An Extended Model for Tracking Accumulation Pathways of Materials Using Input–Output Tables: Application to Copper Flows in Japan

High-resolution mapping and evolution of steel stocks and waste in civil buildings: a case study of Changsha, China

Systematic estimation of steel stocks and waste in urban areas and analysis of its historical evolution pattern is crucial for urban buildings steel recycling and environmental sustainability. However, it is a challenging task to collect big data from different sources and estimate accurately with high resolution. In this study, we proposed a novel hybrid approach (GMB model) to estimate building steel stocks and the annual waste rate through combining Geographic Information System, Material Flow Analysis, and Big Data Mining techniques. We estimated the civil-building steel stocks and amount of waste in Changsha urban area from 1985 to 2020 based on the GMB model, and analyzed the historical evolution pattern of steel stocks by using standard deviation ellipse and kernel density. The results showed that the cumulative steel stock in civil buildings grew from 0.66 million tons in 1985 to 8.26 million tons in 2020. The amount of waste increased by 2557 times. The spatiotemporal analysis showed that variations in distribution of the steel stocks are mainly concentrated in the central city, indicating a "central-peripheral" distribution, with a southward trend in the standard deviation ellipse and a southeast-northwest direction in the center of gravity of the steel stocks. There is low-high and high-low spatial aggregation patterns. We also compared the experimental results with the observed data to determine the feasibility of the GMB model. Our study can promote the management of steel resources recycling and aid to achieve the green and low-carbon goals in sustainable development policies.

Revealing the intersectoral material flow of plastic containers and packaging in Japan

The Japanese government developed a strategy for plastics and laid out ambitious targets including the reduction of 25% for single-use plastic waste and the reuse/recycling of 60% for plastic containers and packaging by 2030. However, the current usage situation of single-use plastics including containers and packaging, which should be a basis of the strategy, is unclear. Here, we identify the nationwide material flow of plastics in Japan based on input-output tables. Of the domestic plastic demand of 8.4 Mt in 2015, 1.6 and 2.5 Mt were estimated to be for containers and packaging comprising household and industry inflows, respectively, through the purchase/procurement of products, services, and raw materials. Considering the current amount of recycling collected from households (1.0 Mt) and industries (0.3 to 0.4 Mt), the reuse/recycling target has already been achieved if the goal is limited to household container and packaging waste, as is the focus of Japan's recycling law. Conversely, the results indicate that it will be extremely difficult to reach the target collectively with industries. Therefore, it is essential that efforts be made throughout the entire supply chain. Food containers and packaging that flowed into the food-processing and food service sectors accounted for 15% of the inflow of containers and packaging into industries. Thus, the key to achieving the reuse/recycling target will comprise the collection of plastic food packaging from not only households but also the food industry. Furthermore, the collection of flexible plastic films used between industry sectors will put the target within reach.