Megacity's pathway toward sustainable food waste management and its environmental performance in a developing country: Evidence from Shanghai, China.

Due to the far distance impact on resident, aquatic and soil ecosystem health, food waste disposal becomes the focus of municipal waste strategy in developing countries. Shanghai is a leading city in China, its evolution of food waste management can indicate the coming future of the nation. In this city, from 1986 to 2020, the open dumping, landfill and incineration of food waste had been gradually banned, replaced by centralized compost and anaerobic digestion and other recovery ways. This study selected ten scenarios, ever used for food/mixed waste disposal in Shanghai, and analyzed the environmental impact change during the period 1986-2020. Life cycle assessment showed that although the generation of food waste raised rapidly, the total environmental impact, which was dominated by Freshwater Aquatic Ecotoxicity Potential, displayed a sharp decrease as 96.09 %, and Global Warming Potential decreased by 28.14 %. Substantial efforts should be made to improve the collection rate of biogas and landfill gas to reduce environmental impact, and quality of residues from anaerobic digestion and compost plants should be improved and utilized in its legal ways. Driving forces for the goal of sustainable food waste management in Shanghai involved economic development, environmental regulations and the supporting national/local standards.

Environmental impacts and nutrient distribution routes for food waste separated disposal on large-scale anaerobic digestion/ composting plants.

Centralized biological treatments, i.e., anaerobic digestion (AD) and in-vessel composting (IVC), were supposed to be the promising processes for the disposal of food waste (FW) after source separation, while the systematic benefits were unclear for FW with high water content, salt and oil and thus influenced the selection by the local decision-makers. In this study, two large-scale working AD and IVC plants were compared for environmental impacts, nutrient recovery and economic benefits. For unit amount of FW, 89.26 kg CO2-eq was released in IVC mainly due to 47.89 kWh electricity consumption, and 57.02 kg CO2-eq was produced in AD. With the application of compost and energy recovery, 26.88 and 93.55 kg CO2-eq savings were obtained in IVC and AD, respectively. NH3 emissions were the main contributor to acidification (0.35 kg SO2-eq) in IVC, while AD exerted less impact on acidification (0.09 kg SO2-eq) and nutrient enrichment (0.25 kg NO3-eq) attributed to the counteract of energy recovery. 2029 would be the inflection point for global warming potential in AD with more clean energy applied in electricity mix in China. For nutrient recovery, more C (8.3%), N (37.9%) and P (66.7%) could be recovered in compost, while those were discharged via leachate and biogas residue in AD. The cost of IVC was 16 CNY/t (2.40 USD/t) lower than AD. Combing the three key indexes and the sale routes of products, IVC was recommended to be used in areas dominated by agriculture and forestry industries, and AD was more suitable for large cities.

City classification for municipal solid waste prediction in mainland China based on K-means clustering.

Cities in mainland China are usually classified according to geographical locations. This traditional city classification system is limited to relative fixed factors, which lives out a gap in terms of the spatial differences of municipal solid waste (MSW). Developing a more comprehensive city classification system is essential for MSW generation prediction and waste management. In this study, six economic, social and climatic indicators that affect MSW generation: population, per capita GDP (PCGDP), environmental sanitation investment (ESI), average temperature, average precipitation, and average humidity, are selected. Weights were calculated for each indicator using a combination of CRITIC weight method and Pearson correlation coefficient prior to cluster analysis. The k-means clustering algorithm was used to classify all cities into four clusters, which differed significantly in the relationships between MSW generation and influencing factors. The results of Kruskal-Wallis test also show that cities in different clusters show different distributions in terms of the indicators selected. The cross-prediction results of the model further validate the reliability of the clustering results from a quantitative perspective. By establishing a city classification system, cities with similar relationships between MSW generation and influencing factors can be placed into one cluster. The model established in one certain city cluster can be used to predict the MSW generation for cities in the same cluster that lack historical data. This may also help to formulate appropriate regional policies according to different relationships between MSW generation and influencing factors, especially for the four city clusters in the mainland China.

Decomposing the decoupling of plastics consumption and economic growth in G7 and China: Evidence from 2001 to 2020 based on China's import ban.

Plastic recycling is critical for dematerializing of plastics. It has a profound implication on decoupling economic growth from environmental pressure and advancing waste plastic governance domestically and internationally while identifying drivers that might improve decoupling. In this study, plastic consumption and recycling patterns are presented, and the factors influencing the acceleration of dematerialization subsequent to the ban were investigated in the G7 countries and China. The results show that plastic consumption increases from 7.60 million metric tons (mt) to 12.60 mt between 2017 and 2019, and subsequently rapidly decreases to 6.84 mt in 2020. The plastic recycling rate drastically decreased by 21.3% in 2017, and decreased slightly from 2017 to 2020, at an annual rate of 2.9% on average. China's ban shocked the decoupling trends, which showed resilience and motivated the development of robust plastic recycling, and the global recycling transformation pattern accelerated the dematerialization of plastics. Decoupling performances of the G7 and China gradually stabilized in 2019, and all the countries were strongly decoupled in 2020, although decoupling index (DI) fluctuates from 2017 to 2020. Among the recycling-trading drivers, the improvement of waste plastic quality in recycling contributes more to decoupling, the recycling rate shows a more negative decoupling effect on China before the ban, and the population effect is weak relative to other influencing factors. The factors revealed the mechanism of decoupling of plastic consumption in the recycling-trading process, and the recyclability improvement in terms of plastic quality is important for dematerialization.