Search

Background: The aim of this study was to evaluate the biogas production of chicken manure (CM) co‐digestion with different types of household waste (soft organic [SO] and food waste [FW]), as well as to evaluate the bacterial load of feeding stock and digested slurry samples before and after anaerobic digestion (AD). The experiment was carried out using lab‐based prototype digesters for co‐digestion of CM with different household wastes (5%). Three experimental groups (T1, T2, and T3) were designed using mixing ratios of SO:CM:H2O:inoculum (5:22.5:22.5:50), FW:CM:H2O:inoculum (5:22.5:22.5:50), and (SO + FW):CM:H2O:inoculum (2.5 + 2.5:22.5:22.5:50). The digesters were set at 28–34°C for 30 days for hydraulic retention time (HRT). Total viable count (TVC), Escherichia coli, and Salmonella spp. counts were determined using the spread plate technique. Results: The study revealed that the highest average cumulative biogas yield was achieved from T1 > T3 > T2, but the concentration of CH4 was found in T3 > T2 > T1. The biogas production between the three groups was statistically nonsignificant (p > 0.05) but the daily concentration of CH4 was found statistically significant (p < 0.05). The average concentration of CH4 and CO2 in biogas was found to be 30% and 68% for T1, 60% and 37% for T2, and 69% and 27% for T3. However, the H2S content was within the acceptable range. The bacterial load was decreased by 2–3 logs before and after AD, and this reduction was statistically significant (p < 0.05). Conclusion: The research found that the co‐digestion of CM with combined household wastes increased the methane concentration in biogas. [ABSTRACT FROM AUTHOR]

Background: The focus of this research was to assess the biogas production of Chicken Manure (CM) collected from hybrid layer chickens fed non‐commercial (CMNC) and commercial (CMC) feed, as well as to evaluate the bacterial load of feeding stock and digested slurry samples before and after Anaerobic Digestion (AD). The effects of the feedstock and digestion composition of CM on biogas production were measured. The experiment was carried out utilizing lab‐based proto‐type digesters for CM with or without inoculum. For each commercial and non‐commercial feed, four experimental groups (CMNC1, CMNC2, CMC1, and CMC2) were designed using mixing ratios of CM: H2O: inoculum (25:25:50) and CM: H2O (50:50). For Hydraulic Retention Time (HRT), the digesters were set up at ambient temperature (28–34°C) for 30 days. The spread plate technique was used to determine the Total Viable Count (TVC), E. coli, and Salmonella spp. counts. Results: The highest average cumulative biogas yield was achieved from CMC2 > CMNC2 > CMC1 > CMNC1. The biogas production of inoculum added groups were statistically significant (p < 0.01) than the without inoculum groups. The average concentration of CH4 and CO2 in biogas was 49% and 51% for CMNC1, 58% and 42% for CMNC2, 46% and 54% for CMC1, 52% and 42% for CMC2. However, the H2S content was within the acceptable range except for the CMNC2 group. The bacterial load was decreased by 2–3 logs before and after AD, and this reduction was statistically significant (p < 0.05). Conclusion: The study concluded that the CM diluted with water and inoculum (25:25:50) ratio was recommended for sustainable biogas production. [ABSTRACT FROM AUTHOR]

Background: Anaerobic digestion (AD) has many benefits and is a safe way to generate energy, address the energy shortage problem, and reduce waste and carbon emissions. The study aimed to determine the performance evaluation of prefabricated polyvinyl chloride (PVC) biogas digester and compare different feeding intervals using cow manure. This study was conducted at ambient temperature in three types of feeding practice (daily, 4‐day, and 7‐day feeding interval) to investigate the variation of biogas production and evaluation of digester performances. The composition of biogas, pH, and total volatile fatty acids (TVFA) were measured regularly and weekly basis. The TVC, Escherichia coli, and Salmonella spp. counts were determined by the spread plate technique method using PCA, EMB agar, and SS agar plate, respectively. Results: The comparison results of daily versus 4‐day feeding interval indicated that the total biogas and methane yield was 34% and 28% higher in 4‐day interval feeding. The average digester performance was also 34% higher in 4‐day feeding interval digester than daily feeding digester. However, the comparison results of daily versus 7‐day interval feeding indicated that the total biogas, methane yield, and digester performance were slightly higher in daily feeding. Before and after AD, the bacterial load (TVC, E. coli, and Salmonella spp. count) was reduced by 2–3 logs, and this reduction was also statistically significant (p < 0.05). Conclusion: The performance of PVC digester was highly satisfactory and good enough to fulfil the demand (0.8–1.6 m3) of a five‐member family for cooking both in urban and rural areas of Bangladesh. [ABSTRACT FROM AUTHOR]

More than 500 million people will be added to Africa's cities by 2040, marking the largest urbanization in history. However, nonrenewable fossil energy sources are inadequate to meet Africa's energy needs, and their overexploitation leads to intensified global warming. Fortunately, Africa has a huge potential for biomass energy, which will be an important option for combating climate change and energy shortage. In this study, we present a typical large-scale biogas plant in Burkina Faso, West Africa (Ouagadougou Biogas Plant, OUA), which is the first large-scale biogas generation plant in West Africa. The primary objective of OUA is to treat human feces, and it serves as a demonstration plant for generating electricity for feed-in tariffs. The objectives of this study are to assess the greenhouse gas reduction capacity and economic, environmental, and social benefits of OUA and to analyze the opportunities and challenges of developing biogas projects in Africa. As a result, the net economic profit of the OUA biogas plant is approximately USD 305,000 per year, with an anticipated static payback period of 14.5 years. The OUA plant has the capacity to treat 140,000 tons of human feces and 3000 tons of seasonal mixed organic waste annually, effectively reducing greenhouse gas emissions by 5232.61 tCO2eq, improving the habitat, and providing over 30 local jobs. Finally, the development of biogas projects in Africa includes advantages such as suitable natural conditions, the need for social development, and domestic and international support, as well as challenges in terms of national policies, insufficient funding, technical maintenance, and social culture. [ABSTRACT FROM AUTHOR]

Abstract: Biogas technology has been promoted worldwide over the past decades, and its use has led to the recognition of the many benefits of domestic biogas digesters. Prefabricated biogas digesters (PBDs) continue to be developed, tested, and extensively applied in developing countries to compensate for the disadvantages of traditional domestic digester models. PBD prototypes are derived from three major types of domestic digester models, namely, the fixed dome, floating drum, and plug flow digesters. Two main streams of PBDs are represented by composite material digesters (CMDs) and bag digesters. PBDs also include off-site constructed ferro- or bamboo-and-cement digesters, as well as assembled digesters. The advantages of PBDs promote the development of different types of PBDs, and several nations have set up special instructions and institutions to promote PBDs. Challenges to PBD dissemination include inferior quality, high investment in CMDs, lagging PBD standardization, low levels of public information about PBDs, and lack of follow-up services. However, based on our literature research and field visits, it could be predicted that PBD technologies will be extensively applied worldwide in the near future. [Copyright &y& Elsevier]

Highlights: [•] Fault tree approach is employed as assessment of small-sized biogas systems (SBS). [•] A nationwide field study was performed in Nepal. [•] Criteria for failures of SBS were defined and elaborated. [•] Weights of five subsystems were determined by Delphi method. [•] Fault tree approach is suitable for SBS although it has not been used until now. [ABSTRACT FROM AUTHOR]

Abstract: China plays a leading role in the worldwide development and dissemination of household-based biogas technology. Since the 1980s, China has developed many types of commercialized or half-commercialized prefabricated biogas digesters (PBDs), which are categorized into three: glass fiber-reinforced plastic digesters, plastic soft digesters, and plastic hard digesters. This paper summarizes the development of PBDs in China, including their key characteristics, manufacturing process, advantages and disadvantages, cost analysis, marketing, and future prospects. Furthermore, the paper highlights and analyzes potential constraints in the promotion of these types of digesters; examples of these constraints include incomplete standardization systems, insufficient demonstration projects, low-quality digesters, and missing authorizations from the inspection department. A preferential policy should be formulated for the prefabricated digester industry. Specifically, the standardization system should be improved, technological innovations should be encouraged, self-regulation of the industry should be intensified, demonstration projects should be implemented, and follow-up services should be improved. PBD technologies can potentially be applied with great reliability and high efficiency not only in China but also in other countries. [Copyright &y& Elsevier]

The anaerobic digestion technology has many advantages and is a sustainable way to produce energy, solve the crisis on energy shortage, and reduce waste stream and carbon footprint. In this field experiment, a mixture of food, fruits, and vegetable waste, dairy manure, and inoculum was anaerobically digested in a constructed water tank digester. This study was performed at ambient temperature under different organic loading rates (OLRs), which were increased every two weeks. Results showed that the optimum feedstock-to-inoculum ratio is 0.4, which resulted in highest specific biogas and methane yields (0.44 and 0.28 Nm3/kg VS, respectively). With the OLRs, the highest yield was observed at 1.4 kg VS/m3 average feeding. When the feedstock-to-inoculum ratio was increased from 0.4 to 0.8, the effect on biogas yield and the volatile solids decreased. Hence, the total cumulative biogas production was approximately 18.5 Nm3 per reactor volume. The pathogen concentration, which was determined in the feedstock and the effluent samples, revealed that the reduction efficiency was relatively low. On the basis of the performance of this field study, emphasizing household organic waste composed with other feed materials to produce bioenergy was feasible. Anaerobic co-digestion produces biogas, contributes to sustainable waste management, and reduces environmental pollution. This scientific study can play a fundamental role in implementing this technology at the household level for efficient biogas production in Bangladesh and worldwide. • A mixture of 5% food, fruit, and vegetable wastes was co-digested with dairy manure. • The inoculum was the only source of dilution media used to enhance the biogas efficiency. • The optimum feedstock-to-inoculum (F/I) ratio was 0.4 in this water tank digester. • A further increase in the F/I ratio reduced the production trend of biogas and CH 4. [ABSTRACT FROM AUTHOR]

Standardization of biogas technology is immensely important for the promotion of the biogas industry worldwide. China has built a complete biogas standard system, which is divided into common, household biogas, biogas engineering, biogas digester for domestic sewage treatment, output utilization, and service system standards. The problems and potential barriers for biogas standardization in China are analyzed and come down to sluggish standard, overlapped standard, government-dominated standard, and lagging international standard. Accordingly, all potential biogas standards should be evaluated and placed under the same department. China Biogas Society and China Association of Rural Energy Industry play leading roles in developing enterprise or group/association biogas standards and ISO biogas standards. The bio-natural gas standard system and experimental standardization should be developed as well to replenish biogas standard system. A paradigm shift in biogas standardization should be from government-dominated to market-oriented model. The lessons learned for other developing countries includes expanding standardization to multi-aspects to realize full lifecycle control and management, building rapid responding mechanism of standardization to adopt industry transformation, integrating outdated standards into new versions, and establishing market-based standard system. • Biogas standard framework in China is presented and elaborated. • Problems and potential barriers for biogas standardization in China are analyzed. • Suggestions and learns learned for other developing countries are presented. • Biogas standardization should cover full lifecycle control and management. • Biogas standardization should shift towards market-oriented model. [ABSTRACT FROM AUTHOR]

Abstract The implementation of the United Nations (UN) Millennium Development Goals (MDGs) and Sustainable Development Goals (SDGs) has resulted in an increased focus on developing innovative, sustainable sanitation techniques to address the demand for adequate and equitable sanitation in low-income areas. We examined the background, current situation, challenges, and perspectives of global sanitation. We used bibliometric analysis and word cluster analysis to evaluate sanitation research from 1992 to 2016 based on the Science Citation Index EXPANDED (SCI-EXPANDED) and Social Sciences Citation Index (SSCI) databases. Our results show that sanitation is a comprehensive field connected with multiple categories, and the increasing number of publications reflects a strong interest in this research area. Most of the research took place in developed countries, especially the USA, although sanitation problems are more serious in developing countries. Innovations in sanitation techniques may keep susceptible populations from contracting diseases caused by various kinds of contaminants and microorganisms. Hence, the hygienization of human excreta, resource recovery, and removal of micro-pollutants from excreta can serve as effective sustainable solutions. Commercialized technologies, like composting, anaerobic digestion, and storage, are reliable but still face challenges in addressing the links between the political, social, institutional, cultural, and educational aspects of sanitation. Innovative technologies, such as Microbial Fuel Cells (MFCs), Microbial Electrolysis Cells (MECs), and struvite precipitation, are at the TRL (Technology readiness levels) 8 level, meaning that they qualify as "actual systems completed and qualified through test and demonstration." Solutions that take into consideration economic feasibility and all the different aspects of sanitation are required. There is an urgent demand for holistic solutions considering government support, social acceptability, as well as technological reliability that can be effectively adapted to local conditions. Graphical abstract Unlabelled Image Highlights • Data for sanitation research from year of 1900 to 2016 have been collected and analyzed. • Hotspots for sanitation research have been discussed for future work based on the keywords data. • The constraints for global sanitation have been identified. • Promising technologies have been evaluated and proposed. [ABSTRACT FROM AUTHOR]

• A novel co-current-flow RPB was developed for ammonia removal of waste leachate. • Gas-liquid film resistance was reduced by RPB to improve the ammonia removal rate. • The ammonia removal rate was improved obviously compared to the normal gravity field. • XGBoost model using small datasets was successfully used for mass transfer prediction. Stripping is widely applied for the removal of ammonia from fresh waste leachate. However, the development of air stripping technology is restricted by the requirements for large-scale equipment and long operation periods. This paper describes a high-gravity technology that improves ammonia stripping from actual fresh waste leachate and a machine learning approach that predicts the stripping performance under different operational parameters. The high-gravity field is implemented in a co-current-flow rotating packed bed in multi-stage cycle series mode. The eXtreme Gradient Boosting algorithm is applied to the experimental data to predict the liquid volumetric mass transfer coefficient (K L a) and removal efficiency (η) for various rotation speeds, numbers of stripping stages, gas flow rates, and liquid flow rates. Ammonia stripping under a high-gravity field achieves η = 82.73% and K L a = 5.551 × 10−4 s−1 at a pH value of 10 and ambient temperature. The results suggest that the eXtreme Gradient Boosting model provides good accuracy and predictive performance, with R2 values of 0.9923 and 0.9783 for K L a and η, respectively. The machine learning models developed in this study are combined with experimental results to provide more comprehensive information on rotating packed bed operations and more accurate predictions of K L a and η. The information mining behind the model is an important reference for the rational design of high-gravity-field-coupled ammonia stripping projects. [Display omitted] [ABSTRACT FROM AUTHOR]

The wide-spread prevalence of unimproved sanitation technologies has been a major cause of concern for the environment and public health, and China is no exception to this. Towards the sanitation issue, toilet revolution has become a buzzword in China recently. This paper elaborates the backgrounds, connotations, and actions of the toilet revolution in China. The toilet revolution aims to create sanitation infrastructure and public services that work for everyone and that turn waste into value. Opportunities for implementing the toilet revolution include: fulfilling Millennium Development Goals and new Sustainable Development Goals; government support at all levels for popularizing sanitary toilet; environmental protection to alleviate wastewater pollution; resource recovery from human waste and disease prevention for health and wellbeing improvement. Meanwhile, the challenges faced are: insufficient funding and policy support, regional imbalance and lagging approval processes, weak sanitary awareness and low acceptance of new toilets, lack of R&D and service system. The toilet revolution requires a concerted effort from many governmental departments. It needs to address not only technology implementation, but also social acceptance, economic affordability, maintenance issues and, increasingly, gender considerations. Aligned with the ecological sanitation principles, it calls for understanding issues across the entire sanitation service chain. Public-private partnership is also recommended to absorb private capital to make up the lack of funds, as well as arouse the enthusiasm of the public. [ABSTRACT FROM AUTHOR]

One of the major challenges for deploying sustainable sanitation technologies and services around the world is financing. The present study applied both qualitative (key informant interviews) and quantitative (household survey) methods to explore sources of alternative financing in Ulaanbaatar, Mongolia, towards deploying sustainable sanitation technologies and services. Microfinance organizations, government subsidies and mining industries may represent potential sources of financing for the implementation of sustainable sanitation technologies and services in Mongolia. Moreover, building social capital among Ger residents and reinventing the idea of ‘corporate WASH responsibility’ could constitute new directions for the future. [ABSTRACT FROM PUBLISHER]

This note from the field shows a novel, hybrid concept of a constructed wetland for the first time in a water-stressed region in the coldest capital in the world, Ulaanbaatar, Mongolia. After selecting a suitable household compound, an ‘Ice-Block Unit’ was designed and constructed to assess its technical performance and capacity to reduce greywater-borne hazards during 2013 and 2014. This system was based on storing water during the winter freezing period as an ice block, and then starting treatment during the summer/non-freezing period. Results showed that the maximum removal rates of chemical oxygen demand (COD), NH 4 + , NO 2 − , total suspended solids (TSS), PO 4 − , and Escherichia coli were up to 100%, 99%, 97%, 97%, 87%, and 98%, respectively. The effluent met the neighbouring country, China's, municipal discharge standard of A grade effluent and could also be considered restricted and unrestricted irrigation water as reported in other studies. The system has proven potential from a technical point of view and can be scaled up to community or cluster levels. This would enable reduction of greywater-borne hazards in low, middle and high income countries with similar contexts. [ABSTRACT FROM AUTHOR]

Current methods for estimating sanitation emissions underestimate the significance of methane emissions from non-sewered sanitation systems (NSSS), which are prevalent in many countries. NSSS play a vital role in the safe management of fecal sludge, accounting for approximately half of all existing sanitation provisions. We analyzed the distribution of global NSSS and used IPCC accounting methods to estimate the total methane emissions profiles from these systems. Then, we examined the literature to establish the level of uncertainty associated with this accounting estimate. The global methane emissions from NSSS in 2020 was estimated to as 377 (22–1003) Mt CO 2 e/year or 4.7% (0.3%–12.5%) of global anthropogenic methane emissions, which are comparable to the greenhouse gas (GHG) emissions from wastewater treatment plants. NSSS is the major option for open defecation and is expected to increase by 55 Mt CO 2 e/year after complete open defecation free. It is time to acknowledge the GHG emissions from the NSSS as a non-negligible source. • The global distribution of NSSS was partially visualized. • The CH 4 emission from global NSSS was tentatively calculated. • The impact of temperature on the in-situ monitoring was briefly analyzed. • The carbon emissions from NSSS and WWTPs were generally compared. [ABSTRACT FROM AUTHOR]

Current methods for estimating sanitation emissions underestimate the significance of methane emissions from non-sewered sanitation systems (NSSS), which are prevalent in many countries. NSSS play a vital role in the safe management of fecal sludge, accounting for approximately half of all existing sanitation provisions. We analyzed the distribution of global NSSS and used IPCC accounting methods to estimate the total methane emissions profiles from these systems. Then, we examined the literature to establish the level of uncertainty associated with this accounting estimate. The global methane emissions from NSSS in 2020 was estimated to as 377 (22–1003) Mt CO 2 e/year or 4.7% (0.3%–12.5%) of global anthropogenic methane emissions, which are comparable to the greenhouse gas (GHG) emissions from wastewater treatment plants. NSSS is the major option for open defecation and is expected to increase by 55 Mt CO 2 e/year after complete open defecation free. It is time to acknowledge the GHG emissions from the NSSS as a non-negligible source. • The global distribution of NSSS was partially visualized. • The CH 4 emission from global NSSS was tentatively calculated. • The impact of temperature on the in-situ monitoring was briefly analyzed. • The carbon emissions from NSSS and WWTPs were generally compared. [ABSTRACT FROM AUTHOR]

There are limited studies that focus on greywater treatment and reuse options, particularly in nomadic societies with unique cultural and climatic conditions. Studies relating to household greywater treatment in nomadic-cultured societies are limited. This study aims to address this gap by examining a case with a high concentration of chemical components in the greywater (e.g. where chemical oxygen demand ranged between 35 and 70,032 mg/L). Specifically, an upgraded greenhouse greywater treatment unit (GH-GWTU) was designed and constructed during the summer of 2013 in Ulaanbaatar, Mongolia, in order to assess the technical feasibility, and up-scaling capability, of the system at the community level. Chemical and biological test results indicated that most parameters (e.g. PO 4 3 − , NO 2 − , NH 4 + ) had a high removal rate of up to 98%. Moreover, the greenhouse may extend the treatment period up to 8 months. This study has shown that GH-GWTU is a potential technology that can significantly reduce the chemicals and biological agents in greywater in Mongolian Ger contexts which may reduce the greywater-borne hazards and vulnerability in the area. It can be replicable both at the household and community scale according to resources available for system operation and maintenance. [ABSTRACT FROM AUTHOR]

The present scoping study seeks to address the sources of water, sanitation, and hygiene (WASH) exposure of residents of peri-urban Ger areas of Ulaanbaatar, Mongolia. Field observations and semi-structured key informant interviews were carried out during 2012 and 2013 to assess the existing WASH situation in the peri-urban Ger areas of Ulaanbaatar, Mongolia. In addition, a knowledge, attitude, and practice (KAP) survey was conducted by Action Contre la Faim (ACF) Mongolia in 210 households to identify the sources of WASH-borne hazards in a statistically representative way. Moreover, the quality of drinking water was analyzed both at the household ( n = 210) and water point (kiosk) ( n = 40) levels to assess the risk of chemical and pathogenic contaminants. Both field observations and interviews revealed that the sanitary environment of the Ger residents is characterized by the lack of a drainage system, unimproved sanitation technology (e.g. unhygienic pit latrines and soak pits), unsafe water supply, and insufficient collection, transportation, and storage mechanisms. Poor infrastructure is associated with low standards of living. The transmission of WASH-borne disease (e.g. diarrhea, dysentery, hepatitis A) is the gravest consequence and source of hazards. The results from the water quality analysis demonstrate that Ger residents are more exposed to biological contamination of stored drinking water by Escherichia coli during the summer (May to August) than in the winter (November to February). During the winter, 36% of household storage containers were contaminated by E. coli at an average level of 12.5 E. coli per 100 ml, while, during the summer, 56% of household storage containers were contaminated at an average level of 50 E. coli per 100 ml. KAP surveys further reveal that the common practice of Ger residents to discharge greywater (with higher chemical oxygen demand) into pit latrines, soak-pits, yards, and streets likely causes environmental pollution and health hazards. Multifaceted WASH-borne exposure was addressed by the scoping study such that various WASH interventions could be planned for the study area and beyond. To tackle the above challenges and problems, a range of appropriate interventions and programs are recommended to reduce the exposure of WASH-borne hazards in the study area and other parts of the world – in both urban and peri-urban settings. The recommendations include: the development and implementation of a water safety plan (WSP), an effective monitoring system for collection, transportation and storage at both water kiosk and household levels, user training for correct use of water containers, effective coordination among stakeholders (including urban planners), development of a household greywater disposal system, and implementation of a functioning solid waste management system. Prior to taking these actions, a detailed study on the ‘pollution load from peri-urban to urban’ should be carried out to assess the WASH-borne vulnerability of both peri-urban and central urban population. [ABSTRACT FROM AUTHOR]

Abstract: A standard methodology is needed to recognize potentially suitable areas for sustainable bioenergy crop production. This facilitates better identification of promising crops and cropping systems, logistical and economic studies, and work needed to meet regulatory criteria. A possible approach is built upon three layers of internationally available spatial data: (1) degrading and abandoned areas, (2) potentially suitable land cover classes, (3) exclusion zones such as nature reserves and areas of high biodiversity. For China, areas identified as potentially suitable range from 1.2 to 6.0% of the national territory, depending on different levels of statistical confidence in degrading area status and allowable limits of terrestrial carbon. Verification on the ground showed that about 60% of points tested conformed to the remote suitability assessment in the scenario, which represents the results for the combination of all degrading areas and a terrestrial carbon stock limit of 200 t ha−1. A top-down approach is useful in framing potentially suitable locations, but a complementary bottom-up analysis is still required to ultimately identify areas for sustainable bio-fuel production. [Copyright &y& Elsevier]

The provision of sanitation services for fast-growing urban populations is one of the world's urgent challenges. Hutong neighborhoods in Beijing, capital of China, cannot be rebuilt due to the protection of historical heritage, while residents still need to keep the habit of defecating in public toilets. One hundred public toilets with non-sewered sanitation in the Hutong neighborhoods of Beijing were visited to investigate the actual operating status in response to the "toilet revolution" campaign. The fault tree approach was used to identify the barriers toward a decent and environment-friendly public toilet and evaluate potential risks from the malfunction of various components. Four subsystems are defined and elaborated to calculate the fault possibility. These subsystems are environment- and user-friendly, regarded as ancillary facilities, and used for fecal sludge (FS) management. Statistical analysis of targeted cases indicated that fault probabilities of environmental considerations, user-friendly considerations, ancillary facilities, FS management are calculated as 0.79, 0.96, 0.96, and 0, respectively. The subsystems were weighted using a Delphi method concept. Results showed that the well operation ratio of Beijing Hutong public toilets is only 32%, and the sanitation service value chain can be further optimized. This study also provides references for other countries, which are dedicated to promoting urban sanitation and public health. • Potential risks of public toilets were identified through Fault Tree Analysis. • A methodology in framing failures of public toilet subsystems is developed. • Delphi method was applied, validated, and found useful in sanitation research. • The barriers toward decent and environment-friendly public toilets are identified. [ABSTRACT FROM AUTHOR]

Rural toilet retrofitting (RTR) is a complex, dynamic system that is affected by many factors and the positive/negative feedback relationships between subsystems and variables. Traditional technologies and management methods face challenges in fundamentally describing and solving problems in RTR. To bridge this gap, this study utilizes system dynamics and causal loop diagrams to explain such problems based on data collected from the stakeholders of the RTR in Jiaozhou from 2018 to 2019. Specifically, this study examines the RTR system from the perspectives of household users, wastewater treatment plants, local governments, grassroots promoters, operation and maintenance personnel, toilet supplier and construction teams, and fecal sludge end users. The factors and processes involved in RTR are identified, and the feedback and relationships among its major stakeholders are established. Results show that the motivation of farmers to engage in RTR is a key variable that affects their final decisions regarding retrofitting and maintaining toilet functions. Meanwhile, the important variables related to the feedback and relationships among the major stakeholders of RTR are mostly focused on policies, subsidies, technology, satisfaction, and cooperation. A scientific analysis method and the updated RTR plan for toilet revolution are then formulated to promote the implementation of RTR in developing countries. • Typical case of rural toilet retrofitting in China is selected and investigated. • System dynamics model for simulating rural toilet retrofitting is developed. • Causal loop diagrams for rural toilet retrofitting are presented and analyzed. • Experience of rural toilet retrofitting is shared for other developing countries. [ABSTRACT FROM AUTHOR]

• 20 randomly real urine samples were collected and analyzed. • Totally 30 antibiotics in the fresh real urine were identified. • Representative antibiotic resistance bacteria and its gene were identified. • Changes of antibiotics, antibiotic resistance bacteria and gens of urine were monitored. Human urine is a source of fertilizer and, with proper management, it can be reused in agriculture. Determining the contamination issue of antibiotics in source-separated urine is important because the majority of antibiotics are excreted with urine. In this study, source-separated urine samples were randomly collected from a male toilet in a university building and analyzed in terms of 30 typical antibiotics (including 14 sulfonamides, 4 tetracyclines, and 12 fluoroquinolones) and tetracycline-resistant Escherichia coli , as well as its antibiotic-resistant genes to determine the contamination characteristics of antibiotic-related pollution in fresh and stored urine. Results showed that 18 out of 30 typical antibiotics were detected in fresh source-separated human urine. The dominant antibiotic was oxytetracycline with a frequency of 100%, followed by tetracycline, sparfloxacin, enrofloxacin, and ofloxacin, which demonstrated a detection frequency of 55%. Among the detected values, sulfonamides (2 antibiotics), tetracyclines (4 antibiotics), and fluoroquinolones (12 antibiotics) had a concentration range of 0.25–2.94, 0.94–41.2, and 0.06–163.16 ng/mL, respectively. Furthermore, tetracycline-resistant Escherichia coli , which was measured using plate count method, and its related gene, tet M, exhibited a maximum cell density of (200,000 ± 5000) CFU/100 mL and (2.73 ± 0.261) × 107 copies/mL, respectively. When the fresh urine was stored in an ambient environment for 30 days to simulate the real circumstances of urine management, a significant reduction in antibiotics and antibiotic-resistant bacteria was observed, while the change in antibiotic-resistant genes was insignificant. The results of this study suggest that risks associated with antibiotics and their antibiotic-resistant bacteria and genes are retained during collection and storage. Hence, these kinds of microcontaminants must be considered in further urine utilization. [ABSTRACT FROM AUTHOR]

China has promoted its biogas industry for a long time and begun to support bio-natural gas (BNG; also known as biogas upgrading or biogas-to-biomethane) projects for the first time in 2015 at the central government level. This study presented a comprehensive overview of the BNG industry in China, including its status quo, national strategic planning, upgrading technologies, investment cost, potential, and opportunities and challenges. A total of 65 BNG demonstration projects were approved by the central government between 2015 and 2017, and 197 projects are expected to have been built by 2020 as part of the 13th Five-Year Plan (2016–2020). BNG is an emerging industry, and its development provides several opportunities, including a huge natural gas demand, national policy incentives, integrated agriculture, and reduced carbon emissions. The challenges and barriers to such developments include the high upgrading cost, fluctuating natural gas prices, unsound market access mechanism for biomethane and biofertilizer, scarce competition-oriented feedstock resources, incomplete standard system and cross-sectorial management, imperfect policy and subsidy mechanism, and lagging technology and equipment. China can learn from other developed countries in four ways. First, the country must enhance the cost effectiveness of its subsidies. Then, China must highlight the operations of its BNG industry and evaluate its performance; prioritize digestate management in the planning stage; improve its project service level and reinforce research and development. The findings of this work provide a valuable reference for other developing countries that intend to address energy shortage issues and integrate waste management into their regional planning. • Current status of BNG industry in China is presented and elaborated. • Opportunities and potential challenges for BNG industry in China are analyzed. • Suggestions for sound development of BNG industry are presented. • BNG development in China could provide references for other developing countries. [ABSTRACT FROM AUTHOR]