Carbon dioxide (CO2) is the primary greenhouse gas contributing to anthropogenic climate change which is associated with human activities. The majority of CO2 emissions are results of the burning of fossil fuels for energy, as well as industrial processes such as steel and cement production. Carbon capture, utilization, and storage (CCUS) is a sustainability technology promising in terms of reducing CO2 emissions that would otherwise contribute to climate change. From this perspective, the discussion on carbon capture focuses on chemical absorption technology, primarily due to its commercialization potential. The CO2 absorptive capacity and absorption rate of various chemical solvents have been summarized. The carbon utilization focuses on electrochemical conversion routes converting CO2 into potentially valuable chemicals have received particular attention. The Faradaic conversion efficiencies for various CO2 reduction products are used to describe efficiency improvements. For carbon storage, successful deployment relies on a better understanding of fluid mechanics, geomechanics, and reactive transport, which are discussed in details.
The large-scale deployment of carbon capture and storage (CCS) is becoming increasingly urgent in the global path toward net zero emissions; however, global CCS deployment is significantly lagging behind its expected contribution to greenhouse gas emission reduction. Reviewing and learning from the examples and history of successful CCS practices in advanced countries will help other countries, including China, to promote and deploy CCS projects using scientific methods. This paper shows that the establishment of major science and technology CCS infrastructures in advanced countries has become the main source of CCS technological innovation, cost reduction, risk reduction, commercial promotion, and talent training in the development and demonstration of key CCS technologies. Sound development of CCS requires a transition from pilot-scale science and technology infrastructures to large-scale commercial infrastructures, in addition to incentive policies; otherwise, it will be difficult to overcome the technical barriers between small-scale demonstrations and the implementation of million-tonne-scale CCS and ten-million-tonne-scale CCS hubs. Geological CO2 storage is the ultimate goal of CCS projects and the driving force of CO2 capture. Further improving the accuracy of technologies for the measurement, monitoring, and verification (MMV) of CO2 storage capacity, emission reduction, and safety remains a problem for geological storage. CO2 storage in saline aquifers can better couple multiple carbon emission sources and is currently a priority direction for development. Reducing the energy consumption of lowconcentration CO2 capture and the depletion of chemical absorbents and improving the operational efficiency and stability of post-combustion CO2 capture systems have become the key constraints to largescale CCS deployment. Enhanced oil recovery (EOR) is also important in order for countries to maximize fossil fuel extraction instead of importing oil from less environmentally friendly oil-producing countries.
Climate change is the greatest environmental threat to humans and the planet in the 21st century. Global anthropogenic greenhouse gas emissions are one of the main causes of the increasing number of extreme climate events. Cumulative carbon dioxide (CO2) emissions showed a linear relationship with cumulative temperature rise since the pre-industrial stage, and this accounts for approximately 80% of the total anthropogenic greenhouse gases. Therefore, accurate and reliable carbon emission data are the foundation and scientific basis for most emission reduction policymaking and target setting. Currently, China has made clear the ambitious goal of achieving the peak of carbon emissions by 2030 and achieving carbon neutrality by 2060. The development of a finer-grained spatiotemporal carbon emission database is urgently needed to achieve more accurate carbon emission monitoring for continuous implementation and the iterative improvement of emission reduction policies. Near-real-time carbon emission monitoring is not only a major national demand but also a scientific question at the frontier of this discipline. This article reviews existing annual-based carbon accounting methods, with a focus on the newly developed real-time carbon emission technology and its current application trends. We also present a framework for the latest near-real-time carbon emission accounting technology that can be widely used. The development of relevant data and methods will provide strong database support to the policymaking for China's ″carbon neutrality” strategy. Finally, this article provides an outlook on the future of real-time carbon emission monitoring technology.
The vision of reaching a carbon peak and achieving carbon neutrality is guiding the low-carbon transition of China's socioeconomic system. Currently, a research gap remains in the existing literature in terms of studies that systematically identify opportunities to achieve carbon neutrality. To address this gap, this study comprehensively collates and investigates 1105 published research studies regarding carbon peaking and carbon neutrality. In doing so, the principles of development in this area are quantitively analyzed from a space–time perspective. At the same time, this study traces shifts and alterations in research hotspots. This systematic review summarizes the priorities and standpoints of key industries on carbon peaking and carbon neutrality. Furthermore, with an emphasis on five key management science topics, the scientific concerns and strategic demands for these two carbon emission-reduction goals are clarified. The paper ends with theoretical insights on and practical countermeasures for actions, priority tasks, and policy measures that will enable China to achieve a carbon-neutral future. This study provides a complete picture of the research status on carbon peaking and carbon neutrality, as well as the research directions worth investigating in this field, which are crucial to the formulation of carbon peak and carbon neutrality policies.
China's energy system requires a thorough transformation to achieve carbon neutrality. Here, leveraging the highly acclaimed The Integrated MARKAL-EFOM System model of China (China TIMES) that takes energy, the environment, and the economy into consideration, four carbon-neutral scenarios are proposed and compared for different emission peak times and carbon emissions in 2050. The results show that China's carbon emissions will peak at 10.3–10.4 Gt between 2025 and 2030. In 2050, renewables will account for 60% of total energy consumption (calorific value calculation) and 90% of total electricity generation, and the electrification rate will be close to 60%. The energy transition will bring sustained air quality improvement, with an 85% reduction in local air pollutants in 2050 compared with 2020 levels, and an early emission peak will yield more near-term benefits. Early peak attainment requires the extensive deployment of renewables over the next decade and an accelerated phasing out of coal after 2025. However, it will bring benefits such as obtaining better air quality sooner, reducing cumulative CO2 emissions, and buying more time for other sectors to transition. The pressure for more ambitious emission reductions in 2050 can be transmitted to the near future, affecting renewable energy development, energy service demand, and welfare losses.
Many cities have pledged to achieve carbon neutrality. The urban water industry can also contribute its share to a carbon-neutral future. Using a multi-city time-series analysis approach, this study aims to assess the progress and lessons learned from the greenhouse gas (GHG) emissions management of urban water systems in four global cities: Amsterdam, Melbourne, New York City, and Tokyo. These cities are advanced in setting GHG emissions reduction targets and reporting GHG emissions in their water industries. All four cities have reduced the GHG emissions in their water industries, compared with those from more than a decade ago (i.e., the latest three-year moving averages are 13%–32% lower), although the emissions have ″rebounded″ multiple times over the years. The emissions reductions were mainly due to various engineering opportunities such as solar and mini-hydro power generation, biogas valorization, sludge digestion and incineration optimization, and aeration system optimization. These cities have recognized the many challenges in reaching carbon-neutrality goals, which include fluctuating water demand and rainfall, more carbon-intensive flood-prevention and water-supply strategies, meeting new air and water quality standards, and revising GHG emissions accounting methods. This study has also shown that it is difficult for the water industry to achieve carbon neutrality on its own. A collaborative approach with other sectors is needed when aiming toward the city's carbon-neutrality goal. Such an approach involves expanding the usual system boundary of the water industry to externally tap into both engineering and non-engineering opportunities.
Oxygen atoms usually co-exist in the lattice of hexagonal boron nitride (h-BN). The understanding of interactions between the oxygen atoms and the adsorbate, however, is still ambiguous on improving adsorptive desulfurization performance. Herein, simultaneously oxygen atom-scale interior substitution and edge hydroxylation in BN structure were constructed via a polymer-based synthetic strategy. Experimental results indicated that the dual oxygen modified BN (BN–2O) exhibited an impressively increased adsorptive capacity about 12% higher than that of the edge hydroxylated BN (BN–OH) fabricated via a traditional method. The dibenzothiophene (DBT) was investigated to undergo multi-molecular layer type coverage on the BN–2O uneven surface via π–π interaction, which was enhanced by the increased oxygen doping at the edges of BN–2O. The density functional theory calculations also unveiled that the oxygen atoms confined in BN interior structure could polarize the adsorbate, thereby resulting in a dipole interaction between the adsorbate and BN–2O. This effect endowed BN–2O with the ability to selectively adsorb DBT from the aromatic-rich fuel, thereafter leading to an impressive prospect for the adsorptive desulfurization performance of the fuel. The adsorptive result was in good accordance with Freundlich and pseudo-second-order adsorption kinetics model results. Therefore, the designing of a polymer-based strategy could be also extended to other heteroatom doping systems to enhance adsorptive performance.
Reductive pretreatment is an important step for activating supported metal catalysts but has received little attention. In this study, reconstruction of the supported nickel catalyst was found to be sensitive to pretreatment conditions. In contrast to the traditional activation procedure in hydrogen, activating the catalyst in syngas created supported Ni nanoparticles with a polycrystalline structure containing an abundance of grain boundaries. The unique post-activation catalyst structure offered enhanced CO adsorption and an improved CO methanation rate. The current strategy to tune the catalyst structure via manipulating the activation conditions can potentially guide the rational design of other supported metal catalysts.
Many natural fibers are lightweight and display remarkable strength and toughness. These properties originate from the fibers' hierarchical structures, assembled from the molecular to macroscopic scale. The natural spinning systems that produce such fibers are highly energy efficient, inspiring researchers to mimic these processes to realize robust artificial spinning. Significant developments have been achieved in recent years toward the preparation of high-performance bio-based fibers. Beyond excellent mechanical properties, bio-based fibers can be functionalized with a series of new features, thus expanding their sophisticated applications in smart textiles, electronic sensors, and biomedical engineering. Here, recent progress in the construction of bio-based fibers is outlined. Various bioinspired spinning methods, strengthening strategies for mechanically strong fibers, and the diverse applications of these fibers are discussed. Moreover, challenges in reproducing the mechanical performance of natural systems and understanding their dynamic spinning process are presented. Finally, a perspective on the development of biological fibers is given.
Tooth enamel, which is a biological tissue mainly composed of well-aligned hydroxyapatite nanocrystals and an interlaced protein matrix, has remarkable mechanical and aesthetic behaviors. Nevertheless, it is challenging to regenerate enamel naturally, and potential pulp involvement and tooth loss may occur. As the hardest biogenic composite material, enamel has long been regarded as a promising load-bearing material. Thus, understanding the enamel formation process and enamel structural motif mechanisms is important for the design and engineering of high-performance biomimetic composites with high strength and physical resilience. Extensive studies have been conducted on mimicking the microstructure and mechanical properties of tooth enamel, and various enamel-like material synthesis protocols have been developed. In light of the engineering fabrication of enamel-like materials, this review focuses on recent progress in synthetic strategies for enamel-mimetic materials and provides a discussion of the potential applications of these materials.
Taming the electron transfer across metal–support interfaces appears to be an attractive yet challenging methodology to boost catalytic properties. Herein, we demonstrate a precise engineering strategy for the carbon surface chemistry of Pt/C catalysts—that is, for the electron-withdrawing/donating oxygen-containing groups on the carbon surface—to fine-tune the electrons of the supported metal nanoparticles. Taking the ammonia borane hydrolysis as an example, a combination of density functional theory (DFT) calculations, advanced characterizations, and kinetics and isotopic analyses reveals quantifiable relationships among the carbon surface chemistry, Pt charge state and binding energy, activation entropy/enthalpy, and resultant catalytic activity. After decoupling the influences of other factors, the Pt charge is unprecedentedly identified as an experimentally measurable descriptor of the Pt active site, contributing to a 15-fold increment in the hydrogen generation rate. Further incorporating the Pt charge with the number of Pt active sites, a mesokinetics model is proposed for the first time that can individually quantify the contributions of the electronic and geometric properties to precisely predict the catalytic performance. Our results demonstrate a potentially groundbreaking methodology to design and manipulate metal–carbon catalysts with desirable properties.
Acute liver failure (ALF) has an abrupt onset with a frequently fatal outcome. Previous studies have found that oral antibiotics prevent drug-induced liver injury in animal experiments, indicating that the gut microbiota plays a critical role in the pathophysiological process. However, the underlying mechanism has not been fully understood. This study explored the comprehensive role of the gut microbiota in ALF using multi-omics. A cocktail of broad-spectrum antibiotics (Abx) pretreatment by gavage for four weeks improved the survival of D-(+)-galactosamine hydrochloride (D-Gal)/lipopolysaccharide (LPS)-induced ALF in C57BL/6 mice. RNA sequencing showed that inflammatory responses were inhibited and metabolic pathways were upregulated in the liver of Abx-treated ALF mice. The 16S rRNA gene sequencing revealed that Abx reshaped the composition and function of the gut microbiota, with an increased proportion of tryptophan (Trp) metabolism. In addition, global metabolic profiling by ultra-performance liquid chromatography–mass spectrometry (UPLC–MS) indicated that the gut microbiota post-Abx intervention reduced Trp excretion, liberated more Trp to the host, and enhanced the kynurenine (Kyn) pathway with increased production of Kyn. As an endogenous aryl hydrocarbon receptor (AhR) ligand, Kyn has anti-inflammatory and immunosuppressive effects. Furthermore, AhR-targeted treatments affected the outcome of ALF mice with or without Abx pretreatment, indicating that AhR directly regulated susceptibility to ALF, at least in part. This study demonstrates that the gut microbiota-dependent control of the Trp metabolism could regulate host susceptibility to ALF by modulating the activity of AhR, and thus provides a promising target for better management of ALF.
Observing the dynamic progress of the brain in response to peripheral nerve stimulation as a whole is the basis for a deeper understanding of overall brain function; however, it remains a great challenge. In this work, a novel mini-invasive orthogonal recording method is developed to observe the overall evoked cortex potential (ECP) in rat brain. A typical ECP atlas with recognizable waveforms in the rat cortex corresponding to the median, ulnar, and radial nerve trunks and subdivided branches is acquired. Reproducible exciting temporal–spatial progress in the rat brain is obtained and visualized for the first time. Changes in the ECPs and exciting sequences in the cortex four months after median nerve transection are also observed. The results suggest that the brain's response to peripheral stimulation has precise and reproducible temporal–spatial properties. This resource can serve as a testbed to explore the overall functional interaction and dynamic remodeling mechanisms between the peripheral and central nervous systems over time.
A composite Air Health Index (AHI) is helpful for separately emphasizing the health risks of multiple stimuli and communicating the overall risks of an adverse atmospheric environment to the public. We aimed to establish a new AHI by integrating daily mortality risks due to air pollution with those due to non-optimum temperature in China. Based on the exposure-response (E-R) coefficients obtained from time-series models, the new AHI was constructed as the sum of excess mortality risk associated with air pollutants and non-optimum temperature in 272 Chinese cities from 2013 to 2015. We examined the association between the ″total AHI″ (based on total mortality) and total mortality, and further compared the ability of the ″total AHI″ to predict specific cardiopulmonary mortality with that of ″specific AHIs″ (based on specific mortalities). On average, air pollution and non-optimum temperature were associated with 28.23% of daily excess mortality, of which 23.47% was associated with non-optimum temperature while the remainder was associated with fine particulate matter (PM2.5) (1.12%), NO2 (2.29%,), and O3 (2.29%). The new AHI uses a 10-point scale and shows an average across all 272 cities of 6 points. The E-R curve for AHI and mortality is approximately linear, without any thresholds. Each one unit increase in ″total AHI″ is associated with a 0.84% increase in all-cause mortality and 1.01%, 0.98%, 1.02%, 1.66%, and 1.71% increases in cardiovascular disease, coronary heart disease, stroke, respiratory diseases, and chronic obstructive pulmonary disease mortality, respectively. Cause-specific mortality risk estimates using the ″total AHI″ are similar to those predicted by ″specific AHIs.″ In conclusion, the ″total AHI″ proposed herein could be a promising tool for communicating health risks related to exposure to the ambient environment to the public.
Preserving Tibet's unique history and cultural heritage relies on the sustainability of the Tibetan croplands, which are characterized by highland barley, the only cereal crop cultivated over 4000 m above sea level. Yet it is unknown how these croplands will respond to climate change. Here, using yield statistics from 1985 to 2015, we found that the impact of temperature anomalies on the Tibetan crop yield shifted from nonsignificant (P > 0.10) in the 1980s and 1990s to significantly negative (P < 0.05) in recent years. Meanwhile, the apparent sensitivity of the crop yield to temperature anomalies almost doubled, from (–0.13 ± 0.20) to (–0.22 ± 0.14) t·ha–1·°C–1. The emerging negative impacts of higher temperatures suggest an increasing vulnerability of Tibetan croplands to warmer climate. With global warming scenarios of +1.5 or +2.0 °C above the pre-industry level, the temperature sensitivities of crop yield may further increase to (–0.33 ± 0.10) and (–0.51 ± 0.18) t·ha–1·°C–1, respectively, making the crops 2–3 times more vulnerable to warmer temperatures than they are today.
Crushed rock layers (CRLs), ventilation ducts (VDs) and thermosyphons are air-cooling structures (ACSs) widely used for maintaining the long-term stability of engineered infrastructures in permafrost environments. These ACSs can effectively cool and maintain the permafrost subgrade's frozen state under climate warming by facilitating heat exchange with ambient air in cold seasons. As convection is a crucial working mechanism of these ACSs, it is imperative to understand the near-surface wind flow (NSWF) across a constructed infrastructure, such as an embankment. This article describes a yearlong field observation of the NSWF across an experimental expressway embankment, the first of its kind on the Qinghai–Tibet Plateau (QTP). The wind speed and direction along a transect perpendicular to the embankment on both the windward and leeward sides and at four different heights above the ground surface were collected and analyzed. The results showed that the embankment has a considerable impact on the NSWF speed within a distance of up to ten times its height, and in the direction on the leeward side. A power law can well describe the speed profiles of NSWF across the embankment, with the power-law indices (PLI) varying from 0.14 to 0.40. On an annual basis, the fitted NSWF PLI far away from the embankment was 0.19, which differs substantially from the values widely used in previous thermal performance evaluations of ACSs on the QTP. Finally, the significance of the NSWF to the thermal performance of the ACSs, particularly the CRLs and VDs, in linear transportation infrastructure is discussed. It is concluded that underestimating the PLI and neglecting wind direction variations may lead to unconservative designs of the ACSs. The results reported in this study can provide valuable guidance for infrastructure engineering on the QTP and other similar permafrost regions.
In modern wireless communication systems, the signal-to-noise ratio (SNR) is one of the most important performance indicators. When the other radio frequency (RF) performance of the components is well designed, passive intermodulation (PIM) interference may become an important factor limiting the system's SNR. Whether it is a base station, an indoor distributed antenna system, or a satellite system, there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks. Especially for systems of high power and wide bandwidth such as 5G wireless communication, PIM interference is even more serious. Due to the complexity and uncertainty of PIM, measurement is the most important means to study and evaluate the PIM performance of wireless communication systems. In this review, the current main PIM measurement methods recommended by International Electrotechnical Commission (IEC) and other standard organizations are introduced, and several key challenges in PIM measurement and their solutions (including the design of PIM tester, the location of the PIM sources, the design of compact PIM anechoic chambers, and the evaluation methods of PIM anechoic chambers) are highlighted. These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.