Ichiro Daigo

During the last two decades, the total material input in Japan has been about 2 billion tons per year, and approximately 50%, i.e., about 1 billion tons, has accumulated as the net addition to stock in the form of buildings, social infrastructure, and various kinds of products. The amount of the net addition to stock is calculated annually from the differential between the input and output. However, the detailed contents of the accumulated stock are unknown. It is said that these unknown content

Steels are produced in large quantities and being recycled at high rate in Japan. However, recycling of steel scraps would lead to the enhancement of contamination of undesirable tramp metals in steel scraps. So, the limitation of recycling of the steel scarps would be expected in the near future. This may increase in the production of virgin steels and environmental impacts associated with total steel production in Japan. The authors have developed a dynamic model to assess the maximum recyclab

Hibernating stock is defined as material stock that is no longer used, but is not yet recovered. Although hibernating stock plays a role in materials recoverability, its contribution to the overall material cycle is not clearly understood. Therefore, an analysis of the time-series potential generation of steel scrap in Japan was performed and compared against the actual recovery, proving that the steel scrap recovered each year exceeds the annual generation potential and providing the first macr

Contamination with tramp elements is a major concern in steel recycling. This study aimed to identify the influence of impurity elements on the major properties of carbon steel. The content of impurity elements in recycled steel was determined via elemental analysis of randomly sampled steel bars. Of the 23 impurity elements considered, 15 were found to be mixed in the recycled steel. Industrial standards stipulate that the six major properties of carbon steel are tensile strength, elongation, y

Abstract The accumulation of impurities in the recycling of steel impacts the quality of secondary steel. Understanding impurity levels is crucial in the context of the proliferation of circular economy policies, expected high recycling rates, and growth of scrap consumption. By assuming the accumulation of impurities to be equal worldwide, the understanding of the extent and variation of the mixing and accumulation was limited in previous studies, and the factors influencing those variations we

Many waste ceramic materials and glasses (CerG) such as glass, concrete, pottery, porcelain, brick, and tiles are landfilled because they have been recognized to be less conducive to recycling. In this study, to enhance the recyclability of ceramic materials and glasses, a linear model to minimize natural resource consumption of CerG materials production is proposed. The model focuses on elementally based contents of substances in the CerG materials. The model demonstrates a case for major indus

Selection of recycling approaches is one of the remaining issues in the life cycle assessment (LCA) and a critical factor for materials selection based on the LCA. While several recycling approaches and allocation methods have been proposed, the impact of the recycling effect determined by different allocation methods on materials selection has yet to be addressed. In this study, we demonstrate the impact of the recycling effect on materials selection in the LCA. First, the appropriateness of th

Steel is one of the most recyclable materials, and thus it is recycled repeatedly. When steel is recovered from end-of-life products, some materials containing tramp elements besides carbon steel are mixed into the scrap. Therefore, we must prevent contamination by tramp elements during repeated recycling. Meanwhile, there is little knowledge on tramp element contents in carbon steel. This study aims to quantify tramp element contents in carbon steel produced in Japan. The tramp element contents

The life cycle of steel begins in the mining of iron-ore from the earth. Steels are produced in steel works and used in various products. Some of the steels are recycled at the end-of-life of the products and used as a resource for the production of steel products in electric furnace, while the other steels are used just one time in products and go into landfill. As the recycle ratios of steel from used products increase, the average number of times of use and residence time of Iron element that

In this study, a random sample of 107 steel bars from Japan and 26 steel bars from China were studied. Each specimen’s elemental composition of tramp elements, such as Cu, Cr, Ni, and Sn, was analyzed. By using the compositions of specific tramp elements, electric arc furnace steel bars were distinguished. The distributions of the tramp element composition were obtained for the Japanese steel bars and represent a larger number of samples than previous studies. Those for the Chinese samples are t

During the last two decades, the total material input in Japan has been about 2 billion tons, and approximately 50%, i.e., about 1 billion tons has accumulated as the net addition to stock in the form of buildings, social infrastructure, and various kinds of products. The amount of the net addition to stock is calculated annually from the differential between the input and the output. Therefore, the contents of the accumulated stock are unknown. It is said that these unknown contents include mat

Avoiding the contamination of tramp elements in steel requires the non-ferrous materials mixed in steel scrap to be identified. For this to be possible, the types of recovered steel scrap used in the finished product must be known. Since the thickness and diameter of steel are important sources of information for identifying the steel type, in this study, the aim is to employ an image analysis to detect the thickness or diameter of steel without taking measurements. A deep-learning-based image a