Observations of greenhouse gases as climate indicators

A Review of the Recent Advances in Composite Membranes for Hydrogen Generation Technologies

Keeping global warming at 2 degrees and below as stated in the "Paris Climate Agreement" and minimizing emissions can only be achieved by establishing a hydrogen (H2) ecosystem. Therefore, H2 technologies stand out in terms of accomplishing zero net emissions. Although H2 is the most abundant element in the known universe, molecular H2 is very rare in nature and must be produced. In H2 production, reforming natural gas and renewable hydrogen processes using electrolyzers comes to the fore. The key to all these technologies is to enhance production speed, performance, and system lifetime. At this point, composite membranes used in both processes come to the fore. This review article summarizes composite membrane technologies used in methane, ethanol, and biomass steam reforming processes, proton exchange membranes, alkaline water electrolysis, and hybrid sulfur cycle. In addition to these common H2 production technologies at large quantities, the innovative systems developed with solar energy integration for H2 generation were linked to composite membrane utilization. This study aimed to draw attention to the importance of composite membranes in H2 production. It aims to prepare a guiding summary for those working on membranes by combining the latest and cutting-edge studies on this subject.

Finely Tuning Metal Ion Valences of [Fe3-xMx(μ3-OH)(Carboxyl)6(pyridyl)2] Cluster-Based ant-MOFs for Highly Improved CO2 Capture Performances

Solvothermal reactions of different trinuclear precursors and 5-(pyridin-4-yl)isophthalic acid (H2L) successfully led to four anionic ant topological MOFs as Fe3-xMx(μ3-OH)(CH3COO)2(L)2·(DMA+)·DMF [M = Mn(II), Fe(II), Co(II), x = 0, 1, 2 and 3], namely, NJTU-Bai79 [NJTU-Bai = Nanjing Tech University Bai's group, Mn3(μ3-OH)], NJTU-Bai80 [Fe2Mn(μ3-OH)], NJTU-Bai81 [Fe3(μ3-OH)], and NJTU-Bai82 [Fe2Co(μ3-OH)], which possess the narrow pores (2.5-6.0 Å). NJTU-Bai80-82 is able to be tuned to the neutral derivatives [NJTU-Bai80-82(-ox), ox = oxidized] with M2+ ions oxidized to M3+ ones in the air and the OH- ions coordinated on M3+ ions. Very interestingly, selective CO2/N2 adsorptions of NJTU-Bai80-82(-ox) are significantly enhanced with the CO2 adsorption uptakes more than about 6 times that of NJTU-Bai79. GCMC simulations further revealed that neutral NJTU-Bai80-82(-ox) supplies more open frameworks around the -CH3 groups at separate spaces to the CO2 gas molecules with relatively more pores available to them after the removal of counterions. For the first time, finely tuning metal ion valences of metal clusters of ionic MOFs and making them from electrostatic to neutral were adopted for greatly improving their CO2 capture properties, and it would provide another promising strategy for the exploration of high-performance CO2 capture materials.

Nanomaterials for photo-electrochemical water splitting: a review

Over the last few decades, the global rise in energy demand has prompted researchers to investigate the energy requirements from alternative green fuels apart from the conventional fossil fuels, due to the surge in CO2 emission levels. In this context, the global demand for hydrogen is anticipated to extend by 4-5% in the next 5 years. Different production technologies like gasification of coal, partial oxidation of hydrocarbons, and reforming of natural gas are used to obtain high yields of hydrogen. In present time, 96% of hydrogen is produced by the conventional methods, and the remaining 4% is produced by the electrolysis of water. Photo-electrochemical (PEC) water splitting is a promising and progressive solar-to-hydrogen pathway with high conversion efficiency at low operating temperatures with substrate electrodes such as fluorine-doped tin oxide (FTO), incorporated with photocatalytic nanomaterials. Several semiconducting nanomaterials such as carbon nanotubes, TiO2, ZnO, graphene, alpha-Fe2O3, WO3, metal nitrides, metal phosphides, cadmium-based quantum dots, and rods have been reported for PEC water splitting. The design of photocatalytic electrodes plays a crucial role for efficient PEC water splitting process. By modifying the composition and morphology of photocatalytic nanomaterials, the overall solar-to-hydrogen (STH) energy conversion efficiency can be improved by optimizing their opto-electronic properties. The present article highlights the recent advancements in cleaner and effective photocatalysts for producing high yields of hydrogen via PEC water splitting.

Rice straw for energy and value-added products in China: a review

The rise of global waste and the decline of fossil fuels are calling for recycling waste into energy and materials. For example, rice straw, a by-product of rice cultivation, can be converted into biogas and by-products with added value, e.g., biofertilizer, yet processing rice straw is limited by the low energy content, high ash and silica, low nitrogen, high moisture, and high-quality variability. Here, we review the recycling of rice straw with focus on the global and Chinese energy situations, conversion of rice straw into energy and gas, biogas digestate management, cogeneration, biogas upgrading, bioeconomy, and life cycle assessment. The quality of rice straw can be improved by pretreatments, such as baling, ensiling, and co-digestion of rice straw with other feedstocks. The biogas digestate can be used to fertilize soils. The average annual potential energy of collectable rice straw, with a lower heating value of 15.35 megajoule/kilogram, over the past ten years (2013-2022) could reach 2.41 × 109 megajoule.

Carbon capture technology exploitation for vanadium tailings and assessment of CO2 sequestration potential

In recent years, the global warming trend is still increasing due to CO₂ emissions from various sources, such as electricity, heat production, industry, and transportation. In the vanadium industry, the vanadium bearing shale is of low grade, and the extraction of the required elemental vanadium produces large quantities of vanadium tailings (VTs). Both the roasting pretreatment of vanadium shale during vanadium extraction and the high-temperature calcination process for the preparation of vanadium products generate large amounts of CO₂ gas. Therefore, it is particularly important to find an effective and environmentally friendly method for the treatment of vanadium tailings and CO₂ generated by the vanadium industry. In this study, a potential method for the indirect carbonation of low calcium VTs under atmospheric pressure conditions was investigated. The carbonation reaction was investigated for different ammonia addition factors and different introduced CO₂ concentrations and temperatures. The carbonation experiments showed that under the conditions of coefficient of ammonia addition of 1.4, reaction time of 60 min and reaction temperature of 60 °C, the utilization rate of calcium in VTs reached 97.9% and the CO₂ uptake of VTs at 0.073 g-CO₂/g, indicating that the carbonation of vanadium with low-calcium VTs was effective. The carbonation product was analyzed and measured using TG, XRD, and SEM-EDS, and it was discovered to be CaCO₃, confirming the feasibility of carbonation reaction with vanadium tailings. Furthermore, the characterization of the carbonation product confirmed the mechanism and safety of the carbonation reaction, laying the groundwork for future applications.

Year-round trace gas measurements in the central Arctic during the MOSAiC expedition

Despite the key role of the Arctic in the global Earth system, year-round in-situ atmospheric composition observations within the Arctic are sparse and mostly rely on measurements at ground-based coastal stations. Measurements of a suite of in-situ trace gases were performed in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. These observations give a comprehensive picture of year-round near-surface atmospheric abundances of key greenhouse and trace gases, i.e., carbon dioxide, methane, nitrous oxide, ozone, carbon monoxide, dimethylsulfide, sulfur dioxide, elemental mercury, and selected volatile organic compounds (VOCs). Redundancy in certain measurements supported continuity and permitted cross-evaluation and validation of the data. This paper gives an overview of the trace gas measurements conducted during MOSAiC and highlights the high quality of the monitoring activities. In addition, in the case of redundant measurements, merged datasets are provided and recommended for further use by the scientific community.

Advances in Ecosystem Services Valuation Studies in India: Learnings from a Systematic Review

Ecosystem services (ES) concept has gained global momentum as they hold immense importance for human well-being. On the other hand, direct and indirect drivers of biodiversity loss have led to deterioration of ecosystem health and their capacity to deliver ecosystem services. Worldwide, ES assessments have been increasingly used by administrators to formulate sustainable and environment centric policies. Similarly, there has been continuous expansion of ES related work in India to capture the material and non-material benefits derived from diverse ecosystems in the country. In the current paper, 105 research articles/reports have been reviewed to assess the growing trajectory of ES research and also to map their methodological approaches. The lacunae in the studies and literature have been critically examined. Analysis of the study shows that ES derived from forests have been captured widely while marine ecosystems have not received appropriate scholarly attention. Similarly, dearth of studies focusing on long- and short-term implications of climate change and other environmental challenges on the ES delivery was also evident. A strong need is felt to integrate interdisciplinary approaches for holistic ES assessment. Also, future ES assessments must assimilate traditional as well as indigenous knowledge systems within ES assessment framework to ensure formulation of tangible, sustainable policies.

XCO2 and XCH4 Reconstruction Using GOSAT Satellite Data Based on EOF-Algorithm

The Greenhouse Gases Observing Satellite (GOSAT) can help to ascertain the global distribution of carbon dioxide (CO2) and methane (CH4), and how the sources and sinks of these gases vary by season, year, and location. However, the data provided by the GOSAT level 2 and 3 products have certain limitations due to their lack of spatial and temporal information; even with the application of the kriging geostatistical method on the level 2 products, the processing algorithms still need further upgrades. In this study, we apply an empirical orthogonal function (EOF)-based method on the GOSAT L3 products (137 images, from January 2010 to May 2021) to estimate the column average of carbon dioxide and methane (XCO2–XCH4) within the entire Earth. The reconstructed results are validated against the Total Carbon Column Observing Network (i.e., TCCON), with 31 in situ stations, and GOSAT L4B column-averaged data, using 107 layers. The results show an excellent agreement with the TCCON data and exhibit an R-squared coefficient of 0.95 regarding the CO2 measurements and 0.86 regarding the CH4 measurements. Therefore, this methodology can be incorporated into the processing steps used to map global greenhouse gases.

Effect of Battery Electric Vehicles on Greenhouse Gas Emissions in 29 European Union Countries

This analysis explored the effect of battery electric vehicles (BEVs) on greenhouse gas emissions (GHGs) in a panel of twenty-nine countries from the European Union (EU) from 2010 to 2020. The method of moments quantile regression (MM-QR) was used, and the ordinary least squares with fixed effects (OLSfe) was used to verify the robustness of the results. The MM-QR support that in all three quantiles, economic growth causes a positive impact on GHGs. In the 50th and 75th quantiles, energy consumption causes a positive effect on GHGs. BEVs in the 25th, 50th, and 75th quantiles have a negative impact on GHGs. The OLSfe reveals that economic growth has a negative effect on GHGs, which contradicts the results from MM-QR. Energy consumption positively impacts GHGs. BEVs negatively impacts GHGs. Although the EU has supported a more sustainable transport system, accelerating the adoption of BEVs still requires effective political planning to achieve net-zero emissions. Thus, BEVs are an important technology to reduce GHGs to achieve the EU targets of decarbonising the energy sector. This research topic can open policy discussion between industry, government, and researchers, towards ensuring that BEVs provide a climate change mitigation pathway in the EU region.

Carbon storage estimation in a secondary tropical forest at CIEE Sustainability Center, Monteverde, Costa Rica

Secondary growth tropical rainforests have the potential to sequester large amounts of atmospheric carbon dioxide and as such are an important carbon sink. To evaluate a local forest, a Carbon Neutrality Program was initiated at the Council on International Educational Exchange, San Luis Campus, Monteverde, Costa Rica. The study was conducted on 50 hectares of forest classified as Premontane Wet Forest. The forest, part of the Arenal-Monteverde Protected Zone, is estimated to be aproximately 50 years old and is in the upper regions of the San Luis valley at 1100 m elevation. Assessment of the carbon stock in trees was carried out in two permanent, 1 hectare plots, 100 m by 100 m, Camino Real and Zapote. The plots were divided into 25 subplots, 20 m by 20 m totaling 400 m² per subplot. Ten subplots in each area were studied which represented 1.6% the total surface area of the forest. All of the trees were measured within the subplots that had a diameter at breast height ≥ 10 cm and the height of 10% of the trees measured. The estimated total CO₂ sequestered by the campus forest was 18,210 ton (in 2019).

Climate Change, Land, Water, and Food Security: Perspectives From Sub-Saharan Africa

The current and projected warming of the earth is unequivocal with humans playing a strong role as both perpetrators and victims. The warming on the African continent is projected to be greater than the global average with an increased average temperature of 3–6°C by the end of the century under a high Representative Concentration Pathway. In Africa, the Sub-Saharan region is identified as the most vulnerable to the changing climate due to its very low capacity to adapt to or mitigate climate change. While it is common to identify studies conducted to assess how climate change independently impacts water, land, or food resources, very limited studies have sought to address the interlinkages, synergies, and trade-offs existing between climate change, water, land, and food (WLF) resources as a system in Sub-Saharan Africa (SSA). The climate change and WLF security nexus, therefore, seeks to address this shortfall in literature and subsequently serve as a relevant source of information for decision-making and policy implementation concerning climate change mitigation and adaptation. In this study, 41 relevant studies were selected from Web of Science, Google Scholar, ResearchGate, and institutional websites. We provide information on the independent relationships between climate change and WLF resources, and further discuss the existing inter-linkages between climate change and the WLF security in SSA using the nexus approach, with recommendations on how decision making and policy implementations should be done using the climate change and WLF security nexus approach.