Global CO2 Emissions Research Articles

Opportunities for carbon sequestration from removing or intensifying pasture-based beef production

Pastures, on which ruminant livestock graze, occupy one third of the earth's surface. Removing livestock from pastures can support climate change mitigation through carbon sequestration in regrowing vegetation and recovering soils, particularly in potentially forested areas. However, this would also decrease food and fiber production, generating a tradeoff with pasture productivity and the ruminant meat production pastures support. We evaluate the magnitude and distribution of this tradeoff globally, called the "carbon opportunity intensity" of pastures, at a 5-arcminute resolution. We find that removing beef-producing cattle from high-carbon intensity pastures could sequester 34 (22 to 43) GtC i.e. 125 (80 to 158) GtCO2 into ecosystems, which is an amount greater than global fossil CO2 emissions from 2021-2023. This would lead to only a minor loss of 13 (9 to 18)% of the global total beef production on pastures, predominantly within high- and upper-middle-income countries. If areas with low-carbon intensity pastures and less efficient beef production simultaneously intensified their beef production to 47% of OECD levels, this could fully counterbalance the global loss of beef production. The carbon opportunity intensity can inform policy approaches to restore ecosystems while minimizing food losses. Future work should aim to provide higher-resolution estimates for use at local and farm scales, and to incorporate a wider set of environmental indicators of outcomes beyond carbon.

An input-output approach to study the impact of carbon taxes in (almost) every country

Some forty carbon tax initiatives have been adopted, and more countries are evaluating the possibility of implementing this instrument every year. However, there is significant heterogeneity in tax rates, type of covered emissions, and regulated sectors, which is explained by the different levels of environmental concern and cost that each country is willing to assume. In this context, the present study simulates various scenarios of carbon taxes in (almost) every country in the world to contribute to the global design of climate change policies. Specifically, input-output tables and sectoral CO2 emissions of each country are used to calibrate the environmental extension of the Leontief price model, obtaining the impacts on prices, production, and emissions at the sectoral, national, or global level. The results show that the same effective tax rate can have very different effects in each country, mainly explained by the composition of the energy matrix. In addition, global CO2 emissions would be reduced by 0.10% ∼ 0.23% for each dollar of CO2 tax applied to all sectors and countries. Finally, a more outstanding commitment from rich countries and larger developing countries is required to contribute more decisively to combating climate change in the short term.

Evaluating tree-ring proxies for representing the ecosystem productivity in India.

Terrestrial ecosystems are one of the major sinks of atmospheric CO2 and play a key role in climate change mitigation. Forest ecosystems offset nearly 25% of the global annual CO2 emissions, and a large part of this is stored in the aboveground woody biomass. Several studies have focused on understanding the carbon sequestration processes in forest ecosystems and their response to climate change using the eddy covariance (EC) technique and remotely sensed vegetation indices. However, very few of them address the linkage of tree-ring growth with the ecosystem-atmosphere carbon exchange, and nearly none have tested this linkage over a long-term (> 100 years) - limited by the short-term (< 50 years) availability of measured ecosystem carbon flux. Nevertheless, tree-ring indices can potentially act as proxies for ecosystem productivity. We utilise the Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP) model outputs for its 140-year-long simulated records of mean monthly gross primary productivity (GPP) and compare them with the tree-ring growth indices over the northwestern Himalayan region in India. In this study, we examine three coniferous tree species: Pinus roxburghii and Picea smithiana wall. Boiss and Cedrus deodara and find that the strength of the correlation between GPP and tree ring growth indices (RWI) varies among the species.

Assessing the Impact of Phase-Change Materials on Enhancing the Thermal Efficiency of Buildings in Tropical Climates

Civil construction and buildings account for a significant 36% of worldwide energy consumption, contributing to 37% of global CO2 emissions. In Brazil, buildings consume a substantial 51.2% of the nation’s electricity production. Remarkably, approximately one-third of this energy is allocated specifically for maintaining thermal comfort within these structures. The thermal performance of a building has a significant impact on its energy efficiency; in this way, technologies developed to contribute to the energy efficiency of envelopes can directly contribute to the reduction in the building’s overall energy consumption. PCMs are technologies capable of absorbing heat without increasing temperature and can contribute to the better energy performance of envelopes. PCMs are used as a thermal performance solution in cold climate regions, and studies show that they are likely to work in buildings in tropical climates. The objective of this work is to analyze the performance of PCMs in tropical regions of the southern hemisphere, specifically in Brazil, and their behavior according to the constructive system used. Computer simulation contributes to an analysis closer to the reality of the implementation of this technology in these regions. This work is carried out with simulations in the software EnergyPlusTM version 24.1. The results demonstrate that PCMs can effectively contribute to a reduction in energy consumption for the thermal comfort of buildings in tropical climates, demonstrating the possible feasibility of the development of this technology for tropical climates.

An integrated management system (IMS) approach to sustainable construction development and management

Construction is significantly contributing to the severe environmental crisis it is facing. The sector consumes over 3 billion tons of raw materials annually, and its activities account for 40% of global CO2 emissions. Traditional integrated strategies toward fragmented sustainability cannot offer total optimization. In this respect, the present research presents an integrated management system (IMS) containing a composite of metrics for sustainable construction management (SCM). This research was specifically geared to test the relationship between the elements of IMS and SCM from the perspective of the construction industry. A quantitative survey tested through 119 professionals was used for data collection. It is established through structural equation modeling (SEM) that the internal consistency of Cronbach’s Alpha 0.72–0.95 and construct validity was strong. The Fornell-Larcker criterion was realized to affirm good discriminant validity. Crucial results identified the presence of significant impacts for quality management (QM) (β = 0.643, p < 0.001), risk management (RM) (β = 0.53, p < 0.001), and safety management (SM) (β = 0.439, p < 0.001). Therefore, this study further enhances the scalability of IMS so that it is practically applied to improve project quality and safety, along with risk management. Future research could also focus on studying the context of the integration of IMS with SCM and continue to work using objective performance measures to validate these findings.

Assessment of the Climate Trace global powerplant CO2 emissions

Assessment of the Climate Trace global powerplant CO2 emissions

Fundamental Understanding of Marine Applications of Molten Salt Reactors: Progress, Case Studies, and Safety

Marine sources contribute approximately 2% of global energy-related CO₂ emissions, with the shipping industry accounting for 87% of this total, making it the fifth-largest emitter globally. Environmental regulations by the International Maritime Organization (IMO), such as the MARPOL (International Convention for the Prevention of Pollution from Ships) treaty, have driven the exploration of alternative green energy solutions, including nuclear-powered ships. These ships offer advantages like long operational periods without refueling and increased cargo space, with around 200 reactors already in use on naval vessels worldwide. Among advanced reactor concepts, the molten salt reactor (MSR) is particularly suited for marine applications due to its inherent safety features, compact design, high energy density, and potential to mitigate nuclear waste and proliferation concerns. However, MSR systems face significant challenges, including tritium production, corrosion issues, and complex behavior of volatile fission products. Understanding the impact of marine-induced motion on the thermal–hydraulic behavior of MSRs is crucial, as it can lead to transient design basis accident scenarios. Furthermore, the adoption of MSR technology in the shipping industry requires overcoming regulatory hurdles and achieving global consensus on safety and environmental standards. This review assesses the current progress, challenges, and technological readiness of MSRs for marine applications, highlighting future research directions. The overall technology readiness level (TRL) of MSRs is currently at 3. Achieving TRL 6 is essential for progress, with individual components needing TRLs of 4–8 for a demonstration reactor. Community Readiness Levels (CRLs) must also be addressed, focusing on public acceptance, safety, sustainability, and alignment with decarbonization goals.

Numerical study on ammonia injection location of ammonia and low-rank coal cofiring in 1000 MWe ultra super critical carolina-type boiler

Global CO2 emissions from coal-fired power plants necessitate innovative solutions to reduce their environmental footprint. Ammonia cofiring has emerged as a promising solution for reducing CO2 emissions in these plants. The ammonia injection optimization is analyzed using computational fluid dynamics simulations in a 1000 MW Ultra Super Critical Coal Fired Power Plant, comparing four injection sites at a 20 % thermal energy cofiring ratio. Results indicated the bottom burner as the most effective location, achieving the lowest NOx emissions (102.20 mg/Nm3) compared to traditional coal-firing (131.78 mg/Nm3). A sensitivity analysis favored bottom and mid burner injections over equal distribution, leading to further investigations into varying injection locations and cofiring ratios (5%–60 %). Increased cofiring ratios decreased gross power output by 3.6 MW per percentage increase in cofiring, alongside shifts in flue gas properties and a complex NOx emission trend. Initially, NOx emissions decreased, with a 0.784 up to 20 % cofiring, but dramatically increased beyond, reaching a ratio of 3.744 at 60 % cofiring. This study reveals critical insights into emission management and highlights the need for improved derating strategies to mitigate acid corrosion risks, marking a significant step towards environmentally sustainable coal power generation.

Integrated Workflow Development for Data-Driven Neighborhood-Scale Building Performance Simulation

Abstract As urbanization intensifies, cities are key contributors to energy consumption and carbon emissions, accounting for a significant portion of global energy use and CO2 emissions. This paper introduces a systematic approach to support the development of urban projects with minimized operational carbon footprints through the integration of data-driven building performance simulation (BPS) tools in early-stage design. Emphasizing the necessity for a collaborative effort among designers, policymakers, and other stakeholders, we discuss the evolution of BPS toward incorporating data-driven tools for energy need reduction and informed decision-making. Despite the proliferation of modeling methods and data-related challenges, we present a theoretical workflow, supported by interactions with design firms in the US and European Union (EU) through interviews. This structured approach, demonstrating adaptability and scalability across urban contexts, foregrounds the potential for future data-driven integration in design practices. Grounded in theoretical concepts and preliminary real-world insights, our work emphasizes the transformation of standard activities toward data-driven processes, showcasing the crucial role of practical experience in advancing sustainable, low-carbon urban development.

Modeling fuel-, vehicle-type-, and age-specific CO2 emissions from global on-road vehicles in 1970–2020

Abstract. Vehicles are among the most important contributors to global anthropogenic CO2 emissions. However, the lack of fuel-, vehicle-type-, and age-specific information about global on-road CO2 emissions in existing datasets, which are available only at the sector level, makes these datasets insufficient for supporting the establishment of emission mitigation strategies. Thus, a fleet turnover model is developed in this study, and CO2 emissions from global on-road vehicles from 1970 to 2020 are estimated for each country. Here, we analyze the evolution of the global vehicle stock over 50 years, identify the dominant emission contributors by vehicle and fuel type, and further characterize the age distribution of on-road CO2 emissions. We find that trucks accounted for less than 5 % of global vehicle ownership but represented more than 20 % of on-road CO2 emissions in 2020. The contribution of diesel vehicles to global on-road CO2 emissions doubled during the 1970–2020 period, driven by the shift in the fuel-type distribution of vehicle ownership. The proportion of CO2 emissions from vehicles in developing countries such as China and India in terms of global emissions from newly registered vehicles significantly increased after 2000, but global CO2 emissions from vehicles that had survived more than 15 years in 2020 still originated mainly from developed countries such as the United States and countries in the European Union. The data are publicly available at https://doi.org/10.6084/m9.figshare.24548008 (Yan et al., 2024).

Modeling building energy self-sufficiency of using rooftop photovoltaics on an urban scale

The significant contribution of buildings to global energy-related CO2 emissions and climate change has led to projections of a carbon–neutral building stock by 2050. This study evaluates the potential contribution of rooftop photovoltaics to urban energy self-sufficiency by developing an enhanced CityBEM framework, our in-house urban building energy model (UBEM). This methodology enables city-scale, simultaneous simulations of building energy use and rooftop photovoltaic retrofitting with low computational time. CityBEM’s robustness and high spatiotemporal resolution facilitate transient simulations of individual buildings with diverse usage types across large urban areas, addressing common computational constraints and input data limitations in UBEM applications. The rooftop photovoltaic model in CityBEM utilizes a comprehensive approach with physics-based modeling of crystalline PVs, model validation, and a proper design of array networks to manage self-shading effects. More than 57,000 buildings with a combined footprint of 32.37 million square meters are located in the simulation test case covering downtown Montreal (Quebec, Canada) and the surrounding areas. Results indicate that rooftop PV adoption in these buildings could potentially generate 5.9 TWh of electricity annually, reduce energy demand by 27.3%, and achieve an average annual energy saving of 40%. This local generation could also reduce operational CO2 equivalent emissions by over 0.2 megatons. Overall, this study highlights the significant potential of rooftop photovoltaics for a cleaner, more energy self-sufficient urban future.

How green can it be? A methodology for calculating green roof retrofit potential in Valencia

Cities are accountable for more than 70% of global CO2 emissions and consume around 65% of the world's energy. In the pathway towards urban decarbonisation, nature-based solutions rise as a promising opportunity. They improve a city's resilience, stabilise temperatures and capture CO2, both mitigating climate change effects and adapting to them. This paper presents a novel methodology to assess the potential effects of green roof retrofit in urban areas, selecting suitable buildings for greening and estimating their decarbonising capacity. The proposed method combines the use of Geographic Information Systems (GIS) and artificial vision algorithms to select the roofs. Once selected, direct carbon sequestration and energetic savings are estimated based on empirical results. This methodology is successfully applied to the L'Illa Perduda neighbourhood of Valencia (Spain) as a case study. The GIS analysis shows that about 50% of the roofs' surface could be greened, directly absorbing around 350 tCO2yr−1 and reducing the energetic emissions of the neighbourhood in about 100 tCO2yr−1 by improving the insulating envelope of the buildings. The artificial vision computation selected 38% of the surface of the neighbourhood residential buildings.

Digital workflow to support the reuse of precast concrete and estimate the climate benefit

Abstract Concrete production contributes to around 8-9% of global CO2 emissions. Reusing building components in a circular economy can contribute to closing material loops and lowering CO2 emissions. When reusing concrete elements, it is necessary to have effective methods for evaluating their reuse potential. In this study, a novel digital workflow is developed to support the reuse of precast concrete elements by evaluating their lifespan based on carbonation depth. The workflow relies on automated retrieval of material quantities and information from a digital model. This model is then coupled with environmental data on construction products and calculation methods for CO2 uptake in concrete by carbonation. The remaining service life of concrete elements was calculated for a case study. For reference, CO2 uptake during the first service life was estimated at 4973 kg CO2 or 4% of the embodied carbon. Hence, the potential benefits of reuse outweigh those of carbonation. The presented approach supports the decision-making process when evaluating the reuse potential for concrete elements. The digital workflow can help designers make quick decisions concerning the lifespan and carbon footprint of concrete. The digital tool can be extended in future work with more parameters to evaluate additional sustainability indicators.

Current advancements in CO2 capture using graphene-based materials

In 2023, global CO2 emissions were 37.4 billion tonnes and a 1.1% increase compared to 2022. Although most countries try to decarbonize their economies, oil and gas supplied 52% of the world's energy needs in 2021, and by 2050 it will be 47%. Therefore, in the future, oil and gas will still account for a considerable percentage of the energy sector. However, the continuous release of CO2 into the atmosphere at this rate can result in severe environmental problems. One of the promising approaches to address this issue is CO2 capture. This captured CO2 can then be stored underground or used to produce commercially valuable products. In recent years, graphene-based materials have gained attention in CO2 capture due to their interesting properties, such as high thermal stability and durability. This review focuses mainly on recently published articles on carbon capture using graphene-based materials.

Scalable ammonia synthesis on the modified crystal structure of Cu3PS4 electrocatalyst

Ammonia production, which is vital for agricultural and industrial applications, typically relies on energy-intensive processes that contribute to global CO2 emissions. Electrochemical nitrogen reduction is a promising alternative, although it faces challenges such as low yield and selectivity. Transition-metal-based catalysts, particularly Cu, are promising for overcoming these limitations. Cu3PS4 catalysts were synthesized and evaluated using a 9 cm2-scale electrode, revealing enhanced performance attributed to change in the crystal and electronic structure of Cu, facilitating N2 adsorption and improving the reaction activity. Notably, the ammonia synthesis rate reached 128 μg h-1 mgcat-1 at −1.0 V vs. RHE and faradaic efficiency was 34 % at −0.8 V vs. RHE. These findings provide potential insights into the improvement of practical electrochemical synthesis of ammonia.

Rapid formation of carbon dioxide hydrate governed by the natural nano-clay for effective carbon dioxide capture

Gas hydrate can separate and capture enormous carbon dioxide (CO2) only using water cages. Capturing CO2 in hydrate form is viewed as a green and effective technology to reduce the global CO2 emission. However, the sluggish kinetics and high cost of kinetics promotors of CO2 hydrate formation limited the application of hydrate-based CO2 capture technology. Here, we used the nano-clay prepared by cheap natural clay to promote the formation kinetics of CO2 hydrate. At the low concentration range, the formation period of CO2 hydrate in the two-dimensional nano-clay dispersion was significantly shorter than that of the one-dimensional nano-clay dispersion. The induction time (5 min) obtained in vermiculite nanoflakes dispersion was shorter than most solid promotors of CO2 hydrate formation kinetics in reported works. Besides, we found that the water molecules near the negatively charged two-dimensional nano-clay surface were more likely to form the cage-like structure than those around the one-dimensional nano-clay surface. The similar hydrogen-bonded structure of the cage-like water with CO2 hydrate made them favorable for the CO2 hydrate formation. These results shed light on the design of the effective kinetics promotors of CO2 hydrate and contribute to develop the hydrate-based CO2 capture technologies.

Behavior of zero cement reinforced concrete slabs under monotonic and impact loads: Experimental and numerical investigations

Currently, there is a shift toward the use of low-carbon construction materials to reduce global carbon dioxide emissions. Zero-cement concrete (ZCC) synthesized from alkaline activated fly ash (FA) is a promising alternative for Portland cement in the construction industry to reduce global CO2 emissions, increase the consumption of waste materials, and save energy. A substantial amount of research on the impact load behavior of ordinary reinforced concrete (RC) structural components has been conducted. However, investigations on the behavior of zero cement concrete (ZCC) slabs under impact loads have not been reported. In this work, twenty simply supported two-way flat reinforced fly ash ZCC slabs (including two normal concrete (NC) slabs as reference samples) were tested under monotonic and impact loads. The test samples were categorized into eight groups on the basis of various parameters. Twelve RC slabs (1 NC and 11 ZCCs) were prepared for repeated impact tests, and eight slabs (1 NC and 7 ZCCs) were prepared for monotonic loading tests. Various parameters were investigated herein, including slab thickness, bar spacing, molarity concentration of alkali activators, hammer height, and hammer mass. Nonlinear finite element models were also developed and validated by using ABAQUS software for additional parametric study purposes. The results revealed that the behavior of ZCC slabs is approximately similar to that of NC slabs. The results also revealed that an increase in the ZCC slab thickness, reinforcement ratio, hammer height, and hammer mass has a noticeable effect on the dynamic response of the slab. However, increasing the molarity concentration of alkali activators has clearly a slight influence on the impact loadtime history. When the slab thickness was increased or the bar spacing was reduced, the static and impact energy absorption capacities were increased by 1.5 and 2.0 times, respectively. For impact load tests, the damage degree, penetration, and cracking pattern at failure were approximately typical for all test samples at the first hit except when the hammer mass and impact height were changed. For the samples subjected to monotonic loading, a flexural response was observed for almost all the slab samples at the first loading stage, and cracking started from the midpoint of the slab and propagated toward the slab edges; ultimately, punching shear failure was observed.

Perception of carbon capture and utilization - a framing analysis of German-speaking media

Carbon dioxide capture and utilization (CCU) technologies are one building block in Germany’s industrial decarbonization strategy. With CCU technologies, carbon dioxide emissions are captured from an industrial point source or the ambient air (direct air capture, DAC) and either used directly as an industrial feedstock or transformed and used as a carbon resource in industry. Despite the potential benefits of CCU in decreasing industrial dependency on fossil fuels and decreasing global CO2 emissions, robust empirical evidence of the general public opinion and societal acceptance of carbon capture and utilization technologies is lacking. Here, we studied the German-speaking media discourse as a proxy for the public discussion of carbon capture and utilization (CCU) technologies. We show that CCU technologies are overall framed more positively than negatively. Responsible for the optimistic framing are the two dominant media frames: “climate protection-frame” and “benefit-frame,” which are mainly used by scientists and policy actors or representatives from the industry sector respectively.

Identification of Yarrowia lipolytica as a platform for designed consortia that incorporate in situ nitrogen fixation to enable ammonia-free bioconversion

Bioconversion processes require nitrogen for growth and production of intracellular enzymes to produce biofuels and bioproducts. Typically, this is supplied as reduced nitrogen in the form of ammonia, which is produced offsite from N2 and H2 via the Haber-Bosch process. While this has revolutionized industries dependent on fixed nitrogen (e.g., modern agriculture), it is highly energy-intensive and its reliance on natural gas combustion results in substantial global CO2 emissions. Here we investigated the feasibility of in situ biological nitrogen fixation from N2 gas as a strategy to reduce greenhouse gas impacts of aerobic bioconversion processes. We developed an efficient and cost-effective method to screen fungal bioconversion hosts for compatibility with the free-living diazotrophic bacterium Azotobacter vinelandii under nitrogen fixing conditions. Our screening revealed that the genus Yarrowia is particularly enriched during co-culture experiments. Follow-up experiments identified four Y. lipolytica strains (NRRL Y-11853, NRRL Y-7208, NRRL Y-7317, and NRRL YB-618) capable of growth in co-culture with A. vinelandii. These strains utilize ammonium secreted during diazotrophic fixation of N2, which is provided as a component of the air input stream during aerobic fermentation. This demonstrates the feasibly of in situ biological nitrogen fixation to support heterotrophic fermentation processes for production of fuels and chemicals.

Development and verification of a multi-component model for steam methane reforming

RELEVANCE. Steam methane reforming is the dominant method of hydrogen production. Its significant share in global CO2 emissions highlights the importance of optimizing technological parameters to reduce environmental impact. The developed multi-component model of steam methane reforming in COMSOL Multiphysics is relevant not only due to its applicability for optimizing existing production facilities but also for its potential in developing new methods for utilizing associated petroleum gas. In the context of import substitution in the hydrogen energy sector, this model is also of interest, allowing for the calculation of technological parameters of industrial installations.THE PURPOSE. The aim of the work is to develop and verify a multi-component model of steam methane reforming.METHODS. The research methodology includes the use of experimental data from the literature and industrial indicators for integration into a multi-component model in COMSOL Multiphysics. This enables the modelling of complex chemical interactions under conditions characteristic of the industrial steam methane reforming process.RESULTS. The developed multi-component model allows calculating key parameters of the steam methane reforming process, including the concentration of components (methane, hydrogen, carbon monoxide, and carbon dioxide) and temperature along the reactor. The model successfully describes the chemical interactions between components and takes into account the influence of operating conditions, such as temperature, pressure, and steam/gas ratio, on process efficiency. The model verification was carried out by comparing the modelling results with experimental data and indicators of real industrial processes. Their correspondence confirms the high degree of reliability and suitability of the model for practical application in engineering calculations and optimization of steam methane reforming processes.CONCLUSION. The conclusions made based on the modelling can be used for further improvement of methane conversion technologies, contributing to their efficiency and environmental friendliness. There is also potential for using the model to calculate the stages of installations for the utilization of products from the processing of associated petroleum gas.