都市鉱山に含まれる元素・素材の関与物質総量を用いたリサイクル性評価手法の開発: 都市鉱石TMRの枠組み構築

摘要

In this study, the total materials requirement (TMR) to recycle chemical elements from the urban ore by recycling (urban ore TMR, UO-TMR) has been compared with the TMR to extract the element from the natural ore by smelting (natural ore TMR, NO-TMR) in order to evaluate the urban ore grade on an equal footing with the natural ore. A framework of UO-TMR based on the NO-TMR framework is developed. To validate the developed framework, the UO-TMR of a laptop PC is estimated assuming gold, silver, copper, iron, aluminum, tantalum and indium are recycled. It is found that the UO-TMRs for gold, silver, copper, iron, aluminum and tantalum are lower than NO-TMR, but that for indium is higher. The ratio of "urban tailings" is at most 60% of the total, which is smaller than that of NO-TMR "tailings". In contrast to the contributions of energy and material inputs for the recycling process, the contribution of transportation is not very large. For the UO-TMR of indium, the contribution of materials for recycling process is extremely large. The availability and scalability of UO-TMR are also discussed.%電子機器，自動車，建築物をはじめとする使用済み製品には種々の有価物が含まれており，これらはいわゆる「都市鉱山」と考えることができる．そして近年，この言葉は環境に関する研究分野だけでなく，一般社会においてもよく知られるようになってきている．原田はいくつかの元素について日本の都市鉱山における蓄積量を報告しており，金は世界の現有埋蔵量の16％である6800トン，銀は22％，インジウムは61％，スズは42％，タンタルは10％が蓄積されていると推定している．