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The pulp and paper industry, which provides cellulose pulp and paper, bio-based energy and chemicals, is one of the largest energy consumers, greenhouse gases (GHG) and pollutant emitters among manufacturing industries. Although the environmental impact of the pulp and paper industry has been extensively studied, life cycle assessment (LCA) results have not yet reached a consensus. By means of a systematic review and meta-analysis, this article contributes to the quantification and harmonization of the life cycle environmental impacts of pulp making and paper making systems. Based on the screening of 45 cases of paper making and 18 cases of pulp making, we found that 1 t of paper results in about 950 kg carbon dioxide (CO 2 ) equivalent (CO 2 -eq) GHG emissions on average. However, there are distinct differences between countries and pulp and paper categories. The dominant factor influencing GHG emissions is energy use. In paper making, the pulp making process is responsible for 62% of energy use, 45% of GHG emissions, 48% of acidification potential, and 49% of eutrophication potential. The kg CO 2 -eq emissions of three different types of pulp were as follows: Kraft, 508 kg CO 2 -eq/t; chemi-mechanical, 513 kg CO 2 -eq/t; and recycled pulp, 408 kg CO 2 -eq/t. Excluding emissions from electricity and steam production, the convergence of carbon emissions is observed within the same categories of pulp. Straw-based pulp caused far more environmental impact than any other type because of the intensive inputs in agricultural activities as well as in the pulp making process. This research highlighted the inconsistencies in functional units, system boundaries, and methodologies and carbon neutrality assumptions in different LCA studies of pulp and paper making. Future studies should focus on the environmental impact of straw-based pulp making, system boundary unification, and calculation of biogenic carbon emissions. [ABSTRACT FROM AUTHOR]

In recent years, the utilization of biomass through advanced power technologies has intensified to achieve carbon neutrality. An oxy-fuel circulating fluidized bed combustor of biomass with higher efficiency supercritical carbon dioxide cycle has been developed with the aim of compensating the penalties for carbon capture and storage. The combustor fuelled with waste paper, waste wood, and cow manure, at an input of 200 ton/day is economically evaluated. Waste paper is on the verge of becoming an economically feasible fuel, more so than the other biomass examined. The use of waste paper led to a positive net present value, an internal rate of return of 3.8%, a benefit-cost ratio of 1.025, and a payback period of 17.7 years. Subsequent sensitivity analyses conducted for the waste paper fuelled power plant indicated that the capital cost is the most influential factor; the boiler, supercritical carbon dioxide cycle, and oxygen fuel combustion system were indicated in descending order of related subdivided sensitiveness. Both renewable energy certificate and carbon credit has contributed to the feasible economic of the system, with former one took precedence over later one. Sensitivity from the technical perspective, improvement in air separation unit is likely to greatly improve the economic feasibility of the proposed system. The power consumption of the air separation unit, as well as that of the carbon dioxide compression and purification unit, were highly sensitive to the implementation cost. [Display omitted] • Integration of oxygen combustion and supercritical carbon dioxide power cycle. • Economic feasibility study of integrated biomass circulating fluidized bed. • Capital cost demonstrated the foremost sensitivity factor. • Waste paper as potential economically feasible fuel. • Innovation in air separation unit improves economic feasibility. [ABSTRACT FROM AUTHOR]

Heating and cooling both make up a large part of the total energy demand in the UK; long-term seasonal thermal energy storage (STES) can address temporal imbalances between varying supply and demand of heat to buildings and processes. Underground thermal energy storage (UTES) can play a role in energy decarbonisation by storing waste heat from space cooling, refrigeration, data processing, industrial processes, harvested summer solar thermal energy or even heat generated by surplus renewable (solar or wind) electricity with fluctuating supply. This paper evaluates a range of UTES technologies in a UK context and addresses geological suitability, storage capacity, low-carbon heat sources, surface heat sources and demand. This review concludes that there is a significant potential for UTES in the UK for both aquifer thermal energy storage (ATES) and borehole thermal energy storage (BTES) systems, coinciding with surface heat sources and demand. Therefore, uptake in UTES technology will help achieve net-zero carbon neutral targets by 2050. There is also scope to utilise UTES technologies within existing subsurface infrastructure. There are 464 oil and gas wells which could be repurposed upon end of life using different UTES technologies. However, the potential for repurposing needs further evaluation; deep single well BTES systems will have a high surface area to volume ratio for storage, reducing the efficiency of such systems and the potential for ATES is limited by issues associated with contaminants. 23,000 abandoned mines underlay ∼25 % of the UKs population and could be utilised for minewater thermal energy storage (MTES). • Review of UTES technology suitability for the UK. • First reporting of details of the Bodyheat BTES system. • Storage capacities for a typical UK BTES system have been calculated. • UTES has a high potential in decarbonising heat in the UK. [ABSTRACT FROM AUTHOR]

High-value utilization of plant resources is crucial for achieving carbon neutrality and complete carbon transformation. Significant progress has already been made in the comprehensive utilization of plant resources through pretreatment methods, particularly the deep eutectic solvent (DES) method for the pretreatment of plant fibers. This method enables sustainable development of lignocellulose deconstruction and high-value utilization. This paper provided a review of the composition, classification, and properties of different types of DES. It also investigated the effects of stoichiometric ratio, temperature, time, microwave, ultrasonic, hydrothermal, and emulsification on lignocellulose deconstruction using the DES. Additionally, the study explored the use and prospects of lignocellulosic fractions in lignin extraction, enzymatic saccharification, and high-value cellulose production using functional DES systems. The evaluation of the DES functionality is conducted through quantum chemistry, molecular simulation calculations, and the DES recycling effects (optimum 10 cycles). The mechanism of DES in lignocellulosic extraction is elucidated, and the prospects for sustainable development are outlined. • DES is capable of deconstructing lignocellulose to achieve high-value plant resources. • The progress of the functional and specific application of DES for lignocellulosic pretreatment has been discussed. • Summary of the evaluation system for the DES functional system and method for the DES pretreated lignocellulose. • Prospects for the future development of the DES system in the field of plant resource extraction. [ABSTRACT FROM AUTHOR]

Aquavoltaic is an essential tool in overcoming the ground-based photovoltaic (PV) development barrier and achieving China's carbon neutrality target. After summarizing aquavoltaic technologies and global cases, this paper assesses the effectiveness of 292 aquavoltaic plants in China using the data envelopment analysis (DEA) method. Six essential input and output variables are included: installed capacity, power generation, occupied water area, construction cost, PV modules, and global horizontal irradiation to offer an appropriate measure of aquavoltaics efficiency in China. This study also performed correlation analysis for PV module type, PV mounting mode, and ownership based on a Tobit regression model. The results show that the efficiencies of China's aquavoltaics have improved significantly between 2014 and 2022, with the emergence and popularity of high-power PV modules playing a pivotal role. Furthermore, the regional study discovered provincial efficiency varies substantially. This paper also gives two reference indicators for new aquavoltaics in the future. • The global aquavoltaic technologies and cases were summarized. • The history and status quo of aquavoltaics in China were reviewed. • Aquavoltaics' energy efficiency has increased significantly in China. • The high-power PV modules have a positive impact on efficiency growth. [ABSTRACT FROM AUTHOR]

In order to keep sustainable development, the Chinese government has issued series of policies to reduce CO 2 emissions. Renewable energy technologies applied in building field, mainly including solar energy and geothermal energy technologies, are recommended because of advances of energy efficiency, environmental protection and economic sustainability. Carbon trading has been widely accepted as an effective market approach, but it hasn’t covered the renewable energy application in building projects in China as yet. Reasonable solutions should be proposed to encourage building projects to participate in the carbon trading market. This paper aims at establishing a feasible mechanism to help improve the carbon market for renewable energy application in buildings. To attend this goal, this paper introduces and analyzes the status of carbon trading market and the position for building projects in China. By comparing the present mechanisms, Programmatic CDM with building portfolio is considered appropriate for building projects with renewable energy application. Volume verifying method, the core of the mechanism, is modified to fit the building projects. Then five different specific cases are studied to prove the practicality and reasonableness of the methodology. Programmatic CDM with modified verifying method is concluded as the proper mechanism for renewable energy application in buildings in carbon trading market. [ABSTRACT FROM AUTHOR]

To achieve the goal of carbon neutrality, society must undertake a comprehensive green transformation and build a decarbonization roadmap. Model simulation is a primary method for designing and analyzing long-term low-carbon roadmaps. This paper aims to examine the various capabilities of Energy-Economy-Environment (3E) models to gain an intuitive understanding of the current status, as well as future development directions and potential, from a low-carbon analysis perspective. By reviewing various existing 3E models considering their modeling approach, theoretical framework and spatiotemporal resolution, the 10 most representative models are selected for an in-depth analysis. According to the evaluation results of the selected models while considering five challenges for future model development, most models perform well in terms of techno-economic resolution and transparency. However, there is still potential for improvement regarding spatiotemporal resolution and the consideration of social factors. Moreover, to bridge the gap between top-down models and the real-world context, it is recommended to combine them with bottom-up models to form hybrid models. Generally, the PRIMES model demonstrates the best overall performance, although it cannot be regarded as perfect. The review and assessment results can provide references for modelers to improve 3E models and serve as a basis for users to choose the most suitable model. • Ten typical 3E models with the highest use frequency are summarized and classified. • Challenges of 3E models for long-term low-carbon roadmaps research are discussed. • An evaluation framework is established for 3E models considering five abilities. • The prospects for future development of 3E models are proposed. [ABSTRACT FROM AUTHOR]

Storing CO 2 and H 2 in underground reservoirs represents an effective approach to sequester increasing amounts of captured CO 2 for carbon neutrality and to store H 2 to promote clean energy revolutions. However, commercial/pilot-scale CO 2 /H 2 storage sites are mainly restricted to conventional oil reservoirs or salt caverns – both capacity and geographic-location limited. This paper presents a systematic review of the feasibility and prospects of CO 2 and H 2 storage in fractured shale reservoirs as secure repositories. Both field pilot and laboratory studies of CO 2 injection in shales are cross-analyzed across various spatial and time scales, to provide a reliable and substantial basis to support new findings. The presence of suitable injectivity and adequate sealing capacity in shale are demonstrated. The fracture networks are shown to provide major storage space in shales, contrasting with the pore system in conventional reservoirs. This difference in storage mechanisms results in an overestimation in the storage capacity of shales when applying porous-medium-based methods. An underestimation in the mass of injection, however, is apparent from a single well for the reported cases due to unknown characteristics of underground fracture networks. The symbiotic storage of CO 2 and H 2 in shale is discussed in its feasibility and ability to improve both CO 2 storage but principally H 2 recovery – due to the presence of a gas cushion. A new equivalent-fracturing method is proposed as a supplement to recalibrate the over- and under-estimated prospects of CO 2 /H 2 storage in shales – a necessary component in reducing carbon emissions and accelerating the energy transition. [Display omitted] • Field pilots and laboratory studies are cross-analyzed and validated. • Fracture networks in shale reservoirs dominate CO 2 and H 2 storage. • Over- (in shales) and under- (in wells) estimations of CO 2 storage are revealed. • New estimation method is proposed for the technically achievable storage capacity. • Symbiotic storage of CO 2 and H 2 in shales is feasible and promising. [ABSTRACT FROM AUTHOR]

With the proposal to achieve carbon neutrality by the mid-21st century, carbon capture, utilization, and storage (CCUS) as a critical negative carbon technology is receiving extensive attention and concerns around the world. Under this context, the development of CCUS and relevant literature both have been experiencing an upsurge. However, the actual scale of CCUS is still far behind our expectations, especially, the various risks and uncertainties associated with its deployment planning have not yet been addressed clearly. Therefore, this paper provides an overview of model-based CCUS deployment pathways toward carbon neutrality, as well as the associated risks of financial, technical, environmental, health and safety (EHS) aspects. On this basis, we scrutinize the potential challenges that could lead to the pace of CCUS deployment inconsistent with the need to achieve a carbon-neutral target. The results suggest that the "Golden Age" of CCUS deployment lies from 2040 to 2060 in the world, while 2030–2050 for China. Furthermore, we found that inadequate exploration in geologic storage capacity also creates a critical conundrum for CCUS deployment and optimization, apart from typical challenges including high failure rate of projects, the lack of financial support and market stimulus, as well as incomplete regulation framework and risk-sharing mechanism. Lastly, this paper points out the further potential research direction, followed by policy implications and recommendations. • A comprehensive reference for CCUS deployment towards carbon neutrality is presented. • We discuss possible risks or uncertain factors for altering CCUS deployment paths and planning layout. • Future needs to improve geological storage exploration and estimation are highlighted. Further potential research direction and policy implications for CCUS are provided. [ABSTRACT FROM AUTHOR]

Emissions trading scheme (ETS) is one of the effective measures to realize energy conservation and emission reduction. In order to set up a nationwide carbon emissions trading mechanism, seven ETS pilots have been launched in China. Firstly, based on empirical investigation and research of seven pilots, this paper analyzed the market efficiency of ETS pilots from four aspects: carbon price, trading volume, market liquidity, and information transparency. The result showed that the market efficiency of ETS pilots is not satisfactory in spite of the fact that system designs of ETS have achieved preliminary result. Then, the reason for low market efficiency of ETS pilots was discussed from some factors such as institutional arrangements, market participants, the supply and demand, etc. Finally, this paper puts forward some policy suggestions to improve the market efficiency of China׳s carbon trading market. [ABSTRACT FROM AUTHOR]

Because China has emerged as the largest greenhouse gas (GHG) emitter in total annual emissions, to accelerate the pace of GHG emission reduction in China is important to the success of global efforts in addressing climate change. Carbon trading is a market mechanism and key instrument in the mitigation of climate change. This paper explores the policy process and development state to date of China׳s carbon-trade market to understand the emergence and development of that market and to understand what barriers are hampering China׳s carbon-trade market development. To achieve this goal, this paper introduces and analyzes China׳s status in the international market, examines the factors driving carbon-market launching by the Chinese government, and traces the development of mandatory carbon-emission trading and voluntary emission trading. It is argued that China׳s carbon-trading market is confronted with challenges such as the absence of a functional carbon-trading market, inaccuracy of the quota allocation, an imperfect trading mechanism, and lagging legislation. At the present stage, shortcomings such as having no real-time carbon price and dominated spot transactions differentiate China׳s trade market substantially from a functional system. A quick market integration of China׳s carbon market appears remote. It is suggested that specific measures be taken to promote the development of the Chinese carbon-trading market. [ABSTRACT FROM AUTHOR]

The issues over increases in energy demand and environmental pollution attributed to excessive use of fossil fuel have been the driving forces of the exploration for eco-friendly resource. Lignocellulosic biomass consisting of carbohydrates and lignin can be a renewable feedstock for replacing fossil fuels in the future because it is a plentiful and carbon neutral material. Especially, lignin, cross-linked phenolic polymers, is a topic of interest owing to its abundant production from pulp/paper industries as well as lignocellulose based biorefinery. The large potential of platform chemicals and biofuels from lignin has opened up an extensive range of opportunities to develop thermal and catalytic conversion technology. Over a few decades, several lignin conversion processes including catalytic pyrolysis, catalytic depolymerization, and catalytic oxidation have been developed to improve target products yields and to suppress side reactions. More recently, lignin-first approaches which maintain carbohydrates intact by selective extraction of lignin as valuable phenolics from whole biomass has been suggested. This review introduces recent ten years progress on thermal and catalytic conversion technology in terms of process type, catalyst development, and target products. This review is expected to offer an influential information for future research into the thermal and catalytic conversion of lignin as well as lignocellulosic feedstock. • Recent discoveries in thermal and catalytic lignin conversion are introduced. • A proper conversion process should be considered depending on the lignin type. • Catalyst plays a decisive role in product distribution and selectivity in process. • The challenges and future perspective of each process is discussed. [ABSTRACT FROM AUTHOR]

In the context of carbon neutrality, renewable energy, especially wind power, solar PV and hydropower, will become the most important power sources in the future low-carbon power system. Since wind power and solar PV are specifically intermittent and space-heterogeneity, an assessment of renewable energy potential considering the variability of wind power and solar PV with high temporal resolution in different regions will facilitate more accurate identification of the decarbonization pathway of power system. In this paper, the complementary output potential of wind-solar-hydro power every 15 min in 31 Chinese provinces is evaluated by developing a multi-objective optimization model based on Nondominated Sorting Genetic Algorithm II. The results show that the total annual complementary power generation potential in China is 17.57 PWh, of which the three components account for 47.8%, 25.3% and 26.9%, respectively. Inner Mongolia and Tibet are the major renewable energy source provinces with annual complementary power generation potential of 5330 TWh and 3907 TWh, accounting for 30.3% and 13.7% of the total power generation potential, respectively. The temporal potential of wind-solar-hydro power varies greatly, with daily potential is more volatile than monthly. Seasonal and spatial heterogeneity of the complemental renewable potential makes some provinces suffer power shortage during long-hours period especially in winter. Our findings will encourage a higher penetration of renewable energy, the promotion of multi-energy complementarity, and the development of inter-provincial power transmission and energy storage infrastructure in China's future power sector. • A multi-objective wind-solar-hydro complementary optimization model is developed. • Electricity supply and demand have gaps at different temporal and spatial scales. • Wind-solar-hydro complementary potential shows great temporal and spatial variation. • Renewable complementarity can improve China's future power system stability. [ABSTRACT FROM AUTHOR]

Net-zero emission and self-sustaining carbon-neutral have been widely encouraged and intensively explored in wastewater treatment, as the wastewater industry accounts for approximately 1.6% of global greenhouse gas (GHG) emissions. However, how to achieve net-zero GHG emission in wastewater treatment from a biological standpoint is still lacking. In this paper, the status of GHG (i.e. nitrous oxide (N 2 O), methane (CH 4) and carbon dioxide (CO 2)) production and emission in wastewater treatment was comprehensively reviewed. Generally, N 2 O emission contributes the majority of the total GHG emissions from wastewater treatment, and the dissolved N 2 O and CH 4 in the effluent should be paid more attention for the further GHG mitigation. Based on the newly identified microbial communities capable of nitrogen removal with less GHG emissions, several alternative integration systems for GHG mitigation were discussed. Coupling denitrifying anaerobic methane oxidation with anammox process shows high nitrogen removal performance and low GHG emissions, which is regarded as a more promising integration system for GHG mitigation. Moreover, the novel strategies to manage N 2 O and CH 4 as energy sources were also demonstrated, aiming to offset certain carbon footprint in wastewater treatment and thus attain net-zero GHG emission. In addition, future challenges and perspectives of above integration systems and strategies were discussed to facilitate the development of environmentally sustainable wastewater treatment. Finally, a prospective hybrid system integrating emission reduction and energy recovery was proposed as an example for achieving net-zero GHG emission from wastewater treatment. [Display omitted] • Status on GHG production and emission in each treatment unit is quantified. • Autotrophic microorganisms play important roles in mitigating GHG emission. • CH 4 is more feasible than N 2 O for energy recovery from mainstream wastewater. • Net-zero GHG emission integrates both emission reduction and energy recovery. [ABSTRACT FROM AUTHOR]

As a non-Arctic country and a major energy consumer, China is increasingly interested in participating in Arctic energy development. This study aims to investigate potential strategies to promote China's participation in Arctic energy development. Accordingly, this study analyzes the strengths, weaknesses, opportunities, and threats (SWOT) of China's participation in Arctic energy development based on a discussion of the current status of Arctic energy development and the Arctic policies of major countries. In addition, this work develops strategies in accordance with the above analysis. The results show that China has strengths in terms of capital, energy demand, policy support, and international cooperation when participating in Arctic energy development, while its weaknesses include the lack of core technology and equipment, high carbon intensity of energy development, and geographical disadvantage. China faces opportunities stemming from conflicts among Arctic states, the advancement of global carbon neutrality, and the development of Arctic waterway while facing threats such as increased competition, international public opinion pressure, high development costs, environmental risks, and pandemic instability. Under an integrated framework, this work offers four strategies: Strength-Opportunity (SO), Strength-Threat (ST), Weakness-Opportunity (WO), and Weakness-Threat (WT). Finally, this study proposes specific measures in four areas, including strengthening policy support, promoting technical research and development, enhancing international cooperation, and improving enterprise competitiveness. [Display omitted] • This study examines China's participation in Arctic energy development. • This paper reviews the status of fossil and non-fossil energy in the Arctic. • This study compares the Arctic energy development strategies of major countries. • This study proposes four strategies, namely SO, ST, WO, and WT. [ABSTRACT FROM AUTHOR]

Emission Trading Scheme (ETS) has become one of the most popular ways to meet CO 2 reduction targets owing to its flexibility and cost effectiveness. This paper applies game theory to analyze the impacts of direct and indirect costs derived from ETS on enterprise's competitiveness and supply partnership. By emphasizing the role of carbon intensity, the results illustrate that an enterprise with lower carbon intensity will have stronger capability to ease the pressures of both direct and indirect costs. From the perspective of direct cost, when reducing carbon intensity to a certain extent, the enterprise will take the advantage of carbon competitiveness to further expand the market share. The enterprise with low carbon intensity can even increase its product output amount instead of damaging it. From the perspective of indirect cost, a downstream manufacturer with lower carbon intensity is more likely to obtain the favor of suppliers. If choosing a downstream partner with high carbon intensity, the supplier may need to reduce the price of its product to ensure the product's demand and profits. Therefore, the implementation of ETS will drive suppliers to choose low-carbon partners, resulting in low-carbon supply partnerships replacing the original one. Based on a numerical example combing with the investigation in Hubei ETS pilot, this research argues for the enlightenment, and implications, of carbon quota constraints as a part of China's emission reduction policies. [ABSTRACT FROM AUTHOR]

The aviation sector has grown at a significant pace in recent years, and despite improvements in aircraft efficiency, the sector's impact on climate change is a growing concern. To address this concern, the International Civil Aviation Organization (ICAO) established the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) to help reduce aviation greenhouse gas (GHG) emissions. This paper presents a methodology agreed by the 193 ICAO member states to evaluate the life-cycle GHG emissions of sustainable aviation fuels (SAFs), in the CORSIA system. The core life-cycle assessment and induced land use change values of SAFs are presented to determine the GHG savings of certified pathways. The paper aims to present that a number of SAFs can yield significant life-cycle emission reductions compared to petroleum-derived jet fuel. This implies the potentially major role of SAFs in reducing aviation's carbon footprint. • The goal of the CORSIA is to reduce GHG emissions from international aviation. • Internationally agreed LCA methodologies for GHG saving potentials are presented. • Sustainable aviation fuels can reduce GHG emissions up to 90%. • SAFs GHG saving can exceed 100% when land use change is included. • Further challenges for reducing the GHG emissions from aviation are discussed. [ABSTRACT FROM AUTHOR]

With the intensification of the greenhouse effect, carbon neutrality has become a global goal. The development of vehicle platoons provides a new idea for energy saving and emission reduction. To explore the practical application prospect of vehicle platoon energy-saving methods and reveal the limitations and improvement direction of current vehicle platoon research, this paper reviews the current research status of vehicle platoon energy-saving methods and analyzes the energy-saving method. The energy-saving methods are summarized from aerodynamic and vehicle speed optimization perspectives. Energy-saving methods based on aerodynamics include field tests, wind-tunnel tests, and CFD. Energy-saving methods based on vehicle speed optimization mainly focus on the acceleration and deceleration behavior optimization of vehicles in the platoon. The limitations and prospects of automotive and vehicle platoon development are also put forward. • Energy-saving methods of platoons based on aerodynamic are reviewed. • Energy-saving methods of platoons based on control and optimization are analyzed. • The prospects of the development of platoons at the national level are discussed. [ABSTRACT FROM AUTHOR]

Emission Trading Scheme (ETS) is one of the most important instruments introduced to meet carbon neutral targets internationally. To reduce carbon emissions, China has established eight regional ETS since 2013 to reduce carbon emissions. However, significant heterogeneities exist across the eight pilots, resulting in distinctively different carbon price movements. Traded as a financial asset, carbon allowance is vulnerable to internal and external shocks. Though carbon prices have been fluctuating fiercely since the inception of the carbon market, little is known about potential carbon price bubbles in any of these pilots. To this end, this paper resorts to the generalized sup Augmented Dickey-Fuller (GSADF) test, which allows the detection of multiple bubbles, as well as the date stamping of bubbles in carbon prices. For the first time, price bubbles are found in the Chinese carbon markets. The empirical results find three bubbles in Guangdong pilot, two bubbles in Tianjin pilot, and one bubble in Hubei pilot. These explosive episodes are closely related to immature market mechanisms and policy implementations. The results provide insightful implications for the upcoming unified national carbon market. • This paper detects the carbon price bubbles in Chinese markets. • Multiple bubbles exist in different pilots. • Not all pilots encounter bubbles. [ABSTRACT FROM AUTHOR]

Global steel production is currently dependent on coal and capital-intensive production facilities with long economic lifetimes. While the Paris Agreement means carbon neutrality must be reached globally by 2050–2070, with negative emissions thereafter, coal-based steel production today accounts for around 8% of global energy-related CO 2 emissions. Its production may stabilize or even decline in industrialized countries, but it will increase significantly in the emerging economies. In the past, the focus of CO 2 reduction for steel has been on moderate emissions reductions through energy efficiency measures and on exploring carbon capture and storage. However, as (1) the cost of renewable electricity is declining rapidly, (2) carbon capture and storage has not materialized yet, and (3) and more and more countries set deep emission reduction targets, electricity- and hydrogen-based steelmaking has gathered substantial momentum over the past half-decade. Given the short time frame and the sector's deep carbon lock-in, there is an urgent need to understand the national climate and energy policy as well as the current implementation of low-CO 2 and renewable electricity that would enable a shift from coal-based to electricity-based steelmaking. In this paper, we first identify the countries that are likely to be major steel producers in the future and thus major CO 2 -emitters. Then we map medium- and long-term CO 2 reduction and renewable targets as well as the current share of low-CO 2 and renewable electricity by country. Based on these data, we develop a set of indicators that map the readiness of steel-producing countries for a sustainable transition. Our findings show that although binding long-term CO 2 reduction targets are being implemented, medium-term CO 2 reduction do not yet affect coal based steel production. Overall, the global steel industry seems not be on track yet, though differences between steel producing countries are large. Common shortcomings across countries are a lack of access to renewable electricity and a lack of demanding medium-term CO 2 reduction targets. The paper ends with recommendations on how to enable a low-carbon transition of the global steel industry in line with the Paris Agreement. • Four major steel producing countries have committed to carbon neutrality by mid-century. • 2030 CO 2 reduction targets do not affect coal-based steelmaking. • Access to renewable electricity is limited in most countries. • One third of the steelmaking countries strongly rely on coal for their economy. [ABSTRACT FROM AUTHOR]

This paper systematically presents a survey of the empirical literature studying the embodied CO 2 emissions in China’s foreign trade (ECCT). Based on the bibliometric method and the online version of Science Citation Index-Expanded (SCI-E) and Social Sciences Citation Index (SSCI), this study summarizes the latest publications regarding ECCT in peer-reviewed journals in terms of quantities, most productive countries, institutions, authors, citations, and disciplines. By using synthetic analysis of keyword frequency, this study reveals the most popular methodologies applied in measuring ECCT, discusses the variation of numerical results in the literature, and reasons and countermeasures for the results uncertainties. Continuous investigation of the literature releases the methodology employed for measuring ECCT becoming more reasonable and the results more critical. However, the numerical results of ECCT are of great discrepancies within given year by different considerations on methodology specification, accounting principles, and data sources and processing. For instance, the estimates of CO 2 embodied in China’s exports changed from 478 Mt to over 3000 Mt and those of in China’s imports ranged from 140 Mt to over 1700 Mt in 2007. Therefore, overcoming data inherent limitations and reducing discrepancies among available databases should be urgently considered. The results imply that the prospective research tendencies on ECCT are to (1) improve China’s regional input-output data and energy intensity data to more precise estimates under global perspective; (2) estimate China’s carbon emission at firm level by different firm ownerships in production and consumption worldwide; (3) assess China’s carbon emission from processing or non-processing trade by compiling more detailed multi-regional input-output table; (4) evaluate city level carbon mitigation capacity in China under global MRIO model; (5) explore new carbon management experience in China’s carbon trading market and new trade expansion policy of ‘ one belt and one road’ in her new growth era. [ABSTRACT FROM AUTHOR]

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 CO 2 by the Earth was evaluated based on the amount of CO 2 released into the atmosphere and the change in atmospheric CO 2 concentration. The impact of different CO 2 emission reduction scenarios on the atmospheric CO 2 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 CO 2 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. • A critical review of sustainable heat production technologies. • A MILP model to achieve carbon emissions neutrality or negative net emissions in the EU by 2050. • Cross-sectoral synthesis of regenerative energy systems – beyond sustainability. • Assessment and prediction of Earth's self-sequestration in the synthesis of regenerative energy systems. [ABSTRACT FROM AUTHOR]

Endeavouring to promote sustainability and citizens' well-being, and attempting to avoid or at least mitigate catastrophic climate change; the European Union adopted in 2019 the "Green Deal" as a new growth strategy, to thus become the first climate-neutral continent by 2050. As an intermediate 2030 target, it set the goals of at least 40% net reduction in greenhouse gas emissions, an increase to 32% share for renewable energy, and 32.5% increase in energy efficiency. Reaching these targets was estimated to require investments of €260 billion/year till 2030, which is 1.94% of EU's annual gross domestic product in 2020. The aim of this paper is to introduce a perspective that attempts to analyse relationships between two exceptionally important and ambitious simultaneous goals of the Green Deal: to achieve net-zero emissions by 2050, as well as the Sustainable Developments Goals, all based on the sustainability environmental, economic and social pillars. The study shows that the link between these two goals, including the cost-benefit effects for all citizens, should be made clearer. Without adequate understanding and monitoring of the consequences of each action, and quantitative indicators for the environmental, economic and social sustainability pillars, the attainment of the goals would be subject to high uncertainty. With ongoing global changes and problems within and surrounding the European Union, implementation of the Green Deal without the noted adjustments poses a potential risk to sustainable development and to the European Union unity. Transition to climate neutrality can be sustainable only if supported by conviction and accord. • The carbon neutrality - sustainable development link must be evidence-based. • The Green Deal focuses inadequately on social dimensions of SD. • Its high cost should be born without major risk to the SDGs. • Need for quantitative socio-economic targets, continuous monitoring and evaluation. • The proposed support mechanisms is unlikely to reach all vulnerable groups. [ABSTRACT FROM AUTHOR]

The paper aims to address the potential of low-carbon and renewable hydrogen in decarbonizing the European energy system; specifically, reducing emissions by 55% in 2030 compared to 1990, and targeting net-zero emissions by 2050. The methodology relies on a cost-optimization modelling approach using three models complementarily: a detailed European TIMES-type model (MIRET-EU); an aggregated model for the European energy system, allowing endogenous cost reductions based on technology deployment in a dynamic programming formulation for investment strategies (Integrate Europe); and a dedicated model for assessing hydrogen import options for Europe (HyPE). Two policy-relevant scenarios have been developed: Technology Diversification (TD) and Renewable Push (RP). Both lead to climate neutrality in Europe in 2050 but the RP scenario differs by setting new reinforced targets for renewable technologies in Europe. Results show that hydrogen production would increase sharply in the coming decades, exceeding 30 million tons (Mt) by 2030 and more than 100 Mt by 2050 in both scenarios. Polyvalence of hydrogen in decarbonizing the European energy system for certain hard-to-abate energy uses in transport and industry is also observed. European hydrogen production relies on a diverse mix including both renewable and low-carbon technologies. It is complemented by hydrogen imports from neighboring regions, that represent between 10 and 15% of total demand in 2050. Access to existing cross-border pipelines is a critical advantage compared to maritime transport. Notably, there are considerable cost reductions due to technology deployment for solar power and hydrogen production by electrolyzers. • European hydrogen demand could exceed 100 million tons per year by 2050. • 15% of H 2 needed to reach carbon neutrality could be imported from outside Europe. • More than half of H 2 is used for transport, the rest is dominated by industry. • 1800 GW of solar and wind power is needed for the roll-out of renewable hydrogen. • Resilience of natural gas in European energy transition by 2050 with uptake of CCS. [ABSTRACT FROM AUTHOR]

In modern power system planning and operation, the relevance of distributed power generation units and demand-side flexibility options grows. As a consequence, smart planning and operation routines become necessary also in the distribution grid. We therefore develop a co-optimization framework to consider transmission and distribution system constraints and their interactions together. This enables bidirectional flows between both systems, supporting a consistent and cost-efficient overall energy system. The key feature of this paper is an automated coupling of two independently and modularly defined systems. It allows a bottom-up modelling approach of energy demands, conversion and storage technologies from both system levels. However, this approach increases the model size significantly. Thus, timeseries aggregation methods are applied to reduce the computational complexity. The results for the optimal planning of the coupled German energy system show that the electrification of heat and mobility sectors in the distribution grid is not only beneficial to achieve carbon neutrality in 2050, but also to particularly make use of additional flexibility potentials. Our results underline a significant positive correlation between a smart operation of heat pumps and charging stations with the maximum integrable capacities of low-cost rooftop photovoltaics in the distribution system. • Open-source framework to couple transmission system and active distribution grids. • Co-optimization of both system levels enables a holistic model with a global optimum. • Case study: German energy system with the carbon-neutrality target by 2050. • Electrification of residential heat and mobility sector to unlock flexibilities. • Gained flexibilities promote 20% higher PV capacities and reduce system costs by 7%. [ABSTRACT FROM AUTHOR]

Building energy-saving retrofit projects (BERPs) have been widely implemented due to pressure to reduce emissions to meet carbon neutrality targets. However, it is still not clear which kind of BERP is most efficient during implementation. This paper proposed a three-stage DEA model for evaluating the efficiency of BERPs. Our research found that ineffective scale was the main reason for the low efficiency of BERPs. Buildings could obtain better energy-saving effects by appropriately expanding the scale of the BERPs. Geographic areas with developed construction industries had larger BERPs with better energy-saving effects. From the perspective of building types, BERPs on shopping malls had the best energy saving efficiency, followed by those on multifunctional buildings and hotel buildings. From the perspective of the retrofit objects, BERPs on heating, ventilation and air conditioning (HVAC) systems had the greatest efficiency, followed by BERPs on building envelopes. This study could suggest preferred strategies for the future development of BERPs. • The efficiency of BERP was evaluated with the three-stage DEA model. • Insufficient of retrofit scale was the main reason for the low efficiency of BERPs. • The BERP of shopping malls have the best energy-saving efficiency. • BERPs on HVAC System are more worthy of being retrofitted. [ABSTRACT FROM AUTHOR]

Carbon Capture Utilization and Storage (CCUS) technology is an essential component to decarbonize society and reach carbon neutrality. Its success depends on not only technological advances but also people's reaction to it. This study applied traditional content analysis to uncover the CCUS reporting landscape and employed the Socio-Political Evaluation of Energy Deployment (SPEED) framework to explore how different aspects of the CCUS value chain were discussed in Chinese newspapers. A total of 492 news items from November 21st 2002 to May 8th 2021 were identified and analyzed. Results showed that news coverage of CCUS technology in China started in 2005. The media explained the nature and sources of carbon dioxide (CO 2), framed CCUS by various terms, for example, " greengen " and " a clean energy technology ", as well as demonstrated various tones in CCUS. The analysis found 71.3% (N = 351) of newsletters took an affirmative stance towards CCUS. It was also revealed that environmental frames appeared in almost every article, while much less attention was paid to other issues. Moreover, this research demonstrated that CCUS-related policies were driving media coverage closely year by year. However, current news presentations were inadequate due to technical misperceptions and a lack of comprehensive coverage. Therefore, this research proposed a science-for-the-community communication strategy that involved several key factors such as policy guidance, newspaper functions at different levels, journalist training, direct engagement of the public as well as student education. • This paper pioneered to investigate Chinese newspaper coverage of CCUS technology. • The frequency of CCUS inclusion in newspapers was somehow affected by policies in China. • CCUS reporting revolved its emission reduction potential, and CCUS influences on health and safety issues were limited framed. • The current CCUS reporting landscape had misperceptions and lacked comprehensive coverage of the value chain. • A science-for-the-community communication strategy that can make media communication effective was proposed. [ABSTRACT FROM AUTHOR]

Abstract: The damage inflicted by global warming is happening far faster than any experts have predicted or anticipated. Since the Kyoto Protocol was signed in 1997 to fight global warming through reducing global greenhouse gases (GHGs) emission, the world climate pattern has worsened at an accelerated rate beyond expectation. While developed countries sanctioned by the protocol are committed to achieve their GHG emission targets, developing nations play similar roles on a voluntary basis. Since almost all of the GHGs emissions come from energy sector, it is obvious that energy policy and related regulatory frameworks play imperative roles in realizing the Kyoto Protocol objectives. With carbon dioxide (CO2) touted as the main remedy in the GHGs emissions, it is only reasonable that carbon trading becomes the essential element in the Protocol. Recently a milestone is marked in the Kyoto Protocol with the 2009 Climate Summit in Copenhagen, Denmark, with all participating countries further committed themselves in fulfilling the protocol''s obligations before the commitment period due in 2012. It is worthwhile to review the various energy efficiency efforts and carbon trading potential in Malaysia, a country which although does not bear any obligation, has ratified and lauded the cause of the protocol. Malaysia as a developing nation is seen as a direct beneficiary from carbon trading and in this paper, how the country energy policies have evolved over the years with concerted efforts from the government to minimize its carbon footprint through numerous energy efficiency implementations are discussed in length. The impact from the 2009 Climate Summit on Malaysia is also briefed. [Copyright &y& Elsevier]

Abstract: Global warming, increased energy demand, and tremendous air pollution are forcing China to revise its energy structure of electricity generation dominated by coal (80% of total electricity) towards low-carbon electricity. Vigorous development of carbon-free energy resources of electricity is a practical way towards low-carbon electricity in China. In this paper, we shall outline renewable power generation (hydropower, wind power, solar energy, biomass energy, nuclear power, ocean energy and geothermal) together with nuclear power for China, present a reserves assessment, the current status, and barriers for further development, and finish with an outlook towards the future. In our view, China has plenty of free-carbon energy resources to revolutionize its electricity structure and redirect it towards low-carbon electricity systems. Needed are the effective energy policies to get to the way. [Copyright &y& Elsevier]

Bioenergy is considered a promising alternative to achieve carbon neutrality and emission reduction. There is a debate over the role of bioenergy in climate change mitigation because of carbon emissions from the production and utilization of biofuels. Recently, studies on emissions of biogenic volatile organic compounds (BVOCs) have substantially increased as they have a significant impact on human health and climate change due to large emissions and high reactivity. A scientometric analysis of 2895 journal papers during 1991 and 2020 related to BVOC emissions from the Web of Science Core Collection was conducted by CiteSpace and Carrot2. Results showed that three main knowledge domains were BVOC emissions and drivers, BVOCs and their oxidation products in biosphere-atmosphere exchange, and soil BVOCs in plant-microbe interactions during the period under study. Generally, the relationships between plant BVOC emissions and environmental variables (e.g., temperature, drought, light solar radiation, humidity, availability of nutrients, carbon dioxide, ozone, etc.) can be investigated by measurement techniques (i.e., chamber) or models (i.e., Model of Emissions of Gases and Aerosols from Nature). Soils could work as both the sink and source of BVOCs through various processes that are affected by soil temperatures, pH, organic matter, and moisture. Anthropogenic activities might affect the emission of BVOCs and promote the formation of BVOC-derived pollutants (e.g., ozone, particles, etc.). Incorporating BVOC emissions and their relationships with pollutants, biomass, and energy into environmental management and decision-making is a promising direction. [Display omitted] • A scientometric analysis was conducted on the research evolution of BVOC emissions. • Ten clusters generated by CiteSpace were logically reclassified into three hotspots. • MEGAN is the most frequently empirical model for BVOC emission assessment. • BVOC-derived pollutants like SOA are likely affected by anthropogenic activities. • Soils in terrestrial ecosystems can act as both the source and sink of BVOCs. [ABSTRACT FROM AUTHOR]

In order to achieve the goal of a carbon neutral EU by 2050 and meet the climate targets of the Paris Agreement, a sustainable, efficient, competitive and secure energy system needs to be developed. This paper presents the synthesis of sustainable renewable energy supply networks within the EU-27, proposing a stepwise energy transition in the transport and power sectors, achieving a carbon net neutral target by 2050. A multi-period mixed-integer programming model is developed, with the objective of maximizing sustainability net present value, considering different biomass and waste resources for the production of biofuels, renewable electricity, hydrogen, food and bioproducts, employing different types of technologies. The results show that, with further development of existing technologies, the goal of a carbon-neutral EU can be achieved without compromising food production. Wind farms have proven to be the most promising solution at present for the rapid expansion of electricity generation from renewable energy sources, while the importance of solar photovoltaics is increasing over the years, reaching the 43% share of electricity generation from RES in 2050. Moreover, the energy transition within the EU could have a significant positive impact on the economic, environmental and also social aspects of sustainability, with more than 1.5 million new job opportunities created across the EU over the next 30 years. [Display omitted] • Mathematical programming approach for the transition to carbon-neutral EU by 2050. • Critical review of technologies and synthesis of renewable energy supply networks. • Sustainable multi-period selection of locations, products and types of technologies. • Large economic, eco and social benefits if optimization is carried out at EU level. • Carbon-neutral EU can be achieved through further development of technologies. [ABSTRACT FROM AUTHOR]

The global energy transition towards a carbon neutral society requires a profound transformation of electricity generation and consumption, as well as of electric power systems. Hydrogen has an important potential to accelerate the process of scaling up clean and renewable energy, however its integration in power systems remains little studied. This paper reviews the current progress and outlook of hydrogen technologies and their application in power systems for hydrogen production, re-electrification and storage. The characteristics of electrolysers and fuel cells are demonstrated with experimental data and the deployments of hydrogen for energy storage, power-to-gas, co- and tri-generation and transportation are investigated using examples from worldwide projects. The current techno-economic status of these technologies and applications is presented, in which cost, efficiency and durability are identified as the main critical aspects. This is also confirmed by the results of a statistical analysis of the literature. Finally, conclusions show that continuous efforts on performance improvements, scale ramp-up, technical prospects and political support are required to enable a cost-competitive hydrogen economy. • Characteristics of hydrogen technologies are presented with experimental results. • Hydrogen powered energy systems are exemplified by worldwide projects. • Current status on cost and performance of hydrogen powered systems is investigated. • A detailed statistical analysis of publications is presented. • Future trends and challenges on technological and social aspects are discussed. [ABSTRACT FROM AUTHOR]

China has become the world's largest carbon emitter, and its commitment to peak carbon emissions by 2030 is important for global development. The construction industry is one of China's biggest carbon emitters, and its peak has a direct impact on China's carbon commitment. Due to the regional heterogeneity of different provinces, the carbon emission of construction industry (CECI) at provincial level is of unique significance. To accurately predict the peak of provincial CECI, a prediction model was established by system dynamics, including direct CECI, indirect CECI and operational CECI. Taking Jiangsu province as an example, the single and multiple scenario settings with increasing R&D investment, promoting energy-saving buildings and implementing carbon trading from 2016 to 2030 was carried out, indicating that: 1) Without any carbon emission reduction measures, the CECI would maintain an annual growth rate of 5.58% to reach 530.61 million tons by 2030, and the indirect and operational CECI account for the majority of total with an average annual growth rate of 8.02% and 2.79% respectively. 2) All three measures had good carbon reduction effects, which would reduce the total CECI by 26.46% 21.68% and 10.68% respectively by 2030, but only when implemented simultaneously can CECI peak before 2030, 308.77 million tons at 2029. In the end, three policy implications was put forward. The framework presented in this paper provided a basis for the prediction of peak CECI in a province or state, which can help policy makers plan a more reasonable low-carbon development roadmap. [Display omitted] • The total carbon emissions of provincial construction industry are predicted. • Direct, indirect and operational carbon emissions are predicted respectively. • The total carbon emissions will not peak before 2030 under the basic scenario. • Carbon emissions will peak at 308.77 million tons in 2029 under multiple scenario. • Encouraging R&D investment, energy-saving buildings and carbon trading are crucial. [ABSTRACT FROM AUTHOR]

As climate change develops, with most of the world population living in urban areas, decarbonisation of cities is among the greatest challenges of the coming decades. In the framework of the EU City-zen project, a number of so-called Roadshows has been organised in ten cities within and outside Europe in order to plan and kick-off their transition towards an energy- and climate-neutral economy. During the Roadshows , a group of experts is engaged to perform co-working activities and participative labs involving local stakeholders. These activities support cities in identifying their own decarbonisation pathways, mainly by combining three mutual processes, i.e. energy design, urban design and carbon accounting. The latter, in particular, has been used to quantify the greenhouse gas emissions of cities and neighbourhoods and to estimate the mitigation effect of a combination of measures towards the desirable condition of carbon neutrality. This exploratory and proactive design process has been successfully demonstrated through intensive workshops and can be potentially replicated in other cities. This paper provides a schematic overview of the main results achieved in the Belgian town of Roeselare, but more significantly it describes the techniques needed to make that cooperative process understandable, impactful and implementable. It is likely that 2050 European goals will drastically change urban environments and socio-economic dynamics in cities, due to the fragmentation of energy sources. Hence, from this standpoint there is a vital need for integrated technologies and infrastructures, a circular economy and community-based processes such as food production, sharing of facilities and valorisation of ecosystem services. The City-zen Roeselare Roadshow brought over 300 stakeholders into the process of re-imagining and visualising their 2050 future city with these solutions. Stakeholders, with no particular expertise in carbon accounting or sustainability, would now have the capability of understanding and applying these solutions in a combined effort to meet the zero-carbon challenge. The approach is generally replicable elsewhere being highly visual, impactful, transferable, and multi-stakeholder friendly. Given that data are made locally available, the combination of this general approach, site-specific assessments and the involvement of both experts and local stakeholders (i.e. policy makers, citizens, etc) allow the transition to start by referring to any real city or neighbourhood. • City-zen Roadshow is performed in a few days to kick-off decarbonisation of cities. • Participative processes contribute to deliver coherent energy transition plans. • Carbon accounting raises awareness on meanings and implications of energy transition. • Outputs are consistent and reliable "future city visions" as 2050 forecasts. [ABSTRACT FROM AUTHOR]

Cities across the globe recognise their role in climate mitigation and are acting to reduce carbon emissions. Knowing whether cities set ambitious climate and energy targets is critical for determining their contribution towards the global 1.5 °C target, partly because it helps to identify areas where further action is necessary. This paper presents a comparative analysis of the mitigation targets of 327 European cities, as declared in their local climate plans. The sample encompasses over 25% of the EU population and includes cities of all sizes across all Member States, plus the UK. The study analyses whether the type of plan, city size, membership of climate networks, and its regional location are associated with different levels of mitigation ambition. Results reveal that 78% of the cities have a GHG emissions reduction target. However, with an average target of 47%, European cities are not on track to reach the Paris Agreement: they need to roughly double their ambitions and efforts. Some cities are ambitious, e.g. 25% of our sample (81) aim to reach carbon neutrality, with the earliest target date being 2020.90% of these cities are members of the Climate Alliance and 75% of the Covenant of Mayors. City size is the strongest predictor for carbon neutrality, whilst climate network(s) membership, combining adaptation and mitigation into a single strategy, and local motivation also play a role. The methods, data, results and analysis of this study can serve as a reference and baseline for tracking climate mitigation ambitions across European and global cities. • 78% of cities have a mitigation plan with targets (avg. 47% GHG reduction). • Only 25% of cities strive for carbon neutrality, most by 2050, avg. By 2045. • 90% of cities striving for carbon neutrality are members of a climate network. • Ambition is driven by city size, climate networks, M-A combination, local motivation. • European cities must double their ambitions to meet the aims set by the Paris Agreement. [ABSTRACT FROM AUTHOR]

Unilateral emission trading may lead to carbon leakage. The leakage direction and channel are critical to multilateral emission mitigation. Despite the increasing number of investigations into the carbon leakage induced by emission trading, there is a lack of empirical research on the specific leakage channels related to the emission trading market. This paper develops a difference-in-difference-in-differences model to identify carbon leakage directions in emission trading pilots in China. The issue of whether market participation and industrial transfer are the specific leakage channels related to emission trading is also examined. Emission trading pilots lead to reverse carbon leakage, which moves from the non-pilot region to the pilot region. Market participation and industrial transfer are confirmed to be the specific leakage channels in emission trading. Of the two channels, market participation is the one that determines the reverse direction. • The carbon leakage direction and channel are identified in emission trading pilots. • Reverse carbon leakage was found in emission trading pilots. • Market participation and industrial transfer are the specific leakage channels related to emission trading. • Leakage switches from reverse to forward if market participation exceeds 5.52%. • Inter-regional and total reverse carbon leakage scales rely on industrial transfer. [ABSTRACT FROM AUTHOR]

The assessment of the social cost of carbon (SCC) is an important basis for formulating regional differentiated climate policies. This paper attempts to assess future SCC for eight Chinese regions by using the regional integrated model of climate and the economy (the RICE model), based on four scenarios, namely baseline (BS), carbon emissions trading (CET), carbon quotas (CQ), and carbon tax (CT) for the period 2005–2050. The results show that under the BS, CET, and CT scenarios, the SCC of China's eight regions increases by $22.26/t C, $20.58/t C, and $19.14/t C, respectively, from 2005 to 2050. The CT scenario performed best in terms of impact on CEs and SCC, but in order to do so they will have to bear certain economic losses. There are differences between the SCC of the eight Chinese regions under different scenarios. Under the BS, CET, and CT scenarios, the areas where SCC is highest are distributed in the Central, North Coast, and Southwest regions, and in the CQ scenario, the high-SCC areas are concentrated in the Southwest, North Coast, and Northeast regions. The low-SCC areas are distributed in the Beijing–Tianjin and South Coast regions under all four scenarios. The central and western regions will become the major energy consuming regions after 2025, so they will face a greater pressure than other regions to reduce emissions. • The RICE model is used to calculate SCC in eight Chinese regions from 2005 to 2050. • Regional economic and carbon emission trends are simulated under four scenarios. • Central and western regions will have highest energy consumption in the future. • SCC has meaningful spatial differences across the eight Chinese regions. [ABSTRACT FROM AUTHOR]

The progressive exhaustion of fossil energy resources and the environmental problems provoked by the excessive use of these resources have driven us to transit from a fossil fuel dependent economy to a more bio-based economy. In this regard, exploiting the organic fraction of municipal solid waste (OFMSW) for producing high value bioproducts and bioenergy under a biorefinery approach has attracted great interest. This paper presents the state of the art of urban biowaste biorefinery concepts. Accordingly, different novel valorization pathways, namely single cell protein, biosuccinic acid, and lactic acid, as well as bioenergy production were consolidated into some scenarios. Moreover, successfully tested hydrogen-assisted biological biogas upgrading was also incorporated into some scenarios as energy source for methanotrophs to upcycle nitrogen rich digestate into single cell protein. Upon the successful lab-scale experiments, different biorefinery platforms were developed and their sustainability was environmentally scrutinized using consequential life cycle assessment. The results obtained herein demonstrated that despite having different net environmental benefits, all the developed scenarios were eco-friendly solutions for valorizing biowaste into bioproducts and bioenergy. Scenarios including microbial protein production led to a saving of −58 to −147 kg CO 2,eq /t biopulp in Climate change category, depending on the biorefining pathway. The net saving in Climate change category achieved for Succinic acid- and Lactic acid-based biorefinery was estimated at −73 and −173 kg CO 2,eq /t biopulp, respectively. Biological biogas upgrading, if implemented, could increase energy payback by 9724 MJ/t biopulp and contribute more to the sustainability of other developed scenarios. Although scenarios with the main focus on bioenergy production outperformed others in terms of environmental sustainability, some complementary factors such as policy decisions, energy directives, economic issues, and carbon trade schemes must be taken into account in order to introduce the best valorization pathway. • A biorefinery platform based on urban biowaste was environmentally scrutinized. • The biorefinery produced bioenergy, microbial protein, succinic acid, and lactic acid. • All developed platforms were found as eco-friendly solutions for waste valorization. • Scenarios focusing on bioenergy outperformed others from environmental viewpoint. [ABSTRACT FROM AUTHOR]