment of such feedbacks in addition to CO2, non-CO2 anthropogenic forcing and natural external variability contributions. FROT (Framework for Radiative cOntributions to Temperature response) allows for an assessment of components of direct radiative impact to the system (climate forcing), as well as Earth system feedbacks concerning heat and carbon. The framework is versatile in terms of applications and allows for exploring individual components contributions to, for example, temperature stabilisation simulations, or comparisons in different models and scenarios, as it can reasonably explain their simulated temperature variability. Here, we apply FROT to both an intermediate complexity and a fully coupled Earth system model, as we simulate highly ambitious mitigation scenarios. Comparing temperature stabilisation scenarios, we can show that both net-zero CO2 emissions and small amounts of positive CO2 emissions could lead to a stable global temperature trajectory. Our assessment reveals that the effects of non-CO2 climate forcings, especially the development of sulphate aerosols in the atmosphere, and the dynamics of the carbon cycle, play a pivotal role in the final level of warming and in enabling a temperature stabilisation. Under highly ambitious climate mitigation scenarios it becomes crucial to include Earth system feedbacks, specifically ocean heat uptake, to understand interannual to decadal temperature development, since previously secondary processes now become increasingly dominant. Our framework offers the opportunity to do so.

Editorial: Will the Road to Carbon Neutrality Become Even More Bumpy Than Ever?

The first-ever global stocktake of what has been achieved and what still must be achieved since the 2015 Paris Agreement on climate change shows that we are not on track to meet the target of limiting global temperature increase in 2050 to 1.5°C above preindustrial levels. Although the EU CBAM is still in its transitional stage and the proposal for a substantial revision of the EU ETD is the only file of the ‘Fit for 55’ package that has not yet been adopted, the EU is one of the better performers on the road to the netzero CO2 emissions target for 2050. In 2023, COP28 has set a new ambitious target for greenhouse gas reductions by 2030. However, the geopolitical situation has dramatically changed by the wars in Ukraine and Gaza. The implications for the energy transition from fossil to renewable sources may make the already bumpy road to carbon neutrality even more bumpy than ever.

Carbon footprint of solar based mini-grids in Africa: Drivers and levers for reduction

The massive development of mini-grids (MGs) is seen as a promising alternative to the extension of national grids to achieve universal access to electricity. MGs based on solar photovoltaic are often recognized fully consistent with net-zero CO2 emissions objectives. However, if they have low or even no direct emissions from diesel consumption, they embed indirect carbon emissions due to solar panels and batteries manufacturing. Electrification policies, mainly based on the levelized costs of electricity (LCOE), should likely account for the carbon footprints (CFP) of possible electrification strategies.In this work, we assess the CFP of hybrid MGs (solar, battery, diesel) for rural electrification in Africa. We consider a large number of MG configurations for many locations across the continent. For each location, we identify the lowest CFP and LCOE, and estimate their dependency to meteorological and socio-economic factors.Our results show that: (i) the lowest CFP depends on location and is around 200gCO2/kWh; (ii) it can be higher than the CFP of certain African national grids; (iii) the CFP of hybrid MGs can be lower than the CFP of MGs relying only on solar PV; (iv) for most techno-economic and environmental assumptions, moderate LCOE increases allow significant CFP reductions.

Solid amine adsorbent with surfactant modification for Direct Air Capture (DAC) under different temperature and humidity conditions

Direct air capture (DAC) technologies have been vigorously pursued to achieve the goal of net-zero CO2 emissions due to the dramatic increase in atmosphere CO2 concentrations and global temperatures. In practical DAC conditions, variations in temperature and humidity can lead to different CO2 adsorption outcomes. Current studies lack comprehensive information on the optimal temperature and humidity conditions for DAC. In this study, a comparison between PMSU-F (impregnating polyethyleneimine (PEI600) on MSU-F support) and PPMSU-F (co-impregnating polyethylene glycol (PEG200) with PEI600 on MSU-F support) under different temperature and relative humidity conditions were conducted. Under dry conditions, the addition of PEG200 effectively enhanced the adsorption capacity, adsorption rate, and amine efficiency and decreased the energy consumption for desorption depending on the comparison of the two absorbents. Under the popular atmospheric temperature ranges (−5 °C–45 °C), an increase in temperature favors CO2 adsorption. Under humid conditions, the presence of PEG200 had a negative effect due to its strong hydrophilicity. By comparing dry and humid conditions, the introduction of moisture generally enhanced overall CO2 adsorption performance, and the adsorption capacity interestingly further increased under low-temperature conditions. The highest CO2 adsorbing capacity of PMSU-F (3.82 mmol/g) and PPMSU-F (3.76 mmol/g) appeared at −5 °C and 75% relative humidity, indicating that low temperature and relatively high relative humidity were more favorable for DAC, which is possibly attributed to the thermodynamic control under low temperatures with moisture. The results indicate that the adsorbents chosen in this study are promising for DAC under low temperatures and relatively high humidity conditions. The performances of modified DAC adsorbents, e.g., adsorption capacity, stability, antioxidant property for industrial-grade DAC system should be evaluated in the next work.

Perceptions of carbon dioxide emission reductions and future warming among climate experts

The Intergovernmental Panel on Climate Change (IPCC) employs emission scenarios to explore a range of future climate outcomes but refrains from assigning probabilities to individual scenarios. However, IPCC authors have their own views on the likelihood of different climate outcomes, which are valuable to understand because authors possess both expert insight and considerable influence. Here we report the results of a survey of 211 IPCC authors about the likelihood of four key climate outcomes. We found that most authors are skeptical that warming will be limited to the Paris targets of well below 2 °C, but are more optimistic that net zero CO2 emissions will be reached during the second half of this century. When asked about the beliefs of their peers, author responses showed strong correlations between personal and peer beliefs, suggesting that participants with extreme beliefs perceive their own estimates as closer to the community average than they actually are.

Carbon management technology pathways for reaching a U.S. Economy-Wide net-Zero emissions goal

The Carbon Management Study Group of the 37th Energy Modeling Forum (EMF 37) designed seven scenarios to explore the role of three potentially key technology suites – point source carbon dioxide capture and storage (PSCCS), direct air capture of carbon dioxide (DACCS), and hydrogen systems (H2) – in shaping the broader technology pathways to reaching net-zero carbon dioxide (CO2) emissions in United States by 2050. Each scenario was run by up to 13 models participating in the EMF 37 study. Results show that carbon dioxide removal technologies were consistently a major part of successful pathways to net-zero U.S. CO2 emissions in 2050. Achieving this net-zero CO2 goal without any form of carbon dioxide capture and storage was found to be impossible for most models; some models also found it impossible to reach net-zero without DACCS. The marginal cost of achieving net-zero CO2 emissions in 2050 was between two and 10 times higher without PSCCS and/or DACCS available. The carbon price at which DACCS was deployed as a backstop technology depended upon the assumed cost at which DACCS was available at scale. Carbon prices were between $250 and $500 per ton CO2 when DACCS deployed as a backstop. The average CO2 capture rate across all models in 2050 in the central net-zero scenario was 1.3 GtCO2/year, which implies a substantial upscaling of capacity to move and store CO2. Hydrogen sensitivity scenarios showed that H2 typically constituted a relatively small share of the overall U.S. energy system; however, H2 deployed in applications that are considered hard to decarbonize, facilitating transition towards net-zero emissions.

Leveraging Flow-Assisted Electrochemistry Toward Decarbonization of Cement Manufacturing

In an effort to decarbonize the global economy by 50% in 2030 and achieve net-zero carbon emissions by 2050, there is a dire need to electrify industrial processes [1]. Approximately 8% of global carbon emissions comes from cement production [2]. Considering the rising demand for cement due to infrastructure expansion, it is critical to develop new concepts for the decarbonization of cement production. With this goal in mind, our work explores the effectiveness of flow-assisted cement electrolysis as a replacement to conventional fossil fuel based high-temperature kilns in cement manufacturing plants [3].In this study, we employ a scalable 3-channel flow-reactor with acidic anolyte, basic catholyte, and a neutral chemical flush in between to generate calcium hydroxide, Ca(OH)2 [4, 5], which is the key ingredient in cement manufacturing. The central channel is separated from either half cells by a cation exchange and an anion exchange membrane. The electrochemical performance of the proposed cement electrolyzer under a variety of operating conditions is investigated by considering the key variables in reactor design, including flow rate, temperature, catalyst choice and feed concentrations, to shed light into the practical challenges of running a 3-channel flow reactor. Our preliminary study indicates that membranes are possibly responsible for a significant fraction of the limited yields of Ca(OH)2. Specifically, the anion exchange membranes tested are susceptible to degradation in alkaline conditions displaying poor ionic conductance, whereas the cation exchange membranes allow significant water crossover. The findings from this study pave the way in understanding key components for cement electrolysis and other electrochemical systems employing 3-channel flow reactors. References DeAngelo, J., et al., Energy systems in scenarios at net-zero CO2 emissions. Nature Communications, 2021. 12(1): p. 6096. Ellis, L.D., et al., Toward electrochemical synthesis of cement—An electrolyzer-based process for decarbonating CaCO3 while producing useful gas streams. PNAS, 2019. 117(23): p.12584. Rissman, J., et al., Technologies and policies to decarbonize global industry: Review and assessment of mitigation drivers through 2070. Applied Energy, 2020. 266: p. 114848. Perego, A., et al., Electrochemical Flow Reactor for Cement Clinker Production. ECS Meeting s, 2021. MA2021-02(27): p. 840. Olsson, J.A., S.A. Miller, and M.G. Alexander, Near-term pathways for decarbonizing global concrete production.Nature Communications, 2023. 14(1): p. 4574.

Opportunities beyond net-zero CO2 for cost-effective greenhouse gas mitigation in China

Achieving net-zero CO2 emissions is the current main focus of China’s carbon neutrality goal. However, non-CO2 greenhouse gases (GHGs) are more powerful climate forcers, making their emission reduction an opportunity to rapidly mitigate future warming. Here, we evaluate non-CO2 mitigation potentials, costs and climate benefits in the context of China’s carbon neutrality goals. The assessment is conducted by coupling the integrated assessment model GCAM with a climate emulator. The findings indicate that mitigation technologies can largely reduce fluorinated gas emissions from industrial sectors, but long-term non-CO2 reductions of energy sector activities rely heavily on fuel switching. Furthermore, the cumulative costs of deploying non-CO2 mitigation technologies are projected to be less than 10% of the total costs of achieving carbon neutrality from 2020 to 2060. If non-CO2 mitigation measures are included in the overall mitigation portfolio, the benefits of avoided warming would by far outweigh the total mitigation cost increase. Our results thus highlight that incorporating a wider suite of GHGs into climate change mitigation strategies can enhance the cost-effectiveness of mitigation efforts.

Deployment expectations of multi-gigatonne scale carbon removal could have adverse impacts on Asia’s energy-water-land nexus

Existing studies indicate that future global carbon dioxide (CO2) removal (CDR) efforts could largely be concentrated in Asia. However, there is limited understanding of how individual Asian countries and regions will respond to varying and uncertain scales of future CDR concerning their energy-land-water system. We address this gap by modeling various levels of CDR-reliant pathways under climate change ambitions in Asia. We find that high CDR reliance leads to residual fossil fuel and industry emissions of about 8 Gigatonnes CO2yr−1 (GtCO2yr−1) by 2050, compared to less than 1 GtCO2yr−1 under moderate-to-low CDR reliance. Moreover, expectations of multi-gigatonne CDR could delay the achievement of domestic net zero CO2 emissions for several Asian countries and regions, and lead to higher land allocation and fertilizer demand for bioenergy crop cultivation. Here, we show that Asian countries and regions should prioritize emission reduction strategies while capitalizing on the advantages of carbon removal when it is most viable.

Solar energy generation from residential buildings, transition of the energy sector from fossils to carbon-free energy and meeting UN SDG

Purpose This study aims to focus on the transition of Kosovo’s energy generation sector from fossil fuels (94%), to renewable sources. The installation of 10 kW photovoltaic (PV) panels in individual houses will mitigate CO2 emissions from electrical energy generation and contribute meeting the sustainable development goals (SDGs; 7, 11 and 13) set by United Nations General Assembly. This study case is based on the installation of PV panels on the roofs, and where possible on the facades of the private residential buildings in seven, the most populated towns of Kosovo (Prishtina, Prizren, Mitrovica, Peja, Gjakova, Ferizaj and Gjilan). Design/methodology/approach This study used the data, in regard to direct normal irradiation, altitude, coordinates, PV system configurations, specific PV power output and optimum tilt of PV panels specific for the selected locations,retrieved from Global Solar Atlas, which is a web-based-tool, as provided by “Solargis,”a company that provides online and commercial solar data resources, selected by The World Bank and the International Finance Corporation. The second software was RETScreen Expert, which is more sophisticated and allows input of more variables with regard to the proposed 10 kW PV system. With the use of RETScreen Expert software, the financial viability of the project, the equity payback period, and the reduction in greenhouse gas (GHG) emissions compared to the base case were assessed. Based on the gained data, the feasibility and outcome of the study case were assessed in terms of power generation, cost and comparison with the present PV installed capacities in Kosovo. Findings Small-scale solar energy generated from individual buildings can make great impact of country’s policies toward lowering CO2 emission as one most influential greenhouse gas in rising average global temperature, improving air quality in towns by lowering emission of harmful gases and particulate matter (PM). As the study foresees installation of 10 kW of PV in residential houses, the calculated yearly energy generation would be around 15 MWh, which is twice of the average of real consumption of a household in Kosovo. This calculated energy generation from private houses is equal in capacity with generation of present PV parks that are connected on grid as reported from Transmission, System and Market Operator of the Republic of Kosovo. This proves that, if implemented, the study outcome would make Kosovo to meet the goal for a carbon free energy and meeting targets of at least three out of 17 SDG set by UNSC. Originality/value This paper’s model provides a ground for a transition of national energy sector from 90% fossils dependence to renewable energy sources (RES). Despite of some barriers such as cost of initial investment, energy storage, lack of government’s incentives and legislative base for households to become prosumer or at best energy self-sufficient buildings, this solution will make Kosovo harness its unused RES and meet targets of Paris Climate Agreement for net zero CO2 emissions from energy production by 2050 and SDG targets.

Potential role of nuclear power in a carbon-free world

Thermal Power Plants (ThPP), along with transport facilities, are the major sources for industrial emissions of carbon dioxide (CO2) believed to be responsible for the greenhouse effect leading to overheating of the lower atmosphere. In the opinion of many scientists, there is a threshold value of the average atmospheric temperature exceeding, which entails the potential for the development of irreversible processes threatening the existence of humankind. To avoid this danger, governments in nearly 200 countries have chosen voluntarily to reach net-zero CO2 emissions by 2050. Renewable Energy Sources (RES), including wind and solar power plants, have been selected as substitutes for ThPPs. However, energy systems based on RES only need to be multiply redundant in terms of installed capacity due to their efficiency being heavily dependent on daily, seasonal and weather factors, leave alone the scale of the required material resources (metals, polymers, concrete, glass, etc.). The major drawback of such energy systems is, however, the RES common-cause failure, e.g., in the event of a global volcanic eruption, when no energy-security requirement can be met to provide energy for satisfying the most vital needs. A need is fully evident for furnishing such energy system with another power source to be not dependent on the event that has caused the mass RES failure. With the net-zero-carbon requirement taken into account, Nuclear Power (NP) appears to be the best option in this respect. Modern NP does not however fully suits this role due to its inherent drawbacks (limited fuel resources, pending Spent Nuclear Fuel (SNF) and RadioActive Wastes (RAW) handling and nuclear-material nonproliferation issues). A potential solution to these drawbacks is a two-component NP technology in a closed nuclear-fuel cycle currently in the process of development. In Russia, where the greatest progress has been achieved in this field of development, under construction is a pilot and demonstration energy complex with the BREST-OD-300 nuclear unit expected to be started up in 2026–2027. Another promising designs to be developed are Small Modular Reactors (SMRs) / Small Nuclear Power Plants (SNPPs).

Deployment of carbon removal technologies could reduce the rapid and potentially disruptive pace of decarbonization in South Africa's climate ambitions

As a developing country, South Africa faces the risk of having to undertake disruptive actions to meet its internationally pledged emission reduction targets. It has become necessary to find alternative measures for South Africa to meet its climate targets without such a disruptive and aggressive transformation of its energy sector. To truly reach net-zero CO2 emissions, South Africa must ensure that residual emissions from its recalcitrant sectors are equally compensated by carbon dioxide removal (CDR). Given the potential for CDR technologies to delay the need for rapid emissions cuts, we leverage this characteristic to explore their role in helping South Africa achieve its climate targets on time, but through a less disruptive and overly aggressive pace of energy system decarbonization. Using an integrated assessment model, we show that while reaching its emission reduction targets, the presence of novel CDR (nCDR) approaches could significantly reduce South Africa's mitigation costs to $155-240/tCO2 instead of $190–590/tCO2 by 2050 in the absence of nCDR. Furthermore, the availability of nCDR may allow for a more gradual transition towards renewable and nuclear power generation compared to scenarios without nCDR. Importantly, we reveal that nCDR could help avoid asset stranding of up to 4–6 GW and $15–25 billion in associated costs between 2016 and 2050. However, this comes at the cost of higher residual greenhouse gas emissions due to the continued reliance on fossil fuels under nCDR availability. Overall, South Africa's priority must remain on decarbonization, especially in sectors where fuel switching and energy efficiency are feasible. Nonetheless, the complementary role of nCDR must not be underestimated, and South Africa should begin investing in these emerging technologies to support its ambitious climate goals.

Taking stock of carbon dioxide removal policy in emerging economies: developments in Brazil, China, and India

ABSTRACT Deliberately removing carbon dioxide from the atmosphere is an important element of bringing mitigation pathways in line with the climate goals of the Paris Agreement. To reach global net-zero CO2 emissions and limit global warming to 1.5°C with no or limited overshoot, global mitigation pathways assessed by IPCC’s Sixth Assessment Report require some world regions to achieve net-negative CO2 emissions with large-scale carbon dioxide removal (CDR) deployment. This raises important questions about the availability and feasibility of CDR deployment in different societal and political contexts. This paper therefore combines an analysis of CDR deployment in a sample of scenarios from the IPCC AR6 database with a bottom-up analysis of the state of CDR governance and policy in countries considered key in scaling up CDR capacity and not yet covered by existing research. In particular, the paper focuses on Brazil, China, and India as important emerging economies and large emitters. We highlight the expected use of CDR methods in those regions in scenarios and systematically assess and compare the level of CDR regulation and innovation across these countries. This comparative perspective has the potential to broaden the understanding of existing and emerging CDR policies and politics. The synthesis of the case studies provides three key contributions to existing literature: First, we explore the state of CDR governance and policymaking in key emerging economies. As in OECD countries, there is a notable lack of CDR regulation and innovation to enable the scale of CDR required in the short- and medium term. Second, we identify that repurposing policies is a key type of emerging CDR policymaking in these countries targeting CDR methods in the land use, land use change and forestry (LULUCF) sector. We find that the repurposing efforts strengthen the level of regulation and innovation for this group of methods. Third, we explore three building blocks (regional differentiation, delay of upscaling, sustainability thresholds) of plausible CDR deployment narratives that could help bridge integrated assessment models and comparative case studies in future research.

Effects of CO2 Geosequestration on Opalinus Clay

CO2 geosequestration is an important contributor to United Nations Sustainable Development Goal 13, i.e., Climate Action, which states a global Net-Zero CO2 emissions by 2050. A potential impact of CO2 geosequestration in depleted oil and gas reservoirs is the variations in induced pressure across the caprocks, which can lead to significant local variations in CO2 saturation. A detailed understanding of the relationship between the pressure gradient across the caprock and local CO2 concentration is of utmost importance for assessing the potential of CO2 geosequestration. Achieving this through experimental techniques is extremely difficult, and thus, we employ a coupled Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) based solver to mimic sub-critical CO2 injection in Opalinus Clay under various pressure gradients across the sample. The geomechanical and multiphase flow modelling utilising Darcy Law helps evaluate local variations in CO2 concentration in Opalinus Clay. Well-validated numerical results indicate favourable sub-critical CO2 geosequestration under a positive pressure gradient across Opalinus Clay. In the absence of a positive pressure gradient, a peak CO2 concentration of 5% has been recorded, which increases substantially (above 90%) as the pressure gradient across the sample increases.

Cross-sectoral assessment of CO2 capture from U.S. industrial flue gases for fuels and chemicals manufacture

Although CO2 impacts the environment negatively, it can be a valuable resource due to its carbon content. The U.S. industry emits over 825 Mt of CO2 annually, with an expected increase in the future. This article analyzes 27 different technology combinations for capturing and using CO2 for industrial feedstocks, including the production of synthetic methane, methanol, and Fischer-Tropsch fuels. The study also estimates and compares the energy requirements for capturing and converting CO2 from 16 different industrial sources, as well as the energy requirements for hydrogen production through state-of-the-art and emerging electrolyzer technologies. Additionally, the study develops a combined scenario that outlines a design for applying an inclusive approach to achieve net-zero CO2 emissions in the industrial sector, incorporating multiple decarbonization measures. The results suggest that the use of CO2 for methane production has the potential to replace all natural gas demands considered in the base case and combined scenarios. However, using CO2 utilization-based Fischer-Tropsch products alone to replace naphtha feedstock and transportation fuels is not sufficient to achieve complete decarbonization in the studied end uses. CO2 utilization-based methanol could potentially substitute for several times the current U.S. methanol production and meet the current global demand for methanol. Moreover, the study conducts an economic analysis to estimate the costs of CO2 utilization, which vary for different industrial sectors and depend on the technologies employed. Overall, this study provides valuable information for policymakers and industry stakeholders who are striving to develop effective strategies to decarbonize the industrial sector.

Environmental evaluation and comparison of hybrid separation methods based on distillation and pervaporation for dehydration of binary alcohol mixtures with life cycle, PESTLE, and multi-criteria decision analyses

To achieve net-zero CO2 emissions by 2050, improving energy efficiency in the chemical industry is crucial. The study focuses on an environmentally friendly hybrid distillation (D)-pervaporation (PV) process to enhance energy efficiency and purity in ethanol–water and isobutanol-water mixtures, these are typical wastes in the chemical industry. Three configurations—D + PV, D + PV + D, and D + PV + D with partial Heat Integration (HI)—are evaluated for separation of ethanol–water and isobutanol-water mixtures employing the Life Cycle Assessment with Environmental Footprint (EF) V3.1 (adapted) and ReCiPe 2016 Endpoint (H) V1.08 methods, using SimaPro V9.5 software and Ecoinvent V3.9.1 database. The study also incorporates a PESTLE analysis and Multi-Criteria Decision Analysis to identify the most advantageous process for ethanol and isobutanol scenarios. The research evaluates these systems in a comprehensive manner, including technology, CO2 emissions, impacts on human health, ecosystems, resources, and Total Annual Cost (TAC). The exploration of hybrid process enhancements includes alternative renewable energy sources (i.e., solar, wind, hydro, and biofuel) and comprehensive heat integration based on Pinch Analysis using Hint V2.2 software. Results indicate that D + PV + D is the most suitable for isobutanol-water scenarios based on MCDA and Pinch analysis. In isobutanol scenarios, D + PV + D + HI reduces CO2 emissions, and human health, ecosystems, and resources impact by 15.5 %, 11.2 %, 12.6 %, and 14.6 %, respectively, with a significant 40.0 % decrease in TAC compared to D + PV. Integrating renewable energy sources further enhances its sustainability, achieving a single score of approximately one-third lower than fossil fuel consumption. Promoting renewable energy and Integrating energy flows align seamlessly with Green Chemistry and Engineering principles, representing a crucial stride towards sustainable and eco-friendly industrial practices.

Multi-scale reduced-order models of electrified wire reactors for carrying-out endothermic reactions

In chemical manufacturing applications with endothermic reactions, the heat of reaction is supplied by burning fossil fuels. Electrified reactors are one of the enticing alternatives to the traditional configurations where heating can be achieved via renewable power, leading to reduced or net-zero CO2 emissions. In this work, we consider flow-through wire-based electrified reactors and develop reduced order model (ROM) for this configuration. The ROM is expressed in terms of multiple concentration and temperature modes that are coupled with various local property dependent transfer coefficients. Steam methane reforming is selected as an example to demonstrate the utility of ROM and reactor configuration for such processes. We present a detailed sensitivity study with respect to space time and feed temperature. In addition, we also investigate the effect of power supply on the reactor performance and compare with the existing literature results. Finally, we provide physical interpretation of the ROM, describe some special cases, and discuss its applicability for other electrified reactor configurations.

Carbon-neutral cement: The role of green hydrogen

Business-as-usual (BAU) cement production is associated with a linear model that contributes significantly to global warming and is dependent on volatile energy markets. A novel circular model is proposed, by adding three power-to-gas system components to current production systems: a calcium-looping (CaL) CO2 capture unit; water electrolysis for hydrogen and oxygen generation; and a methanation unit for synthetic natural gas (SNG) production. The paper presents the first analysis of the combined industrial-scale operation of these components in a closed loop, where the SNG fuels the cement kiln and the CaL unit, while the O2 produced feeds it. The circular, hybrid, and BAU models are compared in three feasibility scenarios. It is concluded that the circular model outperforms the other alternatives environmentally, opening a potential pathway for the cement industry to achieve near net-zero CO2 emissions, reduce energy dependence and improve economic efficiency.

Numerical simulation on gas-solid separation characteristics of in-situ pyrolysis products of tar-rich coal

ABSTRACT Tar-rich coal holds the potential to substitute the supply of oil-gas resources. The in-situ pyrolysis contributes to efficient resource utilization and can potentially achieve net-zero CO2 emissions. However, it is challenging to efficiently separate oil-gas resources, which are predominated by tar, from multiphase products of in-situ pyrolysis of tar-rich coal. Additionally, the difference in fluid properties yields significant influences on separation performance, while the understanding of the separation characteristics of high-viscosity fluid remains insufficient. In this study, the separation process of pyrolysis products from tar-rich coal was investigated using the computational fluid dynamics simulation approach. The flow field, pressure drop, separation efficiency and distribution characteristics were analyzed. The simulation results indicate that the volute cyclone separator exhibits commendable separation efficiency, exceeding 98%. Meanwhile, in handling tars containing a high concentration of light oil, the separator demonstrates remarkable adaptability. The separation efficiency of solid particles decreases from 89% to 83% when the system contains a high content of pitch. The particle diameter exerts great influence on the flow field. The separation efficiencies are 99% and 0.37%, respectively, when the particle sizes are selected as 0.1 mm and 0.001 mm. In the scope of this study, the optimal working conditions of the cyclone separator were determined, which provides data support for improving the separation efficiency and recovery rate of the oil-gas resources.

Emission-side drivers affecting carbon neutrality based on vegetation carbon sequestration: Evidence from China

To address climate change, the world needs deep decarbonization to achieve carbon neutrality (CN), which implies net-zero human-caused CO2 emissions in the atmosphere. This study used emission-side drivers, including socioeconomic and net primary productivity (NPP)-based factors, to determine the changes in CN based on vegetation carbon sequestration in the case of China during 2001–2015. Spatial exploratory analysis as well as the combined use of production-theoretical decomposition analysis (PDA) and an econometric model were also utilized. We showed that CN was significantly spatially correlated over the study period; Yunnan, Heilongjiang, and Jilin presented positive spatial autocorrelations, whereas Guizhou showed a negative spatial autocorrelation. More than half of CN declined over the period during which potential energy intensity (PEIE) and energy usage technological change were the largest negative and positive drivers for increasing CN. PEIE played a significantly negative role in increasing CN. We advise policymakers to focus more on emission-side drivers (e.g., energy intensity) in addition to strengthening NPP management to achieve CN.