Fine particles removal of pyrolysis gasification flue gas from rural domestic waste: Laboratory research, molecular dynamics simulation, and applications.

Chinese rural domestic waste has increased considerably with the modernization of agriculture and urbanization. Pyrolysis gasification is a common high-temperature waste treatment method. However, this method is usually accompanied by a large amount of particle emission. In this study, a rural domestic waste pyrolysis gasification station in Gansu Province, Northwest China, was selected for research. The particle emission characteristics of this station were analyzed, and the results showed that the original particle removal technologies were inefficient in fine particles. Hence, a new method of fine particle treatment, i.e., Cloud-Air-Purifying (CAP) technology, was explored herein. In CAP, fine particles grow in size via heterogeneous condensation in a supersaturated water vapor environment and are then collected efficiently using a supergravity field. A laboratory-scale pyrolysis gasifier and CAP equipment were built. Moreover, the CAP removal efficiency for particles generated from four typical rural domestic waste categories was studied. The results showed that CAP technology considerably increased the efficiency of fine particle removal. However, the removal efficiency for particles released owing to the incineration of wood was only ∼75%. This was because the tar substances formed during wood pyrolysis were attached to the surface of escaping particles, which led to a decrease in their hydrophilicity and particle condensation growth. To address this issue, the improvement in particle hydrophilicity using different surfactants was studied via molecular dynamic simulations. When the increase in water molecule adsorption, surface polarity, and the solid-liquid interaction energy for different surfactants were compared, alkylphenol ethoxylate (OP10) proved to be the most effective surfactant. Finally, the improved CAP technology combined with OP10 was applied to the on-site pyrolysis gasification flue gas treatment. Long term monitoring of the proposed technology revealed that particle removal efficiency remained >94%, exhibiting excellent fine particle removal. The successful application of the proposed technology demonstrates its potential for further application.

Emission behavior and impact assessment of gaseous volatile compounds in two typical rural domestic waste landfills.

Landfill sites are sources of gaseous volatile compounds. The dumping area (LDA) and leachate storage pool (LSP) of two typical rural domestic waste landfill sites in north China (NLF) and southwest China (SLF) were investigated. We found that 45, 46, 61 and 68 volatile organic compounds (VOC) were present in the air of NLF-LDA, NLF-LSP, SLF-LDA, and SLF-LSP, respectively. And there were 27, 29, 35 and 37 kinds of odorous compounds being detected. Oxygenated compounds (>48.88%), chlorinated compounds (>6.85%), and aromatics (>5.46%), such as organic acid, 1-chlorobutane, and benzene, were the most abundant compounds in both landfills. The SLF-LDA had the highest olfactory effect, with a corresponding total odor activity value of 29,635.39. The ozone-formation potential analysis showed that VOCs emitted from SLF landfills had significantly higher potential for ozone formation than those from NLF landfills, with ozone generation potentials of 166.02, 225.86, 2511.82, and 1615.99 mg/m3 for the NLF-LDA, NLF-LSP, SLF-LDA, and SLF-LSP, respectively. Higher chronic toxicity and cancer risk of VOCs were found in the SLF according to method of Risk Assessment Information System. Based on the sensitivity analysis by the Monte Carlo method, concentrations of benzene, propylene oxide, propylene, trichloroethylene, and N-nitrosodiethylamine, along with exposure duration, daily exposure time, and annual exposure frequency, significantly impacted the risk levels. We provide a scientific basis, which reflects the need for controlling and reducing gaseous pollutants from landfills, particularly rural residential landfills, which may improve rural sanitation.

An evaluation of the social dimensions in public participation in rural domestic waste source-separated collection in Guilin, China.

A comprehensive evaluation of public participation in rural domestic waste (RDW) source-separated collection in China was carried out within a social-dimension framework, specifically in terms of public perception, awareness, attitude, and willingness to pay for RDW management. The evaluation was based on a case study conducted in Guilin, Guangxi Zhuang Autonomous Region, China, which is a representative of most inland areas of the country with a GDP around the national average. It was found that unlike urban residents, rural residents maintained a high rate of recycling, but in a spontaneous manner; they paid more attention to issues closely related to their daily lives, but less attention to those at the general level; their awareness of RDW source-separated collection was low and different age groups showed significantly different preferences regarding the sources of knowledge acquirement. Among potential information sources, village committees played a very important role in knowledge dissemination; for the respondents' pro-environmental attitudes, the influencing factor of "lack of legislation/policy" was considered to be significant; mandatory charges for waste collection and disposal had a high rate of acceptance among rural residents; and high monthly incomes had a positive correlation with both public pro-environmental attitudes and public willingness to pay for extra charges levied by RDW management. These observations imply that, for decision-makers in the short term, implementing mandatory RDW source-separated collection programs with enforced guidelines and economic compensation is more effective, while in the long run, promoting pro-environmental education to rural residents is more important.

The Perception and Attitude of Farmers toward Domestic Waste Classifications: A Case Study on Wusheng County, Sichuan Province, China.

The effective treatment of rural domestic waste is the key to solving rural environmental pollution and realizing rural ecological revitalization. Giving full play to the main role of farmers' domestic waste classification can improve the efficiency and effect of domestic waste treatment. To explore the key factors affecting the farmers' perception, attitude, and behavior of domestic waste classification, this study with 318 farmers in Sichuan Province as the research object, the research framework of domestic waste classification behavior was constructed based on the theory of planned behavior, and then, the logistic regression model was used for the empirical test. The results show that the farmers' education levels, subjective norms, relatives' and neighbors' views on waste classification, farmers' awareness regarding the negative environmental impacts caused by waste, farmers' private benefits, and farmers' views on the waste management ability of local governments are significantly positively correlated with the classification behavior of farmers' domestic waste. The distance between farmers' houses and waste collection points is significantly negatively correlated with the classification behavior of farmers' domestic waste. This paper provides a certain theoretical reference for realizing the reduction, resourcization, and positive development of rural domestic waste management in China.

Understanding the key factors determining rural domestic waste treatment behavior in China: a meta-analysis.

The growing interest of policy-makers, environmental stakeholders, and academics in rural domestic waste treatment has made it a recent focus of research in the field of rural human settlements. Many studies have been conducted to understand the related factors; however, their results are inconsistent. Therefore, different from previous studies, the study systematically analyzed and summarized empirical studies on rural domestic waste treatment and explored the key factors that fostered and impeded it. It also examined the reasons for differences in research level and trends in key factors over time. A random-effects meta-analysis of 24 studies revealed that education, political status, perceived value, behavioral attitude, subjective norm, garbage collection facilities and services, environmental knowledge and propaganda, and government policy and regulation had a significant positive correlation with rural domestic waste treatment; perceived value had the highest impact, followed by behavioral attitude. All of the variables had significant heterogeneity. Some of the heterogeneity can be explained by differences in research methods, sample size, and variable measurement methods. An increasing trend was observed in the effects of perceived value, behavioral attitude, and subjective norm. Finally, based on these results, the study provided suggestions on policy and academic aspects.

Environmental and economic assessment of rural domestic waste gasification models in China.

The dispersed sources and inconvenient transportation of rural domestic waste (RDW) lead to difficult centralized treatment. Gasification is suitable for decentralized waste treatment, which can effectively avoid RDW long-distance transportation and reduce dioxin emissions compared with small-scale incineration. Hence, economically-affordable and environmentally-friendly RDW treatment models with different gasification scales are required, and village, town and county models were compared via life cycle assessment (LCA) and life cycle cost (LCC) methods in this study. Furthermore, scenario analysis investigated waste sorting based on two food waste (FW) treatment technologies, different FW separate collection efficiency, and electricity recovery to explore the environmental and economic improvement potentials of three models. LCA results show that electricity consumption and direct emissions are significant contributors to environmental impacts, and the county model outperforms village and town models. Moreover, transportation accounts for 6% of the overall environmental impact in the county model. Scenario analysis reveals that waste sorting and electricity recovery can reduce the overall environmental impact by 29% to 146% for three models. LCC results demonstrate that the town model delivers the lowest economic cost, while the village model is the highest. In scenario analysis, resource utilization of FW and electricity recovery of other waste exhibit promising economic benefits. The findings provide comprehensive references for sustainable RDW treatment.

Microplastics in composting of rural domestic waste: abundance, characteristics, and release from the surface of macroplastics.

The rural domestic waste (RDW) compost has been widely used in agriculture and horticulture, but little is known about microplastics (MPs) in RDW composting. The current work deals with the abundance and characteristics of MPs in RDW composting, and the effects of composting processes on the composition of MPs. Compost samples from two RDW treatment stations were investigated, and a lab-scale experiment was carried out to verify the possible release of MPs from macroplastics (>25 mm) contained in the RDW during composting. MPs were identified using stereo-microscope and µ-FTIR. The average abundance of MPs (0.05-5 mm) in the RDW compost products was 2400 ± 358 items/kg (dry weight), and the main MPs shapes were fibers and films. Polyester, polypropylene (PP) and polyethylene (PE) were the most common polymer types. MPs having a size <1 mm accounted for more than 50% of the total quantity. With the progress of composting, the proportion of MPs having size <1 mm increased, and more foam MPs were observed in the late stage of composting. Under the influence of mechanical force, oxidation and biodegradation, a piece of expanded polystyrene (EPS), PP and PE macroplastic could release 4-63 MPs particles during the composting. Thus, the RDW compost was a significant source of MPs in soils, and the MPs in compost products were closely related to the quantity and type of plastic waste present in RDW, which helped to suggest better MPs control strategies.

Global warming potential of typical rural domestic waste treatment modes in China: a case study in Ankang.

The global problem of domestic waste management increases with rapid population growth and with economic and urban development. In developing countries, treatment of rural domestic waste (RDW) is distinguished from urban waste. Quantitative assessment of greenhouse gas emissions from RDW disposal treatment is needed to achieve carbon neutrality. Reliable global warming potential (GWP) assessments of RDW are not differentiated in the widely accepted "urban-rural integration" centralized disposal model. We considered five different scenarios for RDW management. Scenario 1 (S1), unsanitary landfill (open-air dump); scenario 2 (S2), sanitary landfill; scenario 3 (S3), incineration; scenario 4 (S4), biological + incineration; and scenario 5 (S5), classification + composting + sanitary landfill + recycling. Life cycle assessment was used for GWP, and sensitivity analysis was calculated to point out the sensitive parameter. We found that the mean GWP ranged from 5.14 × 104 to 2.31 × 105 kg CO2-equivalents. Pollution from untreated RDW with landfill gas emissions led to large contributions under all scenarios. The collection and transportation ratio was sensitive to all scenarios, and we found that, if the recyclable materials separated at source were not used efficiently, the impact on GWP would be greater than under the unclassified waste scenarios. A "new urban-rural integration" mode (S5) that included household classification, village collection, town transfer, and county and urban disposal was introduced for RDW management. These quantitative results have a great potential for promoting effective RDW management in China and other developing countries.

Carbon emission and energy potential of a novel spatiotemporally anaerobic/semi-aerobic bioreactor for domestic waste treatment.

The biogas generation mechanism and its utilization potential in a novel spatiotemporally anaerobic/semi-aerobic bioreactor (STASAB) system with three activated bioreactors (C1, C2 and C3) was analyzed. Methane generation potential was obtained by measurements and estimation methods with similar values of 23.38 and 27.79 kg CH4/t waste, respectively. CH4 and CO2 production was quickly achieved in the STASAB, and the total amount of CH4 and CO2 was low due to the mixed leachate-recirculation operation process among bioreactors, which were at different stages of operation. The microbial communities in different bioreactors were diverse. The leachate-recirculation operation was a critical parameter to effectively enhance the microbial community structure in the STASAB, which can regulate CH4, CO2 and N2O production with global warming potential of 7.479 kg CO2e/(t·d). The STASAB had higher energy potential of 1.011 kWh/(t·d) compared with that of conventional landfills and sequentially anaerobic/semi-aerobic bioreactors. Moreover, direct electricity production in the STASAB is recommended for energy utilization with 38.38% GHG emission reduction, and with 131.43 million CNY (Chinese Yuan) benefit per year for national rural waste disposal via utilization of biogas from the STASAB for power generation. Hence, the STASAB shows a notable potential for treating domestic waste in rural areas.

Garbage source classification performance, impact factor, and management strategy in rural areas of China: A case study in Hangzhou.

Garbage classification and reduction is imperative in many developing countries, where the imbalance between the rapid growth of solid waste and insufficient disposal capacity can be challenging. In order to evaluate whether a novel '2 + T' source classification method (biodegradable waste, other waste, and toxic waste) and three types of source classification and resourcing treatment patterns implemented in the rural areas of Hangzhou can be widely applied, field investigations, questionnaire interviews, and factor analysis were carried out comprehensively. By means of '2 + T' source classification method, biodegradable waste, accounting for the largest proportion of rural domestic waste, can be effectively separated for the subsequent reduction and resource treatment. Classified deposition in the doorway and door-to-door collection of biodegradable and other wastes provided the best solution for the accuracy of source classification and public participation. Based on the analysis, appropriate classification methods and patterns, sustainable publicity and supervision of source classification behavior as well as sufficient financial support will be key factors for rural domestic waste classification and resourcing management. These methods have a great potential for promoting solid waste classification in the rural areas of China and in other developing countries.