Anthropogenic CO2 Research Articles

Interconnections between Solar-Driven Ammonia Production and the Water and Distribution Infrastructures at a Global Scale

Ammonia plays a crucial role in the modern agriculture industry, as synthetic nitrogenous fertilizers supply over half of the nitrogen input into croplands. However, ammonia production through the Haber-Bosch process contributes to 1.2% of the global anthropogenic CO2 emissions and 2% of the global energy consumption. Thus, momentum has been building to transition Ammonia production towards renewable and electrified approaches. There are inherent risks and opportunities associated with the adoption of new technologies, and electrifying ammonia production will likely result in a new decentralized market for green ammonia. This work opens the dialogue to consciously create a system that is resilient, sustainable, and globally available.This talk presents a detailed geospatial study on solar-driven ammonia production. First, we identify the spatial distribution of solar-driven ammonia production while considering key economic and performance parameters such as capital cost and energy efficiency. We study how the ammonia production cost distribution changes with the implementation of different technologies (i.e., low-temperature electrochemical ammonia production, lithium-mediated electrochemical ammonia production, and the electrified Haber-Bosch process). Then, we identify key considerations and performance targets (Energy Efficiency, Capital Costs, and Distribution Costs) for solar-driven ammonia production to reach economic feasibility. Finally, we optimize solar-driven ammonia production and distribution networks to decrease production and transportation costs while increasing resiliency towards changes in distribution costs and water scarcity through multi-objective network optimization. Figure 1

The Use of Zinc-Bromine Battery Technology to Remove and Recover Zinc from Scrap and Waste Steel Resources

ZBBs have a high open circuit voltage (1.82 V), a high theoretical energy (> 400 W h-1 kg-1) and high demonstrated power densities (> 100 mW cm-2). Typically, ZBBs adopt a redox flow design involving the use of a Nafion membrane to separate aqueous zinc bromide anolyte and catholyte solutions [1]. In this study, the use of a membrane-free non-flow design was investigated for the purposes of recovering zinc from scrap and waste steel resources [2]. The rationale for this work stems from the greenhouse gas emissions produced by the iron and steel industry, which accounts for between 4-7 % of the anthropogenic CO2 emissions globally [3]. Blast furnace technology is likely to account for most stainless steel production in the coming decades, and therefore a transition to low-carbon and green steel production will require increased steel recycling rates and significantly improved waste and scrap management. To the best of our knowledge, this is the first time a zinc-bromine battery has been investigated for the recovery of materials rather than energy storage.Galvanization of steel is required to prevent rusting and degradation and involves coating the surface of steel in a protective layer of zinc. Galvanization processes account for over 50 % of global zinc consumption and by 2050 the demand for zinc will be 2.7 times greater than that of 2012 [4]. In order to enable recycling of scrap steel directly into blast furnaces, zinc is removed and recovered via mineral acid leaching. This method of recovery has a high zinc extraction efficiency but creates problematic waste streams and has poor energetic efficiency.In this work, the use of a membrane-free zinc-bromine battery has been studied for the purposes of extracting zinc from steel substrates and subsequently re-electroplating onto a conventional carbon foam electrode. The electrical performance of the cell was characterised by charge-discharge profiles and I-V curves. Zinc removal and recovery onto electrodes was characterised using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The work successfully demonstrates that ZBB technology could enable efficient and clean recovery of zinc from metal and waste substrates including scrap steel, slurries generated from basic oxygen steelmaking processes, and secondary vent dust from the primary steelmaking off gas streams. The cell studied in this work enabled dipping of zinc-containing steel substrates directly into the electrolyte solution without disassembly of the battery housing. In addition, the design involved the use of low-cost materials and reagents and potentially offers low balance-of-plant costs.The results show that zinc could be removed from steel surfaces during cell discharge with greater than 99.9 % yield. The Figure shows the extracted zinc could subsequently be re-electroplated onto a standard carbon foam electrode upon re-charging the cell. When a 0.5 V cut-off voltage was used upon discharge, the zinc was recovered selectively from the steel (see Fig. (a)); the surface elemental composition of the carbon electrode measured by EDS after charging was: carbon (26.79 wt%), oxygen (18.06 wt%), zinc (30.03 wt%) and bromine (25.11 wt%). Using a lower cut-off voltage (0.2 V) resulted in the co-extraction of iron from the substrate as well as zinc (see Fig. (b)); in this case, the elemental composition of the carbon electrode after charging was: carbon (27.53 wt%), oxygen (22.65 wt%), iron (4.72 wt%), zinc (24.44 wt%) and bromine (20.65 wt%). Provided a cut-off voltage of no less than 0.5 V was used for discharging, high purity zinc was recovered, and the cell showed good initial durability, with 30 cycles of charge-discharge demonstrated in this work.[1] S. Suresh, M. Ulaganathan, N. Venkatesan, P. Periasamy, P. Ragupathy, High performance zinc-bromine redox flow batteries: Role of various carbon felts and cell configurations. J. Energy Storage, 2018. 20: pp. 134-139.[2] S. Biswas, A. Senju, R. Mohr, T. Hodson, N. Karthikeyan, K. Knehr, A.G. Hsieh, X. Yang, B.E. Koel, D.A. Steingart, Minimal architecture zinc-bromine battery for low-cost electrochemical storage. Energy Environ. Sci., 2017. 10: pp. 114-120.[3] Iron and Steel Technology Roadmap: Towards More Sustainable Steelmaking, Energy Technology Perspectives, International Energy Agency, IEA Publications, Paris, 2020. https://www.iea.org/reports/iron-and-steel-technology-roadmap [accessed 12 April 2022].[4] K.S. Ng, I. Head, G.C. Premier, K. Scott. E. Yu, J. Lloyd, J. Sadhukhan. A multilevel sustainability analysis of zinc recovery from wastes. Resour. Conserv. Recycl., 2016. 113: pp. 88-105.Figure. SEM images showing the carbon foam zinc electrodes after charging the cell. (a) is an electrode when a discharge cut-off voltage of 0.5 V was used, (b) is an electrode when a discharge cut-off voltage of 0.2 V was used. Figure 1

Evaluating Anthropogenic CO2 Bottom-Up Emission Inventories Using Satellite Observations from GOSAT and OCO-2

Anthropogenic carbon dioxide (CO2) emissions from bottom-up inventories have high uncertainties due to the usage of proxy data in creating these inventories. To evaluate bottom-up inventories, satellite observations of atmospheric CO2 with continuously improved accuracies have shown great potential. In this study, we evaluate the consistency and uncertainty of four gridded CO2 emission inventories, including CHRED, PKU, ODIAC, and EDGAR that have been commonly used to study emissions in China, using GOSAT and OCO-2 satellite observations of atmospheric column-averaged dry-air mole fraction of CO2 (XCO2). The evaluation is carried out using two data-driven approaches: (1) quantifying the correlations of the four inventories with XCO2 anomalies derived from the satellite observations; (2) comparing emission inventories with emissions predicted by a machine learning-based model that considers the nonlinearity between emissions and XCO2. The model is trained using long-term datasets of XCO2 and emission inventories from 2010 to 2019. The result shows that the inconsistencies among these four emission inventories are significant, especially in areas of high emissions associated with large XCO2 values. In particular, EDGAR shows a larger difference to CHRED over super-emitting sources in China. The differences for ODIAC and EDGAR, when compared with the machine learning-based model, are higher in Asia than those in the USA and Europe. The predicted emissions in China are generally lower than the inventories, especially in megacities. The biases depend on the magnitude of inventory emissions with strong positive correlations with emissions (R2 is larger than 0.8). On the contrary, the predicted emissions in the USA are slightly higher than the inventories and the biases tend to be random (R2 is from 0.01 to 0.5). These results indicate that the uncertainties of gridded emission inventories of ODIAC and EDGAR are higher in Asian countries than those in European and the USA. This study demonstrates that the top-down approach using satellite observations could be applied to quantify the uncertainty of emission inventories and therefore improve the accuracy in spatially and temporally attributing national/regional totals inventories.

Storing carbon dioxide in deep unmineable coal seams for centuries following underground coal gasification

Underground coal gasification (UCG) has a huge potential in extracting energy from deep coal seams with a low environmental footprint. A vast void space created in a UCG operation serves as an effective sink to anthropogenic CO2 storage and sequestration. To advance the knowledge base regarding CO2 storage in post-UCG cavities, a 3D commercial-scale 990m × 60m × 24 m multi-cavity scenario was constructed to model the transport and fate of the stored CO2 plume at around 1000 m depth for centuries using a coalbed methane (CBM) and CO2 storage dedicated simulator. The effects of the import multiphysics were analyzed. It was revealed that transport phenomena entered a stabilized steady state in 50 years in a multicomponent adsorption system. In addition, the matrix-cleat diffusion exhibited a substantially strong trapping mechanism with an at-equilibrium spread-out speed of 0.24 m/year. Dynamic changes in a cleat system and an injection process were shown to play a minor role. Furthermore, two effective means were proposed for a protracted thousands-of-year simulation of CO2 storage in post-UCG multiple cavities. The relevant findings in this paper would promote the utility and applicability of UCG in the world's deep coal seams for the transition of the coal industry in a carbon-conscious world.

Model Estimates for Contribution of Natural and Anthropogenic CO2 and CH4 Emissions into the Atmosphere from the Territory of Russia, China, Canada, and the USA to Global Climate Change in the 21st Century

Model Estimates for Contribution of Natural and Anthropogenic CO2 and CH4 Emissions into the Atmosphere from the Territory of Russia, China, Canada, and the USA to Global Climate Change in the 21st Century

Environment impact and bioenergy analysis on the microwave pyrolysis of WAS from food industry: Comparison of CO2 and N2 atmosphere.

The alarming output of waste activated sludge (WAS) from industries requires proper management routes to minimize its impact on the environment during disposal. Pyrolysis is a feasible way of processing and valorizing WAS into higher-value products of alternate use. Despite extensive research into the potential of WAS through pyrolysis, the technology's long-term viability and environmental impact have yet to be fully revealed. In addition, the environmental effects of utilizing different pyrolysis atmosphere (N2 or CO2) has not been studied before, although benefits of CO2 reactivity during pyrolysis have been discovered. This study evaluates the process's environmental impact, carbon footprint, and bioenergy yield when different pyrolysis atmospheres are used. The global warming potential (GWP) for a functional unit of 1t of dried WAS is 203.81kg CO2 eq. The heat required during pyrolysis contributes the most (63.7%) towards GWP due to high energy usage, followed by the drying process (23.6%). Transportation contributes the most towards toxicity impact (59.3%) through dust, NOx, NH3 and SO2 emissions. The initial moisture content of raw WAS (65%) greatly impacts overall energy consumption and environmental impact. Pyrolysis in an N2 atmosphere will result in a higher overall bioenergy yield (833kWh/tonne) and a lower carbon footprint (-1.09kg CO2/tonne). However, when CO2 was used, the specific energy value within the biochar is higher (22.26MJ/kg) due to enhanced carbonization. The carbon content of gas derived increased due to higher CO yield. From an energy perspective, the current setup will achieve a net positive bioenergy yield of 561kW (CO2) and 833kW (N2), where end products like biochar, bio-oil and gas can be used for power production. Despite the energy-intensive process, microwave pyrolysis has excellent potential to achieve a negative carbon footprint. The biochar used for soil amendment served as a good carbon sink. The utilization of CO2 as carrier gases provides a pathway to utilize anthropogenic CO2, which helps reduce global warming. This work demonstrates microwave pyrolysis as a negative emission, bioenergy-producing approach for WAS disposal and valorization.

Response of calcareous nannoplankton to the Paleocene–Eocene Thermal Maximum in the Paratethys Seaway (Tarim Basin, West China)

The Paleocene-Eocene Thermal Maximum (PETM) was a rapid global warming occurred 56 million years ago and has been widely viewed as an ancient analogue to the ongoing warming driven by anthropogenic CO 2 emissions. The complete and continuous Paleogene shallow marine strata well preserved and outcropped in the Tarim Basin, northwestern China are ideal to study the paleoenvironmental change of the Paratethys Seaway during the PETM. To date, no high-resolution calcareous nannofossil biostratigraphy has been performed for the PETM interval in the Tarim Basin. Outcrop samples taken from the Qimugen Formation in the Kuzigongsu section contain abundant, moderately well preserved calcareous nannofossils, allowing for the establishment of a high-resolution biostratigraphic framework. Overall, 73 species of calcareous nannofossils from 33 genera were observed, with the dominant species including Coccolithus pelagicus , various Toweius species, Pontosphaera exilis , and Micrantholithus flos. The five calcareous nannofossil datums allow for the recognization of nannofossil Zone NP6 through Zone NP10. The common occurrence of shallow-water taxa ( Micrantholithus ) throughout the section suggests a middle to outer neritic setting as the depositional environment of the Kuzigongsu section. The stratigraphic distribution of “excursion taxa” ( Coccolithus bownii, Discoaster araneus , D. acutus, Rhomboaster spp.) is consistent with the range of negative excursions in δ 13 C carb and δ 18 O carb , indicating that these “excursion taxa” are micropaleontological markers for identifying the presence of the PETM in the Paratethys Seaway. During the PETM, the deteriorated preservation and extremely low abundance of nannofossils and near-zero wt% CaCO 3 values suggest that ocean acidification occurred in the shallow water of the Paratethys Seaway. In addition, a significant increase in the species Neochiastozygus junctus , which is a high productivity indicator suggests increased surface ocean productivity. Higher primary productivity may be triggered by enhanced continental weathering delivering increased nutrient through river runoff. • A new, shallow marine Paleocene–Eocene Thermal Maximum (PETM) record was discovered in the eastern Tethys. • High-resolution calcareous nannofossil biostratigraphy across the PETM was established. • The PETM “excursion taxa” are marker species for identifying PETM record in the eastern Tethys. • Low pre- and syn -PETM carbonate contents were attributed to ocean acidification and terrestrial dilution. • Marine productivity increased during the PETM due to elevated nutrient input from continental weathering.

Accelerated Weathering of Limestone Bicarbonate Induced CaCO3 Precipitation in A Mixture of Sand, Fly Ash and CaO

Excessive generation of CO2 and industrial wastes has sparked environmental concerns around the globe. In this research, Accelerated Weathering of Limestone (AWL) process uses calcium carbonate (CaCO3) to capture CO2 from ambient air. It achieved an absorption efficiency of 31.88 %. The calcium bicarbonate effluent produced via AWL is used to precipitate calcium carbonate in lime mortar (LM) mixture containing sand and calcium oxide (CaO) with fly ash, an industrial waste. This helps develop a novel utilization pathway for the respective wastes via production of a novel green construction material termed bicarbonate lime mortar infused with fly ash (BLMFA). The fly ash addition percentage in bicarbonate lime mortar (BLM) mix are 12.12, 17.15 and 21.63 wt.%. This project also studies the effect of curing time (7, 28 and 88 days) on development of BLMFA strength. Experimental results found that at 7 days, the strength of BLMFA (0.44 to 0.48 MPa) is lower than the conventional LM, which has a strength of 0.52 MPa. However, on 88 days, 17.15 wt.% BLMFA achieved a strength of 0.82 MPa, which is 0.060 MPa higher than the conventional LM sample. In addition, BLMFA also possesses high CaCO3 content of 36.7 to 44 wt.% out of the targeted 54.37 wt.% compared to conventional LM, which could only achieve 27.14 wt.% CaCO3. This indicates that infusion of fly ash can enhance the carbonation efficiency of calcium sources to CaCO3. All in all, AWL process and BLMFA precipitation possess the capability to diminish anthropogenic CO2 while beneficially utilizing industrial waste.

Source‐Labeled Anthropogenic Carbon Reveals a Large Shift of Preindustrial Carbon From the Ocean to the Atmosphere

AbstractTwo centuries of anthropogenic CO2 emissions have increased the CO2 concentration of the atmosphere and the dissolved inorganic carbon (DIC) concentration of the ocean compared to preindustrial times. These anthropogenic carbon perturbations are often equated to the amount of anthropogenically emitted carbon in the atmosphere or ocean, which ignores the possibility of a shift of natural carbon between the oceanic and atmospheric carbon reservoirs. Here we use a data‐assimilated ocean circulation model and numerical tracers akin to ideal isotopes to label carbon when it is emitted by anthropogenic sources. We find that emitted carbon accounts for only about 45% of the atmospheric CO2 increase since preindustrial times, the remaining 55% being natural CO2 that outgassed from the ocean in response to anthropogenically emitted carbon invading the ocean. This outgassing is driven by the order‐10 seawater carbonate buffer factor which causes increased leakage of natural CO2 as DIC concentrations increase. By 2020, the ocean had outgassed ∼159 Pg of natural carbon, which is counteracted by the ocean absorbing ∼347 Pg of emitted carbon, about 1.8 times more than the net increase in oceanic carbon storage of ∼188 PgC. These results do not challenge existing estimates of anthropogenically driven changes in atmospheric or oceanic carbon inventories, but they shed new light on the composition of these changes and the fate of anthropogenically emitted carbon in the Earth system.

Sustainable Sourcing of Raw Materials for Construction: From the Earth to the Moon and Beyond

Each year, nearly 40 billion tonnes of raw materials extracted from the Earth’s crust feed into the construction industry. The associated material flows dramatically contribute to anthropogenic CO2 emissions. Therefore, more sustainable supply chains must be envisaged based on the use of locally available resources and the principles of circular economy. Drawing inspiration from vernacular architecture, innovative solutions for green construction based on sustainable exploitation of local resources can be posited. This strategy has also inspired the proposed practice of in situ resource utilization on planetary bodies such as the Moon and Mars.

Metal-Free N-Doped Carbons for Solvent-Less CO2 Fixation Reactions: A Shrimp Shell Valorization Opportunity.

High anthropogenic CO2 emissions are among the main causes of climate change. Herein, we investigate the use of CO2 for the synthesis of organic cyclic carbonates on metal-free nitrogen-doped carbon catalysts obtained from chitosan, chitin, and shrimp shell wastes, both in batch and in continuous flow (CF). The catalysts were characterized by N2 physisorption, CO2-temperature-programmed desorption, X-ray photoelectron spectroscopy, scanning electron microscopy, and CNHS elemental analysis, and all reactivity tests were run in the absence of solvents. Under batch conditions, the catalyst obtained by calcination of chitin exhibited excellent performance in the conversion of epichlorohydrin (selected as a model epoxide), resulting in the corresponding cyclic carbonate with 96% selectivity at complete conversion, at 150 °C and 30 bar CO2, for 4 h. On the other hand, in a CF regime, a quantitative conversion and a carbonate selectivity >99% were achieved at 150 °C, by using the catalyst obtained from shrimp waste. Remarkably, the material displayed an outstanding stability over a reaction run time of 180 min. The robustness of the synthetized catalysts was confirmed by their good operational stability and reusability: ca. (75 ± 3)% of the initial conversion was achieved/retained by all systems, after six recycles. Also, additional batch experiments proved that the catalysts were successful on different terminal and internal epoxides.

Stable carbon isotopes of dissolved inorganic carbon in the Western North Pacific Ocean: Proxy for water mixing and dynamics

The uptake of atmospheric CO2 and the cycle of dissolved inorganic carbon (DIC) in the ocean are the major mechanisms and pathways controlling global climate change and carbon cycling. The stable carbon isotope (δ13C) of DIC, therefore, provides an important tracer for processes such as air-sea exchange, photosynthesis, and water dynamics in the ocean. Here, we present new δ13C-DIC data on water samples collected from a north-south transect (13°N–40°N, 150°E) in the western North Pacific (NP) Ocean in November 2019 and compare the results with those previously reported for similar transects (149.3°E) during WOCE and CLIVAR projects over the past three decades. The values of δ13C-DIC, ranging from -0.83‰ to 0.86‰, were higher in the surface waters and decreased with depth. The high δ13C-DIC values in the surface waters were influenced primarily by isotopic fractionation during air-sea exchange and photosynthesis. With depth, the movement of different water masses and mixing, as well as bathypelagic respiration in the dark water of the ocean, all play important roles in influencing the distribution and isotopic signatures of δ13C-DIC in the western NP Ocean. The δ13C-DIC values of the 0–200 m water layer varied from -0.17‰ to 0.86‰, with lower values at high latitudes, affected by the low δ13C-DIC values carried by the Oyashio Current to the Kuroshio Extension (KE) region. A downward trend was present in the δ13C-DIC signature from north to south in the North Pacific Intermediate Water (NPIW) and Pacific Deep Water (PDW) in the western NP, which reflected the remineralization of organic matter with a horizontal transport of NPIW and PDW. We found a strong 13C Suess Effect in the upper 2,000 m in the western NP Ocean, and δ13C-DIC at the surface (<50 m) has decreased by 0.60‰-0.85‰ since 1993. The mean δ13C-DIC change in the surface ocean was estimated at 0.28‰ per decade between 1993 and 2019. The air-sea exchange and water mixing in the study area may have accelerated the absorption of anthropogenic CO2 in recent years, which likely caused a slightly faster rate of decrease in the δ13C-DIC from 2005–2019 than that observed from 1993–2005.

High-purity hydrogen production from phenol on Ni-CaO-Ca12Al14O33 multifunctional catalyst derived from recovered layered double hydroxide

Hydrogen production with in situ CO2 capture by the sorption-enhanced steam reforming (SESR) technology is a promising concept to reduce anthropogenic CO2 emissions. A serious disadvantage of SESR processes is the rapid, sintering-induced decay of its cyclic performance. Here, a recovery approach of Ni-Ca-Al layered double hydroxide (LDH) structure with adsorbed tetracycline to develop a multifunctional catalyst is exploited. The in situ formation of carbon template originating from the adsorbed tetracycline allows for the emergence of favorable structure possessing excess porosity along with deposition of small nanoparticles, thus providing physical isolation to inhibit the sintering of Ca and Ni species. As such, 98.3 vol% H2 was stably produced from phenol in 50 cyclic tests, during which only 33 % decrease of sorption-enhancement effect was observed, ensuring superior SESR of phenol performance. This strategy provides a new paradigm for the rational design of materials derived from LDH for high-temperature reactions.

Harvesting, storing, and converting carbon from the ocean to create a new carbon economy: Challenges and opportunities

Ever-increasing anthropogenic CO2 emissions have required us to develop carbon capture, utilization, and storage (CCUS) technologies, and in order to address climate change, these options should be at scale. In addition to engineered systems of CO2 capture from power plants and chemical processes, there are emerging approaches that include the Earth (i.e., air, Earth, and ocean) within its system boundary. Since oceans constitute the largest natural sink of CO2, technologies that can enhance carbon storage in the ocean are highly desired. Here, we discuss alkalinity enhancement and biologically inspired CO2 hydration reactions that can shift the equilibrium of ocean water to pump more carbon into this natural sink. Further, we highlight recent work that can harvest and convert CO2 captured by the ocean into chemicals, fuels, and materials using renewable energy such as off-shore wind. Through these emerging and innovative technologies, organic and inorganic carbon from ocean-based solutions can replace fossil-derived carbon and create a new carbon economy. It is critical to develop these ocean-based CCUS technologies without unintended environmental or ecological consequences, which will create a new engineered carbon cycle that is in harmony with the Earth’s system.

Spatiotemporal association of carbon dioxide emissions in China's urban agglomerations

The reduction of carbon dioxide (CO2) emissions and sustainable development in low-carbon ways are of great significance to urban agglomerations. However, few studies are exploring the relationship between CO2 emissions and socioeconomic development at city levels from the perspective of clusters of regions. Based on the open data of inventory for anthropogenic CO2 emissions, nighttime light data, and population dataset as a proxy for the socioeconomic development levels of urban agglomerations, we used Mann–Kendall trend test, Tapio decoupling analysis, and spatial autocorrelation analysis to explore the spatiotemporal association of CO2 emissions and the impact of socioeconomic development on emissions in the nineteen urban agglomerations in China. Findings showed that the growth of CO2 emissions in China was primarily concentrated in urban agglomerations. The CO2 emissions in eastern coastal and northern urban agglomerations were much higher than those in other areas, while the emissions in western urban agglomerations were the lowest. The periodic characteristics of CO2 emissions were consistent with China's five-year development plan. Urban agglomerations in the early stage from 2000 to 2002 or with developed and stable industrial structures tended to achieve decoupling. High-high (HH) clusters of socioeconomic development with CO2 emissions were mainly distributed in urban agglomerations of the Beijing-Tianjin-Hebei region (BTH), the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), Yangtze River Delta (YRD), Huhhot-Baotou-Ordos-Yulin (HBOY), Shandong Peninsula (SP), and Central Shanxi (CS). Most of the clusters except those in HBOY shrunk from 2000 to 2010 and remained relatively stable from 2010 to 2019. These urban agglomerations should promote synergistic emission reduction. High-low (HL) clusters mostly appeared in central cities with a high socioeconomic level and surrounding cities with low CO2 emissions s, i.e., in urban agglomerations of Chengdu-Chongqing region (CC), the Beibu Gulf (BG), and Lanzhou-Xining (LX). These urban agglomerations with prominent polarization phenomena should adhere to regional overall coordination and thus minimize total regional costs of CO2 emission reduction. The results could provide references for the synergistic reduction of CO2 emissions and the coordinated development in urban agglomerations.

Heterogeneity of Increases in Net Primary Production under Intensified Human Activity and Climate Variability on the Loess Plateau of China

Regrowth of forests is expected to be an important driver in the large uptake of anthropogenic CO2 emissions by the terrestrial biosphere. Yet estimates of carbon sink capacity in mid-high latitude regrowth forests still remain unclear. The Loess Plateau (LP), a key region of the Grain to Green Program (GTGP), leads in the greening of China, while China leads in the greening of the world. For the sake of global ecological sustainability and accurate global carbon sink evaluation, the detection and attribution of vegetation growth on the LP requires further research after 20 years of ecological restoration. In this study, significant continuous rises (increases of 7.45 gC·m−2·a−2, R2 = 0.9328, p < 0.01) in net primary production (NPP) have occurred in the past 20 years. Rapid growth of forest NPP and expansion of forested areas in the southeastern regions has led to vegetation restoration on the LP. Human activities contributed 64.2% to the NPP increases, while climate variations contributed 35.8%. NPP in forests and croplands was dominated by human activities, while grassland NPP was mainly influenced by climate variations on the LP. Meanwhile, a strong El Niño event exacerbated the obstruction of large-scale ecological restoration. These conclusions can provide theoretical support for carbon-cycle assessment and the evaluation of sustainable development.

Hierarchical porous nitrogen-doped carbon supported MgO as an excellent composite for CO2 capture at atmospheric pressure and conversion to value-added products

The recent climate change is causing widespread concern around the world. Since anthropogenic CO2 emissions are recognized as a major contributor to this alarming phenomenon. As a result, there is an urgent need to reduce the carbon footprint and eliminate excess carbon dioxide from the atmosphere. Carbon capture, utilization, and storage are currently the most promising solution to solve this problem. This study reports a simple method for producing a novel hierarchical porous nitrogen and carbon supported MgO material (N@MgO/C) from the abundant bio-waste and magnesium chloride. The topographies of the prepared samples were thoroughly examined by several characterization techniques. The XRD, Raman, and XPS analyses reveal the existence of graphitic carbon. FESEM, and N2 adsorption-desorption studies, reveal a hierarchical porous structure with a mesoporous texture and good surface area (258.98 m2/g). Furthermore, N@MgO/C demonstrated an excellent ability to adsorb CO2 at room temperature with maximum adsorption of 2.55 mmol/g remaining almost stable up to 4 cycles. Moreover, it exhibits good catalytic activity for the cycloaddition of CO2 with various epoxides at atmospheric pressure in the presence of CTAB under the solvent-free condition with a yield of 96% and high stability over five cycles without any modification in its morphology.

Trends in the global steel industry: Evolutionary projections and defossilisation pathways through power-to-steel

Steel production is a carbon and energy intensive activity, releasing 1.9 tons of CO2 and requiring 5.17 MWh of primary energy per ton produced, on average, globally, resulting in 9% of all anthropogenic CO2 emissions. To achieve the goals of the Paris Agreement of limiting global temperature increase to below 1.5 °C compared to pre-industrial levels, the structure of the global steel production must change fundamentally. There are several technological paths towards a lower carbon intensity for steelmaking, which bring with them a paradigm shift decoupling CO2 emissions from crude steel production by transitioning from traditional methods of steel production using fossil coal and fossil methane to those based on low-cost renewable electricity and green hydrogen. However, the energy system consequences of fully defossilised steelmaking has not yet been examined in detail. This research examines the energy system requirements of a global defossilised power-to-steel industry using a GDP-based demand model for global steel demands, which projects a growth in steel demand from 1.6 Gt in 2020 to 2.4 Gt in 2100. Three scenarios are developed to investigate the emissions trajectory, energy demands, and economics of a high penetration of direct hydrogen reduction and electrowinning in global steel production. Results indicate that the global steel industry will see green hydrogen demands grow significantly, ranging from 2809 to 4371 TWhH2 by 2050. Under the studied conditions, global steel production is projected to see reductions in final thermal energy demand of between 38.3% and 57.7% and increases in total electricity demand by factors between 15.1 and 13.3 by 2050, depending on the scenario. Furthermore, CO2 emissions from steelmaking can be reduced to zero.

Hydrate based carbon capture and sequestration (HBCCS): An innovative approach towards decarbonization

The surge in global greenhouse gas emissions (mainly CO2) has introduced the world to the significant problem of climate change. A paradigm shift towards sustainable energy sources is necessary to meet the sustainable development goals (SDGs). Applying carbon capture and sequestration (CCS) technologies could be a suitable approach for minimizing anthropogenic CO2. Implementation of CCS involves enormous capital expenditure along with transportation, sequestration, and purification cost making its adaptability economically unfeasible. A novel approach to hydrate-based CO2 capture and sequestration (HBCCS) has gathered significant attention due to its potential to provide long-term CO2 sequestration. Herein, the methane-carbon dioxide sweeping process (CH4-CO2 replacement) has gained considerable interest as it produces clean energy (natural gas) from natural gas hydrate deposits while sequestering anthropogenic CO2. In this review paper, we presented a thorough assessment of the HBCCS process while highlighting the critical factors along with the economic/environmental/technical barriers controlling its deployment in actual field applications.

Synthesis of a regenerative energy system – beyond carbon emissions neutrality

To keep temperature rise well below 2 °C, production systems should be synthesised in a way that are regenerative, climate-resilient, and equitable, and to maintain biodiversity to preserve life and meet future human needs with the integrity of nature. In line with this approach, this paper presents a stepwise transition to a regenerative energy system in the EU by 2050, with the aim of going beyond carbon neutrality and achieving annual net negative emissions. A mixed-integer linear programming model is developed with the goal of maximising the Sustainability Net Present Value while achieving a balanced solution between all the three basic sustainability pillars. In order to obtain a regenerative system design, the annual self-sequestration of CO2 by the Earth was evaluated based on the amount of CO2 released into the atmosphere and the change in atmospheric CO2 concentration. The impact of different CO2 emission reduction scenarios on the atmospheric CO2 concentration until 2050 was evaluated. The results show that carbon neutrality at the global level could be achieved by 2050 with a 1.63% annual reduction in anthropogenic CO2 emissions. Moreover, the results indicate that if carbon emission neutrality is achieved at the global level in 2050, it could be achieved in the EU as early as 2039, given the Earth's self-sequestration capacity. To go beyond carbon emissions neutrality at the EU level, electricity demand is expected to nearly double, particularly due to the electrification of road transport, the use of heat pumps for heating residential and the tertiary sectors, 6G and IoT widespread out etc.