Three-Phase-Heterojunction Cu/Cu2O-Sb2O3 Catalyst Enables Efficient CO2 Electroreduction to CO and High-Performance Aqueous Zn-CO2 Battery

Zn-CO2 batteries are excellent candidates for both electrical energy output and CO2 utilization, whereas the main challenge is to design electrocatalysts for electrocatalytic CO2 reduction reactions with high selectivity and low cost. Herein, the three-phase heterojunction Cu-based electrocatalyst (Cu/Cu2O-Sb2O3-15) is synthesized and evaluated for highly selective CO2 reduction to CO, which shows the highest faradaic efficiency of 96.3% at -1.3 V versus reversible hydrogen electrode, exceeding the previously reported best values for Cu-based materials. In situ spectroscopy and theoretical analysis indicate that the Sb incorporation into the three-phase heterojunction Cu/Cu2O-Sb2O3-15 nanomaterial promotes the formation of key *COOH intermediates compared with the normal Cu/Cu2O composites. Furthermore, the rechargeable aqueous Zn-CO2 battery assembled with Cu/Cu2O-Sb2O3-15 as the cathode harvests a peak power density of 3.01 mW cm-2 as well as outstanding cycling stability of 417 cycles. This research provides fresh perspectives for designing advanced cathodic electrocatalysts for rechargeable Zn-CO2 batteries with high-efficient electricity output together with CO2 utilization.

Temporal variability of air-water gas exchange of carbon dioxide in clam and fish aquaculture ponds

The growing trend of land-based aquaculture has heightened the significance of comprehensively assessing air-water carbon dioxide (CO2) gas exchange in these inland waters, given their potential impact on carbon neutral strategies. However, temporal variations of partial pressure of CO2 (pCO2) and CO2 flux in clam and fish aquaculture ponds were barely investigated. We assessed the water surface pCO2 in one to five months intervals by deploying a lab-made buoy in three clam ponds and three fishponds located in tropical and subtropical climates. Measurements were conducted over a 24 h period each time, spanning from April 2021 to June 2022, covering the stocking, middle, and harvesting stages of the culture cycle. Diurnal pCO2 variations were dominantly controlled by biologically driven changes in dissolved inorganic carbon and total alkalinity (~97 %), while temperature and salinity effects were minor (~3 %). Clam ponds acted as a sink of atmospheric CO2 during stocking stages and transitioned to a source during middle to harvesting stages. In contrast, fishponds acted as a source of atmospheric CO2 throughout culture cycles and CO2 flux strengthened when reaching harvesting stages. Overall, clam ponds acted as a weak sink for atmospheric CO2 (-2.8 ± 17.3 mmol m-2 d-1), whereas fishponds acted as a source (16.8 ± 21.7 mmol m-2 d-1). CO2 emission was stronger during daytime coinciding with higher windspeeds compared to nighttime in fishponds. We suggest incorporating high temporal resolution measurements to account for diurnal and culture-stage variations, enabling more accurate estimates of air-water CO2 flux in aquaculture ponds. Moreover, the findings of this study highlight the importance of feeding, aeration, and biological activities (photosynthesis, remineralization, and calcification) in controlling the air-water CO2 flux in aquaculture ponds and such information can be used in implementing better strategies to achieve carbon neutral goals.

Current situation, trend, and prospects of research on functional components from by-products of baijiu production: A review

In the present scenario marked by energy source shortages and escalating concerns regarding carbon dioxide emissions, there is a growing emphasis on the optimal utilization of biomass resources. Baijiu, as the Chinese national spirit, boasts remarkably high sales volumes annually. However, the production of baijiu yields various by-products, including solid residues (Jiuzao), liquid wastewater (Huangshui and waste alcohol), and gaseous waste. Recent years have witnessed dedicated research aimed at exploring the composition and potential applications of these by-products, seeking sustainable development and comprehensive resource utilization. This review systematically summarizes recent research, shedding light on both the baijiu brewing process and the bioactive compounds present baijiu production by-products (BPBPs). The primary focus lies in elucidating the potential extraction methods and applications of BPBPs, offering a practical approach to comprehensive utilization of by-products in functional food, medicine, cosmetic, and packaging fields. These applications not only contribute to enhancing production efficiency and mitigating environmental pollution, but also introduce innovative concepts for the sustainable advancement of associated industries. Future research avenues may include more in-depth compositional analysis, the development of utilization technologies, and the promotion of potential industrialization.

Simulation of emission reduction path under the path of differentiated energy transformation in China's industrial cities: a case study of Shanghai

The formulation of long-term step-by-step emission reduction plan is an important step for effective scientific emission reduction. This paper takes Shanghai as the research object, constructs PSO-LSTM model on the basis of STIRPAT model, and further constructs three dynamic policy scenarios combined with China's actual situation and makes short-, medium-, and long-term multivariate predictions for them. The study finds that only the improvement of energy consumption structure has a promotion effect on carbon emission reduction, and urbanization, industrial structure, technology level, population, and economic level all have an increasing effect, and secondly, the carbon emission reduction path of Shanghai basically achieves the core objective of steady decrease under the three scenarios. Secondly, under the three scenarios, Shanghai's carbon emission reduction path basically achieves the core objective of steady decline, but the decline in the GU scenario is more significant. It is recommended that Shanghai further adjusts its industrial structure, optimizes its energy consumption structure, promotes technological innovation and progress, and promotes the development of the circular economy model.

Grazing management for soil carbon in Australia: A review

The livestock industry accounts for a considerable proportion of agricultural greenhouse gas emissions, and in response, the Australian red meat industry has committed to an aspirational target of net-zero emissions by 2030. Increasing soil carbon storage in grazing lands has been identified as one method to help achieve this, while also potentially improving production and provision of other ecosystem services. This review examined the effects of grazing management on soil carbon and factors that drive soil carbon sequestration in Australia. A systematic literature search and meta-analysis was used to compare effects of stocking intensity (stocking rate or utilisation) and stocking method (i.e, continuous, rotational or seasonal grazing systems) on soil organic carbon, pasture herbage mass, plant growth and ground cover. Impacts on below ground biomass, soil nitrogen and soil structure are also discussed. Overall, no significant impact of stocking intensity or method on soil carbon sequestration in Australia was found, although lower stocking intensity and incorporating periods of rest into grazing systems (rotational grazing) had positive effects on herbage mass and ground cover compared with higher stocking intensity or continuous grazing. Minimal impact of grazing management on pasture growth rate and below-ground biomass has been reported in Australia. However, these factors improved with grazing intensity or rotational grazing in some circumstances. While there is a lack of evidence in Australia that grazing management directly increases soil carbon, this meta-analysis indicated that grazing management practices have potential to benefit the drivers of soil carbon sequestration by increasing above and below-ground plant production, maintaining a higher residual biomass, and promoting productive perennial pasture species. Specific recommendations for future research and management are provided in the paper.

Research on the pathway of digital technology to drive China's energy sector to achieve its carbon neutrality goal

With global climate change looming large, there is an urgent need for China's energy sector to take steps towards carbon neutrality. This study aims to explore how digital technologies can contribute to the pathway for China's energy sector to achieve carbon neutrality. By analyzing carbon neutrality policies and digital technology applications, we propose a systematic pathway framework to guide China's energy sector in integrating digital technology to accelerate the pace of achieving carbon neutrality in the energy sector. We first review the current status of carbon emissions and carbon neutrality targets in China's energy sector, and in light of the development trend of modern digital technologies, we propose key application areas for digital technologies in realizing carbon neutrality in the energy sector. Second, we detail the specific applications and effects of digital technologies in energy supply side optimization, energy utilization efficiency improvement, carbon sink management, and smart grid construction. Through theoretical modeling and empirical analysis, we demonstrate the great potential of digital technologies in carbon emission reduction and carbon neutrality in the energy sector and reveal the key role of digital technologies in carbon-neutral pathways. Finally, we propose effective technology implementation measures and point out important challenges and solution paths for digital technologies in carbon-neutral practices. This study provides a scientific basis and guidance for China's energy sector to achieve carbon neutrality with the help of digital technologies and promotes the important steps towards carbon neutrality in China.

Inclusive greenhouse gas budget assessment in turfs: From turf production to disposal of grass clippings

Globally, greenhouse gas (GHG) reduction is a serious concern. To evaluate whether turfs serve as a GHG sink or source, GHG budget assessments for life cycle are required. However, previous studies have only focused on the use of turfs. To bridge these gaps in literature, this study investigated GHG (CO2, N2O, and CH4) emissions from the disposal of grass clippings and soil GHG fluxes in turfs. Additionally, GHG budgets in the turf production phase were assessed. Finally, inclusive GHG budgets from turf production to disposal of grass clippings for four turf uses (soccer stadium, golf course, office, and urban park) were assessed. Grass clippings were disposed in three forms (incineration, leaving as-is, and biochar). We found that GHG emissions from incineration and leaving 1 t-fresh weight (FW) of grass clippings were 0.711 and 0.207 t-CO2e, respectively. Contrastingly, the GHG emissions from the biochar yield from 1 t-FW of grass clippings were -0.200 t-CO2e. Further, annual soil GHG fluxes in newly established Zoysia and Kentucky bluegrass turfs were calculated at 0.067 and 0.040 tCO2e･ha-1･yr-1, respectively. As the turf grass in production fields sequester large amounts of CO2, GHG budgets in turf production phase were estimated at approximately -20 t-CO2e･ha-1･yr-1. Inclusive GHG budget assessment from turf production to disposal of grass clippings showed that turfs only in the urban parks served as a GHG sink and this ability was comparable to CO2 sequestration in forests. To enhance the ability of GHG sinks and to promote changes from a GHG source to GHG sink, our study revealed the importance of reduction of GHG emissions from energy and resource uses (especially fertilizers and gasoline) for turf management.

Emerging trends and advances in valorization of lignocellulosic biomass to biofuels

Sustainable technologies pave the way to address future energy demand by converting lignocellulosic biomass into fuels, carbon-neutral materials, and chemicals which might replace fossil fuels. Thermochemical and biochemical technologies are conventional methods that convert biomass into value-added products. To enhance biofuel production, the existing technologies should be upgraded using advanced processes. In this regard, the present review explores the advanced technologies of thermochemical processes such as plasma technology, hydrothermal treatment, microwave-based processing, microbial-catalyzed electrochemical systems, etc. Advanced biochemical technologies such as synthetic metabolic engineering and genomic engineering have led to the development of an effective strategy to produce biofuels. The microwave-plasma-based technique increases the biofuel conversion efficiency by 97% and the genetic engineering strains increase the sugar production by 40%, inferring that the advanced technologies enhances the efficiency. So understanding these processes leads to low-carbon technologies which can solve the global issues on energy security, the greenhouse gases emission, and global warming.

The impact of industrial land mismatch on carbon emissions in resource-based cities under environmental regulatory constraints-evidence from China

Achieving carbon neutrality has become a global common goal. For China, to reach peak carbon emissions and long-term carbon neutrality, the transformation and development of resource-based cities are essential. This study uses data from 114 prefecture-level resource-based cities from 2008 to 2019 as a sample and empirically tests the impact of industrial land mismatch on carbon emissions using the fixed effects model. In addition, we analyze the heterogeneous influence of environmental regulation as a moderating effect on resource-based cities at different development stages. The study reveals that (1) there is a significant positive correlation between the imbalance in industrial land supply in resource-based cities and carbon emissions. The more severe the imbalance, the higher the carbon emissions. The improper supply mode of industrial land is also positively correlated with carbon emissions, although the impact is not significant. (2) Environmental regulation can significantly curb the carbon emission issues caused by the mismatch and imbalance in the scale of industrial land supply and the improper supply mode of industrial land. (3) Compared to strong resource-based cities, weak resource-security cities have a smaller impact on carbon emissions due to an imbalance in the supply of industrial land. This is mainly because resources in weak resource-security cities are becoming exhausted, making "ecology first, green and low carbon" the main tune for economic and social development. Both types of cities show a positive correlation between the improper supply of industrial land and carbon emissions, although neither is significant. (4) The intensity of the regulatory effect of environmental regulations on resource-based cities is influenced by resource abundance. The suppression of carbon emissions by environmental regulations is more apparent in strong resource-security cities than in weak resource-security cities.

Ammonia-mediated iron cycle for oxidizing agent activation in advanced oxidation process

Removing ammonia (NH4+-N) and recalcitrant organics from low carbon/nitrogen wastewater requires a large amount of chemical reagents and energy. This work reports a new advanced oxidation process to remove recalcitrant organics with the assistant of NH4+-N in low carbon/nitrogen wastewater. Specifically, NH4+-N in wastewater mediated Fe(II)/Fe(III) cycle for the activation of oxidation reagent (e.g., H2O2) (ammonia-mediated AOP) to improve the removal of recalcitrant organics. In ammonia-mediated AOP, NH4+-N, recalcitrant organics, and PO4-P in wastewater were removed by 88.2%, 80.5% and 84%, respectively, with a low H2O2 consuming of only 5 mg/L. The removal efficiency of recalcitrant organics in the ammonia-mediated AOP increased as the concentration of NH4+-N in wastewater increased. Recalcitrant organics can be removed with an efficiency of 74∼82%, when the influent pH was 6∼6.8. This work provides a new and cost-effective approach to drive the iron cycle in Fenton treatment using NH4+-N from wastewater as mediator.

Co-production of spirosiloxane and biochar adsorbent from wheat straw by a low-cost and environment-friendly method

To enhance the value of wheat straw derivatives, wheat straw ash (WSA) was used as a reactant for the first time to synthesize spirocyclic alkoxysilane, an important organosilicon raw material, using an energy-saving and environmentally friendly non-carbon thermal reduction method. After spirocyclic alkoxysilane extraction, the biochar in the wheat straw ash prepared an adsorbent for Cu²⁺. The maximum copper ion adsorption capacity (Q_m) of silica-depleted wheat straw ash (SDWSA) was 31.431nullmg/g, far exceeding those of WSA and similar biomass adsorbents. The effects of the pH, adsorbent dose, and contact time on the adsorption behaviour of the SDWSA for Cu²⁺ adsorption were systematically investigated. The adsorption mechanism of Cu²⁺ by the SDWSA was investigated using the Langmuir, Freundlich, pseudo-first-order kinetic, pseudo-second-order kinetic, and Weber and Morris models by combining the preliminary experimental data and characterization results. The adsorption isotherm and Langmuir equation matched perfectly. The Weber and Morris model can describe the mass-transfer mechanism of Cu²⁺ adsorption by SDWSA. Both film and intraparticle diffusion are rapid control steps. Compared to WSA, SDWSA has a larger specific surface area and a higher content of oxygen-containing functional groups. A large specific surface area provides more adsorption sites. Oxygen-containing functional groups react with Cu²⁺ through electrostatic interactions, surface complexation, and ion exchange, which are the possible adsorption mechanisms for SDWSA. These methods improve the added value of wheat straw derivatives and promote wheat straw ash recovery and centralized treatment. This makes it possible to use the thermal energy of wheat straw and facilitates the treatment of exhaust gases and carbon capture.

Long-Term Air Pollution Characteristics and Multi-scale Meteorological Factor Variability Analysis of Mega-mountain Cities in the Chengdu-Chongqing Economic Circle

Currently, air quality has become central to global environmental policymaking. As a typical mountain megacity in the Cheng-Yu region, the air pollution in Chongqing is unique and sensitive. This study aims to comprehensively investigate the long-term annual, seasonal, and monthly variation characteristics of six major pollutants and seven meteorological parameters. The emission distribution of major pollutants is also discussed. The relationship between pollutants and the multi-scale meteorological conditions was explored. The results indicate that particulate matter (PM), SO2 and NO2 showed a "U-shaped" variation, while O3 showed an "inverted U-shaped" seasonal variation. Industrial emissions accounted for 81.84%, 58% and 80.10% of the total SO2, NOx and dust pollution emissions, respectively. The correlation between PM2.5 and PM10 was strong (R = 0.98). In addition, PM only showed a significant negative correlation with O3. On the contrary, PM showed a significant positive correlation with other gaseous pollutants (SO2, NO2, CO). O3 is only negatively correlated with relative humidity and atmospheric pressure. These findings provide an accurate and effective countermeasure for the coordinated management of air pollution in Cheng-Yu region and the formulation of the regional carbon peaking roadmap. Furthermore, it can improve the prediction accuracy of air pollution under multi-scale meteorological factors, promote effective emission reduction paths and policies in the region, and provide references for related epidemiological research.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11270-023-06279-8.

Emission reduction effect of digital finance: evidence from China

This paper investigates the relationship between digital finance and carbon emissions and explores the ecological effects of digital finance. Based on a panel data of 256 cities in China from 2011 to 2018, this paper investigates the impact of digital finance on carbon emissions and its intrinsic mechanisms. First, digital finance significantly suppresses the intensity of regional carbon emission, and the breadth of coverage, depth of use, and degree of digital support of digital finance together curb regional carbon emissions, with the strongest suppressive effect being the breadth of coverage. In addition, the regression results remain significant after a series of robustness tests. Second, it reveals the potential mechanism of digital finance to curb urban carbon emissions. These mechanisms include the three channels: promoting industrial advancement, green technology innovation, and optimizing labor resource allocation. Third, the heterogeneity test finds that the energy saving and emission reduction effects of digital finance are significantly stronger in non-low-carbon pilot cities with low urbanization rates, confirming the emission reduction utility of digital finance development. Therefore, we should take advantage of digital finance to improve the green development of financial services and adopt diverse policy measures according to local conditions to maximize the ecological effects of digital finance on energy saving and emission reduction. In the context of the development strategy of "carbon peaking and carbon neutral," this study has some implications for management in developing a regional green development system supported by digital finance.

Energy Consumption and Carbon Footprint of 3D Printing in Pharmaceutical Manufacture

Achieving carbon neutrality is seen as an important goal in order to mitigate the effects of climate change, as carbon dioxide is a major greenhouse gas that contributes to global warming. Many countries, cities and organizations have set targets to become carbon neutral. The pharmaceutical sector is no exception, being a major contributor of carbon emissions (emitting approximately 55% more than the automotive sector for instance) and hence is in need of strategies to reduce its environmental impact. Three-dimensional (3D) printing is an advanced pharmaceutical fabrication technology that has the potential to replace traditional manufacturing tools. Being a new technology, the environmental impact of 3D printed medicines has not been investigated, which is a barrier to its uptake by the pharmaceutical industry. Here, the energy consumption (and carbon emission) of 3D printers is considered, focusing on technologies that have successfully been demonstrated to produce solid dosage forms. The energy consumption of 6 benchtop 3D printers was measured during standby mode and printing. On standby, energy consumption ranged from 0.03 to 0.17 kWh. The energy required for producing 10 printlets ranged from 0.06 to 3.08 kWh, with printers using high temperatures consuming more energy. Carbon emissions ranged between 11.60-112.16 g CO₂ (eq) per 10 printlets, comparable with traditional tableting. Further analyses revealed that decreasing printing temperature was found to reduce the energy demand considerably, suggesting that developing formulations that are printable at lower temperatures can reduce CO₂ emissions. The study delivers key initial insights into the environmental impact of a potentially transformative manufacturing technology and provides encouraging results in demonstrating that 3D printing can deliver quality medicines without being environmentally detrimental.

Water footprint of shale gas development in China in the carbon neutral era

The production of shale gas in China has repercussions for the global energy landscape and carbon neutrality. However, limited and threatened water resources may hinder the expansion of shale-derived natural gas, one of China's most promising development prospects. Coupling historical trends with policy guidance, we project that baseline water stress will intensify in two-thirds of China's provinces in the next decade. By 2035, annual water use for shale gas hydraulic fracturing activities is likely to increase to 16-35 million m³, with 13.8-23.7 million m³ of wastewater produced annually to extract 38-48 billion m³ of gas from ∼4800 shale gas wells. Analysis suggests that this projection is based on previously underestimated geological constraints (e.g., deep continental facies) in shale gas development in China. Nevertheless, forecasts suggest that the water footprint of shale development will become impossible to ignore, particularly in drought-stricken areas, indicating the potential risk of competition for water among shale development, domestic use, food production, and ecological protection. Meanwhile, the annual wastewater management market will increase to $0.2 billion by 2035. Our study suggests a critical need to direct attention to the (shale) energy-water nexus and develop multi-pronged policies to facilitate China's transition to carbon neutrality.

Does income inequality reshape the environmental Kuznets curve (EKC) hypothesis? A nonlinear panel data analysis

The COVID-19 pandemic has further increased income inequality. This work is aimed to explore the impact of income inequality on the environmental Kuznets curve (EKC) hypothesis. To this end, income inequality is set as the threshold variable, economic growth is set as the explanatory variable, while carbon emission is set as the explained variable, and the threshold panel model is developed using the data of 56 countries. The empirical results show that income inequality has changed the relationship between economic growth and carbon emissions from an inverted U-shaped to an N-shaped, which means that income inequality redefines the environmental Kuznets curve and increases the complexity of the decoupling of economic growth and carbon emissions. Specifically, economic growth significantly increases carbon emissions during periods of low income inequality, however, as income inequality increases, economic growth in turn suppresses carbon emissions. In the period of high income inequality, economic growth inhibits the increase of carbon emissions. However, with the increase of income inequality, the impact of economic growth on carbon emission changes from inhibiting to promoting. Panel regressions for robustness tests show that this phenomenon is more pronounced in high-income countries. We therefore contend that the excessive income inequality is bad for the win-win goal of economic growth without carbon emission growth, and the income distribution policy should be included in the carbon neutral strategy.

A review of enhanced municipal wastewater treatment through energy savings and carbon recovery to reduce discharge and CO2 footprint

Municipal wastewater treatment that mainly performed by conventional activated sludge (CAS) process faces the challenge of intensive aeration-associated energy consumption for oxidation of organics and ammonium, contributing to significant directly/indirectly greenhouse gas (GHG) emissions from energy use, which hinders the achievement of carbon neutral, the top priority mission in the coming decades to cope with the global climate change. Therefore, this article aimed to offer a comprehensive analysis of recently developed biological treatment processes with the focus on reducing discharge and CO2 footprint. The biotechnologies including "Zero Carbon", "Low Carbon", "Carbon Capture and Utilization" are discussed, it suggested that, by integrating these processes with energy-saving and carbon recovery, the challenges faced in current wastewater treatment plants can be overcome, and a carbon-neutral even be possible. Future research should investigate the integration of these methods and improve anammox contribution as well as minimize organics lost under different scales.

Revitalization of Chinese's manufacturing industry under the carbon neutral goal

Since the beginning of the Industrial Revolution, the manufacturing industry has been crucial for economic growth. China's manufacturing activity began after China approved and opened legal reform to the rest of the world in 1978. There are usually three stages of development, including the catch-up period. At the same time, they reflect the private economic sector, manufacturing, and foreign exchange industries, and the opening up to the international markets. This advancement comes along with high energy consumption, leading to a high rate of pollution. Therefore, this study provides a detailed overview of the "Made in China 2025" pilot target and implementations of policies to achieve a carbon-neutral goal. We assessed the efficiency of implementing policies in the Chinese manufacturing sector and recommended decision-making policies to achieve the "Made in China 2025" plan and the 2030 carbon-neutral goal. The Quantitative Strategic Programming Matrix (QSPM) and SWOT analysis matrix were used to put forward some development strategies to transform and upgrade China's manufacturing industry by combining relevant strategic theories. This study is significant in terms of energy-saving and carbon emission-reducing policy implementations for the Chinese manufacturing industry. In addition, we suggested some measures to achieve a sustainable environment in line with carbon-neutral policies.

A scenario analysis of Chinese carbon neutral based on STIRPAT and system dynamics model

With the statement of Chinese government on energy saving in 2020 at the United Nations General Assembly, carbon neutral was widely spread as a new concept. As a big country, China has the responsibility and obligation to make its own contribution to global climate change. This paper aims to explore and find effective ways for China to achieve carbon neutrality by 2060. We identify the main factors affecting carbon emissions by STIRPAT model; combined with the scenario analysis, we divide the year 2020 to 2060 into three stages: year 2020-2030 is carbon peak stage, year 2030-2050 is rapid emission reduction stage, and year 2050-2060 is complete carbon neutralization stage. At each stage, three development models, high, medium, and low level, were established. There are a total of 27 different scenarios in three stages. A system dynamics model was established to simulate the effects of carbon emission factors and changes in carbon sinks in different scenarios. Finally, 8 paths were found which in line with Chinese current goal of achieving carbon neutrality with treating reach carbon peak in 2030 as an additional filter condition. Comparing per capita GDP levels in different scenarios, we eventually find that keeping economic development at a low level in the first stage, a high level in the second stage, and a medium level in the finally stage, the point where net carbon emissions are less than zero for the first time will appear between year 2056 and 2057. By then, the per capita GDP will reach 144,500 yuan (based on year 2000), nearly four times 2000's. In all, these findings are helpful for policymakers to implement reasonable policies to achieve carbon emission peaking and carbon neutral in China.

A state-of-the-art review of CO2 enhanced oil recovery as a promising technology to achieve carbon neutrality in China

Although there are some review papers on carbon capture, utilization and storage (CCUS), hardly any of these reviews are focused on the role of CO₂ enhanced oil recovery (EOR) in accelerating carbon neutrality in China. In this review, strategies to achieve carbon neutrality is briefly but critically discussed, followed by a review of CO₂-EOR as a promising technology. Especially, data analysis, including the number of publications on China's carbon neutrality, per capita CO₂ emissions, China's power generation, and the crude oil production of China's large oilfields, is carried out to make the discussion more comprehensive. Given the large amount of coal consumed in China, the high percent of electricity generated with coal, and the slow penetration of renewables already observed, it seems unlikely that 2060 targets will be met without CCUS. In order to achieve carbon neutrality, both reduction in carbon emissions and increase in carbon sequestration are inevitable. Furthermore, it is concluded that CO₂ storage through EOR is likely to have a bright future. However, there are some critical issues to be solved, including the technical issues, leakage and safety issues, cost issues, policy issues, etc. In order to turn CO₂-EOR into a reliable and more favorable technology, more research and efforts are needed to solve these issues, including advancing carbon capture technologies, improving storage technologies, developing effective monitoring technologies, deploying government support and incentive policies, etc.

Carbon footprint of cotton production in China: Composition, spatiotemporal changes and driving factors

Analyzing the carbon footprint of crop production and proposing low-carbon emission reduction production strategies can help China develop sustainable agriculture under the goal of 'carbon peak and carbon neutrality'. Cotton is an economically important crop in China, but few reports have systematically quantified the carbon footprint of China's cotton production and analyzed its spatiotemporal changes and driving factors. This study used a life cycle approach to analyze the spatiotemporal changes and identify the main components and driving factors of the carbon footprint of cotton production in China between 2004 and 2018 based on statistical data. The results showed that the carbon footprint per unit area of cotton in Northwest China, the Yellow River Basin and the Yangtze River Basin reached 6220.13 kg CO₂eq·ha^-1, 3528.14 kg CO₂eq·ha^-1 and 2958.56 kg CO₂eq·ha^-1, respectively. From 2004 to 2018, the CFa in the Yellow River Basin and Northwest China increased annually, with average increases of 59.87 kg CO₂eq·ha^-1 and 260.70 kg CO₂eq·ha^-1, respectively, while the CFa in the Yangtze River Basin decreased by an average of 21.53 kg CO₂eq·ha^-1 per year. The ridge regression and Logarithmic Mean Divisia Index (LMDI) model showed that fertilizer, irrigation electricity and agricultural film were the main influences on carbon emission growth at the micro level and that the economic factor was the key factor at the macro level. Improving the efficiency of cotton fertilization and electricity use and ensuring the high-quality development of the cotton industry are effective strategies to reduce the carbon footprint of cotton cultivation in the future. This study comprehensively uses statistical data and mathematical modeling to provide theoretical support for accounting and in-depth analysis of cotton carbon emissions. The results are valuable for policy making related to sustainable development and the low-carbon development of the Chinese cotton industry.

Facilitating developments of solar thermal power and nuclear power generations for carbon neutral: A study based on evolutionary game theoretic method

Solar thermal power and nuclear power generations are two most promising clean energy power approaches, which are effective for reducing carbon emissions. In order to promote the coordinated development of solar thermal power and nuclear power in China under the background of carbon neutral, the current paper develops a partnership comprised by the energy investment company (EIC), solar thermal power plant (STPP) and nuclear power plant (NPP). By utilizing the evolutionary game theory method and current policies of China, the evolutionary process simulations of the three participants under different conditions are conducted, which demonstrate that steady states could be achieved under different partnerships. Impact investigation results of typical influential factors indicate that longer annual operation time of power plant, larger subsidy and higher electricity price sold to the power grid are favorable to promote the partnership smoothly. Suitable investment ratio of the STPP and NPP should be considered as a larger investment ratio of the STPP and NPP has incentive influence on EICs and STPPs but inhibiting impact on NPPs. The results of the current study have certain reference value for the policy and strategy formulations for facilitating the developments of solar thermal power and nuclear power generations.

Elevation of NO3--N from biochar amendment facilitates mitigating paddy CH4 emission stably over seven years

Biochar application into paddy is an improved strategy for addressing methane (CH₄) stimulation of straw biomass incorporation. Whereas, the differentiative patterns and mechanisms on CH₄ emission of straw biomass and biochar after long years still need to be disentangled. Considering economic feasibility, a seven-year of field experiment was conducted to explore the long-term CH₄ mitigation effect of annual low-rate biochar incorporation (RSC, 2.8 t ha^-1), with annual rice straw incorporation (RS, 8 t ha^-1) and control (CK, with no biochar or rice straw amendment incorporation) as a comparation. Results showed that RSC mitigated CH₄ emission while RS stimulated CH₄ significantly (p < 0.05) and stably over 7 experimental years compared with CK. RSC mitigated 14.8-46.7% of CH₄ emission compared with CK. In comparison to RSC, RS increased 111-950.5% of CH₄ emission during 7 field experimental years. On the 7th field experimental year, pH was significantly increased both in RS and RSC treatment (p < 0.05). RSC significantly (p < 0.05) increased soil nitrate (NO₃^--N) compared with RS while RS significantly (p < 0.05) increased dissolved carbon (DOC) compared to RSC. Soil NO₃^--N inhibition on methanogens and promotion on methanotrophs activities were verified by laboratory experiment, while soil pH and DOC mainly promoted methanogens abundance. Significantly (p < 0.05) increased DOC and soil pH enhanced methanogens growth and stimulated CH₄ emission in RS treatment. Higher soil NO₃^--N content in RSC than CK and RS contributed to CH₄ mitigation. Soil NO₃^--N and DOC were identified as the key factors differentiating CH₄ emission patterns of RS and RSC in 2019. Collectively, soil NO₃^--N impacts on CH₄ flux provide new ideas for prolonged effect of biochar amendment on CH₄ mitigation after years.

Integrated anaerobic and algal bioreactors: A promising conceptual alternative approach for conventional sewage treatment

Conventional sewage treatment applying activated sludge processes is energy-intensive and requires great financial input, hampering widespread implementation. The introduction of anaerobic membrane bioreactors (AnMBR) followed by an algal reactor growing species of commercial interest, may present an alternative, contributing to the envisaged resource recovery at sewage treatment plants. AnMBRs can be applied for organic matter removal with energy self-sufficiency, provided that effective membrane fouling management is applied. Haematococcus pluvialis, an algal species with commercial value, can be selected for ammonium and phosphate removal. Theoretical analysis showed that good pollutant removal, positive financial output, as well as a significant reduction in the amount of hazardous activated sludge can be achieved by applying the proposed process, showing interesting advantages over current sewage treatment processes. Microbial contamination to H. pluvialis is a challenge, and technologies for preventing the contamination during continuous sewage treatment need to be applied.

Urban and transport planning pathways to carbon neutral, liveable and healthy cities; A review of the current evidence

INTRODUCTION

Half the world population lives in cities and this is likely to increase to 70% over the next 20 years. Suboptimal urban and transport planning has led to e.g. high levels of air pollution and noise, heat island effects and lack of green space and physical activity and thereby an increase in morbidity and premature mortality. How can better urban and transport planning improve public health?

METHODS

A narrative meta-review around a number of cutting edge and visionary studies and practices on how to improve public health through better urban and transport planning reported in the literature and from meetings over the past few years.

RESULTS

We describe the latest quantitative evidence of how cities can become healthier through better urban and transport planning. It focuses and provides evidence for important interventions, policies and actions that can improve public health, including the need for land use changes, reduce car dependency and move towards public and active transportation, greening of cities, visioning, citizen involvement, collaboration, leadership and investment and systemic approaches. Health impact assessment studies have recently provided new powerful quantitative evidence on how to make cities healthier and will be used as examples. At the same time these measures make also our cities more sustainable (i.e. carbon neutral) and liveable creating multiple benefits.

CONCLUSION

Better urban and transport planning can lead to carbon neutral, more liveable and healthier cities, particularly through land use changes, a move from private motorised transportation to public and active transportation and greening of cities.

Production of long chain alkyl esters from carbon dioxide and electricity by a two-stage bacterial process

Microbial electrosynthesis (MES) is a promising technology for the reduction of carbon dioxide into value-added multicarbon molecules. In order to broaden the product profile of MES processes, we developed a two-stage process for microbial conversion of carbon dioxide and electricity into long chain alkyl esters. In the first stage, the carbon dioxide is reduced to organic compounds, mainly acetate, in a MES process by Sporomusa ovata. In the second stage, the liquid end-products of the MES process are converted to the final product by a second microorganism, Acinetobacter baylyi in an aerobic bioprocess. In this proof-of-principle study, we demonstrate for the first time the bacterial production of long alkyl esters (wax esters) from carbon dioxide and electricity as the sole sources of carbon and energy. The process holds potential for the efficient production of carbon-neutral chemicals or biofuels.

Does carbon reduction increase sustainability? A study in wastewater treatment

This study investigates the relationships between carbon reduction and sustainability in the context of wastewater treatment, focussing on the impacts of control adjustments, and demonstrates that reducing energy use and/or increasing energy recovery to reduce net energy can be detrimental to sustainability. Factorial sampling is used to derive 315 control options, containing two different control strategies and a range of sludge wastage flow rates and dissolved oxygen setpoints, for evaluation. For each, sustainability indicators including operational costs, net energy and multiple environmental performance measures are calculated. This enables identification of trade-offs between different components of sustainability which must be considered before implementing energy reduction measures. In particular, it is found that the impacts of energy reduction measures on sludge production and nitrogen removal must be considered, as these are worsened in the lowest energy solutions. It also demonstrates that a sufficiently large range of indicators need to be assessed to capture trade-offs present within the environmental component of sustainability. This is because no solutions provided a move towards sustainability with respect to every indicator. Lastly, it is highlighted that improving the energy balance (as may be considered an approach to achieving carbon reduction) is not a reliable means of reducing total greenhouse gas emissions.