China's green future and household solid waste: Challenges and prospects

Unlocking high-performance HCl adsorption at elevated temperatures: the synthesis and characterization of robust Ca-Mg-Al mixed oxides

The presence of HCl and SO2 gas imposes limitations on syngas utilization obtained from household waste in a wide range of applications. The hydrotalcite-like compounds (HTLs) have been proved that could remove HCl efficiency. However, the research on impact of synthesis conditions of HTLs and SO2 on HCl removal was limited. In this study, a range of Ca-Mg-Al mixed oxide sorbents was synthesized by calcining HTLs, with variations in crystallization temperature, solution pH, and the Ca/Mg molar ratio. These sorbents were examined for their effectiveness in removing HCl at medium-high temperatures under diverse conditions. The adsorption performance of selected sorbents for the removal of HCl, SO2, and HCl-SO2 mixed gas at temperature of 350 °C, 450 °C, and 550 °C, respectively, was evaluated using thermogravimetric analysis (TGA). It was observed that the HTL synthesis parameters significantly influenced the HCl adsorption capacity of Ca-Mg-Al mixed oxides. Notably, HTLs synthesized at 60 °C, a solution pH of 10-11, and a Ca/Mg ratio of 4 exhibited superior crystallinity and optimal adsorption characteristics. For individual HCl and SO2 removal, temperature had a minor effect on HCl adsorption but significantly impacted SO2 adsorption rates. At temperatures above 550 °C, SO2 removal efficiency substantially decreased. When exposed to a mixed gas, the Ca-Mg-Al mixed oxides could efficiently remove both HCl and SO2 at temperatures below 550 °C, with HCl dominating the adsorption process at higher temperatures. This dual-action capability is attributed to several mechanisms through which HTL sorbents interacted with HCl, including pore filling, ion exchange, and cation exchange. Initially, HCl absorbed onto specific sites created by water and CO2 removal due to the surface's polarity. Subsequently, HCl reacted with CaCO3 and CaO formed during HTL decomposition.

A comprehensive study on criteria of sustainable urban waste management system: using content analysis

The present study was developed to comprehensively analyze experts' views and content of documents focusing on goals and criteria of sustainable waste management system in Tehran, Iran. To this end, the suitable goals for sustainable waste management system in Tehran city were adopted from domestic, national and international documents. For this purpose, 27 national and international documents and 2 domestic documents related to waste management were selected and analyzed by using content analysis according to Gall, 1994. Further, in order to formulate goals in case of bottlenecks and challenges of waste management in Tehran, the focus group technique was used based on Stewart and Shamdasani, 2014. At this stage, 24 key experts in the field of waste management were interviewed in the form of 4 focus groups. Data collection were performed via audio recording and word-for-word implementation of conversations, taking notes and writing field notes. The data collection continued until reaching theoretical saturation. Next, content analysis and coding methods were used to analyze the data. Finally, the goals of waste management were divided into five general categories including: institutional (with emphasis on the integration and inclusion of the key elements of the urban waste management system), technical and infrastructural (with emphasis on the optimization of existing processes in the use of urban waste management technologies), environmental (with emphasis on minimizing the adverse health and environmental effects of the urban waste management system, economic (with emphasis on the economic and financial sustainability of the urban waste management system), and cultural-social (with emphasis on attracting the maximum participation of citizens and service recipients). The results clearly showed that sustainable waste management measures in Tehran should follow these five components in order to reduce the problems caused by unrealistic waste management and make sustainable use of basic, natural, financial and human resources.

Public acceptability and its determinants of unit pricing for municipal solid waste disposal: Evidence from a household survey in Beijing

Unit pricing for domestic waste, or pay-as-you-throw (PAYT), affords a promising policy option for waste classification and reduction at source. As an emerging economy, China intends to adopt the sophisticated instrument of unit pricing. The public attitude to this policy is of high relevance for its actual implementation. For the first time in China, this paper quantitatively examined the acceptability of the policy among urban residents by randomly delivering 632 questionnaires by taking Beijing, a megacity expected to introduce the practice, as an example. Based on the ordered logit model, determinants of acceptability were empirically tested including intrinsic, external and demographic factors. The results show that the acceptability rate of PAYT in Beijing is less than half, with the proportion of firm support reaching only 42.6%. The respectively low acceptability rate indicates substantial compliance costs, due to intensive resistance to policy implementation and more resources to be invested to promote acceptability. Empirical analysis further indicates that (1) regarding demographic features, aged or less educated residents tend to accept unit pricing, (2) as for intrinsic factors, a friendly environmental attitude, deeper understanding of charging policy and better social perception can significantly improve the public acceptability of the policy, and (3) in terms of external factors, better property services and transparent funding mechanisms play significant roles in enhancing public acceptability. These findings are further confirmed by replacing the dependent variable with either the willingness to pay for household waste disposal or the acceptability of the operated sewage treatment fee. The status of residents' preference for specific pricing methods is further investigated with underlying reasons being revealed. For developing regions with an urgent demand for waste reduction, it is proposed to install unit pricing in time to avoid possible growing social acceptability costs. Specific measures are proposed including changes in intrinsic factors, paying attention to focus groups, and building social consensus for unit pricing.

Evaluation of the household solid waste mandatory sorting policy in Shanghai: A 1-year public opinion survey

Sustainable management of household solid waste (HSW) is an essential step in realizing the development of a circular economy (CE). However, for many developing countries, HSW sorting is evolving incrementally, and focusing on the intervention role of policy and the sorting behaviour of residents can help achieve sustainable waste management. This study aims to investigate the main determinants of residents' HSW sorting behaviour and how policy particularly contributes to it. Drawing upon the theory of planned behaviour (TPB) and incorporating experiences, a conceptual framework is tested on a sample of Chinese residents in Shanghai (n = 560, from November to December 2020) using structural equation modelling analysis. The empirical results show that experience and behavioural intention greatly influence HSW sorting behaviour. Moreover, the positive attitude of residents promotes the success of HSW sorting. Subjective norms and perceived behaviour control indirectly affect behavioural intention and behaviour via attitude. The findings of this study provide policymakers with critical factors for the successful implementation of HSW sorting. We also propose policy implications to maintain and improve sorting efficiency from the perspective of residents (education, communication and publicity), neighbourhood committees (degree and efficiency of supervision) and property management companies (good infrastructure, services and processes).

Domestic Waste Classification Behavior and Its Deviation from Willingness: Evidence from a Random Household Survey in Beijing

To realize widespread domestic waste classification (DWC), deviation between residents' waste classification willingness (WCW) and waste classification behavior (WCB) needs to be reduced. Based on an extended framework of the theory of planned behavior, this study investigates residents' WCW, WCB and their deviation through a random face-to-face survey of 632 households in Beijing. By employing the ordered logit model, determinants have been empirically revealed. We find that there is a deviation between WCW and WCB. 54.3% of respondents reported a higher degree of WCW than that of WCB. The deviation is determined by specific external conditions, including attitudes and norms associated with other subjects that are not authoritative regulators, and the implementation of various policy instruments for DWC. The higher the satisfaction with the services of property enterprises, the higher the deviation is. The positive WCB of peers in communities failed to create positive subjective norms, but instead exacerbated free-rider phenomenon by inducing their negative WCB. Flat-rate charge, publicity measures and the effectiveness of DWC within community can significantly reduce the deviation. On this basis, policy suggestions are put forward to further reduce the deviation and improve the rate of DWC.

Feasibility study of the unit pricing system for household wastes sorting in the context of China

Although sanitary household waste disposal was achieved in China, an efficient source separation system has not been built yet. The Unit Pricing System has been proved effective for household waste sorting by developed countries and regions, while rare developing countries have successfully introduced the system in their local context. The study, taking an interactive perspective of dominant factors of residents' waste sorting and governments' intervention, combines theoretical analysis with system simulation to dissect the evolution process of residents' waste sorting and local governments' Unit Pricing System policy making, and to provide a Unit Pricing System policy making tool to support policy implementations. The results suggest introducing a Unit Pricing System can significantly push ahead the household waste sorting behaviour for cities with relatively low initial status of environmental awareness, and immediately trigger sorting behaviours for cities with higher initial status of environmental awareness. The study can also benefit other developing countries when imposing waste sorting management instruments.

Household waste management in Singapore and Shanghai: Experiences, challenges and opportunities from the perspective of emerging megacities

Due to rapid economic development and urbanisation, emerging megacities with dense populations have witnessed a significant increase in waste generation. Megacities face challenges in developing sustainable waste management systems. Considerable heterogeneity exists across megacities in management strategies. The two selected emerging megacities, Singapore (a city-state) and Shanghai, have similar developmental characteristics, but their waste management modes differ strikingly. This study assessed the two modes in terms of management strategies, environmental effects, economic costs, and social outcomes. Environmental footprint analysis and cost quantification were employed for the assessment based on public data. The research results would permit a deeper understanding of the long-term sustainability of each mode while considering the feasibility of implementation across different contexts. It was found that the waste management system in Singapore had a relatively lower environmental impact than Shanghai before Shanghai's new waste segregation and recycling policy in 2019. However, when the effect of fossil fuel substitution is taken into account, the environmental burden in Shanghai can be lowered more substantially than the one in Singapore. Although Shanghai had more economic burden for the waste segregation at source, it tended to implement the circular economy principles (e.g., reduce, reuse, and recycling) better and improve its sense of community significantly. Based on the practical experiences from the two representative megacities, suggestions for better waste management practices were provided for Singapore, Shanghai, and other emerging megacities with similar circumstances. In addition, challenges and opportunities related to household waste segregation and recycling were identified to guide future practices in emerging megacities.

The influence mechanism of household waste separation behavior among college students in the post COVID-19 pandemic period

College students are one of the most important groups of participants and promoters of household waste separation. Taking Ningbo as a case study, an online + offline questionnaire survey among more than 1700 students in 10 colleges is conducted to identify the main factors and pathways influencing waste separation behavior in the post COVID-19 pandemic period. The results show that the KMO statistic is 0.926, Bartlet test is p < 0.001, indicating that questionnaire sample data is suitable for factor analysis. The modified Structural Equation Model test indicates that waste separation behavior of college students mainly results from the combined effect of eight subjective intrinsic factors and seven external situational factors. Among them, the convenience of recycling facilities, the convenience of sorting facilities and the publicity and education of sorting knowledge are the top three factors with the most significant influence. The mean value of epidemic impact factors is 0.277, which is slightly lower than conventional influence factors (0.289). Environmental Norms and Constraints are an essential component in the analysis framework of college students' waste separation behavior. In the future, society and colleges should give full play to the positive influence of the epidemic factor on college students' waste separation behavior.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10163-022-01363-3.

Health concerns among waste collectors during pandemic crisis

The COVID-19 pandemic has negatively affected the economic, social, and psychological aspects globally. COVID-19 can possibly spread through municipal solid waste (MSW) if it is collected, bagged, transported, and disposed inappropriately. Such situation has posed significant challenges to MSW management (MSWM), which has led waste personnel under massive pressure. This study aims to examine the health-protective behavior of sanitation workers/MSW collectors (MSWCs) during the COVID-19 crisis. Quantitative data were collected by using a self-administered survey from 418 MSWCs working in Mainland China. The study extended the traditional health-belief model and proposed education and training as a facet of the behavioral model. Result showed that education and training were a significant predictor of health-protective behavior. Moreover, the moderating incremental influence of regulative assistance significantly affected the behavioral mapping of MSWCs. This study contributes to the literature by mapping the concerns, risks, and challenges experienced by MSWCs in times of a health crisis. Policymakers should specially consider the safety and hygiene concerns of frontline workforce in the whole chain of waste management (including the outsourced operations of MSWM). Lastly, the adoption of smart communication with the frontline workforce (i.e., MSWCs) is in dire need to maintain trust and avoid rumors and misconceptions during the time of a pandemic situation.

Potential climate benefits of reusable packaging in food delivery services. A Chinese case study

In China, the food delivery packaging waste is increasing due to the rapid growth of the sector and the use of single-use packaging to transport the meals. In addition, the recycling rates of current municipal waste management are low. In this regard, this study aims at estimating the climate change impact of current food delivery packaging and its waste treatment, by performing a Life Cycle Assessment with a cradle-to-grave approach. In addition, this article explores the potential benefits of increasing the current recycling rates, the recycled content of the packaging as well as the use of reusable packaging. For this study, the food packaging of a typical dumpling-based meal of the popular Chinese restaurant Xijiade was selected. Based on this menu and the current Chinese consumption patterns, the food delivery packaging in China would have emitted about 13 million tons of CO₂eq. Increasing current recycling rates to 35% would reduce 16% the emissions of single-use packaging, and further decrease (60%) could be found if half of the packaging was made of recycled material. In addition, if single-use packaging was replaced by reusable PP-based packaging (food container and carrier bag), the emissions would potentially be 63% lower than the current situation. In this case, doubling the recycling rates and the recycled content of the reusable food packaging would represent an extra 6 and 17% reduction of emissions, respectively.

Promotion of Household Waste Utilization in China: Lessons Learnt from Three Case Studies

Household waste utilization has been regarded as an important pathway to promote the circular economy paradigm and sustainable development for a long time. However, relevant enterprises are facing dilemmas in terms of the backward disposal methods for food waste, inadequate recycling of low-value recyclable waste and the lack of leading enterprises, resulting in unsustainable expansion of the industry. To address these problems, we investigated governmental departments and 20 household waste utilization enterprises in China. From the investigation, three typical enterprises, representing the advanced technology for food waste, the recycling mode of recyclable waste and the cultivation mode of leading enterprises, were selected for case studies. The results indicate that applying the technology of bioconversion by maggots could improve the utilization of food waste and adopting the “online and offline” dual-channel mode could benefit the recycling of low-value recyclable waste. Additionally, leading enterprises can be cultivated by franchise mode, which can drive the utilization of household waste in China effectively. The findings enrich the theory of household waste utilization in terms of disposal methods, recycling modes and enterprise operation. Practically, this research should enlighten decision-makers to improve household waste utilization. Furthermore, the research results could be generalized in other countries, thereby advancing the household waste management worldwide.

Household Waste Separation Intentions in Mongolia: Persuasive Communication Leads to Perceived Convenience and Behavioral Control

This study contributes by developing a set of household waste separation (HWS) attributes to address waste mishandling and to enhance waste separation intentions in households. In Mongolia, a lack of waste separation at the household level needs to be addressed to improve municipal solid waste management systems. However, prior studies have not established attributes in a hierarchical structure, nor do they understand their cause-effect interrelationships. First, the fuzzy Delphi method (FDM) was used to screen out the unnecessary attributes in qualitative information. The fuzzy decision-making trial and evaluation laboratory (FDEMATEL) was then applied to understand the hierarchical structure of the attributes and their cause-effect interrelationships. The study identifies a valid set of attributes consisting of five aspects and 17 criteria under uncertainties. A hierarchical framework consisting of environmental attitudes, social norms, perceived behavioral control, perceived convenience, and persuasive communication is provided. The findings reveal that persuasive communication and environmental attitudes are causal group aspects. Furthermore, persuasive communication has a strong causal impact and higher importance in improving HWS intentions, and it leads to perceived convenience and behavioral control. For policymakers, credibility of information, knowledge and information, awareness of consequences, willingness to sort, and perceived policy effectiveness are the key causal criteria for enhancing HWS intentions. Theoretical and practical policy implications are discussed.

Embedded Philanthropic CSR in Digital China: Unified View of Prosocial and Pro-environmental Practices

In recent decades, China has transformed from a conventional society into a digitally competitive nation. From an economic perspective, embedded corporate social responsibility (CSR) is gaining a new height where gamified charity is a trendy approach. By adopting the norm activation model from the point of view of the stimulus-organism-response framework, this research theoretically conceptualized the role of the mobile application environment (including telepresence, functional transparency, and accessibility) to map the cognition and philanthropic behavioral intentions of consumers in the gamified setting. The quantified survey comprised 669 respondents. The findings highlighted the critical role of functional transparency and telepresence of a mobile application in driving consumers' warm glow and ascribed responsibility. The research underlined the presence of the unique DNA of Internet Plus Charity (Public Benefits) for prosocial and pro-environmental purposes in China under the umbrella of philanthropic CSR.

The Impact of Reward–Penalty Policy on Different Recycling Modes of Recyclable Resources in Residential Waste

Facing enormous pressure from the rapid growth of waste on the environment and society, many developed countries have combined urban waste recycling systems with waste classification to reduce pollution and recycle resources. However, this technique is not well established in developing countries. From the 2000s, China has carried out many waste classification recycling projects in many pilot cities although they have yet to reach widespread success. This paper focuses on China’s Newest Waste Classification Recycling Project (NWCRP), which was first implemented in Shanghai from 2019 and has a three-echelon supply chain containing waste classification guiders (WCGs), recyclers and demanders. Firstly, two recycling modes in NWCRP are studied: the recyclers of the first mode are dominated by the recycling company (mode RC), and the recyclers of the second mode are dominated by the environmental sanitation engineering group (mode ESEG). Secondly, a reward–penalty policy is proposed, which can be implemented for WCGs or different recyclers in the two modes (RC or ESEG), and the impacts of different scenarios are also compared. The results showed that (1) with increasing reward–penalty intensity, the sorting rate and the profit show upward trends in two modes, while the subsidy efficiency of government decreases; (2) when the reward–penalty policy is implemented for WCGs, the recyclers’ recycling price decreases in the two modes; (3) all scenarios that implement the reward–penalty policy in mode RC have certain advantages in the sorting rate and profit and (4) with increasing reward–penalty intensity and target sorting rate in the reward–penalty policy, the social welfare first increases and then decreases in all scenarios. Finally, some suggestions on the recycling mode and the reward–penalty policy for establishing a 3RW recycling system are provided.

Vermicomposting: A management tool to mitigate solid waste

Solid waste management is a serious ecological problem in Saudi Arabia due to rapid industrialization, population growth and urbanization. Recycling and sorting are in their infancy in Saudi Arabia and huge amounts of mixed household and industrial wastes are still dumped without any pre-treatment. Solid waste management techniques such as incineration, pyrolysis and gasification have high investment costs. Composting and vermicomposting of solid organic waste have been considered as an economically viable and sustainable waste management technologies. However, wastes often contain pollutants, such as heavy metals that are toxic to decomposer micro-organisms. Thus, heavy metals are a challenge for the successful biological treatments. Waste may also contain a mixture of organic pollutants that certain microbes, such as micro-algae are known to degrade. The present review paper focuses on understanding the role of vermicomposting as a management tool in mitigating solid organic wastes. It is noteworthy to mention that the microbes also play a pivotal role in the degradation process, wherein the enzymes secreted during the process aid in decomposition of complex molecules into simpler compounds. Also, the extracellular polymeric substance secreted by the earthworm under metal stress serves a source of nutrient for the bacteria to flourish. Henceforth the goal of discussion in present review shows the way forward in using vermicomposting as a novel approach in dealing with solid organic waste.

EnCNN-UPMWS: Waste Classification by a CNN Ensemble Using the UPM Weighting Strategy

The accurate and effective classification of household solid waste (HSW) is an indispensable component in the current procedure of waste disposal. In this paper, a novel ensemble learning model called EnCNN-UPMWS, which is based on convolutional neural networks (CNNs) and an unequal precision measurement weighting strategy (UPMWS), is proposed for the classification of HSW via waste images. First, three state-of-the-art CNNs, namely GoogLeNet, ResNet-50, and MobileNetV2, are used as ingredient classifiers to separately predict and obtain three predicted probability vectors, which are significant elements that affect the prediction performance by providing complementary information about the patterns to be classified. Then, the UPMWS is introduced to determine the weight coefficients of the ensemble models. The actual one-hot encoding labels of the validation set and the predicted probability vectors from the CNN ensemble are creatively used to calculate the weights for each classifier during the training phase, which can bring the aggregated prediction vector closer to the target label and improve the performance of the ensemble model. The proposed model was applied to two datasets, namely TrashNet (an open-access dataset) and FourTrash, which was constructed by collecting a total of 47,332 common HSW images containing four types of waste (wet waste, recyclables, harmful waste, and dry waste). The experimental results demonstrate the effectiveness of the proposed method in terms of its accuracy and F1-scores. Moreover, it was found that the UPMWS can simply and effectively enhance the performance of the ensemble learning model, and has potential applications in similar tasks of classification via ensemble learning.

Rural Residents' Awareness of Environmental Protection and Waste Classification Behavior in Jiangsu, China: An Empirical Analysis

Achieving waste classification and environmental protection awareness assists in enhancing the rural ecological environment, improves the quality of the rural residents' life, and augments the rate of reusing resources within the rural setups. In order to study the factors influencing rural waste classification and environmental protection awareness, we conducted a project among rural residents of Jiangsu, China. We used both the logistic regression model and the ordinary least squares model to achieve the goals of this paper. Similarly, we found that the households' level of education influenced the rural residents' decision to classify waste and to protect the environment regarding whether a household consists of a village cadre; the availability of public waste collection facilities; the distance between households and the waste collection points; whether the waste is picked, assorted, and collected locally; and the cost of waste disposal. In light of all these factors, we recommended that the authorities should increase the rural residents' waste classification and environmental protection awareness. Also, through the local government, the national government should strengthen and sustain rural waste disposal funds. Finally, there should be stringent laws and regulations outlining the role of the rural residents regarding waste classification and environmental protection awareness.

A stochastic frontier analysis of the efficiency of municipal solid waste collection services in China

Governments in many developing countries, such as China, are investing a lot of human, financial and material resources to ensure that as much of municipal solid waste (MSW) as possible is collected for centralized harmless treatment and disposal. This is regarded as an effective way to alleviate the "waste siege" problem in governance caused by the continuous enormous increase in MSW quantity. Therefore, how to improve the efficiency of MSW collection service system is an important governance issue because the inputs that can be utilized to manage MSW problem are limited due to budget and resource constraints. However, studies on MSW collection efficiency in developing countries like China are under-represented in the existing literature. This paper applies a stochastic frontier analysis (SFA) approach to evaluate the efficiency of MSW collection services in 30 provinces of China from 2008 to 2017, and explore the relative importance of several factors that might influence collection efficiency. The results indicate that there exists considerable room (62.8%) to enhance efficiency since its current efficiency value is merely 0.372. With regard to influencing factors, the proportion of population aged 15-64 appears to have the greatest positive impact on efficiency, along with per capita GDP, added value of tertiary industry and education level. This paper also explores spatial variations of MSW collection efficiency across the eastern, central and western regions. These findings have policy implications and can inform the related government departments how to formulate proper policies to improve collection efficiency.

Determinants of Public-Private Partnership Adoption in Solid Waste Management in Rural China

Rural solid waste management is a severe challenge in China. The Public-Private Partnership (PPP) is an effective method for rural solid waste management. However, policy efforts aimed at stimulating the adoption of PPP in rural solid waste management have been limited in their success. This study aims to empirically investigate the determinants of rural solid waste management PPP adoption in China. First, this study builds a theoretical model that consists of factors related to the institutional environment and market and proposes theoretical hypotheses. Then, using the balanced provincial panel data of 150 samples from 2015 to 2019, this study applies various count regression models and truncated regression models to empirically test the theoretical hypotheses. The results show that provinces with higher fiscal transparency, financial burdens, and market demand tend to adopt more PPP, while provinces with lower per capita GDP and market openness index ratings have a stronger motivation to initiate more PPP. In contrast, investment institutional environment factors have no impact on PPP adoption. To stimulate the development of PPP in rural solid waste management, this study proposed that a good-governed government and a strong market demand are critical foundations, and also a debt-risk prevention and evaluation system should be established to avoid local debt risks resulting from over-adoption of PPP.