[Assessment of the Multidimensional Performances of Food Waste Utilization Technologies in China].

In recent years, China has made great efforts to carry out source-separation in municipal solid waste management; in particular, the utilization of food waste has received increasing attention. Food waste-utilizing technologies, including anaerobic digestion, aerobic biological treatment, and insect feed conversion, are currently applied in China. However, in the existing cases, there were several disadvantages, such as a low rate of utilization, significant environmental impacts, poor economic benefits, etc., as well as a lack of systematic analysis and comprehensive assessment of the performances of food waste utilization technologies. In this study, a four-dimensional performance assessment method (resource efficiency, environmental impact, economic feasibility, and social effect, with 21 indicators) was established for assessing the life cycle process of food waste utilization technologies. We collected detailed information of 14 typical food waste utilization cases in China, and the results showed that the average scores of anaerobic digestion and insect feed conversion were 58.39 and 59.65, higher than those of the aerobic biological treatment (49.16). The highest scores among all subdivision technologies were centralized black soldier fly conversion and mesophilic wet anaerobic digestion, which were 67.14 and 60.82, respectively. With respect to the technologies of different treatment capacities and distribution modes, i.e., centralized and decentralized technologies, the resource efficiency and economic benefit scores of the former were 13% and 62% higher than those of the latter, whereas the environmental impacts and social effect scores of the latter were 8% and 34% greater than those of the former, respectively. In practice, the utilization technology of food waste should be chosen according to local conditions, such as the physical and chemical properties of food waste, the classification of municipal solid waste, financial affordability, collection and transportation distance, etc.

[Characteristics and Environmental Impacts of Materials Stored in Municipal Solid Waste Landfills: A Case Study of the Guangdong-Hong Kong-Macao Greater Bay Area].

The composition of municipal solid waste (MSW) in landfills is complex; additionally, the waste stored in landfills continues to generate greenhouse gases, odors, and ground water pollutants even during the post-closure stage. Therefore, landfills are considered key fields of urban eco-environmental remediation. In this context, it is crucial to understand the storage, composition, physical, and chemical characteristics of waste, as well as its potential environmental impacts. However, very few studies have discussed these topics in detail. In this work, we focused on the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), which has the highest urbanization rate and population density of all China. The generation, stock, physical components, and key elements of MSW in eleven cities of the GBA were analyzed based on both the scientific literature and statistical data. The main results are as follows:① the total amount of MSW produced by the cities was of 26.4 Tg in 2017, with an average annual increment of 0.8 Tg; moreover, the most used disposal method was the sanitary landfill (58.9% of the total); ② the total amount of MSW disposed in the landfills was equal to 230.1 Tg[including mainly food waste (109.6 Tg), plastic (38.9 Tg), and paper (29.6 Tg)]; ③ between 2001-2017, a total of 50.0 Tg of carbon were input in the landfills in the form MSW, of which 7.1 Tg of carbon were emitted as gas and 1.5 Tg were discharged as leachate; moreover, the total landfill carbon stock was equal to 41.4 Tg. Overall, this study provides fundamental data that can be used to determine the environmental impacts of MSW landfills and implement the eco-environmental remediation of urban landfill sites in the GBA.

[Investigation of waste classification and collection actual effect and the study of long acting management in the community of Beijing].

The current position of waste separation and collection are investigated in 600 separation pilot communities of Beijing. According to survey date, it was revealing that correct classification rate and correct putting rate is not high in the pilot communities. It is an important factor that different awareness levels affect correct separation and putting rate, and according to the different breadth of knowledge, awareness divided into two ranges which is 75.6% and 15.5% respectively. However, majority about 60.1% of the population's waste classification knowledge still stay on preliminary stage in the community, and about 24.4% population don't aware of the waste classification. The correct rate of classification operations and putting is relatively low at 4.5% and 31.2% respectively. At the same time, the attention and breadth of publicity and education is not enough, and the management system has not formed. The waste classification recommendations of residents in the community: The publicity of classified knowledge should be strengthen, about 36.84%; then the supervision of waste classification correct putting should also be strengthen, about 35.39%. As a whole, most residents, more than 90%, think that soft power construction should be improved. Therefore, in order to induct residents operating classification practices, it is recommended that promoting the involvement and depth of classification publicity to make use of various Medias and foster ways. The evaluation index system of community's waste classification, combining the hardware facility and the publicity and education, should be build. At the same time, the supervision system which has the better operability should be established, that means the residents will gain long-term sustainability supervision using incentive and punishment ways. In addition, waste classification effect should be become the assessment indexes about city community governance, and improving the public administration level.

[Integrating technologies for urban communities' municipal solid waste minimization].

Municipal solid waste management of urban communities has difficulties of insufficient source separation and food waste's high moisture content, an integrating technology of manual separation, simple compression of food waste, reclaim of food waste and composting leachate was studied. Manual separating rate was 36.8 kg/h, and would increase when the worker became sophisticated. Community separated food waste had high organic matter content of 44.493%, nutrients N, P, K contents of 2.586%, 0.649% and 1.274%, C/N ratio of 17.427, but 0.07-0.82 times lower heavy metals contents compared to centralized separation of mixed municipal solid waste. Moisture content of food waste was still 78.7%, high enough to have negative impacts of composting processes. Composting leachate processing with biological stabilization and dilution showed a fertilizer efficiency, and dry weight of impatiens irrigated with composting leachate was 1.46-2.49 times of tap water irrigation. Integrating technology based on community's manual separation could decrease 52.6% municipal solid waste.

[Adaptive optimized technologies for ecological sanitation and their complex ecological benefits].

Aiming at the ecological characters of the cities in central and west China, several ecological sanitary (ecosan) technologies with different adaptability were integrated, and five adaptive optimized technologies were established. The environmental effects, resources recyclable potential, economic benefits, management difficulties, and public acceptance of each of the technologies were studied, with the possible complex eco-benefits of the technical improvement assessed. The results showed that decentralized ecosan technologies had the advantages of conserving water, recycling nutrients and saving cost, but also had the problems in management and public acceptance. Centralized ecosan technologies had the advantages in management and public acceptance, but were short in high cost and low recycling potential. If the sanitary system was improved through applying ecosan technologies, the greenhouse gases emission (CO2 equivalent) and water pollution (calculated as BOD5) could be reduced by 70% and 30%, respectively, while recycled nutrients (the sum of N, P, K) could be increased by 15 times. The optimized system could supply 3% of domestic energy, 10% of domestic water, and 15% of food demand, and the total cost could be reduced by 56% when the resource-recycling benefits were taken into account.

[Study on technological characters of anaerobic-aerobic bioreactor landfill].

A technology of anaerobic-aerobic landfill bioreactor aimed at reusing landfill site is studied, and it's based on landfill bioreactor technology. A set of stimulating equipment is designed, and the technology characters are studied. In the anaerobic period, technological conditions are controlled by the means of leachate recirculation. The main experimental results are: pH, R1 rises to 6.7 - 7.8 in 6 weeks, and R2 is under 6.8 in 17 weeks; COD concentration of leachate, R1 declines to 10 617 mg/L in 13 weeks, while R2 rises to 60 000 mg/L in 5 weeks, and keeps stabilization in long time; the cumulating methane production, R1 reaches 44% in 8 weeks, while R2 almost cannot produce methane. The stabilization can be evaluated by pH of leachate, COD and BOD5/COD decreasing ratio, and cumulating methane production. They are main evidences to transform anaerobic period to aerobic period. In the aerobic period, odor and moisture are reduced by the means of aeration. The main experimental results are: ammonia concentration reduces to 1.16 mg/m3 in 19 days, and the odor concentration reduces to 19 in 23 days; the moisture of the wastes reduces to 26% in 14 days. The technological indexes to evaluate finishing of this period can be determined by the ultimately purpose of exploited wastes. Numerical modeling has been researched with the use of experimental data. The succession of microbes in the anaerobic-aerobic course is studied by RISA (ribosomal intergenic spacer analysis) analysis. There are 4 preponderant groups in this course, and some facultative anaerobes play important roles in the transition of anaerobic period to aerobic period.